Environ Monit Assess (2011) 183:151195DOI 10.1007/s10661-011-1914-0A review on applicability of naturally available adsorbentsfor the removal of hazardous dyes from aqueous wastePankaj Sharma Harleen Kaur Monika Sharma Vishal SahoreReceived: 29 March 2010 / Accepted: 27 January 2011 / Published online: 10 March 2011 Springer Science+Business Media B.V. 2011Abstract Theeffluentwaterofmanyindustries,such as textiles, leather, paper, printing, cosmetics,etc., contains largeamount of hazardous dyes.Thereishugenumberoftreatmentprocessesaswell as adsorbent which are available for theprocessingof thiseffluent water-containingdyecontent. Theapplicabilityof naturallyavailablelowcastandeco-friendlyadsorbents,forthere-moval of hazardous dyes from aqueous waste byadsorption treatment, has been reviewed. In thisreviewpaper, wehaveprovidedacompiledlistoflow-cost, easilyavailable, safetohandle, andeasy-to-dispose-off adsorbents. These adsorbentsP. Sharma (B) H. KaurDepartment of Chemistry, Lovely School of Sciences,Lovely Professional University, Phagwara 144402,Punjab, Indiae-mail: sharmapankaj47@yahoo.comP. SharmaEnergy and Environment Fusion Technology Center,Department of Environmental Engineeringand Biotechnology, Myongji University, San 38-2,Nam-dong, Cheoin-Gu, Yongin-Si 449-728,Republic of KoreaM. SharmaDepartment of Chemistry, Kurukshetra University,Kurukshetra 136119, IndiaV. SahoreDepartment of Microelectronics & Photonics,University of Arkansas, Fayetteville, AR 72701, USAhave been classified into five different categorieson the basis of their state of availability: (1) wastematerials from agriculture and industry, (2) fruitwaste, (3) plant waste, (4) natural inorganic mate-rials, and (5) bioadsorbents. Some of the treatedadsorbentshaveshowngoodadsorptioncapaci-ties for methylene blue, congo red, crystal violet,rhodamine B, basic red, etc., but this adsorptionprocess is highly pH dependent, and the pH of themedium plays an important role in the treatmentprocess. Thus, in this review paper, we have madesome efforts todiscuss the role of pHinthetreatment of wastewater.Keywords Adsorption Low-cost adsorbents Dyes Wastewater treatment Column studiesIntroductionWith the discovery of the synthetic dyes, the thingsbegantochange. Cheapertoproduce, brighter,morecolor-fast, andeasytoapplytofabricaresome of the characteristic of these newdyes.Scientistshavecompetedtoformulategorgeousnew colors, and synthetic dyes had become obso-lete for most applications. No doubt, this bright-colored material has changed the world; however,the chemicals usedtoproduce dyes are oftentoxic, carcinogenic, or even explosive. Among thedifferent pollutants of aquatic ecosystem, dyes are152 Environ Monit Assess (2011) 183:151195amajor groupof chemicals (Attiaet al. 2008;Namasivayam and Kavita 2002; Goyal et al. 2004;Khattri andSingh1998). Many industries liketextiles, leather, cosmetics, paper, printing, plas-tics, etc., usemanysyntheticdyestocolortheirproducts. Thus, effluents fromthese industriescontain various kinds of synthetic dye stuffs. Forinstancedyes usedinthetextileindustries areclassifiedintothreeclasses: (a)Anionic(direct,acid, andreactivedyes), (b) Cationic(all basicdyes), and(c)Non-ionic(disperseddyes). Basicand reactive dyes are extensively used in the tex-tile industry because of their favorable character-isticsofbrightcolor, beingeasilywatersoluble,cheaper to produce, and easier to apply to fabric(Karadag et al. 2007; Karcher et al. 2002; Purkaitetal.2005).Presenceofcolorandcolor-causingcompounds has always been undesirable in waterforanyuse. Itis, therefore, notatallsurprisingto note that the color in wastewater has now beenconsidered as a pollutant that needs to be treatedbeforedischarge. Thus, colorremoval isoneofthemost difficult requirements tobefacedbythe textile finishing, dye manufacturing, pulp andpaper industries, among others. These industriesaremajor water consumers andare, therefore,asourceof considerablepollution. Inorder toimplement an appropriate treatment process, it isof utmost importance to minimize pollution, andto do that, it is necessary to know its exact nature.Robinsonet al. (2001)madesomegoodeffortstogive some collective informationrelatedtocurrent available technologies and have suggestedan effective, cheaper alternative for dye removaland decolorization applicable on large scale. Theyhavealsoprovidedsomeimportantdatarelatedtothedesorptionof individual textiledyesandasynthetic dyeeffluent fromdye-adsorbed agri-cultural residuesusingsolvents(Robinsonetal.2002a, b, c), which is also important in designingthe adsorption treatment process.Various physical and chemical techniques,other than adsorption, like coagulation, chemicaloxidation, frothfloatation, oxidationor ozona-tion, membraneseparation, andsolvent extrac-tionprocesseshavebeenusedbyanumberofresearchers for the removal of organics as well asinorganicsfromthewastewater; however, theseprocesses are effective and economic, only in thecase where the solute concentrations are relativelyhigh(PanswedandWongchaisuwan1986;MalikandSaha2003; Kochetal. 2002; Ciardellietal.2000; GuptaandSuhas2009). Also, thesetreat-mentsinvolvehighoperationalcostandaerobicdigestion. For instance, photocatalyticdegrada-tionprocesseshaveshownconsiderablesuccessintheremovaloforganicdyesfromwastewater(Li et al. 2008; Pauporte and Rathousky 2007; Jainet al. 2007; Marugan et al. 2007); however, therehavecertainshortcomings. Coagulationprocessproduces large amount of sludge leading to highdisposal costs. Ion-exchangeprocesshasnolossof adsorbent on regeneration; however, it cannotaccommodate wide range of dyes and is expensive.Membrane separation process is also effective intheremoval ofdyes; however, duetorelativelyhigh investment and membrane fouling problem,its application is restricted as there is a widerangeinpHofdyesandeventheconventionalbiological methods are not effective to treat dyebearingwastewaters(Lakshmi et al. 2009). Ad-sorptionhasbeenfoundtobeasuperiortech-niqueas comparedtoother methods of wastetreatment interms of cost, simplicityof designand operation, availability, effectiveness, and theirinsensitivity to toxic substances (Choy et al. 2000;Namasivayam et al. 1996). The more recent meth-odsfortheremoval of syntheticdyesfromwa-terandwastewaterwerecompliedandreportedintheformof reviewarticlebyForgacs et al.(2004). The advantages and disadvantages of thevarious methods werealsodiscussedandtheirefficacies were compared. Adsorption is a physio-chemical wastewater treatment in which dissolvedmoleculesareattachedtothesurfaceofanad-sorbent byphysical/chemical forces. Dependingonthenatureof theinteractions ionic speciesand molecular species carrying different func-tional groups may be held to the surface throughelectrostatic attraction to sites of opposite chargeatthesurfaceorphysiosorbedduetoactionofvanderWaalsforcesorchemisorbedinvolvingstrongadsorbateadsorbentbonding. So, itmaylead to attachment of adsorbate molecules atspecific functional grouponadsorbent surface.It istruethat choiceof adsorbent playsaveryimportant role (Sarma et al. 2008). This techniqueisquitepopularduetoitssimplicityaswell asEnviron Monit Assess (2011) 183:151195 153theavailabilityof awiderangeof adsorbents,andit provedtobeaneffectiveandattractiveprocess for the removal of non-biodegradable pol-lutants (includingdyes) fromwastewater (Hanet al. 2006; Aksu 2005). Most commercial systemsuse activated carbon as adsorbent to remove dyesin water because of its significant adsorption ca-pacity. Althoughactivatedcarbonisapreferredadsorbent, its widespread use is restricted due toits cost. Inorder todecreasethecost of treat-ment, some attempts have been made to find lowcostalternativeadsorbents. Recently, numerousstudies have been conducted to develop cheaperand effective adsorbents from a variety of startingmaterials such as wheat bran carbon (Weng andPan 2006), sludge ash (Rozada et al. 2003), mangoseedkernel(KumarandKumrana2005; KumarandPorkodi 2006), perliteandclay(Acemio glu2005), sawdust (Shuklaet al. 2002; Garget al.2004), sugarcane (Ho et al. 2005a), jute fiber(Senthilkumaar et al. 2005), bagasse pith (McKayet al. 1987), and carbons from agricultural wastes.The effectiveness of a combined reductionbiological treatment systemfor thedecoloriza-tion of non-biodegradable textile dyeing wastewa-terwasinvestigatedbyGhoreishi andHaghighi(2003). In this treatment system, a bisulfite-catalyzedsodiumborohydridereductionis fol-lowedbyactivatedsludgetechniqueinordertoremove the color at ambient temperature andpressure, andthis experimental studyconsistedoftwomajorparts: reductiontreatmentandbi-ological oxidation. Joo et al. (2007) reported thedecolorizationof reactive dyes using inorganiccoagulants and synthetic polymer, and they foundthat the use of inorganic coagulant alone appearedlittle effective in the removal of reactive dyes fromthe real wastewater. However, alum/polymer andferricsalt/polymercombinationsimprovedcolorremoval up to 60% and 40%, respectively.Inthisreview, anextensivelistofadsorbentsobtainedfromdifferent sources has beencom-piled, andthisreviewalsoreportstheoptimumprocessingparametersforgettingmaximumdyeremoval for effluent water. Main emphasis is onthe pH and initial dye concentration in the solu-tion as these two parameter affects the adsorptionprocess more. The other objective to write this re-view paper is to make some comparisons betweentheadsorbent capacityof chemicallymodified,pretreated, and untreated adsorbents.Low cost and easily available adsorbentsKeeping all the above points in view, our labora-tories are contributing more towards the directionof adsorption by cheap adsorbents. Cost is actu-allyanimportant parameter for comparingtheadsorbent materials. Certain waste products fromindustrial and agricultural operations, natural ma-terials, and biosorbents represent potentially eco-nomical alternative sorbents. Many of them havebeen tested and proposed for dye removal.Waste materials from agriculture and industriesA number of agricultural wastes/by-products andindustrial waste products have been proposed bya number of researchers for the dye removalfromaqueous wastewater (NamasivayamandKadirvelu 1994; Pala and Tokat 2002; Crini 2006).Theselow-cost adsorbents areabundant inna-ture, inexpensive, require little processing, and areeffective for dye removal. The recently reportedadsorbents obtained from the industrial waste andagricultural by products with their adsorption ca-pacities (milligrams per gram) aretabulatedinTable 1.Activated carbonActivated carbon adsorption is one such methodwhich has great potential for the removal of dyesfromaqueouswaste. Theadsorptioncapacityofactivated carbon depends on various factors, suchas surface area, pore size distribution, and surfacefunctional groups on the adsorbent, polarity, sol-ubility, and molecular size of the adsorbate, solu-tion pH and the presence of other ions in solution,and so on. The most widely used activated carbonsare microporous and have high surface areas, andas aconsequence, showhighefficiencyfor theadsorptionof lowmolecularweight compoundsand for larger molecules. Zhi-yuan (2008) carriedout anadsorptionstudyof methyleneblueonactivated carbon fiber (ACF). It has been used inadsorption systems including removal of noxious154 Environ Monit Assess (2011) 183:151195Table1 Reviewedresults representingtheadsorptioncapacityof agricultureandindustrial wastematerials for theadsorption of dyes and their optimized pH values for maximum adsorptionAdsorbent Dye pH Adsorption capacity ReferencesRice husk Indigo carmine 5.4 65.90 mg g1Lakshmi et al. (2009)Activated carbon - RHC Acid yellow 36 3.0 86.90 mg g1Malik (2003)Rice husk -picoline 7.0 15.46 mg g1Lataye et al. (2009)Activated carbon Crystal violet 10.8 64.80 mg g1Mohanty et al. (2006)Activated carbon - RHS Crystal violet 10.8 61.60 mg g1Mohanty et al. (2006)Activated carbon - RHZ Acid blue 2.0 55.40 mg g1Mohamed (2004)Rice husk Congo red 6.0 14.00 mg g1Han et al. (2008)Rice husk Safranine 7.0 178.10 mg g1Kumar and Sivanesan (2007)Rice husk ash Brilliant green 3.0 26.20 mg g1Mane et al. (2007a)Sugarcane bagasse Methylene blue 5.8 34.20 mg g1Filho et al. (2007)Sugarcane bagasse Methylene blue 7.0 99.60 mg g1Raghuvanshi et al. (2004)Sugarcane bagasse Methyl red 7.0 54.60 mg g1Azhar et al. (2005)Activated carbon Acid orange 10 7.0 5.78 mg g1Tsai et al. (2001)Sugarcane bagasse Basic violet 3 7.0 3.79 mg g1Khattri and Singh (2000)Sugarcane dust Basic green 4 7.0 3.99 mg g1Khattri and Singh (1999)Activated carbon Acid blue 80 7.0 112.30 mg g1Choy et al. (2000)Activated carbon Acid red 114 7.0 103.30 mg g1Choy et al. (2000)Activated carbon Acid yellow 117 7.0 155.80 mg g1Choy et al. (2000)Activated carbon Reactive blue 2 7.0 0.27 mmol g1Al-Degs et al. (2008)Activated carbon Reactive yellow 2 7.0 0.24 mmol g1Al-Degs et al. (2008)Activated carbon Reactive red 4 7.0 0.11 mmol g1Al-Degs et al. (2008)Activated carbon Methylene blue 3.0 0.93 mmol g1Wang and Zhu (2007)Activated carbon Crystal violet 3.0 0.43 mmol g1Wang and Zhu (2007)Activated carbon Rhodamine B 3.0 0.48 mmol g1Wang and Zhu (2007)Fly ash SFA Methylene blue 5.0 2.40 103mol g1Jano et al. (2003)Fly ash SFA Rhodamine B 5.0 0.60 103mol g1Jano et al. (2003)Fly ash CFA Methylene blue 5.0 3.60 103mol g1Jano et al. (2003)Fly ash CFA Rhodamine B 5.0 1.00 103mol g1Jano et al. (2003)Fly ash CFA Egacid orange II 5.0 4.70 103mol g1Jano et al. (2003)Fly ash CFA Egacid red G 5.0 2.20 103mol g1Jano et al. (2003)Fly ash CFA Egacid yellow G 5.0 1.50 103mol g1Jano et al. (2003)Fly ash CFA Midlon black VL 5.0 3.10 103mol g1Jano et al. (2003)Cotton waste Basic blue 7.0 277.00 mg g1McKay et al. (1999)Fly ash Acid orange 7 7.0 4.00 g g1Albanis et al. (2000)Fly ash Acid yellow 23 7.0 23.90 g g1Albanis et al. (2000)Fly ash Direct yellow 28 7.0 816.00 g g1Albanis et al. (2000)Fly ash Basic yellow 28 7.0 288.00 g g1Albanis et al. (2000)Fly ash Disperse blue 79 7.0 0.06 g g1Albanis et al. (2000)Fly ash Pyridine 6.0 31.06 mg g1Lataye et al. (2006)Fly ash Brilliant green 3.0 65.9 mg g1Mane et al. (2007b)Fly ash Metomega chrome 7.0 742.80 g g1Gupta and Shukla (1996)Sludge ash Methylene blue 4.0 3.5 106mol g1Weng and Pan (2006)Sludge ash Reactive blue 2 7.0 250.00 mg g1Aksu (2001)Sludge ash Reactive yellow 2 7.0 333.30 mg g1Aksu (2001)Activated carbon (sludge based) Basic red 46 11.0 188.00 mg g1Martin et al. (2003)Activated carbon (sludge based) Acid brown 283 3.0 20.50 mg g1Martin et al. (2003)Activated carbon (sludge based) Direct red 89 3.2 49.20 mg g1Martin et al. (2003)Activated carbon (sludge based) Direct black 3.0 28.90 mg g1Martin et al. (2003)Activated carbon (Chemviron GW) Basic red 46 11.0 106.00 mg g1Martin et al. (2003)Activated carbon (Chemviron GW) Acid brown 283 3.5 22.00 mg g1Martin et al. (2003)Activated carbon (Chemviron GW) Direct red 89 4.0 8.40 mg g1Martin et al. (2003)Environ Monit Assess (2011) 183:151195 155Table 1 (continued)Adsorbent Dye pH Adsorption capacity ReferencesActivated carbon (Chemviron GW) Direct black 3.0 18.70 mg g1Martin et al. (2003)Sugar industry mud Basic red 22 7.0 519.00 mg g1Magdy and Daifullah (1998)Activated carbon (oil palm shell) Methylene blue 6.5 243.90 mg g1Tan et al. (2008)Granular activated carbon Basic blue 4 7.0 58.82 mmol g1Noroozi et al. (2008)Granular activated carbon Basic red 18 7.0 116.27 mmol g1Noroozi et al. (2008)Silkworm pupa Basic blue 4 7.0 6.33 mmol g1Noroozi et al. (2008)Silkworm pupa Basic red 18 7.0 0.42 mmol g1Noroozi et al. (2008)Activated carbon W20 Bisphenyl A 9.0 392.00 mg g1Liu et al. (2009)Activated carbon W20N Bisphenyl A 8.0 438.00 mg g1Liu et al. (2009)Activated carbon Reactive red 6.1 181.90 mg g1Senthilkumaar et al. (2006)(coconut tree flower)Activated carbon (Jute fiber) Reactive red 6.1 200.00 mg g1Senthilkumaar et al. (2006)Activated carbon (rice husk) Malachite green 10.2 1.49 mmol g1Guo et al. (2003)Metal hydroxide sludge Reactive red 2 8.6 61.73 mg g1Netpradit et al. (2004a)Metal hydroxide sludge Reactive red 120 8.6 45.87 mg g1Netpradit et al. (2004a)Metal hydroxide sludge Reactive red 141 8.6 51.55 mg g1Netpradit et al. (2004a)Activated carbon (newspaper) Methylene blue 7.0 390.00 mg g1Okada et al. (2003)Powdered activated sludge Direct yellow 12 7.0 98.00 mg g1Kargi and Ozmhc (2004)Charfines Direct brown 7.0 6.40 mg g1Mohan et al. (2002b)Lignite coal Direct brown 7.0 4.10 mg g1Mohan et al. (2002b)Bituminous coal Direct brown 7.0 2.04 mg g1Mohan et al. (2002b)Activated carbon Direct brown 7.0 7.69 mg g1Mohan et al. (2002b)Activated carbon (Cassava peel, Rodamine B 5.6 100% Rajeshwarisivaraj et al. (2001)physical 700C) Direct brown 6.9 10.4% Rajeshwarisivaraj et al. (2001)Activated carbon (Cassava peel, Procion orange 6.7 5.3% Rajeshwarisivaraj et al. (2001)physical 700C) Acid violet 6.8 83.0% Rajeshwarisivaraj et al. (2001)Activated carbon (Cassava peel, Malachite green 6.8 100% Rajeshwarisivaraj et al. (2001)physical 700C) Methylene blue 6.8 100% Rajeshwarisivaraj et al. (2001)Activated carbon (Cassava peel, Rodamine B 7.5 100% Rajeshwarisivaraj et al. (2001)chemical H3PO4) Direct brown 8.3 100% Rajeshwarisivaraj et al. (2001)Activated carbon (Cassava peel, Procion orange 8.3 100% Rajeshwarisivaraj et al. (2001)chemical H3PO4) Acid violet 8.4 86.3% Rajeshwarisivaraj et al. (2001)Activated carbon (Cassava peel, Malachite green 8.3 100% Rajeshwarisivaraj et al. (2001)chemical H3PO4) Methylene blue 8.2 100% Rajeshwarisivaraj et al. (2001)Activated carbon (bagasses) Basic red 22 4.1 608.00 mg g1Juang et al. (2002a)Activated carbon (bagasses) Acid blue 25 5.9 548.00 mg g1Juang et al. (2002a)Activated carbon (beds) Yellow dye 7.0 551.00 mg g1Chern and Wu (2001)Activated carbon fiber (pitch) Acid blue 9 9.0 5.0 104mol g1Tamai et al. (1999)Activated carbon fiber (pitch) Acid blue 74 9.0 9.0 104mol g1Tamai et al. (1999)Activated carbon fiber (pitch) Acid orange 10 9.0 8.0 104mol g1Tamai et al. (1999)Activated carbon fiber (pitch) Acid orange 51 9.0 1.8 104mol g1Tamai et al. (1999)Activated carbon fiber (pitch) Direct black 19 9.0 1.1 104mol g1Tamai et al. (1999)Activated carbon fiber (pitch) Direct yellow 11 9.0 1.8 104mol g1Tamai et al. (1999)Activated carbon fiber (pitch) Direct yellow 50 9.0 2.2 104mol g1Tamai et al. (1999)Activated carbon fiber (pitch) Basic brown 1 9.0 1.4 103mol g1Tamai et al. (1999)Activated carbon fiber (pitch) Basic yellow 9.0 2.2 103mol g1Tamai et al. (1999)156 Environ Monit Assess (2011) 183:151195Table 1 (continued)Adsorbent Dye pH Adsorption capacity ReferencesWaste Fe(III)/Cr(III) hydroxide Congo red 3.0 44.00 mg g1Namasivayam et al. (1994)Activated carbon (filtrasorb 400) Ramazol reactive 5.7 1111.00 mg g1Al-Degs et al. (2000)yellowActivated carbon (filtrasorb 400) Ramazol reactive 5.7 434.00 mg g1Al-Degs et al. (2000)blackActivated carbon (filtrasorb 400) Ramazol reactive 5.7 400.00 mg g1Al-Degs et al. (2000)redSewage sludge ASSg1 Crystal violet 7.0 263.20 mg g1Otero et al. (2003a)Sewage sludge ASSg1 Indigo carmine 7.0 60.00 mg g1Otero et al. (2003a)Sewage sludge ASSg2 Crystal violet 7.0 270.90 mg g1Otero et al. (2003a)Sewage sludge ASSg2 Indigo carmine 7.0 54.40 mg g1Otero et al. (2003a)Sewage sludge PSSg2 Crystal violet 7.0 184.70 mg g1Otero et al. (2003a)Sewage sludge PSSg2 Indigo carmine 7.0 30.80 mg g1Otero et al. (2003a)Waste carbon slurries Basic red 2.0 10.2 105mol g1Gupta et al. (2003)Blast furnace slag Basic red 10.0 1.11 105mol g1Gupta et al. (2003)Metal hydroxide sludge Reactive red 141 8.5 45.00 mg g1Netpradit et al. (2004b)Fly ash Methylene blue 5.0 3.47 mmol kg1Woolard et al. (2002)Sewage sludge Ud Methylene blue 7.0 114.90 mg g1Otero et al. (2003b)Sewage sludge Ad Methylene blue 7.0 87.00 mg g1Otero et al. (2003b)Sewage sludge Up Methylene blue 7.0 31.70 mg g1Otero et al. (2003b)Sewage sludge Ap Methylene blue 7.0 28.70 mg g1Otero et al. (2003b)Sewage sludge Ua Methylene blue 7.0 24.90 mg g1Otero et al. (2003b)Sewage sludge Aa Methylene blue 7.0 28.30 mg g1Otero et al. (2003b)Activated carbon (pinewood) AC1.5 hBasic blue 69 8.0 598.00 mg g1Tseng et al. (2003)Activated carbon (pinewood) AC1.5 hAcid blue 264 8.0 983.00 mg g1Tseng et al. (2003)Activated carbon (pinewood) AC1.5 hMethylene blue 8.0 484.00 mg g1Tseng et al. (2003)Activated carbon (pinewood) AC2.7 hBasic blue 69 8.0 761.00 mg g1Tseng et al. (2003)Activated carbon (pinewood) AC2.7 hAcid blue 264 8.0 1014.00 mg g1Tseng et al. (2003)Activated carbon (pinewood) AC2.7 hMethylene blue 8.0 507.00 mg g1Tseng et al. (2003)Activated carbon (pinewood) AC4.0 hBasic blue 69 8.0 1119.00 mg g1Tseng et al. (2003)Activated carbon (pinewood) AC4.0 hAcid blue 264 8.0 1176.00 mg g1Tseng et al. (2003)Activated carbon (pinewood) AC4.0 hMethylene blue 8.0 556.00 mg g1Tseng et al. (2003)Wheat straw Remazol red 7.0 2.50 mg g1Nigam et al. (2000)Wheat straw Remazol black B 7.0 2.10 mg g1Nigam et al. (2000)Corn-cob shreds Remazol red 7.0 0.60 mg g1Nigam et al. (2000)Corn-cob shreds Remazol black B 7.0 0.60 mg g1Nigam et al. (2000)Activated carbon CC-1 Acid blue 80 7.4 333.30 mg g1Valix et al. (2004)Activated carbon CC-3 Acid blue 80 7.4 59.90 mg g1Valix et al. (2004)Activated carbon CC-5 Acid blue 80 7.4 75.20 mg g1Valix et al. (2004)Activated carbon CC-7 Acid blue 80 7.4 169.50 mg g1Valix et al. (2004)Activated carbon CC-10 Acid blue 80 7.4 277.80 mg g1Valix et al. (2004)Activated carbon CC-15 Acid blue 80 7.4 384.60 mg g1Valix et al. (2004)Parthenium hysterophorus - SWC Methylene blue 7.0 39.70 mg g1Lata et al. (2007)Parthenium hysterophorus - PWC Methylene blue 7.0 88.50 mg g1Lata et al. (2007)Linseed oil cake Basic blue 41 7.0 303.10 mg g1Liversidge et al. (1997)Fly ash: coal Omega chrome 2.0 0.77 mg g1Gupta et al. (1990)red MEFe(III)/Cr(III) hydroxide Direct red 12b 3.0 5.00 mg g1Namasivayam andSumithra (2005)Fe(III)/Cr(III) hydroxide Methylene blue 10.0 10.00 mg g1Namasivayam andSumithra (2005)Corncob Dye mixture 7.0 4.60 mg g1Robinson et al. (2002b)Environ Monit Assess (2011) 183:151195 157Table 1 (continued)Adsorbent Dye pH Adsorption capacity ReferencesBarley husk Dye mixture 7.0 8.30 mg g1Robinson et al. (2002b)Activated carbon Acid red 114 7.0 101.00 mg g1Choy et al. (1999)Activated carbon Polar yellow 7.0 128.80 mg g1Choy et al. (1999)Activated carbon Polar blue RAWL 7.0 100.90 mg g1Choy et al. (1999)Activated sludge Basic red 18 7.0 285.70 mg g1Gulnaz et al. (2004)Activated sludge Basic blue 9 7.0 256.40 mg g1Gulnaz et al. (2004)White ash Congo red 7.0 171.00 mg g1Chou et al. (2001)Pellet adsorbent Congo red 7.0 31.70 mg g1Chou et al. (2001)White ash Congo red 7.0 171.00 mg g1Chou et al. (2001)Pellet adsorbent Congo red 7.0 31.70 mg g1Chou et al. (2001)Coir pith carbon Rhodamine B 11.1 2.56 mg g1Namasivayam et al. (2001a)Coir pith carbon Acid violet 1.5 8.06 mg g1Namasivayam et al. (2001a)Slag Basic blue 9 11.0 9.95 mg g1Ramakrishna andViraraghavan (1997)Slag Acid blue 29 2.0 4.86 mg g1Ramakrishna andViraraghavan (1997)Slag Acid red 91 7.0 2.36 mg g1Ramakrishna andViraraghavan (1997)Slag Disperse red 1 2.0 33.20 mg g1Ramakrishna andViraraghavan (1997)Carbonaceous adsorbent Ethyl orange 7.0 198.40 mg g1Jain et al. (2003)Carbonaceous adsorbent Methylene yellow 7.0 211.90 mg g1Jain et al. (2003)Carbonaceous adsorbent Acid blue 113 7.0 221.20 mg g1Jain et al. (2003)Silk cotton carbon Rhodamine B 6.1 70.00 mg g1Kadirvelu et al. (2003)Silk cotton carbon Congo red 6.7 250.00 mg g1Kadirvelu et al. (2003)Silk cotton carbon Methylene blue 5.1 120.00 mg g1Kadirvelu et al. (2003)Silk cotton carbon Methyl violet 5.0 225.00 mg g1Kadirvelu et al. (2003)Silk cotton carbon Malachite green 4.9 222.50 mg g1Kadirvelu et al. (2003)Coconut tree sawdust carbon Rhodamine B 3.2 247.50 mg g1Kadirvelu et al. (2003)Coconut tree sawdust carbon Congo red 3.5 239.00 mg g1Kadirvelu et al. (2003)Coconut tree sawdust carbon Methylene blue 3.6 225.50 mg g1Kadirvelu et al. (2003)Coconut tree sawdust carbon Methyl violet 3.9 240.00 mg g1Kadirvelu et al. (2003)Coconut tree sawdust carbon Malachite green 3.3 225.00 mg g1Kadirvelu et al. (2003)Maize cob carbon Rhodamine B 3.2 206.60 mg g1Kadirvelu et al. (2003)Maize cob carbon Congo red 5.0 191.40 mg g1Kadirvelu et al. (2003)Maize cob carbon Methylene blue 4.0 233.40 mg g1Kadirvelu et al. (2003)Maize cob carbon Methyl violet 4.3 93.60 mg g1Kadirvelu et al. (2003)Maize cob carbon Malachite green 2.1 120.50 mg g1Kadirvelu et al. (2003)Banana pith carbon Rhodamine B 3.2 206.60 mg g1Kadirvelu et al. (2003)Banana pith carbon Congo red 5.0 191.40 mg g1Kadirvelu et al. (2003)Banana pith carbon Methylene blue 4.0 233.40 mg g1Kadirvelu et al. (2003)Banana pith carbon Methyl violet 4.3 93.60 mg g1Kadirvelu et al. (2003)Banana pith carbon Malachite green 4.1 120.50 mg g1Kadirvelu et al. (2003)Wheat straw Methylene blue 7.0 312.50 mg g1Gong et al. (2008)Wheat straw Citric acid 7.0 227.27 mg g1Gong et al. (2008)Sunflower oil cake AC1 Methylene blue 6.0 10.21 mg g1Karagz et al. (2008)Sunflower oil cake AC2 Methylene blue 6.0 16.43 mg g1Karagz et al. (2008)Sunflower oil cake AC3 Methylene blue 6.0 15.80 mg g1Karagz et al. (2008)Activated carbon (almond shell) Methylene blue 7.0 1.33 mg g1Aygn et al. (2003)Activated carbon (apricot stone) Methylene blue 7.0 4.11 mg g1Aygn et al. (2003)Activated carbon (hazelnut shell) Methylene blue 7.0 8.82 mg g1Aygn et al. (2003)Activated carbon (walnut shell) Methylene blue 7.0 3.53 mg g1Aygn et al. (2003)158 Environ Monit Assess (2011) 183:151195Table 1 (continued)Adsorbent Dye pH Adsorption capacity ReferencesMetal hydroxide sludge Reactive red 2 8.5 62.50 mg g1Netpradit et al. (2003)Metal hydroxide sludge Reactive red 120 8.5 48.30 mg g1Netpradit et al. (2003)Metal hydroxide sludge Reactive red 141 8.5 56.20 mg g1Netpradit et al. (2003)Bark Safranine 7.0 1119.00 mg g1McKay et al. (1999)Rice husk Safranine 7.0 838.00 mg g1McKay et al. (1999)Cotton waste Safranine 7.0 875.00 mg g1McKay et al. (1999)Hair Safranine 7.0 190.00 mg g1McKay et al. (1999)Coal Safranine 7.0 120.00 mg g1McKay et al. (1999)Bark Methylene blue 7.0 914.00 mg g1McKay et al. (1999)Rice husk Methylene blue 7.0 312.00 mg g1McKay et al. (1999)Cotton waste Methylene blue 7.0 270.00 mg g1McKay et al. (1999)Hair Methylene blue 7.0 158.00 mg g1McKay et al. (1999)Coal Methylene blue 7.0 250.00 mg g1McKay et al. (1999)Core pith Acid violet 3.0 1.60 mg g1Namasivayam et al. (2001b)Core pith Acid brilliant blue 3.0 16.60 mg g1Namasivayam et al. (2001b)Core pith Rhodamine B 3.0 203.20 mg g1Namasivayam et al. (2001b)Activated carbon (rice husk) Acid blue 2.0 50.00 mg g1Mohamed (2004)Activated carbon fibers Methylene blue 7.0 99.30 mg g1Zhi-yuan (2008)Rice husk Safranine 7.0 838.00 mg g1McKay et al. (1999)Cotton waste Safranine 7.0 875.00 mg g1McKay et al. (1999)Hair Safranine 7.0 190.00 mg g1McKay et al. (1999)Coal Safranine 7.0 120.00 mg g1McKay et al. (1999)Bark Methylene blue 7.0 914.00 mg g1McKay et al. (1999)Rice husk Methylene blue 7.0 312.00 mg g1McKay et al. (1999)Cotton waste Methylene blue 7.0 270.00 mg g1McKay et al. (1999)Hair Methylene blue 7.0 158.00 mg g1McKay et al. (1999)Coal Methylene blue 7.0 250.00 mg g1McKay et al. (1999)Sugarcane dust Basic violet 10 7.0 50.4 mg g1Ho et al. (2005a)Sugarcane dust Basic violet 1 7.0 13.9 mg g1Ho et al. (2005a)Sugarcane dust Basic green 4 7.0 20.6 mg g1Ho et al. (2005a)Activated carbon (rice husk) Acid blue 2.0 50.00 mg g1Mohamed (2004)Cotton Direct red 28 7.0 1 102kg1Sawada and Ueda (2003)Calcium rich - fly ash Congo red 5.0 4.47 105mol g1Acemio glu (2004)Activated carbon (sewage sludge) Methylene blue 7.0 6.08 mg g1Rozada et al. (2003)Activated carbon (sewage sludge) Saphranine 7.0 11.05 mg g1Rozada et al. (2003)Commercial activated carbon Methylene blue 7.4 980.30 mg g1Kannan and Sundaram (2001)Bamboo dust carbon Methylene blue 7.4 143.20 mg g1Kannan and Sundaram (2001)Coconut shell carbon Methylene blue 7.4 277.90 mg g1Kannan and Sundaram (2001)Groundnut shell carbon Methylene blue 7.4 164.90 mg g1Kannan and Sundaram (2001)Rice husk carbon Methylene blue 7.4 343.50 mg g1Kannan and Sundaram (2001)Straw carbon Methylene blue 7.4 472.10 mg g1Kannan and Sundaram (2001)Sugarcane baggase Methylene blue 7.0 96.56 mg g1Raghuvanshi et al. (2004)Activated sugarcane baggase Methylene blue 7.0 99.63 mg g1Raghuvanshi et al. (2004)Lignin (sugarcane baggase) Methylene blue 4.5 16.50 mg g1Filho et al. (2007)Activated carbon PKN2 Methylene blue 7.0 765.00 mg g1Tseng (2007)Activated carbon PKN2 Acid blue 74 7.0 549.00 mg g1Tseng (2007)Activated carbon PKN2 Basic brown 1 7.0 1453.00 mg g1Tseng (2007)Activated carbon PKN3 Methylene blue 7.0 785.00 mg g1Tseng (2007)Activated carbon PKN3 Acid blue 74 7.0 561.00 mg g1Tseng (2007)Activated carbon PKN3 Basic brown 1 7.0 1529.00 mg g1Tseng (2007)Activated carbon PKN4 Methylene blue 7.0 828.00 mg g1Tseng (2007)Activated carbon PKN4 Acid blue 74 7.0 567.00 mg g1Tseng (2007)Environ Monit Assess (2011) 183:151195 159Table 1 (continued)Adsorbent Dye pH Adsorption capacity ReferencesActivated carbon PKN4 Basic brown 1 7.0 1845.00 mg g1Tseng (2007)Activated carbon (oil palm wood) Methylene blue 7.0 90.9 mg g1Ahmad et al. (2007)Activated carbon C1 Methylene blue 7.0 198.00 mg g1Attia et al. (2008)Activated carbon C2 Methylene blue 7.0 309.00 mg g1Attia et al. (2008)Activated carbon C3 Methylene blue 7.0 362.00 mg g1Attia et al. (2008)Activated carbon C4 Methylene blue 7.0 412.00 mg g1Attia et al. (2008)Activated carbon C5 Methylene blue 7.0 306.00 mg g1Attia et al. (2008)Activated carbon C6 Methylene blue 7.0 316.00 mg g1Attia et al. (2008)Activated carbon Rhodamine B 2.1 5.34 105mg g1Jain et al. (2007)Rice husk Rhodamine B 2.1 5.87 105mg g1Jain et al. (2007)Wheat bran carbon Methylene blue 2.5 222.20 mg g1zer and Dursun (2007)I-GLYTAC-Cotton Acid blue 25 7.0 0.26 mmol g1Bouzaida and Rammah (2002)I-GLYTAC-Cotton Acid yellow 99 7.0 0.18 mmol g1Bouzaida and Rammah (2002)I-GLYTAC-Cotton Reactive yellow 23 7.0 0.19 mmol g1Bouzaida and Rammah (2002)II-GLYTAC-Cotton Acid blue 25 7.0 0.60 mmol g1Bouzaida and Rammah (2002)II-GLYTAC-Cotton Acid yellow 99 7.0 0.39 mmol g1Bouzaida and Rammah (2002)II-GLYTAC-Cotton Reactive yellow 23 7.0 0.39 mmol g1Bouzaida and Rammah (2002)III-GLYTAC-Cotton Acid blue 25 7.0 0.64 mmol g1Bouzaida and Rammah (2002)III-GLYTAC-Cotton Acid yellow 99 7.0 0.41 mmol g1Bouzaida and Rammah (2002)III-GLYTAC-Cotton Reactive yellow 23 7.0 0.41 mmol g1Bouzaida and Rammah (2002)IV-GLYTAC-Cotton Acid blue 25 7.0 0.59 mmol g1Bouzaida and Rammah (2002)IV-GLYTAC-Cotton Acid yellow 99 7.0 0.37 mmol g1Bouzaida and Rammah (2002)IV-GLYTAC-Cotton Reactive yellow 23 7.0 0.37 mmol g1Bouzaida and Rammah (2002)V-GLYTAC-Cotton Acid blue 25 7.0 0.59 mmol g1Bouzaida and Rammah (2002)V-GLYTAC-Cotton Acid yellow 99 7.0 0.36 mmol g1Bouzaida and Rammah (2002)V-GLYTAC-Cotton Reactive yellow 23 7.0 0.36 mmol g1Bouzaida and Rammah (2002)Porous carbon Rhodamine B 3.45 0.90 mmol g1Guo et al. (2005)gases because of its extensive specific surfacearea, high adsorption capacity, well-developed mi-cropores, reproducibility, and processability. Theeffectsofvariousexperimental parameters,suchas the initial methylene blue (MB) concentra-tionandtheACFmass,ontheadsorptionrateswereinvestigated. EquilibriumdatawasfitwellbyaFreundlichisothermequation. Adsorptionmeasurement shows that the process is very fast.Moreover, thermodynamic parameters Go, So,and Howere calculated (Wang and Zhu 2007).Nakagawa et al. (2004) made attempt to eval-uatetheporous properties andhydrophobicityofactivatedcarbonsobtainedfromseveralsolidwastes, namely, wastePET, wastetires, refusederivedfuel, andwastesgeneratedduringlacticacidfermentationfromgarbage. Activatedcar-bonshavingvariousporesizedistributionswereobtained by the conventional steam-activationmethodandviathepretreatment method(i.e.,mixtureofrawmaterialswithametal salt, car-bonization, and acid treatment prior to steamactivation). Theliquid-phaseadsorptioncharac-teristics of organic compounds from aqueous solu-tion on the activated carbons were determined toconfirm the applicability of these carbons, wherereactivedye, Black5, wereemployedas repre-sentativeadsorbates. Authorsreportedthat theactivatedcarbonswithplentiful mesoporespre-paredfromPETandwastetireshadquitehighadsorptioncapacityfor largemolecules. There-fore, theyareuseful for wastewater treatment,especially for removal of bulky adsorbates. Liet al. (2002) reported the displacement of atrazineby the strongly competing fraction of naturalorganic matter (NOM) in batch and continuous-flowpowderedactivatedcarbon(PAC)adsorp-tion system. The extent of atrazine displacementby NOM was found to be dependent on the typeof PAC, whiletherateof displacement was afunctionof PACtypeas well as carbondose.Choy et al. (2000) reportedthe adsorptionof160 Environ Monit Assess (2011) 183:151195threeacidic dyes, AcidBlue80(AB80), AcidRed 114 (AR114), and Acid Yellow 117 (AY117)ontoactivatedcarbon. Inthesamepaper, theyhavealsoreportedtheadsorptionisothermsforthe three single components (AB80, AR114, andAY117)andthreebinarycomponent (AB80 +AR114, AB80 + AY117, and AR114 + AY117),dyesadsorptiononactivatedcarbon.Fourmod-els for predicting the multicomponent equilibriumsorptionisotherms havebeencomparedinor-der todeterminethebest topredict or corre-latebinaryadsorptiondata. Thesefour modelsare the extendedLangmuir isotherm, the sim-plifiedmodel basedonsingle-component equi-libriumfactors, amodifiedextendedLangmuirisothermwithaconstantinteractionfactor, anda modified extended Langmuir isotherm incorpo-ratingasurfacecoverage-dependent interactionfactor. Adsorption of trichloroethylene (TCE) bytwo ACFs and two granular activated carbons pre-loaded with hydrophobic and transphilic fractionsofNOMwasexaminedbyTanjuKaranfiletal.(2006)ACF10. Themostmicroporousactivatedcarbonusedinthis studyhadover 90%of itsporevolumeinporessmallerthan10. Italsohad the highest volume in pores 58 , which isthe optimum pore size region for TCE adsorption,among the four activated carbons. Adsorption ofNOM fractions by ACF10 was, in general, negli-gible. Therefore,ACF10, functioningasamole-cular sieve during preloading, exhibited the leastNOM uptake for each fraction, and subsequentlythe highest TCE adsorption. The other three sor-bents had wider pore size distributions, includinghighvolumesinporeslargerthan10, whereNOMmolecules can be adsorbed. As a result, theyshowed higher adsorption efficiency for all NOMfractions,andsubsequently loweradsorptionca-pacities for TCE, as compared to ACF10.Adsorptionof congored(CR) dyeonbitu-minouscoal-basedmesoporousactivatedcarbon(AC) fromaqueous solutions was reportedbyGrabowska and Gryglewicz (2007). The mesoporecontribution to the total pore volume ranged from52%to 83%. The adsorption tests were performedunderstaticconditionsatsolutionpH7.88.3.Itwasfoundthatthehigherthefractionofmeso-pores witha size between10 and50 nm, theshorter the time to achieve the equilibrium stagefor CRadsorption. The kinetics of adsorptioninviewof three kinetic models, i.e., the first-order Lagergren model, the pseudo-second-ordermodel, and the intraparticle diffusion model,wasdiscussed. Thepseudo-second-orderkineticmodeldescribestheadsorptionofCRonmeso-porousactivatedcarbonverywell. Thecorrela-tion coefficients ranged from 0.980 to 0.991. Theintra-particle diffusion into small mesopores wasfound to be the rate-limiting step in the adsorptionprocess. The equilibrium adsorption data were in-terpreted using Langmuir and Freundlich models.The adsorption of CR was better represented bytheLangmuirequation. Themonolayeradsorp-tion capacity of ACs was found to increase withincreasing boththe mesopore volume andthemesoporecontributiontotheir porous texture.Theeffectofsolutionionicstrengthontheup-take of CRby twodifferent mesoporous car-bons was also investigated. Also, the kinetics andmechanismof MBadsorptiononcommerciallyactivated carbon and indigenously prepared acti-vatedcarbonsfrombamboodust, coconutshell,groundnutshell, ricehusk, andstrawhavebeenreportedbytheKannanandSundaram(2001).Theeffects of variousexperimental parametershave been investigated using a batch adsorp-tion technique toobtain information ontreatingeffluents fromthedyeindustry. Theextent ofdyeremoval increasedwithdecreaseintheini-tial concentration of the dye and particle size oftheadsorbent andalsoincreasedwithincreaseincontact time, amount of adsorbent usedandtheinitial pHof thesolution. AdsorptiondataweremodeledusingtheFreundlichandLang-muir adsorption isotherms and first-order kineticequations.Thekineticsofadsorptionwasfoundto be first order with regard to intra-particlediffusionrate. Theadsorptioncapacities of in-digenous activated carbons have been comparedwiththat of thecommerciallyactivatedcarbon.Theresultsindicatethat suchcarbonscouldbeemployedas the low-cost alternatives tocom-merciallyactivatedcarboninwastewater treat-ment for the removal of color and dyes. Jirankovaet al. (2007) contribution deals with study of thecombinedadsorption-membraneprocessforor-ganicdyeremoval. Adsorptionequilibriumandkinetics of Egacid red sorption on PAC were stud-Environ Monit Assess (2011) 183:151195 161iedinbatchexperiments. Duringthecombinedhollowfibermembranemicrofiltrationoperatedindead-endmode, itwasfoundthatmembranewas effective for removal of PAC particles fromwater suspensions andPACtendencyfor irre-versible membrane fouling was extremely low.The presentedcombinedadsorption-membraneprocess has apotential applicationfor organicdyeremoval. Taperedbedadsorptioncolumns,usingactivatedcarbon, havebeenusedtostudytheremoval of twoorganicpollutants, anaciddye and para-chlorophenol, fromaqueous effluentby McKay et al. (2008). Equilibriumsorptionisothermsweremeasuredtoprovidethesatura-tion capacity (qe) of each pollutant by ChemvironFiltrasorb400carbon, foroperatingcontinuousadsorptioncolumns. TheRedlichPeterson(RP)isothermgivesthebestfitmodel todescribethesorptionprocessoftheseorganicpollutants.The conventional bed depth service time (BDST)modelhasnotbeenappliedtotaperedbedsbe-fore,asthelinearvelocityoffluidiscontinuallychanging along the column. Several others authors(Al-Degs et al. 2008; Wang and Zhu 2007; Nassarand Magdy 1997) have also tested activated car-bon for the adsorption of various dyes.Pereira et al. (2003) reported that the sur-face chemistry of a commercially activated carbonhasbeenselectivelymodified, withoutchangingsignificantlyitstextural properties, bymeansofchemical treatments, usingHNO3, H2O2, NH3,andthermal treatments under aflowof H2orN2, and they found that the surface chemistry oftheactivatedcarbonplaysakeyroleindyead-sorption performance. The basic sample obtainedbythermaltreatmentunderH2flowat700Cisthebest material fortheadsorptionof most ofthe dyes tested. For anionic dyes (reactive, direct,and acid), a close relationship between the surfacebasicityoftheadsorbentsanddyeadsorptionisshown, theinteractionbetweentheoxygen-freeLewis basic sites andthefreeelectrons of thedyemoleculebeingthemainadsorptionmecha-nism. For cationic dyes (basic), the acid oxygen-containingsurfacegroupsshowapositiveeffectbutthermallytreatedsamplesstill presentgoodperformances, showing the existence of two paral-lel adsorption mechanisms involving electrostaticanddispersiveinteractions. Theconclusionsob-tainedforeachdyeindividuallywereconfirmedinthecolorremoval fromareal textileprocesseffluent.Rice husk/rice husk ashRicehuskisinsolubleinwater, hasgoodchem-icalstability, highmechanicalstrength, andpos-sesses a granular structure, making it a goodadsorbent material. Rice husk consists of cel-lulose(32.24%), hemicelluloses(21.34%), lignin(21.44%), andmineral ash(15.05%) andhighpercentageof silicainitsmineral ash, whichisapproximately 96.34%. Pretreatment of rice huskcanremoveligninandhemicelluloses, decreasecellulosecrystallinity, andincreasetheporosityandsurfacearea. Ricehuskcaneasilybecon-verted into rice husk ash (RHA) at 300C whichcontains92%to95%silica. Theadsorbent ob-tainedbythis treatment is light weight withavery external surface area. Lakshmi et al. (2009)carried out study of the adsorptive characteristicsofIndigoCarmine(IC)dyefromaqueoussolu-tion onto RHA. Batch experiments were carriedout to determine the influence of parameters likeinitial pH, contact time, adsorbent dose, and ini-tial dye concentration on the removal of IC. Theoptimum conditions were found to be: pH = 5.4,t = 8 h, and m = 10.0 g L1. The pseudo-second-orderkineticmodel representedtheadsorptionkinetics of IC on to RHA. Equilibrium isothermswere analyzed by Freundlich, Langmuir, Temkin,and Redliche Peterson models using a nonlinearregression technique. Adsorption of IC on RHAwas favorablyinfluencedbyanincreaseinthetemperature of the operation. The positive valuesofthechangeinentropy(So)andheatofad-sorption (Ho); and the negative value of changein Gibbs free energy (Go) indicate feasible andspontaneous adsorption of IC on to RHA.Adsorptionontoactivatedcarbonisapotentmethod for the treatment of dye-bearing effluentsbecauseitoffersvariousadvantagesasreportedby Mohanty et al. (2006). In this study, activatedcarbons, prepared fromlow-cost rice husk bytwodifferent processes: physical activationandchemical activation, wereusedastheadsorbentfortheremoval of crystal violet. Theeffectsofvariousexperimentalparameters, suchasadsor-162 Environ Monit Assess (2011) 183:151195bent dosageandsize, initial dyeconcentration,pH, contact time, and temperature, were investi-gated in batch mode. The kinetic data were wellfitted to the Lagergren, pseudo-second order, andintra-particle diffusion models. It was found thatintra-particlediffusionplaysasignificantroleintheadsorptionmechanism. Theisothermal datacouldbe well describedby the Langmuir andFreundlichequations. Themaximumuptakesofcrystal violet by sulfuric acid activated (RHS) andzincchlorideactivated(RHZ)ricehuskcarbonwerefoundtobe64.875and61.575mgg1ofadsorbent, respectively. The results indicate thatRHSandRHZcouldbeemployedaslow-costalternativestocommerciallyactivatedcarboninwastewater treatment for theremoval of basicdyes. Ithasbeenreportedinoneofthepapersby Dhalan et al. (2006) that the materials, such asRHA, havethepotential tobeutilizedashigh-performancesorbentsforthefluegasdesulfur-izationprocess insmall-scaleindustrial boilers.This study presents findings on identifying the keyfactor for high desulfurization activity in sorbentspreparedfromRHA. Initially, asystematicap-proachusingcentral compositerotatabledesignwasusedtodevelopamathematicalmodelthatcorrelates the sorbent preparationvariables tothedesulfurizationactivityof thesorbent. Hanet al. (2008) reported a continuous bed study byusingricehuskasabiosorbentfortheremovalof CR from aqueous solution. The effects of im-portant factors, such as the value of pH, existingsalt, theflowrate, theinfluentconcentrationofCR, and bed depth, were studied. Data confirmedthat the breakthrough curves were dependentonflowrate, initial dyeconcentration, andthebeddepth. Thomas, AdamsBohart, andYoonNelson models were applied to the experimentaldata in order to predict the breakthrough curvesusingnonlinearregressionandtodeterminethecharacteristic parameters of the column useful forprocessdesign, whileBDSTmodel wasusedtoexpress the effect of bed depth on breakthroughcurves. Theresultsshowedthat Thomasmodelwas found suitable for the normal description ofbreakthroughcurveat theexperimental condi-tion, whileAdamsBohart model was onlyforaninitial part of dynamicbehavior of thericehuskcolumn. Thedatawereingoodagreementwith BDST model. It was concluded that the ricehusk column can remove CR from solution (Malik2003; McKayet al. 1999; Mohamed2004; Hanet al. 2008; Guo et al. 2005; Kumar and Sivanesan2007; Mane et al. 2007a).Sugarcane dustTheadsorptionpotential of agricultural (sugar-cane) by-product, thebaggasewas investigatedinbatchexperiments withtwodifferent formsi.e., rawandchemicallyactivatedforms, fortheremoval of MB dye, with different parameters likedye concentration, contact time, temperature, andadsorbent dose is reported by Raghuvanshi et al.(2004). The removal is better and more effectivewith chemically activated baggase in comparisonto the raw baggase. An average percent removaldifference between the two adsorbents of around18% was achieved under the different experimen-tal conditions. The data fit well in the Freundlichisotherm. Azharet al. (2005)inoneof hispa-pers has reported that adsorbents prepared fromsugarcane baggase-an agro industries waste weresuccessfully used to remove the methyl red froman aqueous solution in a batch reactor. This studyinvestigatesthepotential useof sugarcanebag-gase,pretreatedwithformaldehyde(PCSB)andsulfuric acid (PCSBC), for the removal of methylredfromsimulatedwastewater. Formaldehyde-treatedandsulfuricacid-treatedsugarcanebag-gasewereusedtoadsorbmethyl redatvaryingdye concentration, adsorbent dosage, pH, andcontact time (Tsai et al. 2001). Similar experimentwas conducted with commercially available PAC,in order to evaluate the performance of PCSB andPCSBC. The adsorption efficiency of different ad-sorbents was in the order PAC>PCSBC>PCSB.TheinitialpHof610flavorstheadsorptionofboth PCSBand PCSBC. Adsorbents are veryefficient in decolorized diluted solution. It is pro-posed that PCSB and PCSBC, in a batch or stirredtankreactors, couldbeemployedasalow-costalternativeinwastewatertreatment forthedyeremoval.Filho et al. (2007) carried out an experiment inwhich the adsorption kinetics and equilibrium ofMB onto reticulated formic lignin from sugar canebaggasewas studied. Theadsorptionprocess isEnviron Monit Assess (2011) 183:151195 163pH, temperature, and ionic strength () dependentandobeystheLangmuirmodel. Conditionsforhigheradsorptionrateandcapacityweredeter-mined. Thefasteradsorption(12h)andhigheradsorption capacity (34.20 mg g1) were observedat pH =5.8(acetic acid-sodiumacetateaque-ousbuffer), 50C, and0.1ionicstrength. Theseinteractions between binding sites were detectedthroughScatchardanalysis. Under temperature(50C) control and occasional mechanical stirring,it tookfrom1to10daystoreachequilibrium(Khattri andSingh1999). Thesorptionofthreebasicdyes,namedbasicviolet10,basicviolet1,andbasicgreen4, fromaqueoussolutionsontosugarcanedustwasstudiedbyHoetal. (2001).Theresultsrevealedthepotential of sugarcanedust, awastematerial, tobealow-costsorbent.Equilibriumisotherms wereanalyzedusingtheLangmuir, Freundlich, andthethree-parameterRedlichPetersonisotherms. Inorder todeter-minethebest-fit isothermforeachsystem, twoerror analysis methods were used to evaluate thedata: thelinearcoefficientofdeterminationandthe Chi-square statistic test for determination of anonlinear model. Results indicated that the Chi-squaretest providedabetterdeterminationforthe three sets of experimental data.Cotton wasteCotton is one of the most widely used fibersby the agriculturists. Cotton found naturally andconsisting cellulose exhibits excellent physical andchemical properties in terms of stability, water ab-sorbency, and dye removal ability. Bouzaida andRammah(2002)reportedtheadsorptionofaciddyes ontreatedcottoninacontinuous system.It hasbeenconcludedthatat20Candforthegrafted support at 1.25% of nitrogen, the capacityis around 589, 448, and 302 mg of adsorbed dye,respectively, for acid blue 25, acid yellow 99, andReactive yellow 23 dyes. Sawada and Ueda (2003)studied the solubilization and adsorption behaviorof direct dye oncottoninAerosol-OTreveremicellar system. Cotton fabrics could be dyed indeep shade with direct dye from reverse micellarsystem without adding auxiliaries. Exhaustion ofdye was almost perfect and was very superior tothat inaqueoussystem. Highexhaustionof thedyeinreversemicellarsystemwasattributedtothe very low bath ratio (waterfabric ratio) com-pared to the conventional aqueous dyeing process.It has become obvious that adsorption of di-rectdyeoncottoninreversemicellarsystemissimilartothatinaqueoussystemandfollowsaFreundlich manner.Fly ashAdsorption and removal of commercial dyes werestudied in aqueous suspensions of fly ash mixtureswith a sandy clay loam soil of low organic mattercontent. The commercial dyes, acid orange 7, acidyellow 23, disperse blue 79, basic yellow 28, anddirect yellow28represent the widelyusedni-troazo structures. Batch and column experimentswere carried out by Albanis et al. (2000) at equi-librium conditions for concentrations of dyes be-tween5and60mgL1. Thelogarithmicformof Freundlich equation gave a high linearity andtheKconstantsareincreasingwiththeincreaseof fly ash content in adsorbent mixtures and theaffinitybetweentheadsorbent surfaceandad-sorbed solute. The mean amount of removed dyesbyadsorptionbatchexperimentsinsoilmixturewith20%flyashcontentwereupto53.0%foracidyellow7, 44.9%foracidyellow23, 99.2%fordirectyellow28, 96.8%forbasicyellow28,and88.5%fordisperseblue79.Theremovalofdyes from column experiments decrease with theincreaseof thesolutionconcentrationform10to50mgL1at 20C, showingtheprocess tobe highly dependent on the concentration of thesolution. The mean removed amounts of dyes byadsorption on columns of soil mixture with 20%flyashcontent andfor initial concentrationofdyesolutions50mgL1wereupto33.8%foracidyellow7, 59.4%foracidyellow23, 84.2%fordirectyellow28, 98.2%forbasicyellow28,and 60.3% for disperse blue 79. Moreover, Latayeet al. (2009) reported adsorption of pyridine (Py)fromaqueous solutions, using bagasse fly ash(BFA), whichisasolidwastethatisgeneratedfrom bagasse-fired boilers as an adsorbent. Batchadsorption studies have been performed to eval-uate the influence of various parameters, on theremoval of Pyfromtheaqueoussolutions. Themaximum removal of Py is determined to be 99%164 Environ Monit Assess (2011) 183:151195atlowerconcentrations( CFA-600 > CFA-NaOH, andthecapacitiesforallofthemincreaseduponin-creasingthetemperature(60C > 45C > 30C).Theadsorptions of AR1ontoCFA, CFA-600,and CFA-NaOH, all followed pseudo-second-orderkinetics. Theisothermsfortheadsorptionof AR1 onto the raw and modified coal fly ashesfit the Langmuir isothermquite well; the ad-sorption capacities of CFA, CFA-600, and CFA-NaOHforAR1were92.59103.09, 32.7952.63,and12.6625.12mgg1, respectively. Accordingto the positive values ofHandS, these ad-sorptions were endothermic processes. The AREandEABSerrorfunctionmethodsprovidedthebest parameters for the Langmuir isotherms andpseudo-second-order equations, respectively, inthe AR1CFA adsorption system.Sludge ash/bottom ashWengandPan(2006) reportedthat thekinet-ics and equilibrium adsorption experiments wereconducted to evaluate the adsorption characteris-ticsofacationicdye(MB)ontobio-sludgeash.Results show that the ash could remove the dyeeffectively from aqueous solution. The adsorptionratewas fast andabout 80%of absorbedMBwasremovedin10min.TheadsorptionkineticscouldbeexpressedbythemodifiedFreundlichequation and intra-particle diffusion model. It wasfound that both the initial MB concentration andionic strength could affect the rate of adsorption.The effect of electrical double layer thicknesson the adsorption kinetics was discussed. Theequilibriumadsorptiondatawascorrelatedwelltothenonlinearmultilayeradsorptionisotherm.The maximum adsorption capacities for MB were7.3 106, 6.3 106, 5.0 106, and3.5 106mol g1, respectively, at temperature of 4C,14C, 24C, and34C. Values of thefirst-layeradsorptionenergy, Go, rangedfrom 6.62to7.65 kcal mol1, suggesting that the adsorptioncould be considered as a physical process, whichis simultaneouslyenhancedbytheelectrostaticeffects. Themultilayeradsorptionenergy, Go,rangedfrom-4.51to-5.02kcal mol1, suggest-ingthattheadsorptionwasofthetypical phys-ical type. On the basis of the monolayer dyeEnviron Monit Assess (2011) 183:151195 165adsorptioncapacity, thespecificsurfaceareaofthisashsamplewasestimatedas2.12.9m2g1which is close to the value (3.7 m2g1) obtainedviaBETnitrogengasadsorptionmeasurements.Mittal et al. (2006a)carriedout aninexpensiveadsorption method for the removal of indigocarmine, a highly toxic indigoid class of dye fromwastewaterbybottomash. Attemptshavebeenmade through batch and bulk removal of the dye,and both the adsorbents have been found to ex-hibit goodefficiencytoadsorbindigocarmine.Under batch technique effect of temperature,pH, concentration, dosageof adsorbents, sievesize of adsorbents, etc. have been observed. ThedyeuptakeontoboththeadsorbentsisfoundtovalidateLangmuirandFreundlichadsorptionisothermsmodels. Differentthermodynamicpa-rameters, likeGibbsfreeenergy, enthalpy, andentropy of the ongoing adsorption process, havealso been evaluated (Aksu and Tezer 2000). TheBatchtechniqueemployedforkineticmeasure-ments, andtheadsorptionfollowsafirst-order-rate kinetics for both the adsorbents. The kineticinvestigations also reveal for both the adsorbentsfilmdiffusionandparticlediffusionmechanismsare operative in the lower and higher concentra-tion ranges, respectively. Under the bulk removal,indigocarminehas beenadsorbedthroughthecolumn beds of bottom ash and de-oiled soya, andmore than 90% of the dye material has been re-covered by eluting dilute NaOH solution throughexhausted columns.Tartrazine a highly toxic dye can be adsorbedbybottomashasdemonstratedbyMittal etal.(2006b). Throughthebatchtechnique, equilib-riumuptakeofthedyeisobservedatdifferentconcentrations, pH of the solution, dosage of ad-sorbents, and sieve size of adsorbents. Langmuirand Freundlich adsorption isotherms are success-fully employed on both the adsorbents, and on thebasisofthesemodels, thethermodynamicpara-meters are evaluated. Kinetic investigations revealthat more than 50% adsorption of dye is achievedin about 1 h in both these cases, whereas equilib-riumestablishment takes about 3 to 4 h. The linearplots obtained in rate constant and mass transferstudiesfurtherconfirmtheapplicabilityof firstorderrateexpressionandmasstransfermodel,respectively.Thekineticdatatreatedtoidentifyratecontrollingstepof theongoingadsorptionprocesses indicate that for both the systems, par-ticlediffusionprocessispredominant at higherconcentrations, while film diffusion takes place atlowerconcentrations.Thecolumnstudiesrevealthat about 96%saturationof boththecolumnsisattainedduringtheirexhaustion, whileabout88% and 84% of the dye material is recovered byeluting dilute NaOH solution through exhaustedBottom Ash.Fruit wasteIn this part of the review article, we have tried todiscuss the cellulose-based waste (fruit waste) forthe removal of different types of dyes from water(Table 2). Fruit peel and pith is discarded in thejuice and soft-drink industries all over the world,and India is the second largest consumer and pro-ducer of fruits which also leads to the generationof million tones of fruit waste. Such fruit waste canbe effectively used for the wastewater treatment(Hameedetal. 2008; KumarandPorkodi 2006;Youssef 1993).Yellow passion fruitPavanet al. (2008a) reported that the use ofyellowpassionfruit (YPFW), apowderedsolidwaste, wastestedasbiosorbentfortheremovalof a cationic dye MB from aqueous solution. Ad-sorption of MB onto this low-cost natural adsor-bent was studiedbybatchadsorptionat 25C.Theeffectsof shakingtime, biosorbent dosage,andpHonadsorptioncapacities werestudied.InalkalinepHregion, theadsorptionof MBisfavorable. Thecontact timerequiredtoobtainthe maximum adsorption was 48 h at 25C. Fourkinetic models were tested, being the adsorptionkinetics better fitted to pseudo-first-order and ionexchangekineticmodels. Theionexchangeandpseudo-first-order constant rates were 0.05594and0.05455 h1, respectively. The equilibriumdata was fitted to Langmuir, Freundlich, Sips, andRedlichPetersonisothermmodels. Takingintoaccount the analysis of the normal distribution ofthe residuals (difference of qmeasuredqmodel), thedata were best fitted to Sips isotherm model. ThemaximumamountofMBisabsorbedbyYPFW166 Environ Monit Assess (2011) 183:151195Table 2 Reviewed results representing the adsorption capacity of fruit waste for the adsorption of dyes and their optimizedpH values for maximum adsorptionAdsorbent Dye pH Adsorption capacity ReferencesYellow passion fruit Methylene blue 9.0 16.00 mg g1Pavan et al. (2007)Yellow passion fruit Methylene blue 8.0 44.70 mg g1Pavan et al. (2008a)Mandarin peel Methylene blue 11.0 15.20 mg g1Pavan et al. (2007)Orange peel Rhodamine B 3.0 3.22 mg g1Namasivayam et al. (1996)Orange peel Congo red 5.0 22.40 mg g1Namasivayam et al. (1996)Orange peel Procion orange 3.0 1.30 mg g1Namasivayam et al. (1996)Orange peel Acid violet 17 6.3 19.88 mg g1Sivaraj et al. (2001)Orange peel Direct red 28 8.0 14.00 mg g1Annadurai et al. (2002)Orange peel Direct red 23 2.0 10.72 mg g1Arami et al. (2005)Orange peel Direct red 80 2.0 21.05 mg g1Arami et al. (2005)Orange peel Basic violet 10 8.0 14.30 mg g1Annadurai et al. (2002)Orange peel Methyl orange 5.7 20.50 mg g1Annadurai et al. (2002)Orange peel Methylene blue 7.2 18.60 mg g1Annadurai et al. (2002)Orange peel Rhodamine B 5.8 14.30 mg g1Annadurai et al. (2002)Orange peel Congo red 7.9 14.00 mg g1Annadurai et al. (2002)Orange peel Methyl violet 5.3 11.50 mg g1Annadurai et al. (2002)Orange peel Amido black 10B 5.8 7.90 mg g1Annadurai et al. (2002)Banana pith Direct red 28 8.0 18.20 mg g1Annadurai et al. (2002)Banana pith Basic blue 9 8.0 20.80 mg g1Annadurai et al. (2002)Banana pith Basic violet 10 8.0 20.60 mg g1Annadurai et al. (2002)Banana pith Methyl orange 5.7 21.00 mg g1Annadurai et al. (2002)Banana pith Methylene blue 7.2 20.80 mg g1Annadurai et al. (2002)Banana pith Rhodamine B 5.8 20.60 mg g1Annadurai et al. (2002)Banana pith Congo red 7.9 18.20 mg g1Annadurai et al. (2002)Banana pith Methyl violet 5.3 12.20 mg g1Annadurai et al. (2002)Banana pith Amido black 10B 5.8 6.50 mg g1Annadurai et al. (2002)Banana pith Rhodamine B 4.0 8.50 mg g1Namasivayam et al. (1993)Banana pith Direct red 3.0 5.92 mg g1Namasivayam et al. (1998)Banana pith Acid brilliant blue 3.0 4.42 mg g1Namasivayam et al. (1998)Garlic peel Methylene blue 6.0 142.86 mg g1Hameed and Ahmad (2009)Raw date pits Methylene blue 8.0 80.29 mg g1Banat et al. (2003)Activated date pits (500C) Methylene blue 8.0 12.94 mg g1Banat et al. (2003)Activated date pits (900C) Methylene blue 8.0 17.27 mg g1Banat et al. (2003)Bagasse pith Acid blue 25 7.0 21.70 mg g1McKay et al. (1999)Bagasse pith Acid red 114 7.0 22.90 mg g1McKay et al. (1996)Bagasse pith Basic blue 69 7.0 157.40 mg g1McKay et al. (1996)Bagasse pith Basic red 22 7.0 76.60 mg g1McKay et al. (1996)Bagasse pith Acid blue 25 7.0 17.50 mg g1Chen et al. (2001)Bagasse pith Acid red 114 7.0 20.00 mg g1Chen et al. (2001)Bagasse pith Basic blue 69 7.0 152.00 mg g1Chen et al. (2001)Bagasse pith Basic red 22 7.0 75.00 mg g1Chen et al. (2001)Bagasse pith Basic blue 69 7.0 158.00 mg g1McKay et al. (1987)Bagasse pith Basic red 22 7.0 77.00 mg g1McKay et al. (1987)Bagasse pith Acid blue 114 7.0 22.00 mg g1McKay et al. (1987)Bagasse pith Acid red 25 7.0 23.00 mg g1McKay et al. (1987)Apple pomace Reactive dye mixture 7.0 2.79 mg g1Robinson et al. (2002c)Brazilian pine fruit shell - PW Methylene blue 8.5 185.00 mg g1Royer et al. (2009)Brazilian pine fruit shell - C-PW Methylene blue 8.5 413.00 mg g1Royer et al. (2009)Barley straw Acid blue 40 1.02 104mol g1Oei et al. (2009)Barley straw Reactive black 5 2.54 105mol g1Oei et al. (2009)Olive pomace Reactive red 198 2.0 1.08 104mol g1Akar et al. (2009)Environ Monit Assess (2011) 183:151195 167Table 2 (continued)Adsorbent Dye pH Adsorption capacity ReferencesPith Acid blue 25 5.0 14.30 mg g1Ho and McKay (2003)Pith Basic blue 69 5.0 150.00 mg g1Ho and McKay (2003)Palm fruit bunch Basic yellow 21 7.0 327.00 mg g1Nassar and Magdy (1997)Palm fruit bunch Basic red 22 7.0 180.00 mg g1Nassar and Magdy (1997)Palm fruit bunch Basic blue 3 7.0 92.00 mg g1Nassar and Magdy (1997)Jack fruit peel Basic blue 9 7.0 285.71 mg g1Hameed (2009)biosorbent was44.70mgg1. Inoneof hispa-pers, healsoreportedthat thetotal numberofexperiments for achieving the highest removal ofMB from aqueous solutions using yellow passionfruit peel (Passif lora edullis f. f lavicarpa) andmandarinpeel (Citrusreticulata)asbiosorbentstwoindependentsetsoffull23factorialdesignswith two central points (10 experiments) were ex-perimented. In order to continue the optimizationof the system, a new full 22 factorial design withtwocentral points(sixexperiments)andacen-tral compositesurfaceanalysis(13experiments,divided into four cube points, five center points,and four axial points) were employed for yellowpassion fruit peel (PFP) and mandarin peel (MP),respectively. Using these statistical tools, the bestconditions for MB removal from aqueous solutionwere initially methylene blue (Co) of 3.20 mg L1,pH 9.0forPFPand11.0forMP, andtimeofcontacthigherthan48hforPFPand42.9hforMP (Hameed 2009).Garlic peelHameed and Ahmad (2009) reported the poten-tial of garlic peel, anagricultural wastetore-moveMBfromaqueous solution. Experimentswere carried out as function of contact time, ini-tial concentration(25200mgL1), pH(412),and temperature (303, 313, and 323 K). Adsorp-tion isotherms were modeled with the Langmuir,Freundlich, and Temkin isotherms. The data fittedwell with the Freundlich isotherm. The maximummonolayer adsorptioncapacities werefoundtobe82.64, 123.45, and142.86mgg1at303, 313,and323K, respectively. Thekineticdatawereanalyzed using pseudo-first-order and pseudo-second-ordermodels. Theresultsindicatedthatthegarlicpeel couldbeanalternativeformorecostly adsorbents used for dye removal isothermmodel. Inorder toreducethetotal number ofexperiments for achieving the highest removal ofMB from aqueous solutions using yellow passionfruitpeel (P.edullisf.f lavicarpa) and mandarinpeel(C. reticulata)asbiosorbents, twoindepen-dent sets of full 23 factorial designs with two cen-tral points (10 experiments) were experimented.Orange peel and Banana pithOrangepeel wastewas studiedas averygoodadsorbent for the adsorption of many dyes.Namasivayam et al. (1996) reported the adsorptionof Congored, Procionorange, andRhodamineBdyes. The process was studied at differentconcentrationsofdyes, adsorbentdosage, agita-tiontime, andpHwasfoundtoobeyLangmuirand Freundlich isotherms. Orange peels havealso been investigated as an adsorbent by Sivarajet al. (2001) for the removal of an acid dye:acidviolet17. The adsorptioncapacity Q0was19.88mgg1at initial pHof 6.3. Theequilib-rium time was found to be 80 min for 10, 20, 30,and40mgL1dyeconcentration, respectively.Amaximumremoval of 87%was obtainedatpH2.0 for an adsorbent dose of 600 mg 50 mL1of10mgL1dyeconcentration. Adsorptionin-creases with increase in pH. Maximum desorptionof 60% was achieved in water medium at pH of 10.Namasivayametal. (1998)reportedtheadsorp-tionof direct redandacidbrilliant blue withwaste banana pith by varying the agitation time,dyeconcentration,adsorbentdosage,andpH 9(Annadurai et al. 2002). Theadsorptioncapac-itywas 5.92and4.42mgdyeper gramof theadsorbentfordirect redandacidbrilliant blue,168 Environ Monit Assess (2011) 183:151195respectively. Also the adsorption of Rhodamine-Bhas been reported by Namasivayam et al. (1993).A maximum removal of 87% of the dye was ob-servedatpH4.Orange peelisalsotestedasanadsorbent by Arami et al. (2005), Ardejaniet al. (2007), and Annadurai et al. (2002). Aramietal.(2005)reportedtheadsorptioncapacityofdirectred23anddirectred80tobe10.72and21.05 mg g1, respectively.Plant wasteThe obvious advantage of above discussed adsor-bent for the dyes removal by adsorption treatmentis the lower costs involved. Hence, there is a needtosearchformoreeconomicalandeffectivead-sorbents. Tree fern is naturally and commerciallyavailableinall over theworld. This varietyoftreefernisgenerallymarketedforhorticulturalpurposes because of its character of adsorbabilityto retain water and manure for plants. Tree fernis generally dark brown in color and is a complexmaterial containingligninandcelluloseas ma-jorconstituents(Newman1997).Chemicalsorp-tion can occur via the polar functional groups oflignin, which include alcohols, aldehydes, ketones,acids, phenolic hydroxides, and ethers as chemicalbonding and ion exchange (Adler and Lundquist1963). Treefern, anagriculturalby-product, hasbeen currently investigated to remove dyes fromaqueoussolutions(McKayetal. 1981; Ofomaja2007; OfomajaandHo2007; Hanet al. 2006).Moreover, after cutting off the fruit bunch, mostof the residues are either used as manure or simplythrownawayorburntofftoreducethevolume.The approximate amount of dry matter producedper banana plant is about 1.0, 1.3 and 5.0 g of leaf,pseudostem, andfruits, respectively(HegdeandSrinivas 1991).Plant leaf powderSarma et al. (2008) reported the removal of a basicdyecalledRhodamineBfromaqueoussolutionby adsorption onto a biosorbent, Azadirachta in-dica(neem)leaf powder(AILP). Removal wastestedinabatchprocesswithconcentrationofdyesolution, AILPload, pH, temperature, andcontact time as the working variables. The adsorp-tion was favored by an acidic pH range and wasbestdescribedbyasecond-orderrateequation.Theexperimental datawereverifiedbyfittingintobothFreundlichandLangmuir isotherms.Thermodynamically, the process was found to beexothermic accompanied by a decrease in entropyand increase in Gibbs energy as the temperatureofadsorptionwasincreasedfrom303to333K.Theeffect of solutiontemperatureandthede-termination of the thermodynamic parameters ofadsorptionof RBonAILPenthalpyof activa-tion, entropyof activation, andfreeenergyofactivation, on the adsorption rates are impor-tant in understanding the adsorption mechanism.Therateandthetransport/kineticprocesses ofdye adsorption onto the adsorbents are describedbyapplyingvarious kinetic adsorptionmodels.This would lead to a better understanding of themechanisms controlling the adsorption rate. Thepseudo-second-ordermodel wasthebestchoiceamong all the kinetic models to describe theadsorptionbehaviorofRBontoAILP, suggest-ingthat theadsorptionmechanismmight beachemisorption process. The negative value of theenthalpychangesuggestedthat theriseinthesolution temperature did not favor RB adsorptionontoAILP(Bhattacharyya andSharma 2004).Bestani et al. (2008) identify the effectivenessof alocal desert plant characteristic of South-westAlgeriaandknownasSalsolavermiculata,which was pyrolyzed and treated chemically with a50% zinc chloride solution, to remove methyleneblue and iodine. The natural plant adsorption ca-pacitieswererespectively23and272mgg1formethylene blue andiodine. Corresponding re-sults for the pyrolyzed plant uptakes were 53and951 mg g1, while those for the pyrolyzed plant,chemicallytreatedandactivatedat650C, were130and 1,178 mg g1, respectively. In comparison,thestandardMerck-activatedcarboncapacitieswere 200 mg g1for MB and 950 mg g1for io-dine. Consequently, this low-cost local plant mayalso prove useful for the removal of large organicmolecules as well as potential inorganicconta-minants. The sorptionof methyleneblueontountreated guava leaf powder has been studied byPonnusami et al. (2008). The kinetics of sorptionof methylene blue is described by pseudo-second-order model. Effects of initial dye concentration,Environ Monit Assess (2011) 183:151195 169solution temperature, and adsorbent dosage havebeen studied. The pseudo-second-order rate con-stant has beencorrelatedas afunctionof thesystemvariables. Statistical tools likeStudentst test, Ftest, ANOVA, and lack of fit have beenemployedtodeterminethesignificanceof eachcoefficient that appeared in the model. Model ad-equacy has been checked by residual distribution.The proposed model explains 95.1% of the totalvariation in the response. The development, char-acterization, andapplicationof adsorbents pre-pared from avocado kernel seeds were discussedby Elizalde-Gonzlez et al. (2007), and they cometo the conclusion that a mayor adsorption capacityof thenon-carbonizedadsorbent incomparisonwithcarbonizedsamples is due tothe greateramount of surface acidic groups.Plant f iberThe use of Palmkernel fiber, a readily avail-ableagriculturalwasteproduct, forthesorptionof MBfromaqueous solutionandthepossiblemechanismofsorptionhasbeeninvestigatedbyOfomaja (2008b). The extent of dye removaland the rate of sorption were analyzed usingtwo kinetic rate models (pseudo-first and pseudo-second-orderkineticmodels)andtwodiffusionmodels (intra-particle and external mass transfermodels). Analysis of the kinetic data at differentsorbent dose revealed that the pseudo-first-orderkinetics fitted to the kinetic data only in the first5minof sorptionandthendeviatedfromtheexperimental data. Thepseudo-second-orderki-neticmodel wasfoundtobetterfit theexperi-mental data with high correlation and coefficientsatthevariousfiberdoseused.Thedyesorptionwas confirmed to follow the pseudo-second-ordermodel byinvestigatingtherelationshipbetweenthe amount of dye sorbed and the change inhydrogenionconcentrationof thedyesolutionandalsothedependenceofdyeuptakewithso-lution temperature. It was found that the changeinhydrogenionconcentrationandincrease insorption temperature were directly related to theamount of dye sorbed, and activation energy wascalculated to be 39.57 kJ mol1, indicating thatthe dye uptake is chemisorption, involving valenceforcesthroughsharingorexchangeofelectronsbetweensorbentandsorbateascovalentforces.The intra-particle diffusion and mass transfer rateconstants were observed to be well correlated withsorbentdoseinthefirst5minofsorption,indi-cating that sorption process to be complex. It wasfound that at low sorbent dose, the mass transferis the main rate controlling parameter. However,athighsorbentdose, intra-particlediffusionbe-comes rate controlling.Wu et al. (1999) reported some results of plumkernelsonMB. Theactivationtemperatureandtimetestedwereintheranges 750900Cand14 h, respectively. Adsorption isotherms of twocommercial dyes and phenol from water on suchactivatedcarbons weremeasuredat 30C. Theexperimentalresultsindicatedthatthepreparedactivatedcarbons wereeconomicallypromisingfor adsorptionremoval of dyes andphenol, incontrast to the other commercial adsorbents.Thekineticsandmechanismofadsorptionoftwocommercialdyesbasicred22andacidblue2, phenol, and 3-chlorophenol from water on acti-vated carbons were studied at 30C by Juang et al.(2000). Three simplified kinetic models includinga pseudo-first-order, a pseudo-second-order, andanintra-particlediffusionmodel weretested. Itwasshownthat theadsorptionof bothphenolscould be fitted to a pseudo-second-order ratelawandthatofbothdyescouldbefittedtoanintra-particle diffusion model. Kinetic parameterswerecalculated andcorrelatedwiththephysicalproperties of the adsorbents. Tseng (2007) re-portedthatactivatedcarbonwaspreparedfromplum kernels by NaOH activation at six differentNaOH/char ratios. The physical properties includ-ing the BET surface area, the total pore volume,the micropore ratio, the pore diameter, the burn-off, and the scanning electron microscope (SEM)observationsaswell asthechemical properties,namelyelementalanalysisandtemperaturepro-grammed desorption, were measured. The resultsrevealedatwo-stageactivationprocess: Stage1activatedcarbons wereobtainedat NaOH/charratios of 01, surfacepyrolysis beingthemainreaction; Stage 2 activated carbons were obtainedat NaOH/char ratios of 24, etching and swellingbeing the main reactions. The physical propertiesof stage2activatedcarbons weresimilar, andspecific area was from 1478 to 1887 m2g1. The170 Environ Monit Assess (2011) 183:151195results of reaction mechanism of NaOH activationrevealed that it was apparently because of the lossratioof elementsC, H, andOintheactivatedcarbon, thevariations inthesurfacefunctionalgroupsandthephysical properties. Threekindsof dyes (MB, BB1, andAB74) were usedforanisothermequilibriumadsorptionstudy. ThedatafittedwelltotheLangmuirisothermequa-tion. Inthis work, activatedcarbons preparedbyNaOHactivationwereevaluatedintermsoftheir physical properties, chemical properties, andadsorptiontype, andtheactivatedcarbonplumkernel was foundtohavemost applicationpo-tential. Kumar andKumrana(2005) inoneoftheir papers reportedthesorptionof MBontomango seed kernel particles. The operating vari-ables studied were the initial solution pH, temper-ature, adsorbentmass, initial dyeconcentration,andcontact time. EquilibriumdatawerefittedtoFreundlichandLangmuirisothermequation,andtheequilibriumdatawerefoundtobewellrepresented by Langmuir isotherm equation. Themonolayer sorption capacity of mango seed kernelfor MB sorption was found to be 142.857 mg g1at303 K. The sorption kinetics was found to followpseudo-first-order kinetics model. The MBuptakeprocesswasfoundtobecontrolledbybothsur-faceandporediffusionwithsurfacediffusionattheearlierstages, followedbyporediffusionatlaterstages. Theaverageeffectivediffusionco-efficiency was calculated and found to be 5.66 104cm2s1. Analysis of sorption data using Boydplot confirms that the external mass transfer is theratelimitingstepinthesorptionprocess. Vari-ous thermodynamic parameters such as enthalpyofsorptionHo, freeenergychangeGo, andentropySowereestimated.Thepositivevalueof Hoandnegativevaluesof Goshowthatthesorptionprocessisendothermicandsponta-neous. Jute stick powder has been found to be apromising material for adsorptive removal of CR(C.I. 22120)andRB(C.I. 45170)fromaqueoussolutions demonstratedbyPandaet al. (2008).Physiochemical parameters like dye concentra-tion, solution pH, temperature, and contact timehavebeenvariedtostudytheadsorptionphe-nomenon. Favorable adsorption occurs at aroundpH 7.0, whereastemperaturehasnosignificanteffectonadsorptionofboththedyes.Themax-imumadsorption capacity has been calculatedtobe35.7and87.7mgg1of thebiomass forCR and RB, respectively. The adsorption processisinconformitywithFreundlichandLangmuirisotherms for RBwhereas CRadsorption fitswell toLangmuirisothermonly. Inbothcases,adsorptionoccurs veryfast initiallyandattainsequilibrium within 60 min. Kinetic results suggestthe intra-particle diffusion of dyes as rate limitingstep.Wood shavingJano et al. (2008) reportedthat spruce woodshavingsfromPiceaabieswereusedforanad-sorptiveremoval of bothbasic as well as aciddyes from waters. The sorption properties of thesorbents were modified by treating with HCl,Na2CO3, andNa2HPO4. Thetreatment of thewoodsorbentswithalkalinecarbonatesolutionaswellaswithphosphatesolutionincreasedthesorption ability for the basic dye (MB), whereasthetreatment withmineral aciddecreasedthesorptionabilityforMBtosomeextent.Theop-positeistrueforthesorptionoftheaciddyeEgacidOrange. Themaximumsorptioncapac-ities estimated fromthe LangmuirFreundlichisotherms ranged from 0.060 to 0.165 mmol g1forMB and from 0.045 to 0.513 mmol g1for EgacidOrange. The basic dye sorption decreased at lowpH values in accordance with a presupposed ion-exchangemechanismofthesorption. Thesorp-tion of acid dye, on the other hand, decreased withincreasing pH. The presence of inorganic salts aswell as surfactants exhibited only minor effects onthedyesorption. Similarkindofstudyhasalsobeen reported by Ho and McKay (1998a).Tea wasteThepotentialityofteawastefortheadsorptiveremoval of MB, a cationic dye, from aqueous so-lution was reported by Uddin et al. (2008). Batchkinetics andisothermstudies werecarriedoutunder varying experimental conditions of contacttime, initial MB concentration, adsorbent dosage,and pH. The nature of the functional groups of ad-sorbentandtheircorrespondingfrequenciesareshown by FTIR spectra. The pH of the adsorbentEnviron Monit Assess (2011) 183:151195 171was estimated by titration method and a value of4.3 0.2 was obtained. An adsorptiondesorptionstudy was carried out resulting the mechanism ofadsorption was reversible and ion exchange. Ad-sorption equilibrium of tea waste reached within5 h for MB concentrations of 2050 mg L1. Thesorption was analyzed using pseudo-first-orderand pseudo-second-order kinetics models, and thesorptionkineticswasfoundtofollowapseudo-second-order kinetics model. Theextent of thedye (milligrams per gram) removal increased withincreasing initial dye concentration. The equilib-riumdatainaqueous solutions werewell rep-resentedbytheLangmuirisothermmodel. Theadsorptioncapacityof MBontoteawastewasfoundtobeas highas 85.16mgg1, whichisseveral folds higher than the adsorption capacityof a number of recently studiedinthe litera-turepotential adsorbents. Teawasteappearsasaveryprospectiveadsorbentfortheremovalofmethylene blue from aqueous solution.Oil palm woodActivatedcarbonswerepreparedfromthebio-massofoil palmwoodviatwostages, pyrolysisand physical activation, using an environmentfriendlypyrolysis pilot plant, andanactivationpilot plant; it was studied by Ahmad et al. (2007).The latter uses the outlet flue gases from limestonecalcinationprocessasactivatingagents. Experi-mentalresultsshowedthatpyrolysisandactiva-tionconditionsleadingtovariousfinal averagetemperatures had significant effects on the prop-ertiesofactivatedcarbonsprepared. Methyleneblue adsorption was tested and 90.9 mg g1maxi-mum adsorption capacity was found. The high mi-cropore fraction, N2 adsorption isotherm, and SEMshowedthat these activatedcarbons possessedintricate pore network comprising micropores andnarrowmesopores. FTIRcharacterizationindi-catedthatpyrolysisandactivationtemperaturesaffected the surface functional groups, and max-imum methylene blue adsorption was dependenton BET surface area.Activated carbon prepared from low-cost palmoil fiber has been utilized as the adsorbent for theremoval of basic dye; methylene blue is studied byDarus et al. (2005). Experiments were conductedat different pH, different adsorbent dose, differentinitial concentration of dye, and different contacttime. Themost effectiveof color removal wasoptimum at pH7 and the percentage removal in-creased with the increase in carbon dose while thepercentage removal decreased with the increase ininitial dye concentration. The adsorption equilib-rium for color reached at 90 min of contact time.The results indicated that palm oil fiber could beemployed as low cost alternatives to commerciallyactivated carbon in wastewater treatment for dyeremoval.SawdustSawdust iscomposedof fineparticlesof wood.This material is produced from cutting with a saw,hence its name. Garg et al. (2004) investigates thepotential use of Indian Rosewood (Dalbergia sis-soo)sawdust,pretreatedwithformaldehyde andsulfuricacid, fortheremovalofmethylenebluedyefromsimulatedwastewater. Higheradsorp-tion percentages were observed at lower concen-trations of methylene blue. OptimumpH value fordye adsorption was determined as 7.0 for both theadsorbents. Maximum dye was sequestered within30 min after the beginning for every experiment.The adsorption of methylene blue followed a first-orderrateequationandfittheLagergrenequa-tion well.Inanothercase, Ibrahimetal. (1997)studiedthefactors affectingpreparationof woodsaw-dust and used the obtained adsorbents for the re-moval of anionic dyestuffs. Sawdust was modifiedby reacting with cross-linked polyethylenimine(CPEI)tocreateaminatedadsorbent. Modifiedsawdustwasaddedtoacidicdye(pH 3.0)andshookfor30minat 25C. Thefiltratewascol-lected, and its concentration was determined witha UV spectrophotometer. The results showed thatmodification with CPEI increased the adsorptivityof the sawdust, since the CPEI introduced positivesorptive sites in the form of reactive amino groupsonto the wood material, thus improving the saw-dust reactivityandanionicdyeuptake. Similarresults are also studied by Ferrero (2007), Malik(2003), and zacar and Sengil (2003). The adsorp-tion capacities of plant waste were summarized inTable 3.172 Environ Monit Assess (2011) 183:151195Table 3 Reviewed results representing the adsorption capacity of plants waste for the adsorption of dyes and their optimizedpH values for maximum adsorptionAdsorbent Dye pH Adsorption capacity ReferencesAzadirachta indica (neem) Rhodamine B 7.2 25.80 mg g1Sarma et al. (2008)leaf powderAzadirachta indica (neem) Congo red 6.7 128.30 mg g1Bhattacharyya and Sharmaleaf powder (2004)Activated desert plant Methylene blue 6.4 23.00 mg g1Bestani et al. (2008)Guava leaf powder Methylene blue 7.0 95.10 mg g1Ponnusami et al. (2008)Tea waste Methylene blue 4.3 85.16 mg g1Uddin et al. (2008)Oil palm wood Methylene blue 7.0 90.90 mg g1Ahmad et al. (2007)Oil palm wood Methylene blue 7.2 25.0 mg g1Darus et al. (2005)Palm kernel fiber Methylene blue 7.1 49.96 mg g1Ofomaja (2008b)Mango seed kernel Methylene blue 8.0 142.90 mg g1Kumar and Kumrana (2005)Jute stick powder Congo red 7.0 35.70 mg g1Panda et al. (2008)Jute stick powder Rhodamine B 7.0 87.70 mg g1Panda et al. (2008)Tree fern Basic red 13 7.0 408.00 mg g1Ho et al. (2005b)Saw dust-Walnut Acid blue 25 7.0 36.98 mg g1Ferrero (2007)Saw dust- cherry Acid blue 25 7.0 31.98 mg g1Ferrero (2007)Saw dust- oak Acid blue 25 7.0 27.85 mg g1Ferrero (2007)Saw dust- pitch pine Acid blue 25 7.0 26.19 mg g1Ferrero (2007)Sawdust carbon Acid yellow 36 3.0 183.80 mg g1Malik (2003)Pine sawdust (raw) Acid yellow 132 3.5 398.80 mg g1zacar and Sengil (2005)Pine sawdust (raw) Acid blue 256 3.5 280.30 mg g1zacar and Sengil (2005)Avocado kernel seeds - AGAP Basic blue 41 7.0 72.60 mg g1Elizalde-Gonzlez et al. (2007)Avocado kernel seeds - AGAP1 Basic blue 41 7.0 43.40 mg g1Elizalde-Gonzlez et al. (2007)Avocado kernel seeds - AGAP800 Basic blue 41 7.0 67.10 mg g1Elizalde-Gonzlez et al. (2007)Avocado kernel seeds - AGAP1000 Basic blue 41 7.0 130.20 mg g1Elizalde-Gonzlez et al. (2007)Avocado kernel seeds - AGAP-P-800 Basic blue 41 7.0 125.30 mg g1Elizalde-Gonzlez et al. (2007)Avocado kernel seeds - Basic blue 41 7.0 86.60 mg g1Elizalde-Gonzlez et al. (2007)AGAP-P-N-800Sawdust (Formaldehyde treated) Malachite green 7.0 27.00 mg g1Garg et al. (2003)Sawdust (Sulphuric acid treated) Malachite green 9.0 59.70 mg g1Garg et al. (2003)Wood Basic blue 69 7.0 77.00 mg g1Ho and McKay (1998a)Wood Acid blue 25 7.0 6.14 mg g1Ho and McKay (1998a)Mansonia wood Methtlene blue 10.0 33.44 mg g1Ofomaja (2008a)Sawdust Methylene violet 10.0 21.65 mg g1Ofomaja (2008a)Eucalyptus bark Remazol BB 2.0 34.10 mg g1Morais et al. (1999)Wood chips Remazol red 7.0 2.80 mg g1Nigam et al. (2000)Wood chips Remazol black B 7.0 3.30 mg g1Nigam et al. (2000)Beech sawdust (CaCl2 treated) Methylene blue 11.0 13.02 mg g1Batzias and Sidiras (2004)Beech sawdust (CaCl2 treated) Red basic 22 11.0 23.90 mg g1Batzias and Sidiras (2004)Beech sawdust (original) Methylene blue 11.0 9.78 mg g1Batzias and Sidiras (2004)Beech sawdust (original) Red basic 22 11.0 20.20 mg g1Batzias and Sidiras (2004)Neem leaf powder Brilliant green 7.0 0.55 mmol g1Bhattacharyya and Sharma(2003)Wood shaving untreated Methylene blue 5.0 55.00 mol g1Jano et al. (2008)Wood shaving HCl treated Methylene blue 5.0 39.00 mol g1Jano et al. (2008)Wood shaving Na2CO3treated Methylene blue 5.0 184.00 mol g1Jano et al. (2008)Wood shaving NaHPO4treated Methylene blue 5.0 91.00 mol g1Jano et al. (2008)Wood shaving untreated Egacid orange 5.0 33.00 mol g1Jano et al. (2008)Wood shaving HCl treated Egacid orange 5.0 36.00 mol g1Jano et al. (2008)Wood shaving Na2CO3treated Egacid orange 5.0 211.00 mol g1Jano et al. (2008)Wood shaving NaHPO4treated Egacid orange 5.0 111.00 mol g1Jano et al. (2008)Saw dust Methylene blue 7.0 62.40 mg g1Garg et al. (2004)Environ Monit Assess (2011) 183:151195 173Natural inorganic materialsMost recently, the clay minerals and zeolites werereported to be unconventional adsorbents for theremoval of dyesfromaqueoussolutionsduetotheircheapandabundantresources, highersur-faceareas(LiuandZhang2007). Furthermore,theregenerationoftheselow-costsubstitutesisnotnecessarywhereasregenerationofactivatedcarbonisessential becauseof theabundant re-sources. Clay materials with sheet-like structures(Arbeloaet al. 2002a; Orthmanet al. 2003; Liet al. 2004; Tahir andRauf 2006) andneedle-likestructure(Ozdemiretal. 2006; Alkanetal.2007; Liu and Guo 2006; Huang et al. 2007) havebeen increasingly gaining attention because theyare cheaper than activated carbons, and they alsoprovidehighlyspecific surfacearea(ZhaoandLiu 2008). On the other hand, zeolites are threedimensional,microporous,crystallinesolidswithwell-defined structures that can absorb dyes witha capacity of up to more than 25% of their weightin water. For zeolite, their unique properties suchastheexistenceofhighintra-crystallinesurfacearea, themicroporous/mesoporous character oftheuniformporedimensions, theionexchangeproperties, theabilitytodevelopinternal acid-ity, thethermal stability, andthehighinternalsurfaceareaalongwiththeir abilitytoabsorbmolecules/ionicspeciesintotheirstructuregiverise to great variety of applications which makeszeolitesspecialwhencomparedwithotherinor-ganic materials (Davis 2002). They separate ions,complex ions, and molecules based on size, shape,polarity, and degree of unsaturation.ClayClay material possesses a layered structure and isconsidered to be host material. They are classifiedon the basis of layered structures. There are sev-eral classesof clayssuchassmectites, kalonite,serpentine, vermiculite, and sepiolite (Shichi andTakagi 2000). Grses et al. (2006) investigatedadsorptionkineticsofacationicdye, methyleneblue, onto clay from aqueous solution with respectto the initial dye concentration, temperature, pH,mixing rate, and sorbent dosage in this study. Inorder tounderstandtheadsorptionmechanismin detail, zeta potentials and the conductivities ofclay suspensions at various pH (111) and cationexchangecapacityweremeasured. PorosityandBETsurface area of clay studiedwere deter-mined. Theresults showedthat theadsorptionhasbeenreachedtheequilibriumin1h. Itwasfoundthat theamount adsorbedof methyleneblueincreaseswithdecreasingtemperatureandalso with increasing both sorbent dosage and in-creasing initial dye concentration. Adsorption ca-pacitydecreaseswithincreasingpH, except forthe natural pH(5.6) of clay suspensions. Theadsorptionkineticsof methylenebluehasbeenstudiedinterms of pseudo-first-order, pseudo-second-order sorption, and intra-particle diffusionprocessesthuscomparingchemicalsorptionanddiffusionsorptionprocesses. It was foundthatthe pseudo-second-order mechanism is predomi-nantandtheoverall rateofthedyeadsorptionprocess appears tobe controlledby the morethanonestep.McKayetal.(1985)reportedtheadsorption capacity of fullers earth for basic andacid blue to be 220 and 120 mg g1, respectively.SimilarresultsarealsoinvestigatedbyHoetal.(2001) and Grses et al. (2006). Clays are naturalenvironment-friendly materials with high specificsurface area are now widely used for the adsorp-tionandremoval of theorganicpollutants. LiuandZhang(2007)havereviewedtheadsorptionproperties of the rawclays, activatedclays byacidtreatment orcalcinations, organic-modifiedclays with small molecules or polymers for the ad-sorption, and removal of organic dyes from aque-ous solutions. The development perspectives arealsoproposed. Arbeloaetal. (1998, 2002b)andChaudhuri et al. (2000) investigated the hy-drophobic effect on the adsorption of rhodamine3B dye on laponite particles, hectorite, and mont-morillonite in aqueous suspensions with electronicabsorption and fluorescence spectroscopies. Clayminerals exhibit astrongaffinityfor bothhet-eroatomic cationic and anionic dyes (Table 4).SepioliteSepiolite has been tested as an adsorbent by manyresearchers (Ozdemir et al. 2004). Sepiolite, as anadsorbent, may be a good alternative to these sys-tems. Sepioliteisanaturalhydratedmagnesium174 Environ Monit Assess (2011) 183:151195Table 4 Reviewed results representing the adsorption capacity of naturally available inorganic minerals for the adsorptionof dyes and their optimized pH values for maximum adsorptionAdsorbent Dye pH Adsorption capacity ReferencesClay Methylene blue 7.0 6.30 mg g1Grses et al. (2004)Clay Basic blue 69 7.0 1200.00 mg g1McKay et al. (1985)Clay Acid blue 25 7.0 220.00 mg g1McKay et al. (1985)Clay Acid blue 9 3.0 57.80 mg g1Ho et al. (2001)Clay Basic red 18 3.0 157.00 mg g1Ho et al. (2001)Clay Basic blue 69 7.0 585.00 mg g1El-Guendi et al. (1995)Clay Basic red 22 7.0 488.40 mg g1El-Guendi et al. (1995)Sepiolite Reactive red 239 11.0 108.80 mg g1Ozdemir et al. (2004)Sepiolite Reactive yellow 176 11.0 169.10 mg g1Ozdemir et al. (2004)Sepiolite Reactive black 5 11.0 120.50 mg g1Ozdemir et al. (2004)Sepiolite Reactive blue 221 6.7 55.9 104mol g1Alkan et al. (2005)Sepiolite Acid blue 62 6.7 32.9 104mol g1Alkan et al. (2005)Sepiolite Methylene blue 6.6 1.87 104mol g1Do gan et al. (2007)Am-SiO2Methylene blue 5.0 70.86 mmol kg1Woolard et al. (2002)Red mud Congo red 2.0 4.05 mg g1Namasivayam and Arasi (1997)Spent activated clay Methylene blue 8.0 3.41 104mol g1Weng and Pan (2007)Zeolite Reactive black 5 11.0 60.50 mg g1Ozdemir et al. (2004)Zeolite Reactive red 239 11.0 111.10 mg g1Ozdemir et al. (2004)Zeolite Reactive yellow 176 11.0 88.50 mg g1Ozdemir et al. (2004)Zeolite Methylene blue 7.0 0.045 mmolg1Wang et al. (2005)Zeolite Methylene blue 5.0 33.83 mmol kg1Woolard et al. (2002)Zeolite Alizarin sulphonate 8.0 7.13 mmol kg1Woolard et al. (2002)Perlite Methylene blue 11.0 9.1 106mol g1Do gan et al. (2004)Perlite Methyl violet 9.0 1.4 105mol g1Do gan and Alkan (2003)Ca Montmorillonite Basic green 5 7.0 156.30 mg g1Wang et al. (2004)Ca - Montmorillonite Basic violet 10 7.0 414.90 mg g1Wang et al. (2004)Ti - Montmorillonite Basic green 5 7.0 170.50 mg g1Wang et al. (2004)Ti Montmorillonite Basic violet 10 7.0 961.50 mg g1Wang et al. (2004)Glass powder Carminic acid 7.0 8.2 103mmol g1Atun and Hisarli (2003)Raw kaolin Methylene blue 4.0 13.99 mg g1Ghosh and Bhattacharyya (2002)Pure kaolin Methylene blue 4.0 15.55 mg g1Ghosh and Bhattacharyya (2002)Calcined raw kaolin Methylene blue 4.0 7.59 mg g1Ghosh and Bhattacharyya (2002)Calcined pure kaolin Methylene blue 4.0 8.88 mg g1Ghosh and Bhattacharyya (2002)NaOH treated raw kaolin Methylene blue 4.0 16.34 mg g1Ghosh and Bhattacharyya (2002)NaOH treated