The Trend in Non-emulsion Aqueou

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Law-EmulsivityDetergents or RecyclingandCanservatian, utsa NewSpinon an OldProblembyBlaine .Severin, h.D.,Stephen akiamoh,h'D'.andJanetteMoore

a te r m in im iza t i on ands u r f a c t a n t r e c Y c l e a r etwo of the most imPortant issuesfacing ef f ic ient use of aqueouscleaning technologies. And that'swhy present philosoPhies basedon strong emulsion-forming sur-factants are being re-examined.De te rgen t fo rmu la t i ons tha tform transient emulsions (low-emulsion detergents) can havevery favorable cleaning potential.Several low-emulsivity surfactantsremove oil from sand, glass, andaluminum as efficiently as strongemulsion forming detergents. Thecase for the use of low emulsiondetergents to accomPlish waterrecycle, surfactant recoverY, andreclamation of high PuritY wasteoil is presented in this article'The concePt that the formation'of strong oil-water emulsions arerequired for cleaning solid matri-ceJ is deeply engrained in theenvironmental remediat ion, o i lwell recovery, and Parts cleaningmarkets. Technical reviews otenvironmental surfactant use area v a i l a b l e ( L a k e , L . W . , ' l ' 9 8 9 ,EnhnncedOi l RecoaerY, rent iceHall, Inc., Englewood Cliffs, N.].,Chapter 9, pP 354-476) . AndKanegsberg, 8., and Kanegsberg,8. , 2002, Aqueous Account ing,CleanTech, Yol. 2, No' 6, June,pp . 20 -25 P resen t a rev iew o fm a i n t e n a n c e a n d c o s t i s s u e si n v o l v e d i n t h e a d a P t a t i o n o f

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aqueous cleaning systems.O u r l a b o r a t o r Y a t t h eMichigan Biotechnology Institute(Lansing, MI) , a not- for-Prof i tresearch center, began investigat-ing environmental surfactants forsoil remediation about two Yearsago. With this fresh vision of thes u r f a c t a n t m a r k e t , w e w e r eimpressed that some cleaningsolut ions have excel lent deter-gency, yet exhibit extremelY lowemulsivity.Oi ly compounds aPPear to bereiected from the waterborne sur-factant solution, in other wordstransient emulsions rapidly revertto re lat ively clear Phases' Thissolves two major drawbacks tosoil cleaning, first, the minimiza-t ion of contaminated water Pro-duction and second, the reuse ofsurfactant by recycling the recov-ered water phase.This ar t ic le reviews some otthe properties of transient emul-s i o n f o r m i n g d e t e r g e n t s a n drelates th is informat ion to thepotential for parts cleaning'The Right SurfactantSurfactants work bY lowering thesurface tension between Phases.Surfactants that are strong emul-sif iers lower the surface tensionbetween liquid phases, encourag-ing the formation of oil in watermicelles (Windsor TYPe I), waterin oil micelles (Windsor TYPe II),

or both (Lake 1989). Much of thetechnical literature on environ-mental and oi l recovery sur fac-tant use focuses on detergentsthat form these classes of strongemulsions.Many recommend the additiono f c o - s o l v e n t s , s u c h a s i s o -propanol or butanol to form verYitr.r.g three-phase or middle-phase emulsions (Windsor TYPeIII). These surfactants are gooddetergents because theY cause_water to hold large volumes ofoil in thermodYnamicallY stableemulsions. Unfor tunatelY, theemulsions are difficult to break,creating a large volume of waste-water that is di f f icu l t to t reat .Since most municiPal wastewatertreatment Plants are sensitive tomore than about 10 PPm surfac-tan t l oad , d i r ec t d i scha rge o findus t r i a l was tewa te r ,heavY noil and surfactant, is discouraged.D isposa l o f emu ls ions can beverv costlv.The us-e of strong emulsion-forming surfactants is well estab-l i s h e d i n t h e P a r t s c l e a n i n gbusiness.However, some equiP-ment manufacturers are beginningto promote transient emulsiontechnology for imProved wateru s e , l o w e r s u r f a c t a n t c o s t s ,extended bath l i fe, and lowerwaste disposal costs. Figure 1 isan example of how continuousoil separation and solids mainte-

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nance is env i s ioned (A daP tedf r o m A q u e o u s R e c o v e r YResources, Inc. , Bedford Hi l ls ,NY). Other washer sty les mayalso be adapted for non-emulsionaqueous claning. Three controlloops are recommended. (1) nor-ma1 c leanse r ma in tenance , (2 )solids filtration, and (3) high-effi-ciency oil/water skimmer to keepthe surfactant in i ts most effec-t ive phase composition. In orderfor this technology to work, how-ever, the proper surfactant mustbe selected.Oil HoldingCapacityThe following test demonstratesthe principle that different deter-gents have different oi l holdingcapacity. In this test, solutions ofsurfactant were prepared in 25ml v ia ls. Oi l was added drop-w i s e ( S A E 3 0 n o n - d e t e r g e n tmotor o i l ) and the via ls weregently hand shaken. The shakingcreated transient emulsions. Whenthe shak ing s topped , the o i lwould be either relatively stablein emulsion form, or the emul-sions would begin to break with-i n a f e w s e c o n d s ( t r a n s i e n temulsions).The point at which the surfac-tant solution became thermodY-n a m i c a l l y u n s t a b l e w a s a ni n d i c a t i o n o f t h e b r e a k p o i n tbetween kinematically and ther-modynamically stable emulsions,or an estimate of the oil carryingcapacity of the surfactant.Figure 2 compares the oil car-r y ing capac i t y o l Dawn d ishs o a p , P a l m o l i v e d i s h s o a p ,A lconox (common labo ra to r yglassware detergent) and RhemaSuper Matrix (commercially avail-a b l e i n d u s t r i a l c l e a n s e r ) .Palmolive and Dawn are excellentdetergents, with excellent oil sol-ubility.Alconox and Rhema are excel-lent detergents with extremelylow oi l so lubi l i ty . The mecha-nisms by which detergency (abili-ty to remove dirt or oil from asolid surface) is achieved are dif-ferent. Palmolive and Dawn ar eoil solubilizers, whereas, Alconoxand Rhema are oil mobilizers.Surfactant EvaluationFive surfactants were evaluated

i n t h i s s t u d y , R h e m a S u p e rMatrix, Witconol, Triton, SLS, andDowfax. These are evaluated interms of which surfactant givesthe best results based on the fol-lowing criteria:. Detergency or good oil removalfrom selected solid media Purity of recovered oil. Possibility of being recycled

R h e m a S u p e r M a t r x ( R h e m aProducts, Inc., Dearborne Heights,MI) is a L0 percent sur factantblend in watei. When mixed withoi l , Rhema forms a relat ivelysmall and unstable emulsion thatreadily breaks up, leaving only asmall amount of oil in the sur-f ac tan t so lu t i on . Rhema is ablend of several surfactants in analkaline builder and is manufac-

Technologyppliedby Charlie impsonFor everalundredanufacturerseveragingon- r ow-emulsifyingetergentss atrend hoseimehasnotonly gme, uthasbeen ereorsomeime. or xample,accgrdingo Scott oodsell,residentfRacinelatingRacine,is.)hemgve0n6n-emulsifyingetergentstartedn 1999 fter eengt inoperationt a rade how.t hattimeRacineasexploringembraneiltration,oalescingiltration,nddisc ndbeltskmmers.We ad o inda systemhatwaseasyo maintain,ould xtendhe ifeofthecleanersnd eepheentire latingine leanerin other grds,il-free,ecallsGoodsell.acineelectednon-emulsifyingpproachhat mployssplittingleanerhatcan eused n errousnd on-ferrousetals,long ith kimmingecoveryechnglggyto reclaimil rom tswash ater.Todayacine,hich as kimmingecgverynits n hree f tsplatingines nd lansto addwomore,s recgveringbouthreeo ivedrums er ear f oil hatsburnedorfuel. ccordingoGoodsell,skimmingheoilhas xtendedhe leanerife y wo0 hreetimes,hus uttingur oak leanerxpenset east 0percenter ear'ForGoodsell,n additiono theobviousleaneravings,owmaintenanceverheadmakeshe ystemdeal.Theresveryittle pkeeprmaintenancen heunit. he umpis heonlymgvingart. he nly leaningequiredccasignallys odraint and osehesludgeut f hebottom. herere o ilter artridgesrmembranesoclean.oodsellexplainshat esideseducingleanerostsrhis ystemeepsheentireineree foi lbecauseheresnooil o drag ownhe ine.This lso avesnoneyecauseedonothaveo dumpurgtherhemistriessgften sweusedo, t alsoeducesewgrk ue0poor leaning.The lating rgcesssusednbothack nd arrellatingpplicatigns.Parts re irstrun hroughhesoak leaner,henheelectroleaner,hen otacld nd hen lated.Goodsellescribesheprocesssbeing xtremelyfficientithover 9percentf efflu-ent eingil.Most therystemsan emovesmuchleaners hey ooil. his pproachkeepsllof he omponentsn he leanersudactanhtcetera,nd ot n hewaste il.The etergentsedsE-Kleenrom lectrochemicalroductsnc.EPl,ew erlin, is').Goodselleeshisapproachsa trend ecauset extendshecleanerife,which avesmoney,ltimatelyeepinghe ine leaner,educingejectsueodi pafts.Maria ios re-TreatmentrocessanagertElectroluxome roductsroupivisionFrigidaireEdison,J)agrees ithGoodsell.hehasbeen sing low-emulsifyingapproachinceSeptember000.Prior o that t wasa thermal il/watereparationprocess.lectrolux'shemicalupplieralcoformerlyalgon)ntroducedioso hisech-nology.i0s lso xploredoalescer-typeilseparators.Rios'roup onitorshe ischargeo hePOTWnce ermonthnds ecovering/recy-cling pproximately00 allgnsfol er ay, ith savingsfdisposalgstsfoilywaterin2001 f $11,000.Alsoodayhedischargeo sanitaryewermeetsotal etroleumydrocarbonsermitlimit.Wewere bleo cleanwiceheamountfparts ithgutavngo e-engineerheentrerocess,bservesios. lectroluxome roductsroupunentlyses causticcleanerithsuactant dditiveromNalco hemicalompany.ikeGoodsellios itesowpreventativeaintenancesa benefit,swellaShe actthat oheatS equiredooper-ate hesystem,ndt seasyoclean.he nlyssue iosaced as etting eir eights;however,he epoftshat onceheheightsf heweirs re et, hesystemuns eauti-fully.

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t u red as a 10 Dercen t so l i dssolution (as delivred). Our testsshow that the product is 7.9 per-cent non-volat i le solids in a 24hour dehydration test at 105 C.Doro fax 2A -1 (Dow Chemica lCompany, Midland, MI) is a yel-lowish liquid that is completelyso lub le in wa te r . I t f o rms anunstable emulsion that readi lybreaks up to give a clear surfac-

tan t so lu t i on w i t h pocke ts o fglobular oil. The composition as-de l i ve red i s 47 pe rcen t ben -z ene,L,1 oxyb s, e r ap op yl enesulfonate sodium salt and 1 per-cent sodium sulfate in water. -Ourtests confirm that the oroduct is44.4 percent non-volatil solids ina 24 hour dehydrat ion test at105' C.W i t c o n o l S N - 9 0 ( C r o m p t o n

Corporation, Greenwich, CT) is aviscous whitish suspension that isreadi ly soluble in water up toabout 20 percent. Higher concen-t r a t i ons f o rm wa te r ge ls . I tforms very stable emulsions inthe presence of oil that are diffi-cul t to break. I t solubi l izes o i lr e s u l t i n g i n r e l a t i v e l y l a r g eamounts of o i l in the aqueousphase . Wi t cono l i s a non - ion i csurfactant with a chemical com-position of 100 percent C10-C14ethoxylated alcohols. The productis 90 percent non-volatile solidsin a 24 hour dehydration test at105' C.Triton (Sigma Aldrich, Company, St.Louis, MO) is a colorless liquid,has good solubility in water upto about 20 percent in solution.Higher concentrations in waterare achievable with difficulty. Ahigher concentration of surfactantin water form viscous gels andgranular solids that are unsuit-able for solution chemistry. In thepresence of o i l , Tr i ton forms astable o le ic emulsion and dis-solves oil into the water phase.R e l a t i v e l y a r g e a m o u n t s o f o i la re obse rved in the aqueousphase. Tr i ton is a non- ionic sur-?actant with the chemical compo-s i t i o n , p - t e r t i a r y - o c t y l o x y ,polyethyl a lcohol . The productcontains more than 99 r :ercentnon -vo la t i l eso l i ds in a 24 hou rdehydrat ion est at 105 C.S o d i u n L a u r y l S u l f a t e S L S ) o rsodium dodecyl sul fate (FisherScient i f ic , Fair Lawn, NI) is awhite powder thai is readily so1-uble in water up to 25 percentbut has extremely low solubilitythereafter. It for ms an unstableemulsion in water but solubilizeso i l t o a l a r g e e x t e n t i n t o c l e a rwaterborne micel les. SLS is ananionic surfactant. Our tests showthat the delivered product is 87.4pe rcen t non -vo la t i l e so l i ds asmeasured n a 24 hour dehydra- 'tion test at 105' C.Rapid Oil Detection MethodTo rapidly determine the recoveryof oi l from test surfaces, SudanIV (Fisher Scientific,) was used todye the test oil. Sudan IV prefer-e n t i a l l v d i s s o l v e s i n o i l a n digure 2: Single phase emulsion carrying capacity of some commondetergents.

SoakTank

Sol ids i l ter oop

Solidso WasteThin-Fi lm i l

LeverFollowingWeir

Figure 1: Dual circuit, oil, and solids management concept.

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Mass Fraction Detergent in Total EmulsionSuperMatr ix neatsolut ion,RhemaProducts,nc., armingtonHil ls,Ml )Alconox (10% n water,Alconox, nc.,New York,NY)PalmoliveUltra (neatsolution,Colgate PalmoliveCompany,New Yor[ NY)Dawn Lemon Scent

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remains an insoluble Powder inwater. The dye is intenselY red,as seen in the standard series ofdyed SAE 30 motor oil dissolvedin hexane (Figure 3) . The redcolor may be quantified against avisual standard, or may be quan-tified with a spectroPhotometer.We used the Sudan dye con-cept to quantify an extraction testsuitable for rapid analYsis of oi lr e c o v e r y f r o m t e s t s a m P l e s .Figure 3 shows that the red dYegives a strong visual resPonsebYwh ich dyed o i l can be eas i lYtraced. The test may be used toquant i fv the o i l in the waterphut , r the oil phase maY becollected and the oil quantifiedby extracting the dye from th eemulsion into hexane and ace-tone.All the detergents tested haveslightly different phase distribu-tions. Figure 4 shows a series ofphase via ls contain ing 10g oi l

and 10g of 10 percent surfactantfor each of the test surfactants.The surfactants are placed left toright (Dowfax, Rhema, Witconol,Tr i ton, and SLS) based on thepurity of the oil phase and thepurity of the water phase. OnlYDowfax and Rhema can be con-sidered to be good phase sPlit-t ing detergents (left). Note thes t r o n g e m u l s i o n s f o r m e d b YWi t cono l and T r i t on and thelarge amount of oil present (redcolor) in the water phase of theSLS sample (right).Phase diagrams may be readilYconstructed with these methods,a s s e e n i n F i g u r e s 5 a n d 6 .Phase diagrams are presented inthe tota l mass fract ion format,with the surfactant reported asdelivered by the manufacturer.A s seen in t hese f i gu res , t hea t t r i bu tes o f s tab le emu ls ion -forming and transient-emulsionforming detergents are readi lY

Figure 3: Example standardbility series for rapid visualization of oil solu-

Figure 4: Examples of phase spl i t t ing of var ious sur factants -Dowflax, Rhema, Witconol Triton' and SLS. Circle l0 or request info instantly atwww.leanTechCentralomJanuary 2003 www.cleantechcentral.com


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0.0 1.0

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 .1.0Water

distinguished.Figure 5 is a d iagram for astandard detergent, sodium lau-ryl (dodecyl) sulfate (SLS). Th eregion of the plot that lies abovethe curve, and below about 35percent mass fraction SLS (nearthe l imi ts of solubi l i ty) repre-sents one phase behavior . Theregion below the curve repre-sents two phase behavior. Threeexample test vials (A, B and C)are presented to give a visualiza-t ion of the phase diagram con-struction. The diagram shows theassociated operat ional t ie- l inesfor the three sample examples.

Figure 5: Phase diagram forwith 5 g oil, 15 g surfactant

The vials contain 5 g oil, 15 gsurfactant solution at concentra-tions A = 5 percent, B = 10 per-c e n t , a n d C = 2 5 p e r c e n t i nwater. Note that the water phaseis red, an indication of the pres-ence of oil in the water nhase.The tie-lines indicate that ihe oilphase contains a large mass frac-t i on o f wa te r and the wa te rphase contains a large mass frac-t i o n o f o i l . B o t h p h a s e s a r ethe re fo re cons ide red to be tood i f f i c u l t t o t r e a t f o r s i m p l erecovery and reuse.Figure 6 is the phase diagramfor Rhema Super Matrix deter-

gent formulation. The phase dia-gram is distinctly different thanfor SLS. The location of the tie-l i n e s i n d i c a t e s l o w - e m u l s i o nforming behavior. The two-phaseregion is extremely large. Theone phase region incorporatesthe lower lef t corner and theright hand axis of the diagram.Note that the percent of waterin the oil phase is initially low,and becomes a constant 20 per-c e n t o f t h e o l e i c m a s s a s t h ec o n c e n t r a t i o n o f s u r f a c t a n tincreases. The amount of oil inthe water is consistently less than5 percent tota l mass. Observethat the water layer in the exam-ple phase test vials is light pinkcompared to SLS (Figure 5). Thetie-lines that represent the split ofthe component mass between thetwo phases, A, B, and C indicatethat the water phase and the oilphase are very pure and relative-ly free of the other components.Oil Removal:SingleVolume ExtractionTo determine the ability of thedetergents to remove oi l f romsurfaces, we performed a singleextraction test of oil from whiteOttawa play sand. Samples ofsand (10 g) were dosed with 19dyed oil, then contacted with 20ml of detergent (2.5 percent solu-t ion in water). The slurry washand shaken for 5 minutes thenthe l i qu id was removed andextracted with hexane and ace-tone to recover the dye. See theremoval efficiency data for thevarious surfactants in Table L.S L S , R h e m a , T r i t o n , a n dW i t c o n o l a l l g i v e r e m o v a l sexceeding 90 percent. There is nosigni f icant di f ference in theseresu l t s . Howeve r , Dowfax i sat t racted to the sand part ic lesand removes only aboui 64 per-cent of the oil from sand. Thedifference between Dowfax andthe other detergents is significant.Rhema would be the super iorproduct becauseof i ts h igh ef f i -c iency of o i l removal coupledwith its positive oil-splitting char-acteristics.Oil Removal: assiveCleaningTo test the wetting ability of thesurfactants on various solids, a

SLS Detergent. Test vials are preparedsolution. A=5o/ , B=70 A, C=25 / .

Sufactant

one Phase o'8

Figure 6: Phase diagram for Rhema Super Matrix and SAE 30 motoroil. Test vials are prepared with 5 g oil, 15 g surfactant solution inwater. A=5 / , B=10Y , C=25 A.22 fanuary 2003 www.cleantechcentral.com


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p a s s i v e c l e a n i n g t e s t w a sdfvised. ln th is test , 1 g of o i lwas p laced on a c lean su r facesuch as Plastic, metal, or glass'An aliqubt of 1o ml of 2'5 Pet'cent deiergent was then Pouredon the surfce to cover the oil fora contact Period of 30 seconds'The suriaces were then drainedfor 30 seconds to remove mobi-lized oil and surfactant' The oi lremaining on the sur face wasrinsed with acetone and hexaneinto a collection beaker, and therecovered dYe was quant i f ied 'The removal of oil from glass'a luminum and PolYProPYlenespresented in Table 2' Note thatiemoval of oi l from the varioussur faces is dePendent uPon thetvpe of sur factant used' Tr i ton.L-orr t o i l Poor lY from glassand. aluminum, whereas, Witconolr e m o v e s o i l P o o r l Y f r o mpo lvp roP Y lene . I t maY be con -i r u ' a t h a t t h e l o w - e m u l s i o nforming surfactants (Rhema andDowfai) can be just as effectivein oil removal as the surfactantswith strong emulsion formingcharacteristics (Triton, Witconol 'and SLS).

The ApplicatonEnvironmental clean-up issues.arechanging how we view surtac-tantsl l t does not matter if th esurfactant is used for soil remedi-ation, or degreasing garage floors'

SLSRhemaMatrixWitconolTritonDowfax

o r i n p rec i s ion P ar t s wash ing 'We simPIY cannot allow the vol-umes of wastewater that are cre-a ted by the use o f emu ls ion -forming sur factants. Whenevers u r f a c i a n t s c a n b e r e c Y c l e d ,m o n e y a n d m a t e r i a l s c a n b esaved.Sand washing tests and surfacecleaning tests have shown thatthere iJ verY little difference inthe efficiencY of some commons u r f a c t a n t s t o m o b i l i z e a n dremove oil from a varietY of sur-faces. However, there is a greatdeal of difference in the PuritY otphases recovered based on the' t u o o f s u r f a c t a n t u s e d 'Threfore, the choice of surfactantc a n b e b a s e d o n s o m e o t h e rparameter, such as Phase charac-ieristics. Having good detergencydoes no t necessa r i lYequa te toc rea t i ng s t rong emu ls ions , asdemonstrated bY these data'PerhaPs the 6est aPPlication .ofnon-emulsion surfactants in thepa r t s wash ing indus t rY can beLnderstood bY reviewing Figure6. Note the lower left-hand cornerand, lower r ight-hand corner ofthe diagram (low end tie-lines)'In this Phate region, the deter-gent concentration s verY low (95-Percent andwaer >99 Percent. The detergentremains stronglY in the water

phase. This operational conditionlan b maintained in Parts wash-ing systems bY having ef f ic ientun ctnstant rmoval of traces ofoil Gieure 1) .Low emulsion- forming sur fac-tants and detergent blends ar eavailable. Envirnmental marketpull and simPle Process econom-ics dictate that niw concePts forsur factant use incorPorate thebroad Potential for water mini-mization, high PuritY oil recoverY'and sur fac- tat t t te, ts Possib lew i th these su r fac tan t b lends 'S i m p l e P h a e d i a g r a m s a n dcleaning fests can helP determinethe besl oPerating rangel for theprocess needs. ComPatible deter-gents and seParat ion equiPment re ava i l ab le to mee t the newind ustrial needs. I

ReferencesF o r t i n , 1 . , J v r Y , W ' A ' , a n dA nderson , M .A . e t a l , 1997I o u r n a l o f C o n t a m i n a n tHydrolog) 24' (1997) 247-267'Kueper, B. H., Frind, E' O' ,1992'2-Pase Flow in HeterogeneousP o r o u s M e d i a , 2 ' M o d e lApplication. Water Resour' Res' '27,1.059 -1070Severin, B.F. and Nolan, S', 2002'surfactant RecoverY in a NovelThree Phase Surfactant WashingS ys tem , Th i r d In te rna t i ona lConference, Proceedings of the-B a t t e l l e R e m e d i a t i o n o tth lo r i na ted and Reca lc i t r an tC o m P o u n d s C o n f e r e n c e 'MonteieY, CA MaY 20-23'Wi lson, D.J. , and Clarke, A 'N' '7 9 9 4 , S o i l S u r f a c t a n tFlushing/Washing, ChaPter 10,Environlental Science PollutionControl Series No. 6, Hazardous

Std.Dev.

for various detergents; SAE 30 motorTable 1: Single extraction dataoil from sandDetergent

13Yo8o/o1OYo1lYa9%

92o/o930/o990/o98%64Vo

790/o83olo8390,82%'61%

Site Soil Remediation Theor) andTecnologies,PP' 493-550'

SLSRhemaWitconolTritonDowfax

87 o87o/o81%72081%

Aluminum PolyproPYlenestd-

of oil from various surfaces using a passive clean

About the AuthorsB l a i n e F . S e a e r i n ,P h ' D ' , P ' E ' ,D i r e c t o r o f E n z t i r o n m e n t a lTechno log ies , t eP henB ak iamoh 'Ph.D., pist doctotate tudent chem-istrv, and lanette Moore,Technician3 , a r e w i t h t h e M i c h i g a nBiotechnotogynstitute, Lansing, MI'

5o/s5o/o6%11W4a/o ffi fxr

Table 2: Removaland drain test

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The Trend in Non-emulsion Aqueou