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LouisianaStateUniversityLSUDigitalCommonsLSUMaster'sThesesGraduateSchool2008Fog-smogreactorandphotooxidationofnaphthalenewithinthefogcondensateinaUVlightsetupNehaShrikantDamleLouisianaStateUniversityandAgriculturalandMechanicalCollegeFollowthisandadditionalworksat:https://digitalcommons.
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RecommendedCitationDamle,NehaShrikant,"Fog-smogreactorandphotooxidationofnaphthalenewithinthefogcondensateinaUVlightsetup"(2008).
LSUMaster'sTheses.
3999.
https://digitalcommons.
lsu.
edu/gradschool_theses/3999FOG-SMOGREACTORANDPHOTOOXIDATIONOFNAPHTHALENEWITHINTHEFOGCONDENSATEINAUVLIGHTSETUPAThesisSubmittedtotheGraduateFacultyoftheLouisianaStateUniversityandAgriculturalandMechanicalCollegeinpartialfulfillmentoftherequirementsforthedegreeofMasterofScienceinChemicalEngineeringinTheDepartmentofChemicalEngineeringbyNehaShrikantDamleB.
E.
PuneUniversity,Pune,India,2006December2008iiACKNOWLEDGEMENTSIwouldliketothankDr.
Valsarajforhisguidance,supportandencouragementthroughoutmyresearchwork.
IwouldliketothankDr.
ThompsonandDr.
Henryforservingonmycommittee.
Thedepartmentofchemicalengineeringisthankedfortwoyearsoffinancialaid.
IwanttothankmyfriendsAmol,Akanksha,AnushreeandDhruvafortheirhelpwithmythesiswritingandmylabmatesJingChen,NicholasAshleyandMaomingRenforhelpingmeandsharingsomeoftheirexperienceswithmeforthebettermentofmyresearchwork.
Theyhavenotjustbeenlabmates,butteachersforme.
IwouldliketothankMr.
XiagangXingforhelpingmewiththeScanningElectronMicroscope.
IwouldliketothankPaul,JoeandFredformanufacturingreactorandotherheatexchangerparts.
Ireallyappreciatetheirpromptsupporteventhoughtheyhadmanyotherworkstocomplete.
MysincerethanksgotoDarla,MelanieandDannywhohelpedmefromtimetotimewithmyadministrativerequirements.
IwouldliketothankmymotherandfatherandPushkar,myfiancéefortheircontinuoussupportandfaithinme.
Thisresearchworkisdedicatedtothemandwasimpossiblewithouttheirencouragement.
iiiTABLEOFCONTENTSACKNOWLEDGEMENTS…iiLISTOFTABLES…vLISTOFFIGURES…viABSTRACT…viiiCHAPTER1.
OVERVIEW…11.
1PolycyclicAromaticHydrocarbons…11.
2FogandSmog:Formation,TypesandProperties…31.
3Aerosols…41.
4TheScopeoftheResearch…52.
LITERATUREREVIEW…62.
1Experiment1:UptakeofNaphthalenebyFogDroplets…62.
1.
1Naphthalene…62.
1.
2NaClAerosols…72.
1.
3PartitionCoefficientsandPartitioningPhenomena…82.
1.
4AtmosphericFogComposition…122.
1.
5Smog-Fog-SmogCycle…142.
1.
6UseofReactorsforExperiments…142.
2Experiment2:PhotooxidationofNaphthaleneWithintheFogCondensateinUVLight…163.
EXPERIMENT1:UPTAKEOFNAPHTHALENEBYFOGDROPLETS……….
.
223.
1MaterialsandMethods…223.
1.
1MaterialsandMethodsforSamplePreparation…223.
1.
2EquipmentSpecificationandTechniques…233.
2ExperimentalSetup…253.
3ExperimentalProcedure…303.
3.
1CalculationofPartitionCoefficients…303.
3.
2PhotooxidationReactionofNaphthaleneandFogContainingNaCl……323.
4ResultsandDiscussion…323.
4.
1ResultsandDiscussionfortheNaphthaleneUptakeExperiment……….
323.
4.
2ResultsandDiscussionforthePhotooxidationReactionExperimentInsidetheReactor…374.
EXPERIMENT2:PHOTOOXIDATIONOFNAPHTHALENEWITHINTHEFOGCONDENSATEINAUVLIGHTSETUP…394.
1MaterialsandMethods…394.
1.
1Chemicals…394.
1.
2MethodsandTechniques…404.
2ExperimentalSetup…40iv4.
3ExperimentalProcedure…414.
4ResultsandDiscussion…444.
4.
1AnalysisofaProductFormationUsingtheReactionMixtureContainingNaCl…444.
4.
2AnalysisofaProductFormationUsingtheReactionMixturenotContainingNaCl…505.
CALCULTATIONS…545.
1CalculationsforExperiment1ExplainedinChapter3…545.
1.
1CalculationfortheAmountofNaClRequiredfortheAerosolSolution.
.
545.
1.
2CalculationforNaphthaleneConcentrationfromHPLCData………….
.
555.
1.
3CalculationforΔHandΔSValuesfromVan'tHoff'sEquation……….
.
.
575.
2CalculationforExperiment2ExplainedinChapter4…576.
CONCLUSIONS…596.
1PartitionCoefficientExperiments…596.
2PhotooxidationExperiments…60REFERENCES…61VITA…66vLISTOFTABLESTable1:PropertiesofPAH(Dabestanietal.
,1999)2Table2:PropertiesofNaphthalene…9viLISTOFFIGURESFigure1:GrowthCurvesforCondensationandDispersionNuclei(Krameretal.
,2000)…….
.
.
10Figure2:PartitioningPhenomenon…11Figure3:RelationshipBetweenEnthalpyandEntropyforDifferentN*Values(Davidovitsetal.
,1991)12Figure4:AverageContributionofVariousOrganicCompoundstotheDissolvedCarbonintheFogWater(Rajaetal.
,2007)15Figure5:PossibleMechanismsofaPhotoreactionofPAH(Fasnachtetal.
,2003)…………….
18Figure6:C/Covs.
TimeforBenzopyreneandChrysene(Milleretal.
,2005)21Figure7:ExperimentalSetupforthePartitionCoefficientExperiment…26Figure8:AerosolGenerator(Retrievedfromwww.
TSI.
com)28Figure9:FogCollector…30Figure10:HeatExchangerUsedfortheFogCondensation…31Figure11:ActualStructureoftheObtainedNaClAerosol…33Figure12:DistributionandAbundanceofAerosols…34Figure13:LnKwavs(1/T)forNaphthaleneonFogDroplets…36Figure14:Intelli-Ray600UVLightSetup(TakenFromuvitroninternational.
com)………….
42Figure15:ArrangementsofVialsUnderUVLight(FrontView)43Figure16:SpectrumoftheReactionProductsofthePhotooxidationReactionofNaphthalenewithFogConsistingofNaCl…46Figure17:HPLCTraceShowingPhthalidePeakattheRetentionTime4.
743Seconds.
Absorbanceat254nm…47Figure18:Concentrationvs.
TimeCurveforDecreaseinNaphthalene…49Figure19:Ln(Cno/Cn)vs.
TimeforNaphthalene…49Figure20:IncreaseinBenzaldehydeConcentrationwithTime…50Figure21:GC/MSTraceforProductsofPhotooxidationofNaphthaleneinWaterviiWithoutNaCl…51Figure22:HPLCTraceforProductsofPhotooxidationofNaphthaleneWithinWaterwithoutNaCl52Figure23:GraphforDecreaseinNaphthaleneConcentrationWithTimeforPhotooxidationinWaterwithoutNaCl…53Figure24:Ln(Cno/Cn)vs.
timefornaphthalene…53viiiABSTRACTPolycyclicaromatichydrocarbons(PAHs)formamajorclassofairpollutants.
NaphthaleneisacommonlyfoundPAHintheatmosphere.
Atmosphericfogwatercontainsnaphthaleneabsorbedfromsurroundingair.
Thepartitioncoefficientofnaphthaleneisdefinedastheratiooftotalnaphthaleneconcentrationinfogwatertototalnaphthaleneconcentrationinair.
Thepurposeofthisresearchwastodeterminethepartitioncoefficientsofnaphthaleneforvaryingreactortemperature.
Fogwasartificiallyformedinapredesignedreactor.
NaClaerosolswereusedascondensationnucleiforfogformation.
Fogdropletswereexposedtonaphthalenevaporsinthereactor.
Thereactorprovided62secondsresidencetimeforfogdroplets.
Fogwasthencondensedusingaheatexchangeratthereactoroutlet.
Compressedairwasusedasacarriergasfortheexperiment.
NaphthaleneconcentrationinthecollectedcondensateandexitgaswasdeterminedusingHighPerformanceLiquidChromatography(HPLC).
Partitioncoefficientswerecalculatedat334K,346.
5K,361.
5Kand371.
5K.
Theexperimentalresultsindicatedadecreaseinpartitioncoefficientwithincreasingtemperature.
Earlierworkhasdemonstratedpresenceofproductsofnaphthalenephotooxidationas1-naphthol,naphthoquinones,benzoquinones,phthalideand1,3-indandione.
Theaimofthisresearchwasalsotodetermineproductsofnaphthalenephotooxidationreactionwithinthefogcondensatecontainingwater,naphthaleneandNaClunderUVlight.
ThefogcondensatewasexposedtoUVlightfortimeintervalsbetween0to5hours.
Experimentalobservationsshowedadecreaseinnaphthaleneconcentrationwithtime.
Overallreactionrateconstantkfornaphthalenewasdeterminedtobe0.
00567/minanddetectedreactionproductswerephthalideandbenzaldehyde.
SameexperimentwasperformedusingareactionmixturewhichconsistedonlyofwaterandnaphthalenewithcompeteabsenceofNaClwhichshowedthatthevalueofkwasixdecreasedto0.
00147/minwithcompleteabsenceofbenzaldehydeinthereactionproducts.
Alongwithphthalide,1-3indiandionewasalsoobservedasaproductofthereaction.
ItwasconcludedfromboththeexperimentsthatpresenceofNaClchangedproductformationandreactionrateofnaphthalenephotooxidationandalsoloweredthevalueofpartitioncoefficientat298Kascomparedtopurewater.
1CHAPTER1OVERVIEWVariousindustrialprocessesreleasedifferentchemicalsandgasesintheatmospherecausingairpollution.
Polycyclicaromatichydrocarbons(PAH)formamajorclassofairpollutants.
PAHsarealsoreleasedbyanthropogenicactivities.
Naphthalene,anthracene,pyreneandphenanthrenearesomeofthecommonlyfoundPAHs.
PAHsareabsorbedbywaterbodiesthatcomeincontactwiththem.
Fogisonesuchentity,whichconcentratesgaseousPAHs.
Inthecurrentresearch,thefocusisonabsorptionofnaphthalenebyalaboratorycreatedfogandphotooxidationofthisabsorbednaphthalenewithinfogcondensateinpresenceofUVlight.
Thecurrentchaptergivesanoverviewoftheconceptsandtermsusedinthisthesis.
1.
1PolycyclicAromaticHydrocarbons(PAH)PAHsaretwoormorebenzeneringsfusedtogether.
Theyarestableandeasilysolubleinorganicsolventsandoils.
Theyarehydrophobicandhavehighaffinitytowardorganiccompounds,thereforearereadilyadsorbedonsootparticles,foodandotherorganicmatter.
Theyaregenerallylowvaporpressurecompoundsandcanbeclassifiedonthebasisofthenumberofaromaticringsthatarefusedtogetherinaparticularmolecule.
PAHsarefoundtobecarcinogenicandmutagenic.
ThisbehaviorofPAHscanbeafunctionoftheirnonplanarity(Harveyetal.
,1991).
Ingeneral,nonplanarPAHsarelessstable,morereactiveandmoretoxic(Dabestanietal.
,1991).
AsthenumberofringsinaPAHincrease,itsmolecularweightincreaseswhichresultsinanincreaseinthenumberofisomers.
Table1givescomparisonofthemainpropertiesofthesecompounds.
Incompletecombustionofcarbonaceoussubstanceslikewood,coal,cigarette,keroseneandsmokeisthemainsourceofPAHs(Jenkinsetal,1996).
Householdsources,industrialsourcesaandnaturalsourcesareethreemajoorsourcesoofPAHprooduction.
Hoouseholdsourcesincludefincineratvolcanicfireplaces,aors,aluminueruptions(NautomobileaumsmeltingNikolaouetaandfurnacegandwoodal,1984).
s;industrialdpreservatiolsourcesbeon.
Naturaleingoilpowsourcesarewerplants,weforestfireswastesandAcompounhundredsProtectioAlongwithndssinceinsofPAHsonAgency(Eairpollutiondustrialwasareknown,EPA)on,PAHscstewaterco17havebconstituteevontainsameenlistedavenamajomajorpercentaspriorityporclassoftageofPAHpollutantsbywaterpollHs.
EventhyEnvironmlutinghoughmentalTable1:PropertiesoofPAH(Dabbestaniet.
al.
.
,1999)PropStrucMoleformMoleweightSolubiwa(mg/latpertyctureecularmulaecular(g/mol)ilityinatert200C)CCertainpolycPhenanthrenC14H10178.
231.
28cyclicaromanePyC200atichydrocaryreneC16H1002.
250.
1352rbonshavingAnthracenC14H10178.
231.
3gveryhighmneInsmolecularwePentaceneC22H14278.
36olubleinwaeightsareater3difficulttoanalyzebecauseofanunavailabilityofreferencestandards.
ThesehighmolecularweightPAHsareoftenobtainedasproductsorintermediatesinresearchexperiments.
Therefore,studiesrelatedtoPAHidentificationsandreactionsaregoingonfordecadesandnewwaystoidentifytheproductsandreactionmechanismsarebeinginvented.
1.
2FogandSmog:Formation,TypesandPropertiesAlargeportionofwaterintheatmosphereisinthevaporphase(Ackeretal.
,2007).
Fogisformedwhenvaporcondensesonsolidorliquidbodies.
Whenwatervaporintheatmosphereiscooledadiabatically,itdepositsonaerosolparticlespresentaround.
Thisleadstotheformationofwaterdroplets.
Fogisformedintheformofsuchwaterdropletsthataresuspendedinairneartheearth'ssurface.
Acondensationnucleusactsasthesurfaceonwhichawaterfilmformsandgrowsduringafogdropletformation.
Condensationgrowthoccurswhentheatmospherictemperatureislowered.
Dustparticles,oilaerosolsandothersolidaerosolscanactassuchcondensationnucleiinfogformation.
Fogandclouddropletscanbereadilyformedevenbycarbonaceousaerosols(Benneretal.
,1993).
Fogdropletshaveawidesizerange.
Theirsizecanvaryfromafewmicrometerstotensofmicrometers(Rajaetal.
,2007).
Fogreducesvisibilityandcausesproblemsinrealtimeremotesensing.
Thedifferencebetweenthetemperatureandadewpointshouldbelessthanorequalto5oCandrelativehumidityshouldbenear100%forfogformation.
Fogcanformatmuchlowerrelativehumiditythan100%whencondensationnucleiarepresentabundantlyandarehygroscopic(example,NaClaerosols).
Seafog,valleyfog,steamfogandicefogaresomeofthevarioustypesoffog.
Fogcanbeproducedinalaboratoryandexperimentscanbeperformedusingsyntheticallygeneratedfog.
Productionoffoginalaboratoryneedswatervaporandaerosolsthatactascondensationnuclei.
Suchsyntheticallygeneratedfoghaspreviouslybeenusedtoperformexperiments.
Condensation4nucleusisnecessaryforanartificialfogformation.
Inthisexperiment,NaClaerosolswereusedasthecondensationnuclei.
Smogisacombinationofsmokeandfogandresultsinairpollution.
Smogcancausehealthhazardssuchasinflammationofbreathingpassages;adverseeffectsonlungworkingcapacity,coughanddifferenttypesofrespiratorydisorders.
Pollutedaircontainingacidiccompoundssuchasnitricacidandhydrochloricacidcanincreasehygroscopyofaerosolparticleseffectively,affectingfogformation(Kokkolaet.
al.
,2003).
UVlightpresentintheatmospherecausessmokeandfogtoreact,resultinginformationofmanyhazardousproducts.
Aspecialtypeofsmogcalledphotochemicalsmogformsasaresultofsecondaryproductsformedfromairpollutants.
Inthisprocessofformationofphotochemicalsmog,aphotoncollideswithdifferentairpollutingmolecules.
Thereactionleadstotheformationofsecondarycompoundsthatcombinewithfogtoproducesmog.
OneoftheaimsofthisresearchwastostudythereactionsoffogcondensateenrichedwithnaphthaleneunderUVlightandanalyzethereactionproducts.
Naphthalenebeingatypicalairpollutantintheatmospherewasusedtocreatesmoginthelaboratoryforthisproject.
1.
3AerosolsAerosolsareminuteparticlessuspendedinairthatareinsolidorliquidform.
Aerosolsareatwophasesystem,solidorliquidsuspendedingas.
Theyareusuallyheavierthanairandhenceacontinuousaircurrentisneededtokeepthemsuspended.
Sourcesofaerosolsareduststorms,volcaniceruptions,seaspray,grasslandfiresandmostimportantly,anincompletecombustionofhydrocarbonswhichreleasesaerosolsintheformofheavysmoke.
Theyvarygreatlyintheirstabilitydependingontheparticlesizeandconcentration(Hinds,AerosolTechnology).
5Aerosolshaveawiderangeofsizeandshape.
Thepropertiesofaerosolsdependontheirsize.
Aerosolsaremeasuredintermsofeithermassconcentration(g/m3)ornumberconcentration(number/m3).
Aerosolswhenformedhaveelectrostaticforcesthatneedtobeneutralizedinordertousethemforexperimentalpurpose.
Someofthetypicaltypesofaerosolsarebioaerosols,clouds,haze,fume,dust,smogandsmoke.
Aerosolshavesomecommercialapplicationsincludingspraydryers,productionofpigments,carbonblackandfiberoptics.
Aerosolsaffectvisibility,climateandhumanhealth(Hinds,Aerosoltechnology).
1.
4TheScopeoftheResearch1.
UseofNaClaerosolsasthecondensationnucleiforfogdropletformationinsidethereactor.
2.
Determinationofnaphthaleneconcentrationsinfogcondensateandexitair.
3.
Calculationofpartitioncoefficientsusingconcentrationvaluesataparticularreactortemperatureandobtainingaplotofchangeinthereactortemperatureanditseffectonthepartitioncoefficients.
4.
Carryingoutphotooxidationreactionofnaphthalenewithinthecollectedcondensateandstudyingachangeinconcentrationsofreactantsandproductswithtime.
6CHAPTER2LITERATUREREVIEWAtmosphericfogabsorbssurroundingorganics,manyofwhichcomefromairpollutants.
ThisresearchconcentratesontheuptakeofpolycyclicaromatichydrocarbonsbyfogdropletsandreactionofPAHswithinafogcondensateinpresenceofUVlight.
Resultsofthisresearchwillhelpusunderstandwhatpercentageofnaphthalene(PAH)isabsorbedbyfogdropletsandtheresultingphotoreactionsthatgivevariousproductsthatmayormaynotbeharmful.
Thischapterofthethesisdiscussessomeimportantconcepts,propertiesandstudiescarriedoutbyotherresearcherstounderstandsimilarphenomena.
Knowingtheresultsoftheirexperimentsandcomparingthemwiththeresultsofthecurrentexperiment,wecanverifythedataanddrawimportantconclusions.
Theresearchhasbeendividedintotwoseparateexperiments.
Thefirstsetofexperimentstalksabouttheuptakeofnaphthalenebyfogdropletsatdifferentreactortemperaturesandthesecondsetofexperimentstalksaboutphotooxidationofnaphthaleneatgivenreactionconditions.
2.
1Experiment1:UptakeofNaphthalenebyFogDropletsNaphthaleneisthemostabundantlyfoundpolycyclicaromatichydrocarbonintheindustrialbeltfromHoustontoBatonRougeinUSA.
Itiseasilyabsorbedinbulkwaterandadsorbedonair-waterinterfacesatroomtemperature.
Thefirstsetofexperimentsinthisresearchfocusesontheuptakeofnaphthalenegasbylaboratorygeneratedfogdroplets.
NaClaerosolswereusedascondensationnucleiforfogdropletformation.
Followingsub-sectionsprovidesomeinformationaboutpropertiesofnaphthaleneandNaClaerosolsandfindingsofsimilarstudiesthathadbeencarriedoutbyresearchersinthepast.
2.
1.
1NaphthaleneNaphthaleneisthemostcommonlyfoundpolycyclicaromatichydrocarboninpollutants7andhasbeenusedasaPAHinthecurrentstudy.
ItisalsooneofthosefewPAHsfoundinnaturethatareinvaporform.
AstudycarriedoutinMumbai,Indiainrecentyearssummarizestheconcentrationsofdifferentpollutantsat9differentlocationsincludingcanteens,movietheatersandrestaurants.
Theresultsofthisstudyindicateasignificantpresenceofnaphthaleneasanairpollutantinsevenoutofnineplaces(Shrivastavaetal.
,2007).
NaphthaleneisthesmallestcompoundamongtheclassofPAHthatisalsoknownbynamessuchasnaphthalin,naphthaline,naphtheneandwhitetar.
Itisvolatileandreadilysublimesatroomtemperature.
Ithasacharacteristicodorthatisdetectableat0.
08ppm.
Sourcesofnaphthalenearepetroleumrefineries,coaltardistillation,papermills,motorvehiclesexhaust,woodmills,antisepticsandlubricatingfluidsindustries.
Coalconsistsof10-12%naphthalene.
Naphthaleneisalsousedasarawmaterialfordifferentproductsanditsindustrialdemandsareincreasingfortheproductionofsomemajorsolutionslikephthalicanhydride,azodyes,surfactantsanddispensers.
Table2givenbelowsummarizessomeoftheimportantphysicalandchemicalpropertiesofnaphthalene.
2.
1.
2NaClAerosolsInthisexperiment,NaClaerosolswereusedascondensationnucleiforproductionoffoginthelaboratory.
NaClaerosolswerespeciallyusedbecauseoftheirlargeconcentrationintheatmospherethatcanbeillustratedbythefactthat1000-10000(106metrictons/year)seasalts,whichconsisttypicallyofNaClaerosols,areemittedbyseasprayseveryyear(Suhreetal.
,1995).
NaClaerosolsarehygroscopicandcanformfogbelow100%relativehumidity.
Theyhaveacharacteristiccubicalshapeandhaveparticlesizerangebetween0.
01and10m.
Duetotheirsizerange,theycanbeexaminedunderascanningelectronmicroscope.
NaClaerosolsareusedtypicallyasthetestaerosolsfordirectandindirectatmosphericstudies(Krameretal,2000).
Figure1showsthegrowthcurvesforNaClaerosols.
8Thetypicalgrowthcurveswerestudiedintheexperiment(Krameretal.
,2000)anditwasthenconcludedthatgrowthofNaClaerosolsbycondensationofwatervapordependsontheirdiameter.
Asshowninfigure1,higherdiameterofthecondensationnucleiresultsinthesmallergrowthfactorwithincreasingrelativehumidity;whereagrowthfactoristheratioofmeasuredequivalentdiameterDtothediameterofdryaerosold.
NaClaerosolsaregenerallyproducedinalaboratorybyanaerosolgeneratororanebulizer.
AerosolsolutionsusedfortheproductionofNaClaerosolsaresaltsolutions,typicallyconsistingofalcohol,waterandNaCl.
ChargeneutralizersareessentialtoremoveachargeonNaClaerosols.
Inthecurrentexperiment,partitioncoefficientsofnaphthalenewerecalculatedatvariousreactortemperatures.
NaClaerosolswereusedasthecondensationnucleiforfogdropletformationinthisexperimentbecauseoftheirhygroscopyandmostimportantlytheirabundanceintheatmosphere.
Theseaerosolsalsoinducedsalinitytothefogcondensateandreactionswereperformedlaterusingthissalinecondensate.
2.
1.
3PartitionCoefficientsandPartitioningPhenomenaHundredsofdifferentpollutantsarepresentintheatmosphere.
Differentareasoftheworldhavebeenstudiedfordecadestounderstandthemechanismthatcontrolsthefateofthesepollutants.
Fromacompleteclassofpollutants,organicshavebeenofamajorinteresttomanyresearchersandithasbeenfoundthatthemainphenomenacontrollingtheirbehavioristheirequilibriumpartitioningintwodifferentphases(Hoffetal.
,1993).
Manystudiesexplainthatincaseofthepartitioningbetweenairandwaterphases,air-waterinterfaceplaysasignificantroleinchemicalabsorptioninfluencingchemicaleffects(Chenetal.
,2006)Table2:PropertiesoofNaphthalene(Retrieveedfromwwww.
oehha.
ca.
ggov)MoSoVapoPropeStructMolecularolecularweiolubilityinwDensity(gAppearMeltingpoBoilingPoorpressureatertyureformulaight(g/mol)water(mg/l)g/cm3)anceoint(oC)oint(oC)t25oC(N/mm2)9SolidValueC10H8128.
17301.
14whiteflakes81.
221811sFigure1:Growthcurvesforcondensationanddispersionnuclei(Krameretal.
,2000)Partitioncoefficientisdefinedastheratioofaconcentrationofatracegasinfogdropletstoitsconcentrationinsurroundingair.
Partitioncoefficientisafunctionoftemperature.
Inthisexperimentachangeinthevalueofpartitioncoefficientwithtemperaturewasstudied.
Equation(1)givenbelowgivesamathematicalrelationbetweentheconcentrationsofnaphthaleneinwaterandair(Chenetal.
,2006)KWACWCA(1)Where,forthecurrentresearchexplainedinthefollowingchapters,CAistheconcentrationofnaphthaleneinexitairandCWisthetotalconcentrationofnaphthaleneinfogcondensateandKWAisthepartitioncoefficientofnaphthalenebetweenexitairandfogcondensate.
10Ithasbeenfoundthatpartitioningofachemicalatanair-waterinterfaceisgovernedbymassaccommodationcoefficientαwhichisaprobabilityofamoleculeofachemicalgettingadsorbedexplaineddonanintedthisproceserfacewhenssofthisadsnitstrikessorptionas:theinterfacce.
Nathansoon(Nathanssonetal.
,11996)(EquatiosurfaceaeithergetcouldfurtrulydepphenomeFigure2ETheGibbprocess.
enthalpyonpartitiontakenfroandlrepresetadsorbedbrthermixwipendsontenon.
2:PartitioninEveryadsorpbs'freeenerEnthalpyvavaluedetermionconstantnomNathansoentsaliquidbytheratekaiththebulkltheratioofngphenomenptionprocessrgycanbedaluedeterminminesthesotatair-waterngnsonetal.
,19phase.
Amoadsorgetdesliquidphasefksol.
andnonshasafreeedividedtotwnesiftheprolubilityandrinterface.
Ikadss→nlkdesorb11996).
Whereoleculeingasorbedintheebytransporkdesorb.
Figuksol((2),grepresenasphaseafteegasphaseartationratekure2illustntsagaspherstrikingthagainbykdesksol.
So,afatetratestheahase,srepreheinterfacecorb.
ThemoleofthechemabovementiesentscouldeculemicalionedenergyassocwopartsaserocessisexohencetheprIthasbeenociatedwithienthalpyandothermicorerocess.
Effecobservedthaitataparticdentropyasendothermicctoftemperaatastemperaulartemperasociatedwitc.
Thesignoatureisdomatureofasyature.
ththeoftheminantystemincreases,solubilityofagasinwaterreducesbecauseofanincreaseinnegativeenthalpyassociatedwiththeprocess.
Workhasbeendonetofindthecorrelationsbetweenenthalpyandentropyassociatedwiththeprocess.
AccordingtoDavidovits(Davidovitsetal.
,1991),thisrelationshipcanbepresentedwiththehelpofthefollowingfigure.
ThegraphshowsthechangeofenthalpywithentropyfordifferentvaluesofN*.
ThevalueofN*representstheaveragenumbersizeofthecriticalcluster,meaningthatforthecaseofN*=2.
4,itisthemoleculeofachemicalitselfaccompaniedandcoatedby1.
4watermolecule.
Figure3:RelationshipbetweenenthalpyandentropyfordifferentN*values(Davidovitsetal.
,1991)Thereareseveralmethodstofindthepartitioncoefficients.
Someofthemareactualconcentrationmeasurements(generallyfollowedbymanyresearchers)anddeterminationofsolubilitybyUVabsorption.
2.
1.
4AtmosphericFogComposition12Atmosphericfogreadilyabsorbssurroundingpollutants.
Solubilityofpollutantsinfog13varieswiththeatmospherictemperatureanddropletdiameteroffog.
Fromtheearlierstudy,ithasbeenfoundthatanincreaseinafogdropletdiameterlowersabsorptionofthesurroundingPAHs.
Extensiveefforthasbeenputintostudyingthechemicalcompositionofnaturallygeneratedfog.
Ithastypicallybeenfoundthatthereisawiderangeoforganicandinorganicchemicalspresentinfog.
Thesechemicalcompoundsarepresenteitherasabsorbedgasesorcondensationnucleiforfogformation.
Fogmostlyconsistsofacidiccompoundslikenitricacid,formicacid,aceticacid,carbonylsandbicarbonyls,aromatichydrocarbonslikenaphthalene,phenanthrene,benzene,longchainalkanesandotherfunctionalgroups(Herckesetal.
,2007).
Inarecentstudy,ithasbeenfoundthatfoginHoustonandBatonRougeconsistedofionicspeciesofCl-,NO2-,NO3-,SO42-,Na+,NH4+,K+,Mg2+andCa2+(Rajaetal.
,2007).
AworkcarriedoutinAgra,Indiashowedthatalongwiththecomponentsmentionedabove,thereweresomeacidicanionspresentsuchasCH3COO-,HCOO-(Lakhanietal.
,2007).
.
Duetotheacidicandalkalinecompoundsmixedinfog,pHrangesfrom2.
6to7.
2dependingonthelocationoffogcollection(Rajaetal.
,2007).
Hydrophobicorganiccontaminants(HOC)aredepositedonthegroundduetofogwaterandrainwater.
IthasbeenfoundthatthereisagreaterinfluenceofsubmicronparticlesinpartitioningofHOCs.
(ItwasevidentfromthepreviousworkthatHOCshaveaffinitytowardssubstratessuchasdissolvedorganicmatterpresentinfogandhenceHOCshavemajorcompositionsinfogdroplets(Posteretal.
,1996)).
ItwasfoundinthestudycarriedoutbyPoster(Posteretal.
,1996)thatbiphenylcompounds,phenanthrene,pyrene,chrysene,benzofluranthrene,indenopyreneandbenzoperylenewerepresentinmajorconcentrationsinrainandfogwaters.
InastudycarriedoutbyPoster(Posteretal.
,1996)andGlotfelty(Glotfeltyetal.
,1987)fogcondensatewasfilteredorthesubmicronparticles.
Itwasobservedthatthe14concentrationsofPAHsmeasuredinambientairwerelowerbythefactorof100thantheonespresentinfogwater.
Thisresultindicatedthatfogwassupersaturatedwithrespecttoambientairconcentrations.
Manydifferentcompoundsdetectedinfogareeitherpresentviaabsorptionorphotochemicalreactions.
Therefore,investigationofthereactionsofdifferentcompoundsinfogwaterbecomesessential.
2.
1.
5Smog-Fog-SmogCycleFogcontentssuchasairpollutantsandaerosolsabsorbedwithinthefogdropletssettleontheearth'ssurface.
Theseentitiesaredepositedonthegroundwhenfogdissipates.
Thesmog-fog-smogcycleistheprocesswherebyenhancedsecondaryaerosolsproducedbyfogprocessingfurtheractassmogcondensationnucleiforfurtherfog(Rajaetal.
,2007).
Inordertounderstandthefogprocessingandsmogchemistry,collectionandanalysisoffogusingdifferenttechniquesisessential.
Severalstudieshaveconcludedthepresenceofcarbonaceouscompoundsincollectedfogsamplesfromvariouslocations.
Thesourcesofsomeofthesecompoundswereidentifiable,butmanyarestillunidentifiableandpredictedtoberesultingfromthephotochemicalreactionswithinfog.
AstudycarriedoutinBatonRouge,LAandHouston,TXshowedalargenumberofcompoundsinthefogwater(Rajaetal.
,2007).
Theresultshowedacontributionofdifferentairpollutantstowardthepresenceofdissolvedcarbon(DOC)infog.
Theresultsaresummarizedinfigure4.
Asshowninfigure4,morethan41.
6%unknowncarbonhasbeendetectedinBatonRougeand37%hasinHouston.
Tounderstandthesourcesofthisnonidentifiablecarbon,itisessentialtocarryoutphotochemicalreactionsontheartificiallygeneratedfog.
2.
1.
6UseofReactorforExperimentsEnvironmentalphenomenaarerecreatedinthelaboratoryforthepurposeofunderstandingthemcompletely.
Reactorsareusedforstudyingsuchenvironmentalprocesses.
Experimentsrelatedtotheuptakeofgasesbyfogdropletsorwaterfilmsaretypicallycarriedoutinsuitablereactors.
Chen(Chenetal.
,2006)usedaglassboatreactorforcarryingoutanexperimentrelatedtotheuptakeofPAHsbyathinwaterfilm.
AfallingdropletreactorwasusedbyRaja(Rajaetal.
,2006)forstudyingpartitioncoefficientsofseveralPAHsinthewaterdropletsanddependenceofpartitioncoefficientsondropletdiameters.
Figure4:Averagecontributionsofvariousorganiccompoundstothedissolvedcarboninthefogwater(Rajaetal.
,2007).
AsetupconsistingofareactorwasusedbyBenner(Benneretal.
,1981)forstudyingoxidationofwaterdropletscontainingsootparticles.
AsimilarsetuptotheonementionedforBenner'sexperimentisusedinthisresearchforstudyingtheuptakeofnaphthaleneonthefogdropletsthataresynthesizedartificiallyinsidethereactor.
Reactorlengthdeterminedthe1516residenceandreactiontimesforthecompleteprocesswhichmaybelessormorethantheactualtimetakenforthesimilarprocessintheatmosphere.
2.
2Experiment2:PhotoOxidationofNaphthaleneWithintheFogCondensateinUVLight.
PAHsinairarenotonlyadsorbedbyfogdroplets,buttherealsooccursaphotooxidationreactionofthesePAHsinpresenceofnaturallyavailableUVlight.
Productsofthereactioncanbevariousdependinguponthereactionconditionsandcatalystsavailable.
Thesecondsetofexperimentsdiscussesaphotooxidationreactionofnaphthaleneinthecollectedfogcondensatefromexperiment1.
ThisfogcondensatealsocontainedNaCl.
ReactionproductsandreactionmechanismwereobservedtounderstandtheeffectofNaClinareactionmixtureandcomparedtootherworkthathasbeendonebefore.
TheFollowingsectiondiscussesapreviousworkcarriedoutbyothersthatprovidesnecessaryinformationaboutreactionproductsandmechanismunderdifferentreactionconditions.
Italsodiscussesdifferentpathwaysinwhichthereactioncanpossiblyproceedresultingintheobservedproducts.
Aphotooxidationreactionisatypeofreactioninwhichlightinducedoxidationofareactanttakesplaceduetooxygenorozone.
Productsofthesereactionsmayormaynotbemoretoxiccomparedtotheparentreactant.
Othertermscloselyrelatedtophotooxidationreactionsarephotoexcitationprocessinwhichachemicalspecieslosesoneormoreelectrons;photooxygenationprocesswhereinanoxygenatomisretainedintheproductandphotoinitiatedoxygenationinwhichthereisnoelectronicexcitationofeitherthesubstrateortheoxygen(IUPACcompendiumofchemicaltechnology,vol2,1997).
Photocatalyticreactionsusephotonsascatalystandalterthereactionrates.
Photocatalyticreactionshaveapplicationsinwaterandsewagetreatment.
Organicmatterdissolvedinwaterbodies,especiallyPAHsareknowntoabsorbUVgreatlyaPAHsarreactionsheterogenhomogenprocessiaquaticpandundergorehomogenesthatoccurneousproceneousproceinabulkphplantsandorphotooxidaeousreactionrattheintessonfilmss(Streaowhaseofwatrganismshasationreactionnsthatoccuterfaces.
Phmsurfaceswskietal.
,terhasbeensalsobeenrensinthebuurinbulkphhotoreactionscompared2003).
Phonstudied.
Peported(Lanulkphase.
ThasesofairsofPAHstotherateotooxidationPhotoinducedndrumetal.
,hetwotypeorwateranoccurataesatwhichofPAHsdtoxicityof,1987;HuanesofreactiondheterogenafasterratehtheyoccuinhomogenfsomePAHngetal.
,199nsofneouseviaurinneousHsin97).
PprocessesoutbyBephenanthAccordinolycyclicarsofoxidatioeltran(Beltrhrenefor2ngtohisfindromatichydron.
PAHscaranetal.
,199differentcdings,UVrarocarbonscaanbeoxidiz95),hestudicasesnameladiationkineanbedegrazedbyintroiedthereactilyUVpyroeticsfolloweadedinanaducingozonionmechaniolysisanddthesimpliqueousmedne.
IntheexismsofPAHUVcombinfiedpathgivdiumbydiffxperimentcaHsanthracennedwithozvenbyreactiferentarriedeandzone.
ions:PAHPAH*PPTondiffereifUVradradiationhigherinFPAHsinandOH-AH*AH*Theexpressioentreactiondiationisconalone.
TherntheregionsasnachtandaqueousmeasexplainedPAHproduconsfortherconditionsuombinedwitrefore,thephwherehigheBlough(Faediumandgdinfigure5ctsrateofchangused.
Itwasthozone,thehotodegradaerozonefluxgeofPAHcalsoobserveentheratesationsofdissxisavailablconcentratioedasaresulofdegradatisolvedPAHe(Beltranetnwerecalcultofoxidatioionaremucsbynaturaltal.
,1995).
ulateddepenonsofPAHshfasterthanUVlightwndings,thatnUVwillbesnachtetal.
,2003)carriiedoutphotoodegradationnofseveralgaveareacti.
Figuresho17ionpathwayowspossiblefortheactucombinatioualexcitationnsofreactionsandroleoonpathwaysofO2afterexcitationofasinglePAHmoleculewherePstandsforaPAHmoleculeandP+istheresultantPAHcationradical.
Figure5:PossiblemechanismsofaphotoreactionofPAH(Fasnachtetal.
,2003)18Ithasalsobeenstudiedthat,PAHswhendissolvedinalkanes,formalkylatedPAHsunderUVlight.
TheproductformationismainlybecauseoftheC-CandC=O/C-OHbondsformed.
UVlightwasthemajorcauseforthereactiontotakeplace.
SeveralproductsofanthraceneandphenanthreneweredetectedandwereproducedfromenergytransferbyexcitedPAHs(Mahajanetal.
,2002).
ArmstrongcarriedoutaphotooxidationofPAHsinseawaterandconcludedthattherateofphotodegradationwasveryhighinseawaterascomparedtopurewater(Armstrongetal.
,1966).
Photoreactionsofbenzopyrene,chryseneandfluorinewerestudiedbyMiller(Milleretal.
,2000).
HeconcludedthatUVspectrumandconcentrationofthePAHsare2majorfactorsdecidingthedegradationrate.
Forasuccessfulphotoreaction,emissionspectrumofUVshouldoverlaptheabsorptionspectrumofthemainreactant.
Reactionratescanalsodifferdependinguponinitialconcentrationofthetargetreactant.
Figure6givesthe19differencebetweentheratemechanismofbenzopyrene(BAP)andchrysene(CHR)attheirdifferentinitialconcentrations.
C/Co%vs.
TimegraphisplottedinthefigurewhichindicatesthatatlowerinitialconcentrationsofthePAHs,rateofdegradationwasfasterthantheratefoundathigherinitialconcentrations.
Photochemistryoforganicshasnotonlybeenstudiedinaqueousmediumbutalsounderdifferentreactionconditions.
Photoreactionsoforganicsinwatericeandice-waterinterfacehavealsobeenextensivelystudied.
Photooxidationinicetakesplaceathigherratesthaninthebulkairorwater.
Thisisbecauseofahigherconcentrationofhydroxylradicalsavailableonicesurface(Domineetal.
,2008).
Whenphotochemistryofmonochlorophenolswasstudiedinwaterice,thereactionresultedinseveraldifferentproductsbecauseofthecouplingreactionsduetoaggregationofmonochlorophenolonthegrainboundaries.
Themajorproductsofthereactionweremembersofphenolichalogenatedcompounds.
PhotoreactionofPAHsinicecausestheirreductionandleadstotheformationofketones,alcoholsandbridgingethers.
KetonesgenerallydisturbaromaticityoftheparentmoleculebutalcoholsandethersdonotbreaktheringstructureofPAH(Bernsteinetal.
,1999).
NaphthalenehasbeenusedasaPAHinthecurrentstudy.
Researchershavepreviouslyfocusedonthephotodegradationofnaphthaleneandsubstitutednaphthaleneindifferentreactionconditionsandwithdifferentcatalysts.
Wasserman(Wassermanetal.
,2004)studiedphotooxidationreactionsofmethylnaphthaleneswithamajorreactionproductasendoperoxide1-5.
Itwasobservedthatmethylsubstitutednaphthalenesweremorereactivethanunsubstitutednaphthalenes.
Aphotolysisofnaphthalenecarriedoutonhexanefilminabsenceofairresultedin30%degradationofnaphthalene.
Majorproductsofthereactionwere2-carboxybenzaldehydeand3-phenyl-2-propanal.
ExperimentsfornaphthalenephotodegradationinultrapurewatersupportedbyTiO2catalystwerecarriedoutwiththehelpofhighandlowpressuremercury20lamps.
Itwasobservedasaresultoftheexperimentthatarateofphotodegradationofnaphthalenewashigherforhighpressuremercurylamp.
Theexperimentalsoindicatedthat25%to40%conversionofnaphthalenewasobserveddependingonthetypeoflamp.
Thereactiondidnotleaveanyintermediatesafter500minutesofreaction(Garcia-Martinezetal.
,2005).
PhotodegradationofnaphthaleneonwaterfilmsandbulkwaterwerecarriedoutbyChen(Chenetal.
,2007)withasetupinwhichnaphthaleneflowwasconstant.
UVlampswereusedforphotodegradation.
Theobservedkineticsofthephotoreactionwereindicativeoftheimportanceofsurfaceareatovolumeratioforheterogeneousreactionsasstudiedintheexperiment.
Humicacidspresentinsurfacewaterfilmswasalsoanimportantfactoraffectingtherateofphotoreactions.
InthelaterexperimentbyChen,theeffectofsurfactantsonnaphthalenephotodegradationwasstudiedwithSuwanneeRiverfulvicacid(SRFA).
ForlowSRFAconcentration,surfacereactionsofnaphthaleneonwaterwereenhancedforthinwaterfilmsthanthickerfilms.
Differentexperimentscarriedoutbyresearchersputsomelightonthefactorsthataffectreactionratesandexplainproductformationmechanismsunderdifferentreactionconditions.
Thecurrentresearchdealswithdifferentproductsofphotooxidationreactionsofnaphthaleneinfogcondensate.
ThefogcondensatealsocontainedNaCl.
Fromtheearlierdiscussionsregardingthefactorsaffectingphotodegradations,NaClwasexpectedtoaffecttheproductformationandratemechanism.
Figure6:C/Covs.
timeforbenzopyreneandchrysene(Milleretal.
,2005)2122CHAPTER3EXPERIMENT1:UPTAKEOFNAPHTHALENEBYFOGDROPLETSThescopeofthisexperimentwastostudytheuptakeofpolycyclicaromatichydrocarbon(naphthalene)andarelationbetweenpartitioncoefficientsofnaphthaleneandvariousreactortemperatures.
3.
1MaterialsandMethods3.
1.
1MaterialsandMethodsforSamplePreparationChemicalswererequiredforthepreparationofaerosolsolutionandtitrationsolutions.
NaphthalenewasthemostessentialchemicalthatwasusedasaPAHforstudyingpartitioncoefficients.
AerosolSolution:Aerosolsolutionwasa50%mixtureofisopropanolreagentandwaterv/v.
1.
36gramsofNaClwasthoroughlymixedintothesolutionforproductionofNaClaerosols.
Isopropanolreagent(≥98%)wasobtainedfromSigmaAldrich.
NaClwasobtainedfromFluka.
Allchemicalswereusedassuchwithoutdilution.
Theaerosolsolutionwascoveredproperlyafteritspreparationtoavoidlossofisopropanolbyevaporation.
Thisprecautionwasessentialtopreservethedesiredconcentrations.
Titrationchemicals:Titrationexperimentrequired0.
1MAgNO3solutionandsodiumchromateindicator.
AgNO3wasorderedfromFluka.
SodiumchromatewasobtainedfromSigmaAldrich.
Forpreparing0.
1Msolutionofsilvernitrate,tionswerecarriedout.
followingcalculaMolarity=(3)23Forsilvernitrate,xgramsofsilvernitrate169=0.
1(4)Forpreparationof0.
1Msolution,16.
9gramsofsilvernitratewasdissolvedin1literofwater.
0.
02gramsodiumchromatewasdissolvedin1literofwater.
Naphthalene:Naphthalene(≥99.
9%)wasobtainedfromSigmaAldrich.
Gaseousnaphthalenethatwasrequiredfortheexperimentwasobtainedbypassingastreamofcompressedairthroughapackedbedofnaphthalene.
Packedbedofnaphthaleneconsistedof0.
02gnaphthalenepergramsupport.
Solvents:AcetonitrilewasusedasasolventforHPLCanalysis.
Acetonitrile(≥99%)orderedfromMallinckrodtChemicalswasusedaspurchased.
Inthelatterpartofthisexperimentasexplainedin3.
2,naphthalenefromexitairwasadsorbedonpolymer.
Acetonitrilewasalsousedtodissolvethisadsorbednaphthalenefordeterminationofthenaphthaleneconcentrationintheexitairstream.
3.
1.
2EquipmentSpecificationsandTechniquesAerosolGenerator:TSImade3450VibratingOrificeAerosolGeneratorwasused(TSIincorporated,MN,USA)forproductionofNaClaerosols.
Itwasoperatedataconstantliquidfeedratethroughavibratingorifice.
Motorspeedwassetat0.
1X10-4cm/s.
Flowrateoftheaerosolsolutionwaskeptat3.
3cm3/min.
35morificewasusedwhichproducedNaClaerosolsrangingfrom1to40mparticlesize.
Theorificewasmadeupofstainlesssteel.
Asyringeselectedwas60ml(asadvisedinthemanual).
Afrequencyoforificevibrationwassetat80kHz.
Neucleospotswere24usedaschargeneutralizersforaerosolsandwereorderedfromTSI.
Weightoftheaerosolgeneratorwas20pounds.
Theacrylicdryingcolumnheightwas60cm.
HighPerformanceLiquidChromatography(HPLC):HPLCwasusedfordetectionofnaphthaleneinthesamples.
AdvantagesofusingHPLCareasfollows:1.
NumberofstepsrequiredforthesamplepreparationarelessthanGC/MS2.
Liquidchromatographscanbeconnectedtohighlyselectivefluorescentdetectors.
3.
LiquidchromatographscanalsobeconnectedtoUVdetectors.
Intheexperiment,Agilenttechnologies1100seriesHPLCwasusedwitha.
Onlinedegasser(modelG1379A)b.
Quaternarypump(modelG1311A)c.
Autosampler(modelG1313A)d.
Columnthermostat(modelG1316A)e.
DiodearrayUVdetector(DAD)(modelG1315A)f.
Massspectrometer(modelG1956B)UltraAqueousC18columnhaving0.
25m*0.
0021mdimensionswith5mparticlesizewasused.
ThemethodusedforthedetectionofnaphthalenewasCHENUD1foritsaccurateresults.
MethodSpecificationsareasFollows.
Stoptimeoffluorescencedetectorwas9min.
Detectionwavelengthwassetat254nm.
Solventsusedwere30%waterand70%acetonitrile.
Columnflowratewas0.
5ml/min.
Autosamplerhadanormalinjectionmode.
Injectorvolumewas25L.
SpectrumrangeforDADwasfrom190nmto400nm.
Columnthermostatwassetat30°C.
Mobilephasestartedat100%5MAmmoniaformatesolutionhavingpH3.
0.
Itwasheldfor10minutesandthenacceleratedto25100%methanolin60minutesandwasheldtherefor15minutes.
Atthistimetheflowratewas2*10-7m3/min.
ScanningElectronMicroscope(SEM):Joelmade840ASEMwasusedtodetectNaClaerosolsonthetape.
TheSEMhadavariableacceleratingvoltageof20,000Vandacceleratingcurrentof1to10namp.
MagnificationrangeprovidedbytheSEMwas10Xto300000Xandmaximumresolutionwas10nm.
Maximum6inchsamplecouldbeobservedunderthemicroscopeand360°completerotationofthesamplewaspossible.
3.
2ExperimentalSetupFigure7describestheexperimentalsetupthatwasusedtodetermineconcentrationsofnaphthaleneinfogcondensateandexitair.
Valuesoftheseconcentrationsataparticularreactortemperaturewereusedtodetermineavalueofpartitioncoefficientofnaphthalene.
Theexperimentwasrepeatedfordifferentreactortemperatures.
Reactor:Reactorwasa162cmlongglasscolumnwithaninnerdiameterof4.
5cm.
Ithadfiveinletsandoneoutlet.
NaClaerosols,watervapor,PAH(naphthalene),compressedairasacarriergasandtheprobesforthetemperatureandrelativehumidity(RH)meterwereintroducedintothereactorthroughthefiveinlets.
Theoutletwasconnectedtoaheatexchanger.
Aheatingtapewaswoundaroundthereactorbodytovaryitstemperature.
ThereactorhadacasingforUVlighttubesthatwasusedforphotoreactions.
ReactorInlets:NaClAerosols:Theaerosolgenerator(figure8)describedinsection3.
1.
2wasusedtoproduceNaClaerosols.
1.
36gramsofNaCldissolvedinthemixtureof50%isopropanolandwater(byvolume)wasusedasanaerosolsolution.
Detailedcalculationforthesequantitiesisexplainedinchapter5.
35μmorificeand60mlsyringewasselectedfortheexperiment.
Aerosolsolutionwasintroducedintotheaerosolgeneratorusingasyringe.
NaClaerosolswereproducedbymeansofavibratingorificeintheaerosolgenerator.
Aerosolsenteredthedryingcolumnaftercomingoutfromtheorifice.
Theywerewetandchargedaftertheirproduction.
Inthedryingcolumn,agentleliftwasprovidedbytheliftairsupplyandwetaerosolsfromtheorificeweredriedbyanairdrag.
Chargeonaerosolswasremovedbyusingchargeneutralizers.
Theseneutralizerswereattachedtotheinnerwallsofthedryingcolumnwiththescotchtape.
Theseneutralizersarecalledasnucleospots.
Figure7:Experimentalsetupforthepartitioncoefficientexperiment26AflexiblehosewasusedtocarryNaClaerosolsfromthedryingcolumntothereactor.
27Oneendoftheflexiblehosewasconnectedtotheend(top)ofthedryingcolumnandotherendoftheflexiblehosewasconnectedtooneoftheinletsofthereactor.
ItwasessentialtoensuresteadystreamofNaClaerosolsfromtheflexiblehoseintothereactor.
Theexperimentsuggestedinaerosolgeneratormanualwasperformedforverificationofanaerosolstream.
Fortheverificationexperiment,Scotchtapewasattachedtotheendoftheflexiblehosethatwasconnectedtothereactorinletsothataerosolscomingoutfromtheflexiblehosewouldsticktothetapeinsteadofdirectlyenteringintothereactor.
Then,thesyringewasfilledwithanaerosolsolutionandfixedtoaninjectionportoftheaerosolgenerator.
Syringemotorwasstartedandaerosolswereproducedcontinuously.
Thesyringewasrefilledthreetofourtimesandthesolutionwasintroducedintotheaerosolgeneratorforproductionofaconsiderablenumberofaerosols.
Aerosolgeneratorwasthenswitchedoff.
Thetapeattachedtotheflexiblehosewasremovedandexaminedunderascanningelectronmicroscope(SEM).
SpecificationsoftheSEMareexplainedin3.
1.
2.
NaClaerosolswereobservedgluedtothetape.
Aboveexperimentusingascotchtapeprovedthatastreamofaerosolswasenteringintothereactor.
Nextstepwastomakesurethataerosolswerereachingthereactoroutletthatwasatthetopofthereactor.
Experiment1requiredahumidenvironmentinsidethereactor.
Therefore,toensureanupliftofaerosolsinthehumidenvironmentinsidethereactor,acontinuoussupplyofwatervaporandacarriergaswasprovided.
Thewatervaporwassuppliedbyboilingwater.
Thisprocedureincreasedrelativehumidityofthereactor.
ApieceofScotchtapewasattachedtotheoutletofthereactor.
Aerosolgeneratorwasstartedandsimilarprocedureasexplainedearlierwasfollowed.
ThetapewasremovedafterproducingsufficientnumberofaerosolsandwasexaminedunderSEM.
WaterVapor:Waterwasheatedto100oCinabeaker.
Asmallstreamofcompressedairwaspassedthroughtheboilingwaterandintroducedintothereactorthroughoneoftheinlets.
Thisprocessresultedin82%relativehumidityinsidethereactor.
Figure8:Aerosolgenerator(Retrievedfromwww.
TSI.
com)Naphthalene:28Toprepareanaphthalenesource,chromosorbPwasmixedwithasolutionofhexanecontainingpurenaphthalene.
Hexanewasevaporatedlaterwhichgave0.
02gramsnaphthaleneadsorbedpergramofsupport.
2stainlesssteelcolumnswerepackedwith15gramseachofthischromosorbPasanaphthalenesource.
Astreamofcompressedairwaspassedthroughthepackednaphthalenecolumn.
Thisstreamwasthenintroducedintothereactorthroughoneoftheinletsasanaphthalenesource.
Theflowrateofcompressedaircontainingnaphthalenewassetat291977ml/min.
ReactorOutlets:Thereactorhadoneoutletwhichwasconnectedtoashellandtubeheatexchanger.
Theinitialexperimentalsetupconsistedofapassivefogcollector.
Atypicalfogcollectorusedinalaboratoryforfogcollectionisshowninfigure9.
Ithadarectangularhollowstainlesssteelcasingwithinwhichwasasetofparallelplatesseparatedby2.
3mmfixedat35°tohorizontal.
Fogenteredthroughthecasingandseparatedfromthecarriergasbyimpactiononthesmallgapbetweentheparallelplates.
Efficiencyofthefogcollectorwasdeterminedtobeonly22%.
Thisefficiencywasverylowandunacceptablefortheexperiment.
Toincreasetheefficiencyoffogcondensation,ashellandtubeheatexchangerwasdesigned.
Efficiencyofthefogcondensationbyheatexchangerwasdeterminedexperimentallyandwasfoundtobe86%.
TheHeatExchanger:Figure10showstheshellandtubeheatexchangerthatwasusedforthisexperiment.
Waterwasusedasashellsidefluid.
Theshellhadoneinletandoneoutletforthecoolingwater.
PortAwasaninletandportBwasanoutletforthecoolingwater.
TheIWAKImademagneticpumpof3gpmcapacitywasusedtocirculatethecoolingwater.
Inlettemperatureofthecoolingwaterwas280K.
Reactorcontentswereusedasatubesidefluid.
Thetubehadthreeoutletsandoneinlet.
ReactorcontentsenteredtheheatexchangerthroughportC.
Reactorcontentswereseparatedasfogcondensateandcarriergasaftercondensation.
FogcondensatewascollectedfromportsDandEandacarriergaswaspulledoutbyaThomasmadelightpumpof4gpmcapacityconnectedaftertheheatexchangerthroughportF.
Apurposeofemployingthelightpumpwastoenhanceflowofacarriergasthroughtheactivatedcarboncolumnsconnectedtotheoutletofthepump.
Thispumphad2inletsandoneoutlet.
Atubefromthereactoroutletwasconnectedtooneinletofthepumpandanothertubewhoseoneendwasopentoatmospherewasconnectedtotheotherinletofthepump.
Thisarrangementwasmadetoavoidtheexcessiveairpullbythepumpfromthereactor.
Theoutletofthepumpwasconnectedtoactivatedcarboncolumns.
Thepurposeoftheactivatedcarboncolumnwastoadsorbanynaphthaleneintheexitair.
Figure9:Fogcollector3.
3ExperimentalProcedure3.
3.
1CalculationofthePartitionCoefficientsAsimultaneousinflowofnaphthalene,aerosols,watervaporandthecompressedairsupplyintothereactorwasessentialfortheexperiment.
Temperatureofthereactorwassetat334K.
Themixtureretainedinsidethereactorfor62seconds.
Duringthecourseofresidencetimeofthemixturewithinthereactor,surroundingnaphthalenewasabsorbedbythegrowingaerosolsorfogdroplets.
Thereactorcontentswerethenpassedthroughtheheatexchangerconnectedtotheoutletofthereactorwherefogwascondensedandcollected.
30Collectedcondensatecontainedaerosolsandnaphthalene.
Toensurethepresenceofsodiumchlorideinthecollectedcondensate,thecondensatewastitratedagainstAgNO3solutionusingsodiumchromateasthetitrationindicator.
Acolorchangefromnocolortoorangewasindicativeofthepresenceofchlorideionsinthesolution.
Figure10:HeatexchangerusedforthefogcondensationTheconcentrationofnaphthaleneinthefogcondensatewasmeasureddirectlybyHPLCanalysis.
Fordeterminationofnaphthaleneconcentrationintheexitairstream,apolymertubewasinsertedinthetubeconnectingthereactoroutlettothepumpinlet.
Airstreamwaspassedthroughthepolymertubeandnaphthaleneintheexitairwasadsorbedonthepolymer.
Thetubewasremovedafter10minutesandthecontentsweremixedwith5mlacetonitrile.
Naphthalenethatwasadsorbedonpolymerwasdissolvedinacetonitrile.
Polymerwasinsolubleinacetonitrile.
After7to8hoursofmixingtime,1mlacetonitrilewasremovedandanalyzedusingHPLC.
31Calculationsfornaphthaleneconcentrations(giveninchapter6)wereperformed.
Valuesoftheconcentrationsofnaphthaleneinfogcondensateandexitairwereobtainedandavalueofthepartitioncoefficientwascalculatedusingequation(1).
Thesameexperimentwasrepeatedforreactortemperatures346.
5K,361.
5K,371.
5Kandvalueofthepartitioncoefficientateach32reactortemperaturewascalculated.
Aplotofdifferentreactortemperaturesandpartitioncoefficientswasobtained.
3.
3.
2PhotoOxidationReactionofNaphthaleneandFogContainingNaClThenextstepinexperiment1afterfindingthevaluesforpartitioncoefficientswastostudyphotooxidationofnaphthaleneinfogcontainingNaClasthecondensationnuclei.
Residencetimeprovidedbythereactorwas62seconds.
Reactiontimewasthereforealso62seconds.
Tostarttheexperiment,UVlighttubesinthecasingsurroundingthereactorbodywereswitchedON.
Theexperimentwasstartedexactlythesamewayasmentionedinsection3.
3.
1.
ThecollectedcondensatewasexaminedforthereactionproductsbyusingHPLC.
3.
4ResultsandDiscussion3.
4.
1ResultsandDiscussionfortheNaphthaleneUptakeExperimentIntheexperiment,initially,averificationexperimentwascarriedoutinwhichatapewasattachedtotheflexiblehoseandtothereactoroutletasexplainedin3.
3.
1toensureasteadystreamofaerosolsintothereactor.
Figure11showsaclose-upviewoftheNaClaerosolobtainedasaresultwhenobservedunderthescanningelectronmicroscope.
TheequivalentdiameterofNaClaerosolswasintherangeof1-10m.
Thespecificaerosolshowninthefollowingfigurehasadiametercloseto4m.
Figure11showsatypicalshapeoftheNaClaerosols.
TheNaClaerosolwasdistortedcubicalinshape.
Shapedependsonseveralfactorssuchasdiameteroftheaerosol,vibrationfrequencyoftheorificeandstabilityofaerosols(Hinds,AerosolTechnology).
Thenextstepwastoensureanupliftofaerosolsinsidethereactor.
Figure12belowshowsanabundanceofNaClaerosolsobtained.
Carefulobservationshowspresenceofawaterfilmaroundtheaerosols.
Thisprovedthattheaerosolswereindeedformedwithawaterfilmanditwasthereforepossibletogeneratefogdropletswithinthereactor.
Thenextstepwastoensureanupliftofaerosolsinsidethereactor.
Figure12belowshowsanabundanceofNaClaerosolsobtained.
Carefulobservationshowspresenceofawaterfilmaroundtheaerosols.
Thisprovedthattheaerosolswereindeedformedwithawaterfilmanditwasthereforepossibletogeneratefogdropletswithinthereactor.
Figure11:ActualstructureoftheobtainedNaClaerosolThenextstepwastoensureanupliftofaerosolsinsidethereactor.
Figure12belowshowsanabundanceofNaClaerosolsobtained.
Carefulobservationshowspresenceofawaterfilmaroundtheaerosols.
Thisprovedthattheaerosolswereindeedformedwithawaterfilmanditwasthereforepossibletogeneratefogdropletswithinthereactor.
Theresultsofexperiment1demonstratedthatfogcanbegeneratedinalaboratoryusingthegivensetup.
TheexperimentalsoshowedthatgeneratedandgrownNaClaerosolswhichresultedinfogdropletswerecapableofabsorbinggaseousnaphthalene.
33Thepartitioncoefficientofnaphthalenewasfoundtoincreasewiththereactortemperatureasexpected.
Figure13showsaplotoflnKwavs1/T(K-1).
Fromtheplottedgraph,someimportantconclusionscanbedrawn.
Van'tHoff'sequationbepidacanexlaneslnKΔHRTΔSR(5)Where,-ΔHistheenthalpyandΔSistheentropyoftheprocess.
RistheuniversalgasconstantandTisthetemperature.
Figure12:Distributionandabundanceofaerosols34Followingequation5andfigure13,twoimportantvaluescanbecalculated.
Fromtheplottedgraph,35ΔHobs=-18.
44kJ/molΔSobs=-35.
45J/molKThecorrelationcoefficientwas0.
987showingthatoverthementionedtemperaturerange,thefitwassatisfactory.
Boththeenthalpyandentropyarenegativeindicatingthattheprocesswasexothermic.
WiththeobtainedvaluesofΔHandΔS,ΔGcanbecalculatedbytheequationΔG=ΔH-Δ(6)TSKwa=exp(ΔGRT(7)ΔGhasanegativevalueforausedtemperaturerange.
Thisshowsthathigherenergywasnecessarytodissolvenaphthaleneinthefogdropletsasthetemperatureincreased.
Therefore,intheactualexperiment,observationsindicatedthatahigherpercentageofnaphthalenewasretainedinexitairandthispercentageincreasedasthetemperatureofthereactorwasincreased.
Iftheabovegraphwasextendedtoreach298K,wegetKwavalueforthecurrentexperimentas24.
11.
ThisvaluecanbecomparedtotheKwavalueofpurewaterforpreviousexperimentscarriedoutbyresearchers.
Alaee(Alaeeetal.
,1996)calculatedKwatobe58forbulkphasewhereasNISTbookgivesthevalueof64.
ThisdifferenceinthevalueofpartitioncoefficientforpurewaterandcurrentstudywasduetotheinducedsalinitybecauseofNaClpresenceinthefogcondensate.
IthasbeenobservedthatincreasingconcentrationofNaCldecreasesapartitioncoefficientvalue.
Arecentstudycarriedoutshowedthatthevaluesofenthalpyandentropyassociatedwiththepartitioningprocessofnaphthaleneinathinwaterfilmwere-22kJ/moland-41J/molK(Chenetal.
,2006).
ItwasalsoobservedthatthevalueofKwaincreasedwiththedecreasingthicknessofthewaterfilm.
Onsimilarlines,ithasbeenalsoshownthat,thereisaconsiderableincreaseinKwawithdecreasingfogdropletdiameter(Mooreet.
al.
,2003).
y=2219.
x‐4.
264R=0.
98711.
21.
41.
61.
822.
22.
42.
60.
002650.
00270.
002750.
00280.
002850.
00290.
002950.
0030.
00305lnKwa1/T(K‐1)Figure13:lnKwavs1/Tfornaphthaleneonfogdroplets36ΔGhasanegativevalueforausedtemperaturerange.
Thisshowsthathigherenergywasnecessarytodissolvenaphthaleneinthefogdropletsasthetemperatureincreased.
Therefore,intheactualexperiment,observationsindicatedthatahigherpercentageofnaphthalenewasretainedinexitairandthispercentageincreasedasthetemperatureofthereactorwasincreased.
Iftheabovegraphwasextendedtoreach298K,wegetKwavalueforthecurrentexperimentas24.
11.
ThisvaluecanbecomparedtotheKwavalueofpurewaterforpreviousexperimentscarriedoutbyresearchers.
Alaee(Alaeeetal.
,1996)calculatedKwatobe58forbulkphasewhereasNISTbookgivesthevalueof64.
ThisdifferenceinthevalueofpartitioncoefficientforpurewaterandcurrentstudywasduetotheinducedsalinitybecauseofNaClpresenceinthefogcondensate.
IthasbeenobservedthatincreasingconcentrationofNaCldecreasesapartitioncoefficientvalue.
Arecentstudycarriedoutshowedthatthevaluesofenthalpyandentropyassociatedwiththepartitioningprocessofnaphthaleneinathinwaterfilmwere-22kJ/moland-41J/molK(Chenetal.
,2006).
ItwasalsoobservedthatthevalueofKwaincreasedwiththe37decreasingthicknessofthewaterfilm.
Onsimilarlines,ithasbeenalsoshownthat,thereisaconsiderableincreaseinKwawithdecreasingfogdropletdiameter(Mooreet.
al.
,2003).
TitrationwasperformedtoverifypresenceofNaClinthecollectedcondensate.
Inthetitrationexperiment,AginAgNO3solutionreactedwithchlorideionstoformAgClsolutionandinpresenceofsodiumchromateindicator.
Colorofthesolutionchangedfromcolorlesstolightorange.
Thereactionoccurredasperthefollowingequation(Thecentralscience,experiment7,retrievedfromwww.
earlham.
edu)AgNO3(aq)+Cl-(Inwater)AgCl(s)+NO3-(aq)CalculationsfordeterminingNaClconcentrationinwateraredetailedincalculationssectionofthischapter.
NaClconcentrationwasdeterminedfromtheknownquantitiessuchasmolarityofAgNO3solution,andvolumeofcondensateandthevolumeofAgNO3thatwasrequiredforthereaction.
Theresultsshowedthataverageconcentrationof2.
66g/lofNaClwaspresentinthecollectedfogsamples.
3.
4.
2ResultsandDiscussionforthePhotooxidationReactionExperimentInsidetheReactor.
Aftersuccessfulcompletionofpartitioncoefficientexperiments,thesameexperimentwascarriedoutwithUVlightsonthereactorswitchedonasexplainedin3.
3.
2.
FogcondensatewascollectedandanalyzedonbothGC/MSandHPLC.
Thereactiontimewas62seconds.
GC/MSandHPLCcanonlybeusedtodetectorganicsiftheyareinmeasurableconcentrationranges.
InitialanalysisdidnotshowanyobservablereactionproductswhichindicatedthattheproductswerepresentinminutequantitiesthatwerenotdetectablebyGC/MSortheywerenotformedatall.
Therefore,possibly,theproductswerepresentinminuteconcentrationbutwerenotdetectable.
Onewaytodetectproductswastoconcentratethem.
Forconcentrationofproducts,anexperimentwasperformedwheretheproductswereextractedusinghexane.
Hexaneservesasabettersolventfortheorganicproductsthanwater.
Ablow38downprocedurewascarriedoutforthissolution.
Inthisprocedure,nitrogenwasblownovertheextractedhexanesolution.
Hexane,beingmorevolatilethantheproducts,evaporatedprogressivelyandproductswereconcentratedintheresidualhexane.
TheseproductswerefurtheranalyzedonGC/MS.
SimilarprocedurewascarriedoutforHPLCusingacetonitrilewhichisagoodsolventforHPLCanalysis.
Inboththecases,afterconcentrationoftherespectivesolutions,noproductwasdetected.
Itwasthenconcludedthattherewerenoproductsofthereactionforthereactiontimeof62seconds.
Therefore,asmallreactiontimewasnotenoughfortheproductformationandapossibilityofoccurrenceofthereactioninsidethereactorwasveryrare.
Experimentalsetupforabulkphasereactionprovidedanadjustablereactiontime.
ThereactionwascarriedoutinabulkphasewiththeUVlightsetup.
Thischapterexplainedresultsanddiscussionsrelatedtothefirstpartoftheresearch.
Thefollowingchapterwillexplainprocedureandresultsforthesecondpartoftheresearch.
SecondpartoftheresearchwasrelatedtothephotooxidationreactionsofnaphthaleneinthecollectedfogcondensateunderUVlightinabulkphaseofwaterinthementionedUVlightsetup.
39CHAPTER4EXPERIMENT2:PHOTOOXIDATIONOFNAPHTHALENEWITHINTHEFOGCONDENSATEINAUVLIGHTSETUPResearchexperimentsofuptakeandUVinducedphotooxidationreactionsofpolycyclicaromatichydrocarbonsinwaterhavebeenofmajorinteresttomanyresearchersforyears.
WhenwaterbodiesandfogabsorbsurroundingpollutantsthatcontainPAHs,UVlightintheatmosphereoxidizestheminpresenceofwater.
Thisprocessresultsinnumerousproductsofthereactionthatgetdissolvedinsurroundingwater.
Inthisresearch,naphthalenewasusedasthemostabundantlyfoundPAHinclassofpollutants.
PhotooxidationofnaphthalenewithinfogcondensateinpresenceofUVlightwascarriedoutandtheprocessrevealedsomemajorproductsofthereaction.
Thischapterfocusesonthereactionmechanismanddifferentproductsthatwereobtainedasaresult.
4.
1MaterialsandMethods4.
1.
1ChemicalsChemicalsrequiredfortheexperimentincludedcalibrationstandardsandsolvents.
Benzaldehyde(≥98.
5%)wasobtainedfromAlfaAesar.
ItwasusedasacalibrationstandardforGC/MSanalysis.
Forthecalibrationpurpose,benzaldehydewasdissolvedinhexaneandcalibratedfordifferentconcentrations.
Hexane(≥98.
5%)wasorderedfromSigmaAldrichandusedasanexchangesolventforGC/MSanalysis.
Acetonitrile(≥99%)wasusedasasolventfortheHPLCanalysis.
ItwasobtainedfromMallinckrodtChemicals.
Phthalideand1,3-indandionewererequiredascalibrationstandardsforthedetectedreactionproducts.
Phthalide(98%)and1,3-indandione(≥98%)wereorderedfromSigmaAldrich.
HeliumandArgonwereusedascarriergases.
ThesewereorderedfromCapitolWeldersasandwhenrequired.
404.
1.
2MethodsandTechniquesGasChromatographywithMassDetection(GC/MS):Agilent6890NGaschromatographwasusedwithamassdetector(5973)andaninjector(7683).
EPA8270methodforsemivolatileswasusedfordetectionofreactionproducts.
Inthemethod,sampleinjectionvolumewas1μlandtherewerethreepreinjectionsandthreepostinjectionsofthecarriersolventhexane.
Agilent19091S.
433columnwasused.
Columnflowwaskeptat1ml/minandpressurewas8.
9psi.
Heliumwasusedasacarriergaswith250°Cheatertemperature.
Injectorwasinapulsedsplitlessmode.
Oventemperaturewasinitiallyheldat70°Cfor5minutes,thenrampedto270°Cwith15°C/minandheldfor7minutes.
Itwasthenrampedupto300°Cwith15°C/min.
UVLightSetup:UVITRONIntelli-ray600;UV00000832wasusedastheUVlightsetupforthisexperiment(UVITRONinternational,MA,USA).
IntensityoftheUVlightandanexposuretimewereadjustable.
ThedistanceofasamplefromtheUVlampswasalsoadjustable.
140V600Ametalhalidelampswereusedwith32mmarclengthandhorizontalburningposition.
Thelamphadatypical1000hourslife.
Theradiationfluxwas110W;315-400nm.
Operatingtemperaturewas10to40°typical.
Maximum8"*6"curingareawasavailable.
4.
2ExperimentalSetupTheexperimentdescribedinchapter1indicatedthatthereactiontimeof62secondswasinsufficientforthephotooxidationreactionofnaphthalene.
So,abulkphasereactionwascarriedoutusingcollectedfogcondensateandaUVlightsetupinwhichUVexposuretimeandhencethereactiontimewasadjustable.
41UVLight:Figure14showstheUVlightsetupusedforthisexperiment.
TheUVlightsourcegenerated5W/m2energy(photonflux)whensetat50%intensitywith6inchdistancebetweenthesamplesandtheUVlightsource.
Thesetupwascoveredwithastainlesssteelsheettoprotectsurroundings.
ReactionMixture:Thecollectedfogcondensatefromtheexperimentdescribedinchapter1wasusedasthereactionmixtureforthisexperiment.
Thereactionmixturedidnothaveprovisionforacontinuousinflowofnaphthalene.
Thereactionceasedwhentheconcentrationofnaphthaleneinthecondensatewasverylow.
Itwasthereforenecessarytoensureaconsiderableconcentrationofnaphthaleneinthecondensate,essentialforcompletionofthereaction.
So,thecondensatewasenrichedinnaphthalenebybubblingnaphthalenethroughthecondensateforfourtofivehours.
4.
3ExperimentalProcedureTheobjectivesoftheexperimentwereasfollows:1.
TofindproductsofUVphotooxidationreactionofnaphthaleneinsalinefogcondensate.
2.
Tocalculateareactionrateconstantfornaphthalenedegradation.
3.
Toobserveconcentration-timedataforthemajorproductformation.
4.
TocalculateareactionrateconstantfornaphthalenedegradationusingareactionmixturenotcontainingNaClandcompareitwiththeresultsobtainedin2.
Fivevialsof4mlvolumeeachwerefilledwiththeprocessedandcondensateenrichedwithnaphthaleneandcontainingNaCl.
AllthevialsweretightlyclosedandplacedparalleltoeachotherundertheUVlight.
Placingthevialshorizontallyandparallelprovidedsamesurfaceareaforthereactiontothecontentsinallfivevials.
TheUVlightwasstartedandUVintensitywasadjuvialwaslowestexoffivehbecauseiidentificaustedto10%removedfroxposuretimehours.
Conteitcandetectationofthepoftheactuaomtheappaeofonehouentsineachtminuteconproductsthroalintensity.
AaratusaftereurandlastvihvialwerencentrationsoughalibrarAsimplifiedeveryhour.
ialremovedanalyzedonoftheprodurysearch.
darrangemenThevialwhfromtheappnGC-MSauctsandGCntisshownhichwasremparatushadandHPLC.
C/MSwasusinfigure15movedfirsthanexposureHPLCwassedforthed.
OnehadaetimeuseddirectFigure14Aexperimereactionacetonitrrespectiv4:Intelli-rayAftertheanentswerepeproductsanileandhexvely.
Also,thy600UVlignalysisoftherformedtondnotintrodxanewereheproductsghtsetup(Tahereactionensurethatducedfromianalyzedsethatwereob42akenfromuvmixtureinttheproducimpuresolveparatelyinbservedintvitroninternanallfivevctsobservedents.
Forthentheirpurethereactionational.
com)vials,additiinanalyseseseverificatformsonwereordereonalverificsweretheationexperimHPLCandedfromchemcationactualments,dGCmicalsuppliersandanalysisofthepurepurchasedchemicalswascarriedouttomatchtheirretentiontimewiththatoftheobservedproducts.
Figure15:ArrangementofvialsunderUVlight(Frontview)ItwasalsoimportanttoobservedifferenceinproductformationbyphotooxidationreactionofnaphthaleneinafogcondensatecontainingNaClandinafogcondensatewithoutNaCl.
AnotherexperimentwascarriedoutwiththereactionmixturecontainingwaterandnaphthalenewithoutanyNaCl.
Forpreparingthisreactionmixture,naphthalenewasbubbledthroughacondensedwatervaporuntilitsconcentrationreached26mg/l.
ThiswasusedasareactionmixtureandplacedintheUVlightapparatusinvialsasmentionedearlier.
EachvialwasremovedaftereveryonehouranddecreaseinnaphthaleneconcentrationwasobservedonGC.
Also,productsofthereactionwerestudiedbyHPLCandGC/MSanalysis.
43444.
4ResultsandDiscussionThereactionmixtureconsistedofnaphthalene,waterandsodiumchloride.
Photooxidationreactionofnaphthaleneoccurredinpresenceofanultravioletlight.
PresenceofNaClresultedinformationofdifferentreactionproductsthanthosewhichweregenerallyobservedasaresultofphotooxidationreactionofnaphthalenewithwaternotcontainingNaCl.
4.
4.
1AnalysisofaProductFormationUsingtheReactionMixtureContainingNaCl.
TheanalysisofthereactionmixtureinvialsplacedintheUVlightsetupwascarriedoutusingGC/MSandHPLCasmentionedintheproceduralsection4.
3.
BenzaldehydewasdetectedasthemajorproductofthereactiononGC/MS.
HPLCwasusedtodetectotherproductspresentinminuteconcentrations.
ThemajorproductfoundusingHPLCanalysiswasphthalide.
Figure16showsthespectrumofGC/MShavingbothnaphthaleneandbenzaldehyde.
Naphthalenewasseenat10.
4minutesonandbenzaldehydepeakwasseenat5.
6minutes.
Fromtheearlierwork,benzaldehydewasneverdetectedastheproductofaphotooxidationreactionofnaphthalenewithpurewaterthatdidnotcontainNaCl.
FromtheworkdonebyChen(Chenetal.
,2006),themainproductsofthereactionobservedwerecoumarin,phthalide,1,3-indandioneand1-naphthol.
AsexplainedbyMcConkey(McConkeyetal.
,2001),photooxidationofnaphthaleneinaqueoussolutioninducedbynaturalsunlightrevealed11majorproductsand40minorproductswhenanalyzedonHPLC.
Majorproductsincluded1-naphthol,coumarin,isobenzofuranone,1,2-naphthoquinone.
Apartfromthephotooxidationofnaphthaleneinaqueousmedium,otherenvironmentalconditionssuchasaphotooxidationreactionofnaphthaleneinpresenceoftitaniumperoxideandhydrogenfluorideresultedinthesimilarproducts(Dasetal.
,1994).
StudiesrelatedtoproductsofnaphthalenemetabolismwerecarriedoutbyTingle,Wilsonandotherresearchers(Tingleetal.
,1993;Wilsonetal.
,1996).
Whentheproductsofnaphthaleneinaqueousenvironmentswerecomparedtothe45naphthalenemetabolismproducts,theywerefoundtobesimilar.
Ascomparedtoalltheseproductsobtainedinpreviouswork,benzaldehydewasanewproduct.
ItwasthereforesuggestedthatpresenceofNaClinthereactionmixturechangedthereactionmechanismandtheproductformation.
AtraceofHPLCanalysisshowninfigure17illustratespresenceofphthalideasamajorproductofthereaction.
PhthalidewastheonlyproductdetectedwithHPLCanalysisinaconsiderableconcentrationandmatchedwiththeearlierworkdonewithwaternotcontainingNaCl.
FigureshowstheanalysisofthereactionmixtureonHPLCafter4hoursofreactiontime.
PhthalidepresencewasconfirmedbymatchingtheUVspectraandretentiontimeofpurephthalidedissolvedinacetonitrile.
Retentiontimewasmatchedwithatoleranceof0.
1minutes.
Formationof1,4-naphthaleneendoperoxidecouldbethemaincauseforformationofphthalidewith(2,4)photocycloadditionofoxygenasanintermediateforthereactionasexplainedbyMcConkey(McConkenyetal.
,2001).
Themainfocusofexperiment2wastoobserveandstudythedecreaseinconcentrationofthenaphthaleneandincreaseinconcentrationofbenzaldehydethatwasareactionproductwiththereactiontimeof5hours.
Theaimofexperiment2wastoalsocalculatethereactionrateofnaphthalenedegradationfromtheavailableconcentration-timedata.
Figure18showsdecreaseinconcentrationofnaphthalene(Cn)withincreasingtime.
Theinitialconcentrationwas26mg/l.
After5hours,4.
2mg/lconcentrationofnaphthalenewasobserved.
Forcalculationofanoverallreactionrateconstantofnaphthalene,orderofthereactionwasdeterminedfirst.
AsexplainedinbyFogler(FoglerH.
S.
,elementsofChemicalReactionEngineering,3rdEd.
),verificationoforderofthereactionwasdonebyplottingvariousgraphs.
Theresultshowedthatitwasafirstorderreaction.
TheequationforfindingreactionrateconstantforfirstorderreactionislnCC=k.
t(8)Figure16:SpectrumofthereactionproductsofthephotooxidationreactionofnaphthalenewithfogwaterconsistingofNaCl.
Figure19showsthegraphthatwasobtainedbyplottingln(Cno/Cn)vs.
timeforthereaction,whereCnoistheinitialconcentrationofnaphthalene.
Alinearfitwasaveryclosematchtothedatapointsplottedwiththecorrelationcoefficient0.
977.
Thenatureoftheplotwasindicativeofthefirstorderofthereaction(Foger,Elementsofchemicalreactionengineering;O.
Levenspiel,Chemicalreactionengineering).
46Withappropriatecalculations(explainedlaterinsection3.
6ofthischapter),rateconstant"k"fortheoverallreactionwasfoundtobe5.
75*10-3/min.
ThisvalueofthereactionrateconstantwashigherthanthevalueobtainedbyChen(Chenetal.
,2006)thatwasoftheorderof10-4.
Asdiscussedinthepaper,reactionrateconstantfordifferentwaterfilmthicknesseswasdifferent.
Naphthalenedegradationrateconstantwasfoundtoincreasewithdecreasingfilmthickness.
Thiswasindicativeofincreaseinthereactionratevaluewithincreasingsurfacetovolumeratio.
Figure17:HPLCtraceshowingphthalidepeakattheretentiontimeof4.
743seconds.
Absorbanceat254nm.
Asimilarapproachcanbeputforthforadropletreaction.
Thecurrentphotooxidationexperimentwasperformedinabulkphaseofwater.
Ifphotooxidationreactionofnaphthalenewascarriedoutwithinfogdroplets,therecouldbethesimilarrateconstantvalues.
Itcouldthereforebeassumedthat,ifthisreactionwascarriedoutwiththesetupofexperiment1,and5hoursofreactiontimewasprovided,thenthereactionrateconstantwouldincreasewithdecreasingdropletdiameterdependingontheconcentrationofnaphthaleneadsorbedonfogdroplets.
47BenzaldehydewasseenasamajorreactionproductwithGC/MSanalysis.
Figure20givesanincreaseinbenzaldehydeconcentrationwithincreasingtime.
Fromtheavailabledata,itwasobservedthatbenzaldehydeformationstartedbetween2to3hours.
Intheshapeofthecurve,itcanbeseenthatbenzaldehydeformationwasafirstorderreactionasexplainedbyFogler.
051015202530050100150200250300350Cn(mg/l)Time(min)Figure18:Concentrationvs.
timecurvefordecreaseinnaphthaleney=0.
005xR=0.
97700.
20.
40.
60.
811.
21.
41.
61.
82050100150200250300350ln(Cno/Cn)Time(min)48Figure19:ln(Cno/Cn)vs.
timefornaphthalene49Benzaldehydehasbeenobservedasanintermediateduringthephotodegradationofnaphthaleneinpreviouswork.
IntheresearchdonebyGuillard(Guillardetal.
,1992)anexperimentwascarriedoutwhichfocusedonreactionproductsofaphototransformationofnaphthaleneadsorbedonTiO2.
Thisexperimentresultedin2majorproductsphthalicanhydrideandbenzoicacid.
Theintermediatesforthisreactionincluded1,4-naphthoquinoneandbenzaldehyde.
Benzaldehydewasanintermediateforbenzoicacidformation.
Similarproductsofthereactionwerealsoobservedfromtheadsorptionofnaphthaleneonflyashandferricoxideinthesameresearch,butwithlesserconcentrations.
AsimilarworkwasalsocarriedoutbyFox(Foxetal.
,1983).
forsubstitutednaphthaleneandtheresultsoftheexperimentofnaphthaleneoxidationshowedpresenceofbenzaldehyde.
Thesestudieshaveprovedthatbenzaldehydecanbeaproductofnaphthalenedegradation.
Inthepresentresearch,benzaldehydewasobservedunderdifferentreactionconditionsthanthoseusedbyGuillardandFox.
Reactionconditionscanaffecttheoverallreaction.
AstudycarriedoutbyArmstrong(Armstrongetal.
,1966)shedssomelightontherateconstantforseawateroxidationofthedissolvedorganicmatter.
Fromhiswork,organicmatterfollowedfirstorderkineticsforcarbonandrateconstantforthedegradationoftheorganiccarbonwasabout0.
05/min.
ThepresentexperimenthadamajorroleofNaClconcentrationinthereactionmixture.
Similartoseawaterreactions,NaClmayhavealteredthereactionrateandproductformationinaphotooxidationreactionofnaphthaleneinthecurrentresearch.
AstudycarriedoutbyArmstrong(Armstrongetal.
,1966)shedssomelightontherateconstantforseawateroxidationofthedissolvedorganicmatter.
Fromhiswork,organicmatterfollowedfirstorderkineticsforcarbonandrateconstantforthedegradationoftheorganiccarbonwasabout0.
05/min.
ThepresentexperimenthadamajorroleofNaClconcentrationinthereactionmixture.
Similartoseawaterreactions,NaClmayhavealteredthereactionrateandproductformationinaphotooxidationreactionofnaphthaleneinthecurrentresearch.
‐10123456789120170220270320Cb(mg/l)Time(min)Figure20:Increaseinbenzaldehydeconcentrationwithtime.
4.
4.
2AnalysisofaProductFormationfromtheReactionMixturenotContainingNaClAverificationexperimentasexplainedin4.
3wascarriedouttoensurethattherewasnopresenceofbenzaldehydeasoneofthereactionproductsofnaphthalenephotooxidationwithincondensatenotcontainingNaCl.
Thisexperimentwasalsoperformedtoensurethatthereactionwasgivingallsimilarproductsthatwereobservedinearlierstudies.
Figure21showsaGC/MSspectrumforanalysisofthereactionmixtureafter4hoursofreactiontime.
Fromthefigure,itcanbeseenthattherewasnopresenceofbenzaldehydeasaproductofthereaction.
Naphthalenepeakisseenat10.
4minutes.
Thisresultmatcheswithotherstudiesdonewithpurewaterasexplainedearlierinthissection.
50IdentificationofotherproductswhichwereinsmallconcentrationsandundetectableonGC/MSwasnecessary.
HPLCwasusedtodetectthoseproducts.
1,3-indandioneandphthalidewereobservedasthemajorreactionproducts.
TheywereconfirmedbymatchingtheirrespectiveUVspectraandretentiontimestopurestandardsforHPLC.
Theseweresomeoftheproductsobtainedinsimilarreactionsinearlierresearchworks.
However,otherproductslikenaphthoquinonesandnaphtholswerenotobservedonHPLCinthecurrentexperiment.
Theywereeithernotpresentorwerepresentinundetectablysmallconcentrations.
Figure22showsHPLCtraceforthereactionproducts.
1,3-indandionecanbeseenatretentiontimeof3.
754minutes.
Phthalidewasobservedat4.
451minutes.
Figure21:GC/MStraceforproductsofphotooxidationofnaphthaleneinwaterwithoutNaCl.
51Decreaseinconcentrationofnaphthalenewasalsostudiedforthisexperimentwiththeobtaineddata.
Figure23showsdecreaseinnaphthaleneconcentrationwithtime.
Thecurveissimilartotheoneshowninfigure18.
Fogler(Fogler,Elementsofchemicalreactionengineering)givesanexplanationfornatureofacurveandrelatedreactionorder.
Itwasconcludedbyadatafitthatitwasafirstorderreaction.
Chen(Chenetal.
,2006)hadconcludedthatsimilarreactionconditionsresultedinafirstorderreactionofnaphthalene.
Forthefirstorderreaction,plotofln(Cno/Cn)vs.
timewasobtainedasdirectedbyFoglertocalculatethereactionrateconstant.
Figure24showsthenatureofthisplot.
Astraightlinepassingthroughorigin(0,0)wasobtained.
Withthesimilarcalculationsasexplainedabove,thereactionrateconstantforanoverallreactionwasobservedtobe1.
47*10-3/min.
FromtheobservedvalueofthereactionrateconstantforphotooxidationofnaphthalenenotcontainingNaClitwasevidentthatNaClalteredtheoverallrateofreaction.
InthepresenceofNaCl,thereactionrateconstantwashigherthantheoneobtainedinabsenceofNaCl.
Figure22:HPLCtraceforproductsofphotooxidationofnaphthalenewithinwaterwithoutNaCl.
52051015202530050100150200250300350Cn(mg/l)time(min)Figure23:GraphfordecreaseinnaphthaleneconcentrationwithtimeforphotooxidationinwaterwithoutNaCl.
y=0.
001xR=0.
96600.
050.
10.
150.
20.
250.
30.
350.
40.
45050100150200250300350ln(Cno/Cn)Time(min)Figure24:ln(Cno/Cn)vs.
timefornaphthalene.
5354CHAPTER5CALCULATIONS5.
1CalculationsfortheFirstExperimentExplainedinChapter35.
1.
1CalculationfortheAmountofNaClRequiredfortheAerosolSolutionNaClaerosolswereusedintheexperimentascondensationnucleiforfogdropletformation.
TheaerosolsolutionforproductionofNaClaerosolsconsistedof50%isopropanolandwaterbyvolumeand1.
36gramsofpureNaClcrystals.
ThecalculationofNaClquantityisasfollows,referredfromtheaerosolgeneratormanual.
ThedesiredsizeofthedryNaClaerosolwas3.
5m.
Thediameterofthewetaerosolscomingoutfromtheorificewas40m(fromthevaluesmentionedinthetableinthemanual)(C+I)=DD(retrievedfromtheaerosolgeneratormanual)(8)WhereDdisthedropletdiameterofthewetaerosolcomingoutfromtheorifice,Dpistheaerosolparticlediameter.
CisthesoluteconcentrationoftheNaClandIistheimpurityconcentration.
CI(.
)3=0.
00067Consideringtheimpuritywas0.
00004.
C0.
00064Forthecalculationofthesolute(NaCl)needed,sincemeasuringthevolumeofthesolidisdifficult,thevolumewasconvertedtoweightusingthedrydensityofNaClwhichwas2.
164g/cm3So,thefinalequationforthecalculationesolutequantity.
NCofthtooktheform:*.
NCNC=.
NC55Therefore,1.
36gramsofNaClwasmixedin1literofthesolvent.
5.
1.
2CalculationofNaphthaleneConcentrationfromHPLCDataHPLCwasusedintheexperimenttodetermineconcentrationsofnaphthaleneinfogcondensateandexitair.
HPLCgivesapeakfordifferentanalyzedcompoundstorepresenttheirabsorption.
ItwasthereforeessentialtocalculateactualconcentrationofnaphthalenefromtheareaunderapeakprovidedbyHPLCanalysis.
Thefollowingsectionexplainsexamplecalculationsaretheconcentrationsataparticularreactortemperature.
Similarcalculationswerecarriedoutfordifferentreactortemperatures.
Usingthedefinitionofpartitioncoefficientexplainedbyequation(1)insection2.
1.
3,calculationswerefirstperformedforobtainingactualconcentrationvaluesandthencalculatingpartitioncoefficient.
AfterobtainingvaluesforareaunderthepeakfornaphthalenebothinairandcollectedcondensatefromHPLCanalysis,followingcalculationwasperformed.
Fixedvalues:Fn=Flowrateofcarriergascontainingnaphthalene=1977ml/min=1.
977l/minTa=Exposuretimeofpolymertubetoairstream=10minCs=Stabilityconstantfornaphthalene=3.
565Tw=Exposuretimeforfogandnaphthalene=62seconds=1.
01minVelocityofcarriergas/reactorlength=255.
32/162=1.
01min=62secondsVg=volumeofacetonitrileusedfordissolvingadsorbednaphthalene=5ml=0.
005lVariables:Vc=volumeofcondensatecollected(l)A=AreaunderthepeakCa=Concentrationofnaphthaleneinexitingair(g/l)56Cw=Concentrationofnaphthaleneincollectedcondensate(g/l)Calculationsforliquidcondensate:Cw=AVcCsFnTw(9)Calculationsfornaphthaleneinair:CA=AVgCsFnTa(10)Fromtheseformulae,at334KA=1891forliquid,34500forgasVc=102.
5mlCs=3.
565Fn=1.
977lpmTw=1.
01minVg=5mlTa=10minPuttingvariablesandconstantsintheaboveformulaeCw=18910.
10253.
5651.
9771.
01=346.
05CA=345000.
0053.
5651.
97710=31.
1So,fromthedefinition,partitioncoefficientKwa=.
.
=11.
111Thissamplecalculationwasperformedfor334K.
Similarcalculationswereperformedfortemperatures346.
5K,361.
5K,371.
5K57Thesecalculationscarriedoutatdifferentsystemtemperaturegavedifferentvaluesofpartitioncoefficient.
5.
1.
3CalculationforΔHandΔSfromtheEquation.
Fromtheequation(5)mentionedinthischapter,alinewithequationy=2219x-4.
264wascomparedtotheslopeandintercepttermsintheequation.
-ΔH=2219*8.
3142=18.
449KJ/molΔS=-4.
264*8.
3142=-35.
45J/mol.
K3.
5.
4CalculationofNaClconcentrationobtainedinthecollectedcondensate.
Toachieve0.
1Msilvernitratesolution,16.
9gofsilvernitratewasmixedin1literofwater.
MofCl-=MofAgNO3*mlofAgNO3mlofCondensate(11)MofCl-=0.
1*.
=0.
076MSo,aftermultiplyingbythemolecularweightofchlorine,ConcentrationofNaClobtained=2.
66g/l5.
2CalculationsforExperiment2ExplainedinChapter4Therateconstantofoverallreactionfordecreaseinnaphthaleneconcentrationwascalculatedasfollows.
Sincethereactionisfirstorder,thefollowingequationholdsgood.
ForfirstorderrcteaionCkCn(12)IntegratingtheaboveequationfromCnotoCnandfrom0totgivesln(CCkt(13)58Takingtheappropriatehalflifevaluesofln(Cno/Cn)=0.
75andtime=130minutesk=0.
00576/min.
Similartothisprocedure,areactionrateconstantforthereactionmixturenotcontainingNaClwascalculatedtobe0.
00147/min.
59CHAPTER6CONCLUSIONSTheresearchfocusedonpartitioncoefficientsofnaphthaleneforfog-airsystemanddiscussedthereactionproductsofabsorbednaphthalenewithinthecollectedfogcondensatecontainingNaClinpresenceofUVlight.
TheFollowingconclusionscanbedrawnfromtheexperimentsperformed.
6.
1PartitionCoefficientExperimentsExperimentsdemonstratedasuccessfulmethodofcreatingfoginthereactor.
FogdropletsformedwithNaClcondensationnucleicouldbeexaminedunderSEMandthedropletdiameterswereverified.
Fromtheexperimentsperformedforpartitioncoefficientsofnaphthaleneitwasobservedthatconcentrationofnaphthaleneinexitairstartedincreasingandthatinthefogcondensatestarteddecreasingwithincreasingreactortemperature.
So,aconclusioncanbedrawnthatthevalueofKwadecreaseswithincreasingreactortemperature.
ItcanalsobeconcludedthatpresenceofNaClasthecondensationnucleidoesnotalterorreversetherelationshipbetweenpartitioncoefficientsandtemperaturewhencomparedtootherstudies.
TheobservationsuggestedthatthevalueofthepartitioncoefficientatroomtemperaturefornaphthalenewaslowerthanthevalueobtainedforthesimilarsystemsinabsenceinNaClinwater.
Therefore,itwasconcludedthatsalinitydecreasesthepartitioncoefficientvaluesatroomtemperature.
ThisconclusionwasconsistentwiththeresultspresentedbyAlaee(Alaeeetal.
,2006).
Itwasalsoobservablethatthoughfogwasformedinsidethereactor,anattempttocarryoutphotooxidationreactionofnaphthalenein62secondsreactiontimeinsidethereactorwasnotsuccessful.
Thismeantthatphotooxidationreactionisnotaninstantaneousreactionandabiggerreactororarecyclereactorwhichcouldprovidemuchhigherresidencetimewasrequiredto60carryoutthistypeofareactioninsidethereactor.
Itcanberecommendedthat,withthehelpofabiggerreactor,naphthaleneaswellascertainotherpolyaromaticscanbestudiedfortheirphotoreactionsonfogdropletsandproductscanbeobserved.
Asexplainedabove,insteadofNaCl,otheraerosolscanbeusedascondensationnucleiandtheireffectonpartitioningoforganicscanbestudiedaswell.
6.
2PhotooxidationExperimentsThestudyofthenaphthalenephotooxidationreactionsshowedthatwiththeusedsetupandgivenmethod,thereactioncantakeplaceanddifferentproductsofthereactioncanbeanalyzedwithGC/MSandHPLC.
ExperimentshowedthattheoverallrateofnaphthalenephotoderadationwithinwatercontainingNaClwas5.
76*10-3/min.
Theproductsofthereactionweremainlyphthalideandbenzaldehyde.
AnotherexperimentwasperformedinabsenceofNaClinwaterwhichshowedthattheoverallrateofphotodegradationofnaphthalenewas1.
47*10-3/min.
whichwaslowerthatthevaluementionedaboveandtheproductsofthereactionwere1,3-indandioneandphthalidewithcompleteabsenceofbenzaldehyde.
Aconclusionwasthereforedrawnthatundersimilarphysicalconditionsforthereaction,presenceofNaClwasresponsibleforthefasterdegradationofnaphthaleneandproductformation.
Benzaldehydewasdetectedasanintermediateinsomeofthereactionsasdiscussedinsection3.
6.
Withthisexperiment,itwasshownthatforthediscussedphysicalconditionsforthereactionandinthepresenceofNaCl,benzaldehydecanbeobtainedasamajorreactionproduct.
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66VITANehaShrikantDamlewasborninJune,1985,inMumbai,India.
ShecompletedherhighschoolstudiesandcollegefromPune,India.
ShegraduatedfromPuneUniversity,India,inAugust2006earningBachelorofEngineeringdegreeinthechemicalengineeringdiscipline.
InAugust2006,shewasadmittedtoLouisianaStateUniversity,ChemicalEngineeringDepartment.
TheresheworkedunderDr.
KalliatT.
ValsarajandcompletedherresearchworksuccessfullyinMay2008.
SheisapresentcandidateforthedegreeofMasterofScienceinChemicalEngineering.