Download - Nanotechnology of Foam: Water Filtration

Nanotechnology of Foam: Water Filtration • July 2015

Nanotechnology of Foam: WaterFiltration

Shravan [email protected]

Kevin [email protected]

Michelle [email protected]

Shivani [email protected]

New Jersey Governor’s School of Engineering & Technology

I. Abstract

In an effort to develop an effective and cheapmethod of purifying water, experiments wereperformed to determine the possibility of utiliz-ing sol-gel products as water filtration devices.If sol-gel products were used as water filters, itwas theorized that they would be just as effec-tive as simple water filtration units at removingcontaminants from water. These materials werecompared to common filtering materials in termsof flow rate and extent the amount of contam-inants removed. Alone, different filter compo-nents did not filter contaminated water well buthad much faster flow rates when compared tomixed-media filters.

When combined, the filters work much bet-ter than they did alone. Also, they work bestwhen they are organized with fine materials atthe top and coarse materials at the bottom.Moreover, alum, a flocculent, purifies the fil-trate even further. Sol-gels and foams were alsotested as filters, as sol-gels are very porous andare very cheap to create. Unfortunately, neitherthe foams nor the gels that were tested seem tobe viable options for filtration systems becausethe foams were unable to allow contaminatedwater to flow through them.

II. Introduction

Seven hundred and fifty million people areforced to drink water contaminated by viruses,bacteria, and macrocontaminants every day.1 Incountries, especially developing countries, trou-

bled by drought and disease, there is a need fora cheap and efficient way to obtain clean waterfrom unsanitary sources without the use of elec-tricity, thermal energy, or other equipment thatis not readily available. Common filters such asthe Lifestraw R© and Lifesaver R© bottle are tooexpensive for large populations in developingcountries to benefit greatly from.2,3 It is neces-sary that a cheaper filter be made so that themajority of people can benefit.

Polluted water sources can include contam-inants such as bacteria, viruses, and other wa-terborne pathogens.4 Since all of these contam-inants vary in size and shape, many differenttypes of filter components are often combinedto effectively clean the waters. However, evencomprehensive and cheap filtration techniquescannot wholly purge water of small viruses andbacteria.5 Only a new, alternative filtrationmethod could filter out the smallest viruses andbacteria.

In theory, reducing the pore diameters offilters would limit the amount of contaminantsremaining in the water. Viruses are the smallestharmful contaminants; they have a minimumsize of 40 nm.6 The sol-gel process, dependingon the specific techniques used, can be a rela-tively inexpensive means of creating foams withpores as small as 2 nm in diameter.7 Watermolecules are only 2.75 Angstroms (0.275 nm)in length.8 This specificity is even more effec-tive than the leading commercial water filter,Lifestraw R©, which cannot filter the smallestviruses.9

1


III. Background

I. The Sol-Gel Process

Sol-gel, the abbreviated term for "solutiongel", describes a process used to create porousmaterials with novel properties such as super-hydrophobicity and high thermal insulation.9

This wide range of possibilites allows the prod-ucts of the sol-gel process to be applied in manydifferent fields of technology.

The sol-gel process involves the reaction ofa precursor, a chemical that contains many ele-ments of the future gel, with a liquid medium.11

When the two initially react, the molecules cre-ate a network suspended in liquid. After sometime, which varies depending on the procedureperformed, the molecules form an inorganic net-work and the substance turns into a gel. The gelbecomes a continuous, solid shell encapsulatinga liquid, formed by the entanglement of poly-mers within the sol. Finally, when the gel beginsto dry, the liquid contained inside evaporates,causing the substance to shrink and turn into afoam.

In particular, gels made of collodial silicawere used for this experiment. As they are gen-erally softer and more flexible than foams, theyare easier to create into filters. Moreover, thegels used in this experiment were porous and,therefore, could be used as potential water fil-ters.

II. Nanotechnology of Foam

Foams synthesized using the sol-gel processare extremely porous and lightweight.7 By usingthe precursor tetraethoxysilane (TEOS), porousfoams are created from the process. In this ex-periment, some of the foams tested for theirfiltration properties were not created using thetraditional precursor method. By replacing theTEOS with methyltriethoxysilane (MTES), thefabrication process is expedited and creates anaerogel.14 Aerogels in particular have very largesurface areas and very low densities because oftheir high porosity, with surface areas typicallyranging from 600-1000 nm.7 They also consistof 95% air and have pores ranging from 2-200

nm in size.10 One noteworthy feature of thismethod is that it makes superhydrophobic aero-gels without subsequent surface modification.14

Superhydrophobicity, literally "water fearing",refers to the ability of a substance to be ex-tremely hard to wet.

Because of its porous nature, an aerogelcan potentially serve as an effective water filter.When contaminated water flows through thefoam, contaminants are prevented from passingthrough, due to their relatively large size.

III. Mixed-Media Filters

Most filter setups tested in this project con-taining different materials can be classified as amixed-media filter. Mixed media filters consistof layers of various filtering materials, each withdifferent porosities, densities, and properties.When water flows through a mixed-media filter,each layer removes a certain amount of contami-nants, and the end result is a much cleaner watersample. These filters are effective at removingmacrocontaminants that are easily separatedfrom the water, but are ineffective at removingmicrocontaminants that are either dissolved inthe water or too small to be trapped by thepores. Mixed media filters were used in thisexperiment because many commercial filtrationsystems are mixed-media filters, in addition tothe fact that sol-gel products could easily beincorporated into the filtration system. How-ever, it is unclear as to the most efficient way toorganize the filter components within a mixed-media filter. Therefore, one component of ourexperiment involved testing the layout of thefilter components within mixed-media filters.

IV. Filtration Procedures

This experiment involved two major steps:testing the filtering properties of various materi-als, foams, and gels, and then comparing theireffectiveness.

2


I. Filtering Properties

I.1 Testing Sol-Gel Products

To test the filtration properties of aerogelsand gels, a number of tests were performed.First, the foams were placed into a plastic fun-nel with a tight seal so that water would notleak through the sides. Water was then droppedonto the foams with a pipette. Then, anotherapproach was taken to get more results. Thespout of a burette was inserted into the topof the foam, and then 1000 mL of water waspoured into the burette in an attempt to forcethe water through the foam.

When testing gels, plastic funnels were sealedat their narrow ends with layers of the silica gel.Three filters were constructed, with one, two,and five layers of gel. The plastic funnels werefilled with 10 mL of water and were placed ingraduated cylinders.

Fig 1: Setup of Silica Gel inserted into plasticfunnel

I.2 Testing Common Filtering Materi-als

The next part of the experiment involveddetermining the filtering properties of differentfiltering components. The different componentsincluded coffee filters, charcoal, ceramic beads,fine sand with .15 mm grains, and coarse sandwith .37 mm grains. The coffee filters served asthe control for this experiment and were placedinto a glass funnel. All the other componentswere placed into glass funnels along with thecoffee filters so that the fine particles would stay

elevated. The other filtering components weretested individually during separate runs, duringwhich 100 mL of different contaminant solutionswere poured through the filters.

The substances used as contaminants werecorn starch, dextrose, and plant protein. Thecontaminated water consisted of 5 mL of cornstarch in 95 mL of distilled water, 7.7 g of dex-trose in 90 mL of distilled water, and 5 mL ofplant protein in 95 mL of distilled water.

The filters were suspended by ring standsand extension clamps. 10 mL of each contam-inant solution were funneled through the vari-ous water filter components. Graduated cylin-ders were used to measure the amount of con-taminated water that passed through the filtercomponents. Lugol’s solution, Benedict’s solu-tion, and Biuret Reagent solution, which testfor starch, sugar, and protein, respectively, wereused as indicators to observe the quantities ofthe different contaminants remaining in the fil-trate. The equipment used with those methodsincluded test tubes, test tube stands, and a hotwater bath.

I.3 Constructing Mixed-Media Filters

Five different filters were created to researchthe filtration properties resulting from differentmixed-media patterns. The container of each fil-ter was an empty plastic water bottle suspendedupside down, with the bottom of the bottle cutoff. Filter Setup 1, as shown in Figure 2, con-tained 45 g of ceramic beads, 50 g of coarsesand, 50 g of fine sand, and 5 g of charcoal, inthat order, from the bottom to top of the filter.Filter Setup 2, as shown in Figure 3, containedthe same amounts of the same materials, but inthe reverse order, with ceramic beads at the topof the filter and carbon at the bottom.

3


Fig 2: Filter Setup 1 (from bottom to top):ceramic beads, coarse sand, fine sand, charcoal

Fig 3: Filter 2 (bottom to top): charcoal, finesand, course sand, ceramic beads

Filter Setup 3 contained 15 g of charcoal,150 g of fine sand, 150 g of coarse sand, 135 g ofceramic beads, and 150 g of gravel. This filtersetup was made in the same order as Filter Setup

2, with added gravel, but the quantity of eachmaterial was tripled. The amount of materialwas increased in order to give the filter a largersurface area for the solution to pass through.For Filter Setups 1 and 2, 50 mL of water weredripped onto the surface through a burette tosaturate the filter, and for Filter Setup 3, asshown in Figure 4, 200 mL were dripped ontothe surface through a larger burette, to saturatethe filter.

Fig 4: Filter Setup 3 (from bottom to top):charcoal, fine sand, course sand, ceramic beads,

gravel

Filter Setup 4 consisted of the same mate-rials and had the same order as Filter Setup 3,but without any charcoal in the setup. 200 mLof tea were dripped onto this setup as well. Thisfilter was constructed specifically to ascertainthe impact of carbon on the tea, and to deter-mine if any carbon was present in the filtrate ofthe other setups.

To further determine if the order of filters(pore diameter order) affected filtration, anotherfilter setup was constructed. Filter Setup 5, asshown in Figure 5, was constructed in the re-verse order of Filter Setup 3; from top to bottom,the setup consisted of 15 g of charcoal, 150 g of

4


fine sand, 150 g of coarse sand, 135 g of ceramicbeads, and 150 g of gravel.

Fig 5: Filter Setup 5 (from bottom to top):ceramic beads, coarse sand, fine sand, charcoal

I.4 Testing Mixed-Media Filters

In the first filter setup, the materials werearranged so that the filter component with thesmallest pore diameters was on the top, andthe filter component with the largest pore di-ameters was on the bottom. The other filtersetup was arranged so that the filter componentwith the largest pore diameters was on the top,and the filter component with the smallest porediameters was on the bottom. The reason fortesting two different orders was to ascertain themost accurate and efficient organization of filter-ing components. The charcoal was consideredto have very fine pore diameters, as the roundnuggets that compose charcoal have both mi-cropores of 1-3 nm and macropores of 3-10,000nm.15

A burette then dripped tea into each filterto test the filters’ abilities to separate the chem-ical components of tea, particularly tannic acid,from the water that the tea was made with.Tannic acid (C76H52O46) is a relatively largepolymer that mixes well with water but can

still be separated without a chemical process.16

Filter Setups 1 and 2 filtered 100 mL each oftea, while Filter Setup 3 filtered 200 mL of tea.Another setup, Filter Setup 4, was constructedat this point.

Both Filter Setups 3 and 5 were first sat-urated with 200 mL of water. Then, 200 mLof a Coca-ColaTM and PepsiTM mixture weredripped into each setup. The effectiveness of thefilters was determined by observing the color ofthe filtrates and the pH of the filtrates. Theseobservations were made to see if the filters re-moved phosphoric acid or Caramel E 150D, themain color of Coca-ColaTM and PepsiTM.17 ThepH of the soda mixture and the total time forfiltration were recorded, as well as the pH andcolor of the filtrate after passing through eachsetup.

Afterwards, alum, a coagulant, was added tothe other filtrates to see the difference in filtrate.1 g, 1.5 g, 2 g, and 2.5 g of alum each was addedto four different quantities of 8 mL of filtratefrom Filter Setup 3 in the test involving theCoca-ColaTM-PepsiTM mixture.

In order to test the filtration properties ofthe filters made, solutions containing differentcontaminants commonly found in unfiltered wa-ter were mixed together, and 200 mL were addedto each filter. The contaminants used were thesame as the ones used in the testing of commonfiltering materials. All water used was distilledwater. Food dye was added as a separate con-taminant, as were the Coca-ColaTM/PepsiTM

mix and tea.

II. Surfactant Hydrophilicity

One of the superhydrophobic aerogels wastreated with a solution of polyethylene glycoland titanium dioxide. First, a brush was used tospread a fine layer of the solution on the top ofthe aerogel. In the end the foam was set uprightand drops of the TiO2-PEG solution were addedonto the surface to be absorbed over a 24 hourperiod. Titanium dioxide is hydrophilic, so itwas placed on top of the gel to see if it wouldaid in water absorption.

5


V. Results


I.1 Testing Sol-Gel Products

When water was first dripped onto the aero-gels with a pipette, the water did not passthrough the aerogels.

Moreover, when a significant amount of forcewas applied to the aerogel, water was not ableto flow through.

Similarly, the gels absorbed a very minimalamount of water. The filter with 1 layer of gelseemed to allow 10mL of water to pass throughin 10 minutes, but then a crack in the seal wasdiscovered and the data had to be discounted.The filter with 2 layers of gel allowed 2mL ofwater to pass through in about 5 days, and thefilter with 5 layers of gel did not let any waterflow through.

I.2 Testing Common Filtering Materi-als

None of the filters completely prevented thestarch and sugar contaminants from passingthrough the filtrate. The protein contaminantwas not present in any of the filtrates accordingto the lack of change in the biuret reagent; how-ever, the biuret reagent solution may not haveworked properly. The results for the varioussolutions to filter through a filter component islisted in Table 1 for starch, Table 2 for dextrose,and Table 3 for protein.

Table 1 - StarchFilter Component Contaminant

present?Coffee Filter YesCeramic Beads YesFine Sand YesCoarse Sand InconclusiveCharcoal Yes (but less reagent

change)Table 2 - Dextrose

Filter Component Contaminantpresent?

Coffee Filter YesCeramic Beads YesFine Sand Yes*Course Sand Yes*Charcoal Yes

*Note: Indicator turned from orange to greenover time (more to less contaminant), but con-taminant still presentTable 3 - ProteinFilter Component Contaminant

present?**Coffee Filter InconclusiveCeramic Beads InconclusiveFine Sand InconclusiveCourse Sand InconclusiveCharcoal Inconclusive

**Note: Protein indicator did not show presenceof protein in any sample, including test of 50%water 50% protein, so indicator is suspected tobe expired or defective

I.3 Testing Mixed-Media Filters

Filter Setup 3 filtered about 66 mL of teaand Filter Setup 5 filtered about 82 mL of tea,as shown in Figure 6. Filter 1 was able to filterthe tea in sixteen minutes and sixteen seconds,whereas the amount of time Filter 5 took to filterthe tea was not recorded because the flow ratewas not consistent and therefore not accurate.

Fig 6: Filtrate obtained from filter 5

Filter Setup 3 was able to filter the mixtureof Coca-ColaTM and PepsiTM, and changed thepH of the mixture from 2.5 to 5. The mixture

6


appeared to be a slightly paler color of the orig-inal mixture. Filter Setup 5 was able to changethe mixture’s pH from 2.5 to 5 as well. The colorof the mixture after passing through the filterwas a pale, almost white, liquid. The filtratefrom Setup 5 was much paler and overall lighter.Both filters were able to filter the mixture inabout the same amount of time – fifty minutes.

When alum was used to clear the murkyfiltrate from the bottle filters, a clear, honey-colored solution, shown in Figure 8, was ob-tained that contrasted strongly with the previ-ous opaque appearance, shown in Figure 6. Thefiltrate was much lighter and clearer, as the finerparticles present earlier were no longer in thefiltrate.

Fig 7: Filtrate after alum added

Fig 8: Filtrate after alum removed with coffeefilter

II. Surfactant Hydrophilicity

The titanium dioxide based coating wasnever fully absorbed by the foam because of thehydrophobic nature of the foam. The coatingremained on top of the foam, and when waterwas dropped onto the surface of the foam, thewater was repelled and formed smaller beads.

VI. Discussion/Analysis


From the results, it appears that the con-taminated water took longer to flow throughsubstances with small pore diameters and flowedfaster through substances with large pores.Moreover, the contaminants were still present inmost of the filtrate. In the case of protein, thetests were inconclusive. This suggests that thefilter components by themselves did not removedifferent contaminants. In addition, the proteinindicator did not show presence of protein inany sample, including in a test of 50% waterand 50% protein, so the indicator was suspectedto be expired or defective.

7


II. Reorganization of Different Filters

Removing carbon from a filtration systemhinders its filtration properties. When compar-ing Filter Setup 3 to Filter Setup 4, the filtratefrom Filter 4 was much murkier than the filtratefrom Filter 3. Often in the form of charcoal, car-bon is useful in filtering organic material, suchas protists and many microorganisms. In addi-tion, it has a high functional surface area (largearea of filtering substance exposed to substance),which is useful as contaminants are more likelyto become trapped. One of the negatives ofcarbon is that the carbon is a likely breedingground for bacteria, as its moist and dark natureis ideal for bacteria growth. Therefore, carbonfilters need to be disinfected after multiple uses,which is one negative concerning their overallusefulness.18

When comparing Filter Setup 1 and FilterSetup 2, it appears that Filter 1 was able toremove more particles than Filter 2 becauseFilter 1 had less filtrate than Filter 2. Thissuggests that more particles and contaminatedwater were trapped within the filter itself. More-over, when comparing Filter Setup 3 and FilterSetup 5, Filter Setup 5 appeared to removemore particles than Filter Setup 3 because therewas less dye in the filtrate of Filter 5 and sinceFilter 5 seemed to have less filtrate; however,the results may have been skewed due to thepresence of runoff water already present in thefilter. Therefore, the most efficient arrangementof filter components is from fine to coarse.

Because of faulty burette adjustment equip-ment, it was difficult to maintain a steady flowof droplets from the contaminant solution inthe burette to the top of the filter, so this mayhave changed the results, as the rate of addingcontaminant varied per test.

Using alum as a coagulant for fine particlesleft over in the filtered solutions proved to bevery effective at filtering even more contami-nants from the original simulated contaminantmixture. Alum works by attracting fine particlesand grouping them together, eventually gettingthe groups to a size that can be trapped byfilters.22 In this case, the alum coagulated fine

particles in tea and soda, and the groups werelarge enough to be removed by coffee filters.

III. Cost Analysis of Filters

The cost of each filtering component affectsthe overall price of the filter. Sand of vari-ous sizes can cost about $4.15 for forty-eightpounds.26 250 coffee filter papers cost $7.49.25

Gravel costs $4.77 for sixty pounds.30 Carbonpowder costs $10 for 6 oz.29 Four hundred andfifty grams of ceramic beads cost $9.95.21 Com-pared to filters such as the Lifestraw R©, thefilters made during the experiment were muchcheaper. While the Lifestraw R© costs $31.95,Filter Setups 1 and 2 cost $1.34, Filter Setups3 and 5 cost $3.98, Filter Setup 4 cost $3.09 tomake.23 Also, the alum adds $.04 to the filters’costs. One pound of alum costs is $9.47. More-over, the silica foams cost $.96 to make. 18 Lcolloidal silica cost $346.28 The silica aerogelscost about $1.50 to make since the TitaniumDioxide costs $27 for one pound.24

Filters 1 and 2 (Thin material layers)

(45g ∗ $9.95/450g) + (50g ∗ $4.15/21772.4g)+ (50g ∗ $4.15/21772.4g) + (5g ∗ $10/170.097g)

+ (1count ∗ $7.49/250count) = $1.334 (1)

Filters 3 and 5 (Thick material layers)

(15g∗$10/170.097g)+(150g∗$4.15/21772.4g)+(150g ∗$4.15/21772.4g)+(135g ∗$9.95/450g)+ (1count ∗ $7.49/250count) = $3.98026 (2)

Filter 4 (No charcoal)

(150g∗$4.15/21772.4g)+(150g∗$4.15/21772.4g)+(135g ∗$9.95/450g)+(135g ∗$4.77/27215.5g)

+ (1count ∗ $7.49/250count) = $3.098 (3)

IV. Surfactant Hydrophilicity

Without added chemicals or pressure, thesurfactant coating was not absorbed by the foamand had no impact on the hydrophobic nature

8


of the foam. This coating is not a viable so-lution without added chemicals that would en-sure the absorption of the coating by the foam.With the addition of ethanol or another alcohol,which foam is attracted to, the foam may haveabsorbed the solution, but without any otherchemicals added, the foam’s hydrophobic na-ture would simply prevent the titanium dioxidesolution from being absorbed.

VII. Conclusion

I. The Sol-Gel Method

Although the sol-gel method is useful inquickly producing foams with nanoscale pores,the foams used were ineffective as water filtersdue to their superhydrophobicity. The foamsdid not absorb any water, even when the wa-ter pressure was increased to 1 L. In addition,since the aerogels were very brittle, passing wa-ter through them at high pressures could causethem to crumble and recontaminate the filtrate.Without significant modifications to the foams,they are unable to be used as water filters.

II. Future Research

With limited time and resources, the sol-gelproducts could not be chemically transformedinto more viable filters. However, many possibledirections can be taken in the future concerninghydrophobic aerogels and water filtration.

Coating the hydrophobic aerogel could becoated with a more hydrophilic substance. Ahydrophilic solution of TiO2, PEG, and otheralcohols could be applied to both ends of theaerogel.18 This would mimic the phospholipidbilayer in biological cells and could increase theefficiency and flow rate of the aerogels used. Thehydrophilic coating would draw water into thefilter, while the hydrophobic part would filterthe water to a large degree due to its small porediameter. Finally, the water would be able toexit the aerogel via the hydrophilic coating onthe other side of the foam. Through this method,the pore diameters would be efficiently utilized,and the hydrophilic additions could help trans-

port water across the filter at a faster rate. Thismay improve the filtration properties of sol-gels.

The hydrophilic coating could also be madeslightly basic in order to increase the pH ofthe water being filtered. This would render thefilter helpful in regions of the world that areinfamous for pollution, as contamination tendsto make water slightly more acidic.20 Adding ahydrophilic and basic coating to aerogel filterswould neutralize the water acidity of pollutedwater to a degree safe for consumption. Thismodification would also be useful in hydroponicsand irrigation systems to channel clean water tofresh produce, as plants are very susceptible tochanges in water pH as well.20

Future experiments could also attempt heat-ing up the aerogels to a maximum temperatureof 450 Centigrade, which would increase thepore diameter of the aerogel. This could leadto potential water absorption despite the foam’ssuperhydrophobicity.31

In addition, one could experiment to see thebest placement of foams within a conglomera-tion of filter components. Sol-gel foams couldpotentially become the final processing unit in acollection of other cheap filters with large porediameter. The foams are very brittle; exposingthem to large contaminants could damage them.Thus, if the foams were to be used in commer-cial water filters, they would need to be used inconjunction with other filtering components.

Finally, in an effort to create filters thatcan aid many people in developing nations ata time, perhaps one could design a quick, largescale water filtration system containing silicaaerogels. This could be attained by engineeringcheap, commercial processes for aerogel produc-tion. Moreover, this can be achieved by alteringthe chemical makeup of the foams and sol-gelproduction techniques. For example, althoughwe added a solution of titanium dioxide andPEG to our solution, we could have added analcohol such as ethanol to allow the solution toabsorb into the foam. However, since adding anethanol coating to the foam could contaminatefuture filtrates, alternatives to alcohol wouldhave to be researched.

9


VIII. Acknowledgements

The authors would like to thank Dr. LisaKlein for guiding and mentoring them, allowingthem to use her facilities, and for making muchof this work possible. They would also like tothank Elizabeth McGinley for giving them guid-ance and for overseeing this research opportunity.Finally, they would like to thank Program Di-rector Dr. Ilene Rosen, Associate Director DeanJean Patrick Antoine, the New Jersey Gover-nor’s School of Engineering & Technology, andRutgers University for creating the opportunityfor them to explore their interests in engineeringand nanotechnology through scientific researchand the potential real world application of theirfindings.

They would also like to thank the sponsorsof the NJ Governor’s School of Engineering andTechnology: Silverline Windows, Lockheed Mar-tin, South Jersey Industries, Inc., Novo NordiskPharmaceuticals, Inc. and NJ Resources, andthe Rutgers School of Engineering.

References

[1] World Health Organization Progress on Drink-ing Water and Sanitation: 2014 Update.Geneva, Switzerland: World Health Orga-nization and UNICEF, 2014. Web. 18 July2015.

[2] Barksdale, Martha, and Kate Kershner. ‘Lifes-traw Distribution - How Lifestraw Works’.HowStuffWorks. N.p., 2015. Web. 18 July2015.

[3] HydrateLife,. ‘Lifesaver Bottle’. N.p., 2012.Web. 18 July 2015.

[4] People.uwec.edu,. ‘Common Water PollutionSources’. Web. 18 July 2015.

[5] Filtration Facts. Environmental ProtectionAgency, 2005. Web. 18 July 2015.

[6] GE Power & Water: Water & Process Tech-nologies. 1st ed. General Electric Company,2013. Web. 18 July 2015.

[7] Energy.lbl.gov,. ‘Surface Chemistry : SilicaAerogels’. Web. 18 July 2015.

[8] Walters, Adam. ‘A Performance Evaluation OfThe Lifestraw: A Personal Point Of UseWater Purifier For The Developing World’.University of North Carolina at Chapel Hill,2008. Print.

[9] NASA,. ‘Aerogels: Thinner, Lighter, Stronger’.N.p., 2011. Web. 18 July 2015.

[10] Klein, Lisa C. ‘Advanced Fabrication: Sol-GelProcessing’. 2015. Presentation.

[11] Cai, Jenny et al. Utilizing Porous MaterialsFor Oil Spill Cleanup. 2010.

[12] Gollakota, Kiran et al. Nanoengineering OfSol-Gel Materials For Thermal Insulation.2008.

[13] Freedman, Max. ‘Rapid Aerogels’. 2015. Pre-sentation.

[14] Juhola, A. J., and Edwin O. Wiig. ‘Pore Struc-ture In Activated Charcoal. I. Determina-tion Of Micro Pore Size Distribution’. J.Am. Chem. Soc. 71.6 (1949): 2069-2077.Web. 19 July 2015.

[15] Pubchem.ncbi.nlm.nih.gov,. ‘Tannic Acid:Chemical and Physical Properties’. N.p.,2007. Web. 18 July 2015.

[16] What Is In Coca-Cola? A Briefing On OurIngredients. The Coca-Cola Company, 2011.Web. 18 July 2015.

[17] Water Treatment Implementation For Develop-ing Countries. Center for Affordable Waterand Sanitation Technology, 2015. Web. 18July 2015.

[18] Aegerter, Michel, and Martin Mennig. ‘CoatingAnd Material Properties’. Sol-Gel Technolo-gies For Glass Producers And Users. 1st ed.Kluwer Academic Publishers, 2004. Print.

[19] Epa.gov,. ‘Effects Of Acid Rain - HumanHealth’. N.p., 2012. Web. 18 July 2015.

10


[20] http://www.amazon.com/Ceramic-Seed-Beads-Black-Grams/dp/B00J0JJFP8/ref=sr_1_15?ie=UTF8&qid=1437249962&sr=8-15&keywords=ceramic+beads (18 July 2015)

[21] Water.me.vccs.edu,. ‘Coagulation’. N.p., 2015.Web. 21 July 2015.

[22] http://www.amazon.com/LifeStraw-Bottle-Integrated-1000-Liter-Filter/dp/B00H90PFOK (18 July 2015)

[23] http://www.amazon.com/Titanium-Dioxide-Powder-1-Lb/dp/B004W0EQB8/ref=pd_sim_364_71?ie=UTF8&refRID=05FJHWXCDJG6VV1MY26V (18July 2015)

[24] http://www.walmart.com/ip/Bunn-Flat-Bottom-Commercial-Coffee-Filters-250ct/15686242 (18 July 2015)

[25] http://www.homedepot.com/p/Unbranded-48-lb-Leveling-Sand-98000/10034338. (18July 2015)

[26] http://www.amazon.com/Barry-Farm-Alum-1-lb/dp/B00016Q6BK (18 July 2015)

[27] http://www.sigmaaldrich.com/catalog/product/aldrich/420840?lang=en&region=US (18 July 2015)

[28] http://www.dickblick.com/products/generals-powdered-charcoal/ (18 July 2015)

[29] http://www.homedepot.com/p/SAKRETE-All-Purpose-60-lb-Gravel-40200302/100350267 (18 July 2015)

[30] Shi, Fei et al. ‘Effect Of Heat Treatment On Sil-ica Aerogels Prepared Via Ambient Drying’.Journal of Materials Science and Technol-ogy 23.3 (2007): 402-6. Web. 21 July 2015.

[31] Uic.edu,. N.p., 2015. Web. 21 July 2015.

11

http://www.amazon.com/Ceramic-Seed-Beads-Black-Grams/dp/B00J0JJFP8/ref=sr_1_15?ie=UTF8&qid=1437249962&sr=8-15&keywords=ceramic+beads





http://www.amazon.com/Titanium-Dioxide-Powder-1-Lb/dp/B004W0EQB8/ref=pd_sim_364_71?ie=UTF8&refRID=05FJHWXCDJG6VV1MY26V




http://www.sigmaaldrich.com/catalog/product/aldrich/420840?lang=en&region=US



Download - Nanotechnology of Foam: Water Filtration

Top Related