organophilization of a brazilian mg-montmorillonite

Organophilization of a BrazilianMg-montmorillonite without prior

sodium activation

MANOELLA SILVA CAVALCANTE1 S IMONE PATRIacuteCIA ARANHA PAZ2 ROcircMULO SIMOtildeES ANGEacuteLICA1 EDSON NORYUKI ITO3 AND

ROBERTO FREITAS NEVES1

1 Programa de Poacutes-Graduaccedilatildeo em Geologia e Geoquiacutemica Instituto de Geociecircncias Universidade Federal do ParaacuteCampus do Guamaacute 66075-110 Beleacutem Paraacute Brazil

2 Faculdade de Engenharia de Materiais Campus de Ananindeua Universidade Federal do Paraacute Ananindeua ParaacuteBrazil

3 Departmento de Engenharia de Materiais Universidade Federal do Rio Grande do Norte Natal-RN Brazil

(Received 5 September 2015 revised 17 February 2016 Editor George Christidis)

ABSTRACT The use of Mg-montmorillonite in the production of organoclay without sodiumactivation was investigated For this purpose organophilization experiments were carried out by varyingthe concentration of two surfactants hexadecyltrimethylammonium (HDTMA+) and dodecyltrimethy-lammonium (DTMA+) ions These surfactants were used at concentrations 07 10 and 15 times that of thecation exchange capacity (626 meq100 g) of the clay with a reaction time of 8 h at temperatures of 25 and80degC X-ray diffraction (XRD) results confirmed the intercalation for both in natura and activated samplesThe Fourier-transform infrared (FTIR) spectroscopy and XRD results showed that the ratio of gauchetransconformers decreased with increased basal spacing The results of thermodifferential and thermogravi-metric analysis (DTADTG) confirmed the thermal stability of the organoclay up to 200degC permitting theuse of suchmaterial in the synthesis of polymerclay nanocomposites obtained by the melt blending ThusMg-montmorillonite can be intercalated with alkylammonium ions without prior Na-activation to formorganoclays The possibility of using natural (non-activated) Mg-montmorillonite represents a significantdifference in terms of processing cost in comparison with existing Ca-montmorillonite in Brazil or evenwith imported bentonites that require Na-activation during beneficiation

KEYWORDS Mg-montmorillonite organoclay sodium activation smectite bentonite

The process of organophilization of bentonites withalkylammonium ions has been used widely mainlybecause of the facility to intercalate such ions into theinterlayer space of montmorillonite Once merged thehydrophilic character on the surface of clay mineralschanges to hydrophobic and the organic-inorganichybrid material formed exhibits chemical and physicalproperties of both clay minerals and organic compounds

(Lagaly et al 2006 Ruiz-Hitzky amp Van Meerbeek2006) This type of material referred to as an organoclayis potentially indicated for use as an adsorbent fororganic pollutants (eg oil spills and their derivatives inwater bodies) as rheology-control agents as drillingmud fluids and more recently in the synthesis ofnanocomposites (Paiva et al 2008 CMS 2013)

In general the interlayer space of an in naturamontmorillonite is occupied by water molecules andcations (mainly Na+ K+ Mg2+ Ca2+) that are weaklybound to the clay-mineral layers These cations balancethe negative charge generated by isomorphic

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Clay Minerals (2016) 51 39ndash54

substitutions in the TOT structure of the clay mineralwhich are easily replaced by cationic species externalto the structure especially in liquid medium due toincreased mobility (Moore amp Reynolds 1997 Guumlven2009 Dohrmann et al 2012) This crystallochemicalcharacteristic grants montmorillonite a large cationexchange capacity (CEC) that must be taken intoaccount in any organophilization process as well as thecomposition of exchangeable cations (McAtee et al1959 Mermut amp Lagaly 2001 He et al 2010)

Bentonite ndash both natural and modified ndash is anextremely versatile clay due to the variety of propertiesit can exhibit in response to minor modifications inmontmorillonite Each type of bentonite meets therequirements of different specific applications accord-ing to their characteristics Wyoming bentonite(Na-montmorillonite) for instance is excellent foruse in drilling fluids and casting but is inadequate foroil bleaching or in the manufacture of catalysts On theother hand bentonites from Mississippi (Ca-mont-morillonite) are good for use in bleaching oils andcasting but cannot be used in well drilling (Grim1968) For organophilization the Wyoming type isconsidered to be the most suitable because Na+ is moreeasily exchanged for alkylammonium ions than Ca2+

(Theng et al 1967 Murray 2007) However becauseNa-bentonite deposits are rare the commercially moreavailable Ca varieties are transformed intoNa-bentonites by chemical treatment with Na reagents(Na2CO3 is the most widely used) ndash a process known atthe industrial level as sodium activation The samehappens at the laboratory scale where the process isused to exchange the cations in liquid phase

The occurrence of a Mg-montmorillonite known aslsquoFormosarsquo bentonite in northeastern Brazil wasdescribed by Paz et al (2012) This cationic type hasnot been described previously among known Brazilianbentonites occurrences and has attracted considerableattention due to the predominance of Mg in theinterlayer space This feature motivated the presentwork which aimed to evaluate the feasibility ofsynthesizing organoclays using Formosa bentonite(Mg-montmorillonite) as the starting materialwithout prior Na-saturation leading to cost savingsin the synthesis process

MATER IALS AND METHODS

Mg-montmorillonite

Approximately 40 kg of bentonite containingMg-montmorillonite was collected from the location

described and sampled for the first time by Paz et al(2012) Composite sampling was conducted at variouspoints within the same outcrop (06deg25prime12S 46deg10prime52W) which is located next to highway MA006 in the city of Formosa da Serra Negra southernMaranhatildeo State Brazil

At the laboratory the initial sample (sim40 kg) wasdried at 60degC and homogenized and a 5 kg sub-samplewas extracted for the present study The first step in thepreparation of the material was crushing in a RETSCHjaw crusher model BB2 The sample was then groundin an HERZOG orbital mill (Shatter Box) modelHSM100 and sieved manually to achieve a classifi-cation size of lt015 mm (100 Mesh) The materialretained in the sieve was ground again in the orbitalmill until the entire sample passed through the sieveTo ensure the homogeneity of the material quarteringwas conducted according to the elongated and conicalheap methods

Surfactants

The organic salts used in the synthesis of organo-clays were hexadecyltrimethylammonium bromide(HDTMA) and dodecyltrimethylammonium bromide(DTMA) (Merck Shouchardt Germany)

Reference materials

Three reference samples were used in this study(1) two smectite clays from the USA SWy-2(Na-montmorillonite CEC 85 meq100 g) and SAz-1(Ca-montmorillonite CEC 123 meq100 g) Theywere obtained from the Source Clays Repository ofThe Clay Minerals Society and (2) a commercialorganoclay Cloisitereg 10A (surfactant dimethylbenzyl hydrogenated tallow quaternary ammonium)sold worldwide by Southern Clay Products Inc

Treatment with sodium carbonate (Na+

activation)

For Na+ activation 25 kg of Mg-bentonite wasmixed with 6625 mL of 2 M Na2CO3 solution whichcorresponded to a CEC of 100 meq Na+100 g clayThe mixture was homogenized manually and aged for7 days in a moist chamber at 100 relative humidityThe material was stirred for 1 min daily After 7 daysthe final wet product was dried at 60degC and pulverizedin a mortar The methodology described was based onthe activation step carried out by those industries whichspecialize in the exploration for and beneficiation of

40 Manoella Silva Cavalcante et al

bentonite The suffix lsquoActrsquo was added to the Na-activated sample ie Mg-montmorillonite-Act

Organophilization process

The variables studied are as follows (1) in naturaand Na-activated clays as starting materials(2) HDTMA+ and DTMA+ as surfactant ions (3)07 10 and 15 times CEC of Mg-montmorillonite as thesurfactant concentration and (d) 25 and 80degC oftemperature A summary of the experiments alongwith the code used for each product is shown in Table 1

100 g of clay was mixed with 700 mL of water in aglass reactor under vigorous mechanical agitation for2 h After this period the surfactant was added andagitation of the mixture was maintained for 8 h Theclay was then washed and filtered with distilled waterto remove the remaining surfactant dried at 60degCdisaggregated manually by crushing in a mortar sievedand homogenized to lt015 mm

AnalysesX-ray diffraction The Mg-montmorillonite preparedwith and without activation the organoclays and thereference materials were examined using a PANalyticaldiffractometer model XacutePERT PRO MPD (PW 304060) with a PW305060 (θθ) goniometer a ceramicX-ray Cu anode (Kα1 = 1540598 Aring) with a long fine-focus (2200W60 kV) nickel Kβ filter 40 kV voltage30 mA current and 002deg2θ step size The specificconditions for each method used are shown below(1) For powder samples scan range 3ndash70deg2θ fornatural and activated Mg-montmorillonite when com-pared with the reference smectite clays and 2ndash18deg2θfor organoclays Cloisite 10A andMg-montmorillonitewith and without Na-activation 30 s scanning time perstep fixed anti-scatter slit of 14deg 5 mm mask andsample rotation of 1 revolution sndash1

(2) For oriented samples in glass slides scan rangeof 3ndash35deg2θ timestep of 10 s divergent slit of 18deganti-scatter slit of 14deg and 10 mm mask withoutrotation The oriented samples were X-rayed air driedfollowed by ethylene glycol (EG) solvation andheating at 550degC for 2 h The Hofmann amp Klemen(1950) treatment was applied namely Li+ saturationheating at 300degC for 12 h and EG solvation

X-ray fluorescence spectrometry The XRF spectrom-eter employed was a wavelength-dispersive (WDS)sequential Axios-Minerals model (PANalytical) with aceramic X-ray tube and a rhodium anode of maximum

24 kW power level The specimens were prepared asglass discs (1 g of sample plus 6 g of lithiummetaborate) using the IQ+ program of PANalyticalrsquosSuperQ Manager Measurements of loss on ignition(LOI) were made on independent test portions of eachmaterial by heating for 1 h at 1000degC in a mufflefurnace

Thermal analysis The measurements were carried outon sim17 mg of sample in a PL Thermal ScienceSTA10001500 simultaneous thermal analyzer(Stanton Redcroft Ltd) with a cylindrical verticalfurnace a digital converter coupled to a microcom-puter The experiments were performed on aluminacrucibles over the temperature range of 25ndash1100degC aheating rate of 20degCmin and air flow

Exchangeable cations and cation exchange capacityThe Ca2+ and Mg2+ exchangeable cations wereobtained by extraction with 1 N KCl and weremeasured using EDTA as the titrant and EriochromeBlack Tas the indicator The K+ and Na+ exchangeablecations were obtained by extraction with Mehlichsolution and were measured using a BENFER flamephotometer (BFC 150 model) The CEC was definedas the sum of the exchangeable cations (Ca2+ +Mg2+ +K+ + Na+) This is the standard method used for CECanalysis by the Brazilian Agency for AgriculturalResearch (EMBRAPA 1998)

Fourier transformed infrared spectroscopy Theseanalyses were performed on a Thermo IR100 FTIRspectrometer in the spectral range 4000ndash400 cmndash1Each spectrum is the sum of 64 scans with 4 cmndash1

resolution The samples were prepared with the KBrmethod at a ratio of 1 mg of sample to 150 mg of KBr

RESULTS AND DISCUSS ION

Characterization of the Mg-bentonite

Identification of mineral constituents The dominantmineral is montmorillonite with main peaks at152 nm (d001) 0445 nm (d100) and 0149 nm (d060)(Fig 1) Minor phases present are kaolinite (072 nm)hematite (0270 nm and 0251 nm) K-feldspar(0423 nm and 0379 nm) and anatase (0351 nmand 0189 nm) (Fig1)

The XRD pattern of the oriented clay fraction(Fig 2) contains montmorillonite illite and kaolinite(d001 spacings of 151 nm 10 nm and 072 nmrespectively) Illite was not identified in the bulk

41Organophilization of Mg-montmorillonite

sample due to the low concentration of this mineral(Fig 1) After EG solvation the 001 diffractionmaximum shifted from 151 nm to 171 nm and thed002 reflection appeared at 085 nm indicating puresmectite with no interstratification After heating at550degC for 2 h the main peak of smectite shifted to0995 nm due to the collapse of the layer

When montmorillonite was subjected to lithiumsaturation and heating Li+ cations migrated in theoctahedral sheet neutralizing the layer charge whichoriginated from the isomorphic replacement of Al3+ byMg2+ or Fe2+ and resulted in collapse of the layerwhich then forms a pyrophyllite-like structure(Greene-Kelly 1952) This behavior was observedwith the Mg-montmorillonite in the present study(Fig 2) After saturation with Li+ (Hofmann ampKlemen 1950) the d001 value of sim097 nm confirmedthat the smectite present was a montmorillonite inaccordance with Paz et al (2012)

The XRD pattern of theMg-montmorillonite samplewas compared with Ca- and Na-montmorillonites

(Fig 1) The Mg- and Ca-montmorillonites exhibitd001 spacing at sim152 nm and the Na-montmorillonited001 spacing at 127 nm According to Yildiz amp Kuscu(2007) diffraction maxima at 148ndash155 nm indicatethe presence of Ca-Mg-smectites as in Mg-montmor-illonite and SAz-1 clays and maxima at sim125 nmindicate the presence of Na-montmorillonite as in thecase of SWy-2 smectite Na-activated Ca-Mg-smec-tites also show d001 asymp125 nm due to the exchange ofthe interlayer cations Mg2+andor Ca2+ by Na+ as wasobserved for Mg-montmorillonite-Act (Fig 1)

Chemical composition The chemical composition ofthe Mg-montmorillonite sample and the referencesamples SWy-2 and SAz-1 are shown in Table 2 SiO2

and Al2O3 are the main constituents of all clays TheMg-montmorillonite sample has the smallest SiO2

content relative to the reference sample probablybecause of the absence of quartz The abundance ofAl2O3 is comparable in all samples

TABLE 1 Coding of organoclays

Mg-montmorillonite SurfactanttimesCEC

(meq100 g clay) Temperature (degC) Code

WithoutNa+ activation

DTMA(D)

07 25 07XD2580 07XD80

10 25 10XD2580 10XD80

15 25 15XD2580 15XD80

WithNa+ activation

07 25 07XD25-Act80 07XD80-Act

10 25 10XD25-Act80 10XD80-Act

15 25 15XD25-Act80 15XD80-Act


HDTMA (HD) 07 25 07XHD2580 07XHD80

10 25 10XHD2580 10XHD80

15 25 15XHD2580 15XHD80

WithNa+ activation

07 25 07XHD25-Act80 07XHD80-Act

10 25 10XHD25-Act80 10XHD80-Act

15 25 15XHD25-Act80 15XHD80-Act


The Mg-montmorillonite sample exhibits greaterFe2O3 contents than the reference samples a featurethat is characteristic of Brazilian bentonite clays Theexplanation for this lies in the presence of hematitewhich influences the colour of the sample directlyimparting a reddish-brown hue The SWy-2 and SAz-1bentonites exhibit a greyish color

The only sample with a relatively large Na2O content(198) was SWy-2 which represents a rare smectiteclay in which Na+ is naturally the main interlayer cationIt is therefore identified in the CMS Source ClaysRepository as a Na-montmorillonite SAz-1 has thelargest CaO content (295) and is known as a Ca-montmorillonite because Ca2+ is the main constituent inthe interlayer space Magnesium may be present both inthe octahedral sheet and in the interlayer space TypicallyMg2+ as well as Fe2+ is present in the octahedral sites ofthe montmorillonite replacing the Al3+ and generating acharge imbalance (of sim02ndash06) in the layer which iscompensated for by the interlayer cations (Guggenheimet al 2006) In the case of the Mg-montmorillonitesample Mg2+ is present both in the octahedral sheet andin the interlayer space In this respect Mg-

montmorillonite differs from the reference clays fromthe USA and Brazil which have been described in theliterature as polycationic (Amorim et al 2004 Moraeset al 2010) To confirm the predominant cation presentin the interlayer space an analysis of the exchangeablecations was carried out as described in the followingsubsection The greater TiO2 and K2O contents in theMg-montmorillonite sample in comparisonwith those ofSWy-2 and SAz-1 are mainly related to the presence ofanatase and K-feldspar as accessory minerals in the clay

The results of the chemical analysis carried out inthis study were compared with the results of Paz et al(2012) for Mg-montmorillonite and of Mermut ampCano (2001) for SAz-1 and SWy-2 The valuesobtained in the present study are comparable to thosereported in the literature

Composition of exchangeable cations and cationexchange capacity The composition of the exchange-able cations of the Mg-montmorillonite sample and theCEC showed that Mg+ is the predominant exchange-able cation confirming its cationic type (Table 3) TheCEC value of Mg-montmorillonite (626 meq100 g)

FIG 1 Comparison of XRD patterns of the Mg-montmorillonite with and without Na activation with those of theSWy-2 and SAz-1 bulk samples


was less than for Na-montmorillonite (85 meq100 g)and Ca-montmorillonite (123 meq100 g) both fromBorden amp Giese (2011) even when compared with thereference value of 748 meq100 g obtained by Pazet al (2012) which used the ammonium acetatemethod while in this work lsquoKCl + Mehlichrsquo was usedThe CEC value is important in the calculation of thesurfactant-ion concentration used in the synthesis oforganoclays because the quantitative exchangerequires a certain excess of alkylammonium salts inrelation to the CEC (Lagaly et al 2006) In this casethree concentration values were used as follows 0710 and 15 times 626 (CEC of Mg-montmorilloniteobtained in this work) with the main objective ofcomparing the products obtained from the two cationictypes (magnesian and Na-activated)

Organoclays

The XRD patterns of organoclays showed thatthe variation of basal-spacing values (d001) ofMg-montmorillonite in natural and Na-activatedforms reflect directly the type and concentration ofthe surfactant (Figs 3 4) The basal spacing of

the organophilic smectite results from the sum of thefollowing components (1) thickness of the claymineral layer (096 nm) (2) the height of the polarend of the organic cation and (3) the number of layersof the organic species For example the molecularconformation of HDTMA+ can exhibit two values(051 or 067 nm) depending upon the height of thepolar end if perpendicular or parallel to the montmor-illonite layers (Harris et al 1999 He et al 2006 Huet al 2013) (Fig 5) Thus a monolayer intercalationresults in a d001 of 147 nm (perpendicular) or d001 of163 nm (parallel)

According to Lagaly et al (2006) short-chainalkylammonium ions are arranged in monolayerswhile longer chain are arranged in bilayers with thealkyl chain axes parallel to montmorillonite layersMonolayers and bilayers exhibit basal spacings ofsim14 nm and sim18 nm respectively Intermediatesim16 nm spacing may indicate mixed layering ofmonolayer and bilayer complexes Therefore accord-ing to the aforementioned models for the arrangementsof the alkylammonium ions in the montmorilloniteinterlayers (Lagaly et al 2006 Hu et al 2013) theorganophilic products obtained in this work can be

FIG 2 XRD patterns of the oriented lt2 mm fraction of the Mg-montmorillonite after air-drying glycolation heatingat 550degC and Hofmann-Klemen treatment


discussed as follows all organoclays with07 times DTMA+ concentration showed d001asymp 145 nmwhich indicates a monolayer structural arrangement(Fig6a) (Lagaly et al 2006) with molecular con-formation perpendicular to the smectite layer Thetemperature and Na+-for-Mg2+ exchange did not affectthe structural arrangement type

The 10 times D25 organoclay showed a broad diffrac-tion band which can be related to two peaks (145 and161 nm approximately) indicating the possiblecoexistence of monolayer arrangements with perpen-dicular and parallel conformation in the montmoril-lonite interlayer (Harris et al 1991 He et al 2006Hu et al 2013) Alternatively the peak at 161 nmalone may indicate monolayerbilayer transition(Lagaly et al 2006) The remaining samples with10 times DTMA (Fig3) display a bilayer arrangementbecause they showed a d001 value between 184 and196 nm (Fig 6b)

The organoclays with 15 times DTMA+ obtained fromthe synthesis conditions studied are exhibited in Fig 3Three organoclays showed d001 asymp 20 nm even whenthe temperature and the cationic conditions of thestarting clay varied This may be a pseudotrilayerconformation (Fig 6d) according to Lagaly et al(2006) Only one organoclay with 15 times DTMA+

showed a smaller d001 value (182 nm) also indicatinga bilayer arrangement

The XRD patterns of the organoclay with 07 timesconcentration of HDTMA+ surfactant exhibited d001 asymp162 nm (Fig 4) indicating the presence of a monolayer

arrangement with parallel molecular conformation ormixed layering of monolayer and bilayer as mentionedbefore for the organoclays obtained from DTMA+ Thevariation of temperature as well as the type ofexchangeable ions in the interlayer space do not influencethe type of structural arrangement of the organoclay

The samples 10 times HD25 and 15 times HD25-Actshowed peak values of sim196 nm which representbilayer arrangement The remaining samples showedd001 gt 22 nm suggesting paraffin-type arrangement Inthis type the organic compounds are inclined and theangles vary according to the charge or the packingdensity of the layer (Fig 6ef) (Beneke ampLagaly 1981)

The angle of inclination (α) in paraffin-typearrangements can be calculated using the followingequation Sinα = (dndashh)l where d is the basal spacingh is the layer thickness (096 nm) and l is the length ofthe organic ion chain (in the case of HDTMA =253 nm) (Mermut amp St Arnaud 1990 Mermut 1994Hu et al 2013) The tilting angle for organoclays withvalues between 23 and 24 nm is sim32ndash35deg For thosewith d001 asymp 27 nm the angle is sim44deg (Fig 6f)

Note that in previous studies of the synthesis oforganoclays Na-montmorillonite or Na-activated ben-tonitewere used (LeeampLee 2004 Xi et al 2005 Zhouet al 2007 Nikolaidis et al 2012 Filippi et al 2013Tsai et al 2013) Since the 1960s it has been largelyconsidered that this type is more effective thanCa-montmorillonite (Theng et al 1967) In thepresent study organoclays derived from Mg-montmor-illonite were obtained with similar characteristics to

TABLE 2 Elemental composition of Mg-montmorillonite SWy-2 and SAz-1

(wt)

Mg-montmorillonite SWy-2 SAz-1

This work Paz et al (2012) This work Mermut amp Cano (2001) This work Mermut amp Cano (2001)

SiO2 4810 4813 6374 6146 6076 5965TiO2 116 149 013 009 019 025Al2O3 1866 1740 1880 2205 1724 1998Fe2O3 1265 1408 373 437 144 177CaO 031 027 047 118 295 315MgO 388 373 224 294 588 676MnO 014 017 ndash ndash 008 ndashK2O 156 159 064 020 016 019Na2O ndash ndash 198 147 ndash 006P2O5 002 005 005 ndash 003 ndashLOI 1350 1308 723 576 1127 817Total 9998 9989 9901 9952 100 9998

LOI Loss on ignition as determined by heating at 1000degC after drying at 105degC ndash below detection limit


those obtained after Na-activation even when producedat different temperatures

The variation in the d001 spacing can be related to thechain length of organic cations (the DTMA+ ionpresents 12 carbon atoms while HDTMA+ has 16carbon atoms) and packing density Moreover theorganoclays synthesized with 10times and 15times the CEC(D and HD) exhibited d001 spacing similar to 10ACloisite (Table 4)

Conformational identification of intercalatedorganic compounds

In all organoclays intercalated with DTMA+ andHDTMA+ the presence of FTIR absorption bands at2800ndash3000 cmndash1 and 1400ndash1600 cmndash1 was observed(Figs 7 8)

The bands at sim2920 cmndash1 and sim2850cmndash1 originatefrom the asymmetric (υas) and symmetric (υs) stretch-ing of ndashCH2 bonds of the amine chain respectively

(He et al 2004 Fatimah amp Huda 2013) These bandsin particular υas are extremely sensitive to conform-ational changes in the alkyl chains of amine (Vaiaet al 1994 Xi et al 2005 Zhou et al 2007 Maet al 2010) and bands appear in this region only whenthe alkyl chains are highly ordered (all with transconformations) This is due to increased packingdensity enabling greater ordination of surfactant withtrans conformation in the interlayer (Vaia et al 1994)

A decrease in the frequency of the asymmetricstretching band with increasing surfactant concentrationas well as with increasing chain length (HDTMA+ gtDTMA+) was observed (Table 5) This suggests thatincreased packing density favours trans-type orderedconformations which allows structural arrangementsinvolving greater basal spacing In addition all organo-clays exhibited υas values similar to those of Cloisite 10A

Correlation of the FTIR (υas) and XRD (d001) resultsshowed that the decreased frequency of asymmetricstretching which is associated with an increase in trans

TABLE 3 Composition of exchangeable cations and total CEC of the Mg-montmorillonite

Mg-bentonite Experimental method

(meq100 g of clay)

CEC (meq100 g of clay)Mg2+ Ca2+ Na+ K+

This work KCl + Mehlich 475 85 53 13 606Paz et al (2012) Ammonium acetate 602 99 33 14 748

FIG 3 XRD patterns with d001 of organoclays with DTMA+


conformation is correlated with larger basal spacingsof the organoclays This confirms the foregoinginterpretation of the structural arrangements presentin the organoclay products

The singlets present in the 1400 cmndash1 to 1600 cmndash1

region (Figs 7 8) are related to the liquid-like molecularstructure or disordered hexagonal packing of thematerial (Weers et al 1990 Zhu et al 2005) Withincreasing packing density and surfactant ion concen-tration this singlet tends to form two scissoringvibrations (δ) This is observed in all organoclays andmore intensely in Cloisite 10A The singlets aresensitive to interactions of the amine molecules withinthe alkyl chain and to the type of structural arrangementThus when the first band exhibits frequency variation inthe range 1466ndash1472 cmndash1 there is increased ordering(all trans conformation) of the alkyl chains of the amine

Conversely bands of low frequency and decreasedintensity indicate weaker interaction and greater move-ment of the ionic bonds The second frequency at1487 cmndash1 tends to decrease with increased orderingthis is observed in clays intercalated with the twosurfactants used (Zhu et al 2005)

Thermal stability

Due to the low temperature of decomposition of theintercalated organic ions the thermal stability oforganoclays is one of the major problems in thepreparation of nanocomposites by fusion (Hedleyet al 2007)

Three main regions are observed indicated as a band c in Fig 9 the first corresponds to endothermicwater desorption the second with two peaks

FIG 4 XRD patterns with d001 of organoclays with HDTMA+

FIG 5 Molecular conformation of HDTMA+ (a) plane perpendicular to the plane of the montmorillonite layer (b) planeparallel to the plane of the montmorillonite layer


corresponds to the decomposition of the quaternaryammonium salt which is exothermic and the third isascribed to the release of carbonaceous residues fromthe montmorillonite interlayer space Delbem et al(2010) observed similar behaviour in organoclaysproduced from bentonites from Paraiacuteba State Brazil

Region a shows an inverse relationship between theamount of water desorbed from inorganic cations andthe amount of water removed from the intercalatedorganic cations This is because the greater the changein polarity of the interlayer species the greater theconsequent change in the character of the clay from

FIG 6 Orientations of alkylammonium ions in the basal spacing of silicates (a) monolayer with perpendicularconformation (b) monolayer with parallel conformation (c) bilayer (d) pseudotrilayer and (ef ) paraffin-type

arrangements of alkylammonium ions with different tilting angles of the alkyl chains

TABLE 4 Alkyl-chain arrangements in the interlayer space of the Mg-montmorillonite

Organoclay withoutNa activation d001

Alkyl chainarrangement

Organoclay withNa activation d001


07XD25 145 Monolayer 07XD25-Act 145 Monolayer07XD80 145 07XD80-Act 14507XHD25 161 07XHD25-Act 16207XHD80 164 07XHD80-Act 16310XD25 145 and

161MonolayerBilayer 10XD25-Act 185 Bilayer

10XD80 184 Bilayer 10XD80-Act 19510XHD25 196 10XHD25-Act 242 Paraffin10XHD80 236 Paraffin 10XHD80-Act 23215XD25 207 Pseudotrilayer 15XD25-Act 204 Pseudotrilayer15XD80 207 15XD80-Act 182 Bilayer15XHD25 272 Paraffin 15XHD25-Act 19615XHD80 272 15XHD80-Act 272 ParaffinCloisite 10A 199 ndash


hydrophilic to hydrophobic the greater is the effect-iveness of the organophilization and the less solvatedwater is present (Guggenheim amp Koster van Groos2001 Xie et al 2001 Paz et al 2012) The TG results

for the organoclays revealed a significant decrease inwater loss in this region relative to the amount of Mg-montmorillonite (986 Paz et al 2012) similarresults were obtained for Cloisite 10A (Tables 6 7)

TABLE 5 Frequency values of the asymmetric stretching bands of organoclays

Organoclaywithout Na activation υas (cm

ndash1)Organoclay

with Na activation υas (cmndash1)

07XD25 2926 07XD25-Act 292607XD80 2926 07XD80-Act 292610XD25 2926 10XD25-Act 292510XD80 2925 10XD80-Act 292415XD25 2925 15XD25-Act 292415XD80 2925 15XD80-Act 292507XHD25 2920 07XHD25-Act 292007XHD80 2920 07XHD80-Act 292010XHD25 2919 10XHD25-Act 291910XHD80 2919 10XHD80-Act 291915XHD25 2918 15XHD25-Act 291915XHD80 2918 15XHD80-Act 2918Cloisite 10A 2923

FIG 7 FTIR spectra of organoclays with DTMA+ and cloisite 10A


FIG 8 FTIR spectra of organoclays with HDTMA+ and cloisite 10A

FIG 9 DTA diagrams of organoclays with DTMA+ and HDTMA+ and cloisite 10A


In region b mass loss was observed to range from1014 to 2383 (Tables 6 7) The percentages of massloss of the surfactant were estimated subtracting themass loss of Mg-montmorillonite from 200 to 800degC

due to dehydroxylation from the total mass loss of theorganoclays from 200 to 850degC (Hedley et al 2007)The Δm was greater for those products with moreeffective organic ion intercalation and greater for

TABLE 6Weight loss determined by TG of organoclays without Na activation and with intercalated DTMA+ andHDTMA+

Organoclay withoutNa activation

Water loss ()(20ndash200degC)

Mass loss of surfactant ()(200ndash800degC) Residual organics () Total mass loss ()

Region (a) Region (b)

Cloisite 10A 338 087 4197

07XD25 535 1014 053 194407XD80 415 1093 021 191610XD25 584 1120 039 212510XD80 387 1350 033 215815XD25 479 1649 016 253315XD80 504 1656 040 257307XHD25 538 1436 040 23907XHD80 545 1389 052 236810XHD25 458 2393 028 327010XHD80 518 1594 039 253215XHD25 426 1646 013 248115XHD80 486 2362 018 3200

TABLE 7 Weight loss determined by TG of organoclays with Na activation and intercalated DTMA+ andHDTMA+

Organoclay with Na+

activation

Water loss ()(20 to 200degC)

Mass loss of surfactant() (200degC to 800degC) Residual organics () Total mass loss ()


Cloisite 10A 338 087 4197



species with larger molecular weight (HDTMA+ gtDTMA+) In region b there is also a tendency for theformation of a second exothermic peak in theorganoclays produced This second peak is character-istic of organoclays containing high concentrations oforganic ions (He et al 2005)

Region c corresponds to products associated withresidual organic carbon The higher the salt concen-tration the greater the amount of residue produced bythe organoclay This is of great importance for thesynthesis of nanocomposites because this residue mayact as a flame retardant (Yariv 2004 Carrado ampKomadel 2009)

All organoclays intercalated with DTMA+ andHDTMA+ showed very similar carbon residue values(lt1) (Tables 6 7) suggesting that the concentrationof the organic salt (07 10 and 15) has no influence

CONCLUS IONS

The Mg-montmorillonite described here can be usedfor synthesis of organophilic clays both in the activatedand the natural forms The synthetic organoclays thatyielded the best results in this study were thoseintercalated with HDTMA+ For most of the synthesisconditions used here natural Mg-montmorillonitegave a greater yield of intercalated organic ions thanNa-activated montmorillonite This finding is ofeconomic interest in the industry because it eliminatesone step in the synthesis process

ACKNOWLEDGEMENTS

The authors thank the National Council for Scientific andTechnological Development (Conselho Nacional deDesenvolvimento Cientiacutefico e Tecnoloacutegico ndash CNPq) forfunding the Project ldquoAtivaccedilatildeo e Desativaccedilatildeo Soacutedica de(CaMg)-Bentonitas Brasileirasrdquo (Edital Universal142011 Processo 4771962011-0) an MSc scholarshipfor the first author and a grant to the third author (RSAngeacutelica PQ 3053922014-0)

REFERENCES

Amorim LV Gomes CM Lira HL Franccedila KB ampFerreira HC (2004) Bentonites from Boa VistaBrazil physical mineralogical and rheologicalproperties Materials Research 7 583ndash593

Beneke K amp Lagaly G (1982) The brittle mica-likeKNiAsO4 and its organic derivatives Clay Minerals17 175ndash183

Borden D amp Giese RF (2001) Baseline studies ofthe Clay Minerals Society Source Clays Cationexchange capacity measurements by the ammonia-electrode method Clays and Clay Minerals 49 5444ndash445

Carrado KA amp Komadel P (2009) Acid activation ofbentonites and polymerndashclay nanocompositesElements 5 93ndash98

Clay Minerals Society (CMS) (2013) Glossary for ClayScience Project httpwwwclaysorgGLOSSARYGlossIntrohtml

Delbem MF Valera TS Valenzuela-Diaz FR ampDemarquette NR (2010) Modification of aBrazilian smectite clay with different quaternaryammonium salts Quiacutemica Nova 33 2 309ndash315

Dohrmann R Genske D Karnland O Kaufhold SKiviranta L Olsson S Tze MP Sandeacuten T Sellin PSvensson D amp Valter A (2012) Interlaboratory CECand exchangeable cation study of bentonite buffermaterials I Cu(II)-triethylenetetramine methodClays and Clay Minerals 60 2 162ndash175

EMBRAPA ndashBrazilian Agricultural Research Corporation(1998) Manual de Meacutetodos de Anaacutelises de SoloMinistry of Agriculture Livestock and Food Supply

Fatimah I amp Huda T (2013) Preparation of cetyltrimethyl-ammonium intercalated Indonesian montmorillonite foradsorption of toluene Applied Clay Science 74115ndash120

Filippi S Paci M Rossi FBD amp Polacco G (2013)XRD study of intercalation in statically annealedcomposites of ethylene copolymers and organicallymodified montmorillonites 1 Two-tailed organo-clays Journal of the Taiwan Institute of ChemicalEngineers 44 123ndash130

Greene-Kelly R (1952) Irreversible dehydration inmontmorillonite Clay Minerals Bulletin 1 221

Grim RE (1968) Clay Mineralogy McGraw-Hill BookCo Inc New York 596 pp

Guggenheim S Adams JM Bain DC Bergaya FBrigatti MF Drits VA Formoso MLL Galaacuten EKogure T amp Stanjek H (2006) Summary ofrecommendations of nomenclature committees rele-vant to clay mineralogy report of the AssociationInternationale Pour lrsquoEtude des Argiles (AIPEA)nomenclature committee Clays and Clay Minerals54 761ndash772

Guggenheim S Van K amp Gross AF (2001) Baselinestudies of the Clay Minerals Society Source ClaysThermal analysis Clays and Clay Minerals 49433ndash443

Guumlven N (2009) Bentonite ndash clays for molecularengineering Elements 5 89ndash92

Harris DJ Bonagamba TJ amp Schmidt-Rohr K (1999)Conformation of poly(ethylene oxide) intercalated inclay and MoS2 studied by two-dimensional double-quantum NMR Macromolecules 32 6718ndash6724


He H Frost RL Bostrom T Yuan P Duong L YangD Xi Y amp Kloprogge JT (2006) Changes in themorphology of organoclays with HDTMA+ surfactantloading Applied Clay Science 31 262ndash271

He H Frost R amp Zhu J (2004) Infrared study ofHDTMA+ intercalated montmorillonite SpectrochimicaActa Part A 60 2853ndash2859

He HP Ding Z Zhu JX Yuan P Xi YF Yang D ampFrost RL (2005) Thermal characterization of surfac-tant-modified montmorillonites Clays and ClayMinerals 53 286ndash292

He HP Ma YH Zhu JX Yuan P amp Qing YH (2010)Organoclays prepared from montmorillonites withdifferent cation exchange capacity and surfactantconfiguration Applied Clay Science 48 67ndash72

Hedley CB Yuan GB amp Theng KG (2007) Thermalanalysis of montmorillonites modified with quaternaryphosphonium and ammonium surfactants AppliedClay Science 35 180ndash188

Hofmann U ampKlemen E (1950) Loss of exchangeabilityof lithium ions in bentonite on heating Zeitschrift fuumlrAnorganishe und Allgemeine Chemie 262 95ndash99

Hu Z He G Liu Y Dong C Wu X amp Zhao W (2013)Effects of surfactant concentration on alkyl chainarrangements in dry and swollen organic montmoril-lonite Applied Clay Science 75ndash76 134ndash140

Lagaly G (1986) Interaction of alkylamines withdifferent types of layered compounds Solid StateIonics 22 43ndash51

Lagaly G Ogawa M amp Deacutekaacuteny I (2006) Clay mineralorganic interactions Pp 309ndash377 in Handbook ofClay Science (F Bergaya BKG Theng amp G Lagalyeditors) Developments in Clay Science 1 ElsevierAmsterdam

Lee JY amp Lee HK (2004) Characterization oforganobentonite used for polymer nanocompositesMaterials Chemistry and Physics 85 410ndash415

Ma Y Zhu J He H Yuan P Shen W amp Liu D (2010)Infrared investigation of organo-montmorillonitesprepared from different surfactants SpectrochimicaActa Part A 76 122ndash129

McAtee JL (1959) Inorganic-organic cation exchangeon montmorillonite American Mineralogist 441230ndash1236

Mermut AR amp Lagaly G (2001) Baseline studies of theClay Minerals Society Source Clays Layer-chargedetermination and characteristics of those mineralscontaining 21 layers Clays and Clay Minerals 49393ndash397

Mermut AR (1994) Problems associated with layercharge characterization of phyllosilicates Pp106ndash122 in Layer Charge Characteristics of Clays(AR Mermut editor) CMS Workshop Lectures 6The Clay Minerals Society Boulder Colorado USA

Mermut AR amp Cano AF (2001) Baseline studies of theclay minerals society source clays Chemical analyses

of major elements Clays and Clay Minerals 49381ndash386

Mermut AR amp St Arnaud RJ (1990) Layer chargedetermination of high charge phyllosilicates byalkylammonium technique 27th Annual Meeting ofthe Clay Minerals Society Columbia MissouriProgram and Abstracts p 86

Moore DM amp Reynolds Jr RC (1997) X-rayDiffraction and the Identification of Clay MineralsOxford University Press New York

Moraes DS Angeacutelica RS Costa CEF Rocha FilhoGN amp Zamian JR (2010) Mineralogy and chem-istry of a new bentonite occurrence in the easternAmazon region northern Brazil Applied ClayScience 48 475ndash480

Murray HH (2007) Applied Clay MineralogyOccurrences Processing and Application of KaolinsBentonites Palygorskite-Sepiolite and CommonClays Elsevier Amsterdam pp 111ndash130

Nikolaidis AK Achilias DS amp Karayannidis GP(2012) Effect of the type of organic modifier on thepolymerization kinetics and the properties of poly(methyl methacrylate)organomodified montmorillon-ite nanocomposites European Polymer Journal 48240ndash251

Paiva LB Morales AR amp Diacuteaz FRV (2008) Naoverview on organophilic clays properties routes ofpreparation and applications Applied Clay Science42 8ndash24

Paz SPA Angeacutelica RS amp Neves RF (2012) Mg-bentonite in the Parnaiacuteba Paleozoic Basin northernBrazil Clays and Clay Minerals 60 3 265ndash277

Ruiz-Hitzky E amp Van Meerbeek A (2006) Clay mineraland organoclayndashpolymer nanocomposites Pp 583ndash622 inHandbook of Clay Science (F Bergaya BKGTheng amp G Lagaly editors) Developments in ClayScience 1 Elsevier Amsterdam

Theng BKG Greenland DJ amp Quirk JP (1967)Adsorption of alkylammonium cations by montmor-illonite Clay Minerals 7 1ndash17

Tsai T-Y LinM-J Chuang Y-C ampChou P-C (2013)Effects of modified clay on the morphology andthermal stability of PMMAclay nanocompositesMaterials Chemistry and Physics 138 230ndash237

Vaia RA Teukolsky RK amp Giannelis EP (1994)Interlayer structure and molecular environment ofalkylammonium layered silicates Chemistry ofMaterials 6 1017ndash1022

Weers JG amp Scheuing DR (1990) In Fourier TransformInfrared Spectroscopy in Colloid and Interface Science(DR Scheuing editor) ACS Symposium Ser 447American Chemical Society Washington DC

Wen X He H Zhu J Juna Y Ye C amp Denga F (2006)Arrangement conformation and mobility of surfac-tant molecules intercalated in montmorillonite pre-pared at different pillaring reagent concentrations as


studied by solid-state NMR spectroscopy Journal ofColloid and Interface Science 29 754ndash760

Xi Y Ding Z He H amp Frost RL (2005) Infraredspectroscopy of organoclays synthesized with thesurfactant octadecyltrimethylammonium bromideSpectrochimica Acta Part A 61 515ndash525

XieW Gao Z Pan W-P Hunter D Singh A amp Vaia R(2001) Thermal degradation chemistry of alkylquaternary ammonium montmorillonite Chemistryof Materials 13 2979ndash2990

Yariv S (2004) The role of charcoal on DTA curves oforgano-clay complexes an overview Applied ClayScience 24 225ndash236

Yildiz A amp Kuscu M (2007) Mineralogy chemistry andphysical properties of bentonites from BaoumlrenKuumltahya W Anatolia Turkey Clay Minerals 42399ndash414

Zhou Q Frost RL He H Xi Y amp Liu H(2007) Adsorbed para-nitrophenol on HDTMABorganoclaymdashA TEM and infrared spectroscopicstudy Journal of Colloid and Interface Science 307357ndash363

Zhu J He H Zhu L Wen X amp Deng F (2005)Characterization of organic phases in the interlayer ofmontmorillonite using FTIR and 13CNMR Journal ofColloid and Interface Science 286 239ndash244


substitutions in the TOT structure of the clay mineralwhich are easily replaced by cationic species externalto the structure especially in liquid medium due toincreased mobility (Moore amp Reynolds 1997 Guumlven2009 Dohrmann et al 2012) This crystallochemicalcharacteristic grants montmorillonite a large cationexchange capacity (CEC) that must be taken intoaccount in any organophilization process as well as thecomposition of exchangeable cations (McAtee et al1959 Mermut amp Lagaly 2001 He et al 2010)

Bentonite ndash both natural and modified ndash is anextremely versatile clay due to the variety of propertiesit can exhibit in response to minor modifications inmontmorillonite Each type of bentonite meets therequirements of different specific applications accord-ing to their characteristics Wyoming bentonite(Na-montmorillonite) for instance is excellent foruse in drilling fluids and casting but is inadequate foroil bleaching or in the manufacture of catalysts On theother hand bentonites from Mississippi (Ca-mont-morillonite) are good for use in bleaching oils andcasting but cannot be used in well drilling (Grim1968) For organophilization the Wyoming type isconsidered to be the most suitable because Na+ is moreeasily exchanged for alkylammonium ions than Ca2+

(Theng et al 1967 Murray 2007) However becauseNa-bentonite deposits are rare the commercially moreavailable Ca varieties are transformed intoNa-bentonites by chemical treatment with Na reagents(Na2CO3 is the most widely used) ndash a process known atthe industrial level as sodium activation The samehappens at the laboratory scale where the process isused to exchange the cations in liquid phase

The occurrence of a Mg-montmorillonite known aslsquoFormosarsquo bentonite in northeastern Brazil wasdescribed by Paz et al (2012) This cationic type hasnot been described previously among known Brazilianbentonites occurrences and has attracted considerableattention due to the predominance of Mg in theinterlayer space This feature motivated the presentwork which aimed to evaluate the feasibility ofsynthesizing organoclays using Formosa bentonite(Mg-montmorillonite) as the starting materialwithout prior Na-saturation leading to cost savingsin the synthesis process

MATER IALS AND METHODS

Mg-montmorillonite

Approximately 40 kg of bentonite containingMg-montmorillonite was collected from the location

described and sampled for the first time by Paz et al(2012) Composite sampling was conducted at variouspoints within the same outcrop (06deg25prime12S 46deg10prime52W) which is located next to highway MA006 in the city of Formosa da Serra Negra southernMaranhatildeo State Brazil

At the laboratory the initial sample (sim40 kg) wasdried at 60degC and homogenized and a 5 kg sub-samplewas extracted for the present study The first step in thepreparation of the material was crushing in a RETSCHjaw crusher model BB2 The sample was then groundin an HERZOG orbital mill (Shatter Box) modelHSM100 and sieved manually to achieve a classifi-cation size of lt015 mm (100 Mesh) The materialretained in the sieve was ground again in the orbitalmill until the entire sample passed through the sieveTo ensure the homogeneity of the material quarteringwas conducted according to the elongated and conicalheap methods

Surfactants

The organic salts used in the synthesis of organo-clays were hexadecyltrimethylammonium bromide(HDTMA) and dodecyltrimethylammonium bromide(DTMA) (Merck Shouchardt Germany)

Reference materials

Three reference samples were used in this study(1) two smectite clays from the USA SWy-2(Na-montmorillonite CEC 85 meq100 g) and SAz-1(Ca-montmorillonite CEC 123 meq100 g) Theywere obtained from the Source Clays Repository ofThe Clay Minerals Society and (2) a commercialorganoclay Cloisitereg 10A (surfactant dimethylbenzyl hydrogenated tallow quaternary ammonium)sold worldwide by Southern Clay Products Inc

Treatment with sodium carbonate (Na+

activation)

For Na+ activation 25 kg of Mg-bentonite wasmixed with 6625 mL of 2 M Na2CO3 solution whichcorresponded to a CEC of 100 meq Na+100 g clayThe mixture was homogenized manually and aged for7 days in a moist chamber at 100 relative humidityThe material was stirred for 1 min daily After 7 daysthe final wet product was dried at 60degC and pulverizedin a mortar The methodology described was based onthe activation step carried out by those industries whichspecialize in the exploration for and beneficiation of






























DTMA(D)

07 25 07XD2580 07XD80

10 25 10XD2580 10XD80

15 25 15XD2580 15XD80

WithNa+ activation

07 25 07XD25-Act80 07XD80-Act

10 25 10XD25-Act80 10XD80-Act

15 25 15XD25-Act80 15XD80-Act


HDTMA (HD) 07 25 07XHD2580 07XHD80

10 25 10XHD2580 10XHD80

15 25 15XHD2580 15XHD80

WithNa+ activation

07 25 07XHD25-Act80 07XHD80-Act

10 25 10XHD25-Act80 10XHD80-Act

15 25 15XHD25-Act80 15XHD80-Act










Organoclays
















(wt)
















(meq100 g of clay)









Thermal stability























ndash1)Organoclay















Cloisite 10A 338 087 4197



Organoclay with Na+

activation




Cloisite 10A 338 087 4197






CONCLUS IONS


ACKNOWLEDGEMENTS


REFERENCES




















































































DTMA(D)

07 25 07XD2580 07XD80

10 25 10XD2580 10XD80

15 25 15XD2580 15XD80

WithNa+ activation

07 25 07XD25-Act80 07XD80-Act

10 25 10XD25-Act80 10XD80-Act

15 25 15XD25-Act80 15XD80-Act


HDTMA (HD) 07 25 07XHD2580 07XHD80

10 25 10XHD2580 10XHD80

15 25 15XHD2580 15XHD80

WithNa+ activation

07 25 07XHD25-Act80 07XHD80-Act

10 25 10XHD25-Act80 10XHD80-Act

15 25 15XHD25-Act80 15XHD80-Act










Organoclays
















(wt)
















(meq100 g of clay)









Thermal stability























ndash1)Organoclay















Cloisite 10A 338 087 4197



Organoclay with Na+

activation




Cloisite 10A 338 087 4197






CONCLUS IONS


ACKNOWLEDGEMENTS


REFERENCES
































































Organoclays
















(wt)
















(meq100 g of clay)









Thermal stability























ndash1)Organoclay















Cloisite 10A 338 087 4197



Organoclay with Na+

activation




Cloisite 10A 338 087 4197






CONCLUS IONS


ACKNOWLEDGEMENTS


REFERENCES


































































(wt)
















(meq100 g of clay)









Thermal stability























ndash1)Organoclay















Cloisite 10A 338 087 4197



Organoclay with Na+

activation




Cloisite 10A 338 087 4197






CONCLUS IONS


ACKNOWLEDGEMENTS


REFERENCES


































































(meq100 g of clay)









Thermal stability























ndash1)Organoclay















Cloisite 10A 338 087 4197



Organoclay with Na+

activation




Cloisite 10A 338 087 4197






CONCLUS IONS


ACKNOWLEDGEMENTS


REFERENCES




























































Thermal stability























ndash1)Organoclay















Cloisite 10A 338 087 4197



Organoclay with Na+

activation




Cloisite 10A 338 087 4197






CONCLUS IONS


ACKNOWLEDGEMENTS


REFERENCES









































































ndash1)Organoclay















Cloisite 10A 338 087 4197



Organoclay with Na+

activation




Cloisite 10A 338 087 4197






CONCLUS IONS


ACKNOWLEDGEMENTS


REFERENCES


































































Cloisite 10A 338 087 4197



Organoclay with Na+

activation




Cloisite 10A 338 087 4197






CONCLUS IONS


ACKNOWLEDGEMENTS


REFERENCES



























































CONCLUS IONS


ACKNOWLEDGEMENTS


REFERENCES
























































organophilization of a brazilian mg-montmorillonite

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