40 Theuseofreusable,affordable,andinertadsorbentsasameanstomitigatecopperpollution, 41 withalesserburdenontheenvironment,hasbeenattractingsomeattention.However,aiding 42 theadsorptionprocessofapromisingadsorbent,suchasexpandedvolcanicglass(perlite), 43 withareducingcompanion,suchassolidiron,thatcandisplaceanddisposeofcopperfrom 44 pollutedwaterhasneverbeentestedbefore.Inthislaboratorystudy,weinvestigatedthe 45 removalofCu2+,resultingfromcontaminatingfreshwaterwithcoppersulphatepentahydrate, 46 usingsimultaneousornon-simultaneous(sequential)mixesofexpandedperliteandironcoarse 47 powderover23hours.Thepercentageofcopperremovedwascalculatedat15min,40min, 48 120min,300min,and1380minusinginducedcoupledplasma(ICP-OES).Arapidremoval 49 of71%at120minwasachievedwhentheperliteandironwereaddedsimultaneouslyin 50 separatepermeablepouches;theapplicationoftheironaftertheperliteledto78%ofremoval 51 at1380minthatwasalmostidenticaltowhatwasaccruedviaperlitealone(77%).This, 52 therefore,suggeststhatthepresenceofironismostadvantageousintheshortrunasitleadsto 53 fastuptakeofCu2+,attributabletothecombinedactionofthereductionofCu2+byironand 54 Cu2+adsorptionbyperlite.Furtherinvestigationinsupportoftheresultswascarriedoutusing 55 Energy-DispersiveX-RaySpectroscopy(EDAX),X-RayDiffraction(XRD),Brunauer, 56 EmmettandTeller(BET),andFourier-TransformInfraredSpectroscopy(FTIR).Thefindings 57 ofthismultidisciplinaryworkprovideinsightsandmechanismsforheavymetalremovalfrom 58 waterinarelativelyshorttimeusinganoveltime-specificcombinationofironandperliteand 59 thusmeritwidertestingacrossdifferentclassesofadsorbents,pollutants,andwatersystems. 60 61 Keywords:Perlite,iron,heavy-metalpollution,adsorbents,reactivityseries,watertreatment 62 63 64 65 66 67 68 69 70 31.Introduction 71 Theongoingrapidincreaseinglobalpopulation,coupledwithclimatechange,hasbeen 72 leadingtounprecedentedincreaseddemandsonwaterformyriadapplications[1,2].Thisis 73 alarminglyincreasingtheburdenontheenvironmentespeciallyinurbanisedandheavily 74 industrialisedareaspronetoheavymetalpollution[3].Despitebeingessentialforlifein 75 minimalamounts,coppereasilyaccumulatesintheenvironmentandinorganismswithfar- 76 reachingnegativeconsequencesontheterrestrialandaquaticecosystems[4-7].Copper 77 pollutioncanbetheresultofvariousnaturalandanthropogeniccausesincludingtheextensive 78 useofcoppersulphatepentahydrateCuSO4.5H2Oinindustries,agriculture,andpondtreatment 79 fromalgae[8,9]. 80 Conventionalmethodsusedintheindustryfortheremovalofheavymetalionsin 81 aqueoussolutionsincludechemicalprecipitation,ionexchange,membranefiltrationand 82 adsorption[10,11].Adsorptionisquiteeffective,easytoapplyandeconomical[11-15]; 83 however,testingtheadsorptionofheavymetals,suchasCu2+,withcompanionreactivemetals 84 isstilllargelyunexplored.Adsorptionprocesses,attheliquid-solidinterface,arecentraltothe 85 chemicalindustryastheyarewidelyusedinlubrication,flotationofminerals,watertreatment 86 andoilrecovery[12].Theadsorptiondependsprimarilyonthecharacteristicsoftheadsorbent 87 andtheadsorbatebutalsoonvariables,suchas,contacttime,temperature,pHlevel,andthe 88 initialconcentrationofadsorbates[13]. 89 Adsorptionusingperlite(amorphousvolcanicglass)[14]hasbeenattractingattention 90 duetothepromisingpropertiesofhighporosity,chemicalinertness,environmentalsafety,fast 91 kinetics,lowbulkdensity,andaffordability[14-16].Expandedperliteischemicallytreated[15] 92 priortotheextractionofheavymetalsfromcontaminatedaquaticmedia[15,17],withan 93 optimalcopperadsorptionatpHof6.5[17].Treatedanduntreatedformsofperliteareboth 94 showntobeeffectiveinCu2+removal[15].However,supportingtheperliteadsorptionofthe 95 targetspecieswithcopper-displacingelectrochemicallyactivemetals,suchasiron,hasbeen 96 thusfaroverlooked;perlite-metalcombinationsmayreducethefinancialandenvironmental 97 burdenoftheconventionalperlitepre-treatments.Iron,higherinthereactivityseries,can 98 displacecopperinsolution[18].Thereforeitmightbepredictedthataddingacopper-displacer 99 (ironinitssolidformFe(s))toaccompanytheadsorbent(perlite)mayenhanceCu2+removal. 100 Interestingly,thesetwocopper-removalmechanismshaveyettobetestedinsimultaneousor 101 sequentialfashions. 102 4Inthislaboratorywork,weexaminedtheremovalofCu2+,resultingfrom 103 contaminatingfreshwaterwith0.07g/lofcoppersulphatepentahydrateCuSO4.5H2O,using 104 expandedperliteanddifferentmixesoftheperliteandironcoarsepowder,withtheaimof 105 acceleratingtheamountofCu2+removalovertime. 106 107 2.Methods 108 2.1.Materials 109 Horticulturalmedium-gradeperlitepelletsP35(Al2CaFe2K2MgNa2O12Si)wasacquired 110 fromGrowTechnology©(UK)andusedasanadsorbentinthecurrentstudy;theperliteis 111 brilliantwhitebeads(1-2mm)expandedunderheating(760°C–1100°C)tovolumesthatare 112 severaltimesbiggerthanthoseoftheoriginalparticlesizesofthesiliceousglassyvolcanic 113 (magmatic)mineral[15].Theheatingcausesthestructuralcrystallinewaterintheperliteto 114 vaporiseresultinginrapidexpansionyieldinghighporosity[19,20]. 115 Theperlitebeadswereenclosedinpermeableinertpolyestercopolymer(lycra)mesh, 116 purchasedfromalocalretailer(Manchester,UK),customisedaspouchesandsealedwith 117 elasticbands).Asperlitehasalowerdensitythanwater,thepoucheswerekeptsubmergedby 118 attachingthemtothebottomofthebeakerusingQuickTackadhesiveputty(inertnon- 119 hazardoussyntheticrubber)acquiredfromQ-connect©(UK).Ironcoarsepowder,obtained 120 fromEiscoLabs©(USA),wasusedaloneandincombinationwithperlitesimultaneouslyand 121 sequentiallyasspecifiedbelow. 122 2.2.Experimentalmedium 123 Freshwater(Aqua,hereafter)wassimulatedartificiallysensu[21]byusingthree 124 laboratorystocksolutions,namely;stocksolutionA(117.6g/l,calcilumchloridedehydrate 125 CaCl2.2H2O[FisherScientific©,UK]),stocksolutionB(25.2g/l,sodiumbicarbonate 126 NaHCO3[Honeywell©,Germany]),andstocksolutionC(0.07g/l,seleniumdioxideSeO2 127 [MerckKGaA©,Germany]plus0.33g/lsodiumchlorideNaCl[ChanteSel©,UK],all 128 dissolvedinhighpuritymilli-QwaterwithapH~7. 129 2.3.Contaminant 130 Aquawascontaminatedwith0.07g/lofcoppersulphatepentahydrateCuSO4.5H2O 131 (Sigma-Aldrich©,UK)tomimicpossiblecoppercontaminationassociatedwithindustrialised 132 activities.Theremovedcopperfromthetreatedsolutionateachsamplingtimewas 133 proportionallycalculatedrelativetotheinitialcopperconcentrationbeforetreatment. 134 52.4.Experimentdesign 135 Theperliteonlytreatment(Ads,hereafter)included2gofperliteinthepouch;whereas 136 1.5gofperliteand0.5gofironwereusedintheiron-perlitepouches(Ads-Fe,hereafter);the 137 irononlytreatment(Fe,hereafter)included0.5gofironinthepouch.Thebeakerswere 138 coveredwithcling-filmtominimiseevaporation.Therespectivecombinations(Ads,Ads-Fe, 139 Fe)weretestedinthecoppersulphatecontaminatedAquafortheremovalofcopperions.The 140 combinationsweredividedintothreecategories:1)independent(AdsorFe:perliteoriron 141 wererespectivelyappliedaloneinthebeaker);2)simultaneous(Ads-Fe:perliteandironwere 142 appliedtogetherasaphysicalmixtureinonepouch,orperliteandironwereaddedin 143 individualco-occurringpouches;3)sequential(eithertheapplicationofperlitepouchpreceded 144 theapplicationoftheironpouchwithatimelagof40minorviceversa).Thetreatmentofthe 145 contaminatedAqua(300ml,asspecifiedabove)inPVCbeakers(500ml)wastestedunderthe 146 saidcombinationsat20℃-22℃. 147 2.5.Samplingtime 148 Foreachrepeat(specifiedbelow)ofeverytreatment,5samplesweretakeninaspanof 149 23h.TheadsorptionofCu2+hasbeenshowntobemosteffectivewithagitationduringthefirst 150 twohours[16].Forthisreason,ashaker(InforsLtd.©,UK)wasusedforthefirst5hoursto 151 ensuregoodcontactbetweentheAquaandthecontentofthepouch.Assuch,10mlsamples 152 weretakenusingfreshvolumetricpipetteswithanemphasisonshorter,yeteffective,Cu2+153 removaltimes(15min,40min,120min,300min,and1380min),fromeachrepeatthen 154 temporarilystoredinFalcontubespriortoanalysis. 155 2.6.CharacterisationoftheremovedCu2+156 Aninductivelycoupledplasmaopticalemissionspectrometry(ICP-OES,hereafter) 157 wasusedtomeasuretheconcentrationsofCu2+intheaqueoussolutionsatthe5different 158 samplingtimes.TheelementalcompositionoftheperlitebeadswasdeterminedusingEnergy 159 DispersiveX-RaySpectroscopy(EDAX);Brunauer,EmmettandTeller(BET)wasusedto 160 measuretheaverageporediameterandthesurfaceareaoftheperliteadsorbent;Fourier- 161 FransformInfraredSpectroscopy(FTIR)wasusedtomonitorchangesinthefunctionalgroups 162 thatcharacterisetheinteractionofCu2+withtheadsorbent,andX-RayDiffraction(XRD)was 163 usedtoinvestigateanystructuralchangesthatmayhaveoccurredtotheperlite. 164 Insum,theprimaryfocusoftheICP-OESanalysisofthisworkwasquantifyingthe 165 amountofCu2+removedtodeterminetheeffectivenessofAds,FeandAds-Feformitigating 166 6thecopperpollution.Inaddition,thepHandconductivity(t=0,t=5handt=23h)ofthe 167 Aquaweredeterminedusingaprobe(EutechPC2700,ThermoScientific©). 168 2.7.Statisticalanalysis 169 Descriptively,thearithmetic(mean)andstandarderrorofthemean(SEM)were 170 calculatedforthepercentageofCu2+removal(obtainedfromtheICP-OES)pertreatment 171 combinationandsamplingtime.Amixedeffectgeneralisedlinearfit(GLMM,logistic 172 regression)bymaximumlikelihood(Laplaceapproximation)wasappliedinR[22],usingthe 173 packagelme4[23]andamodeloptimiserbobyqa[24],totesttheCu2+removalasafunctionof 174 thetreatmentcombination(predictor1)andsamplingtime(predictor2),andtheirinteraction. 175 Thetreatmentcombinationwasmadeupof6levels(Ads[perlitealone,baseline],Fe[iron 176 alone],Ads-Fe(Sim1)[simultaneousapplicationofperliteandironasamixinasinglepouch], 177 Ads-Fe(Sim2)[applicationofAdsandFeasseparateyetco-occurringpouches],Ads-Fe(Seq1) 178 [sequentialapplicationoftheperlitepouch(Ads)40minutesaftertheapplicationoftheiron 179 pouch(Fe),bothpouchesthenremaineduntiltheendoftheexperiment],Ads-Fe(Seq2) 180 [sequentialapplicationoftheironpouch(Fe)40minutesaftertheapplicationoftheperlite 181 pouch(Ads),bothpouchesthenremaineduntiltheendoftheexperiment]).Thesamplingtime 182 wasacategoricalvariableoffivelevels(15min[baseline],40min,120min,300min,1380 183 min).Thebeakerwasrandomised(randomeffect)inthisrepeatedmeasureanalysis.Predictor 184 3wasthetimelagof40min,acategoricalvariablereferringtotheabsenceofthesimultaneous 185 applicationoftheperliteandtheiron(No[baseline])orthepresenceoftheirsimultaneous 186 application(Yes).ThemaineffectsofthemodelwererevealedbyapplyinganAnova 187 commandusingtheRpackagecar[25].Intotal,therewere6treatmentsx3repeatsx5 188 samplingtimes=90readings;theomissionof8valuesacrosstreatmentreadingsduetoerrors 189 resultedinatotalof82readings. 190 3.ResultsandDiscussion 191 Overall,themosteffectiveandrapidmitigationofcopperpollutionof50%was 192 achievedafter15minofapplicationwithAds-Fe(Sim2)(simultaneousseparateAdsandFe 193 pouches),whichwasremarkably13%and39%moreeffectivethanAds(1-2mmperlitebead 194 size)andFe(ironcoarsepowderof0.841mm),respectively.Thehighestcopperremovalwas 195 reachedasearlyas120minunderAds-Fe(Sim2)(71%),suggestinganadditiveeffectofthe 196 AdsandFeinthiscombinationasisatleast15%moreeffectivethaneachconstituentofthe 197 combinationwhenappliedalone.Further,thehighestlevelsofCu2+removalattheendofthe 198 7experiment(1380min)wereachievedunderAds-Fe(Seq2)(78%)(sequentialapplicationof 199 Ads40minfollowingtheapplicationofFe)thatwascloselyfollowedbyAds(77%),Figure1. 200 3.1.AdsvsFe 201 Adsremovalofcopperfromthemedium,viaadsorption[15,17],graduallyincreased 202 overtimefrom37%at15minto77%at1380min.Bycontrast,althoughCu2+removalbyiron 203 intheFetreatment,viadisplacementresultingincopperprecipitation,showedasimilartrend 204 at300min,thedifferencesinremovalbetweensamplingtimepointsunderFeweremore 205 apparentthanthoseobservedunderAds.However,attheendoftheexperiment(1380min) 206 copperremovalundertheFedecreasedby13%whencomparedtothereadingat300min, 207 Figure1.ThiscanbeattributedtoreachingasaturationpointinthecaseoftheFeupto1380 208 min;alsotheCu2+removaldifferedbetweentheperlite(lowerdensitywithhighporosity)and 209 theiron(higherdensity),irrespectiveoftheironweight(0.5g)thatwas~33%oftheweightof 210 perliteinanycombinationthatincludedbothperliteandiron).Inourstudy,theperliteinthe 211 Adsfunctionedthroughadsorption[26]:1)physisorptioncausedbytheVanderWaal’sforces 212 attractingCu2+tothesolidporoussurfaceoftheperlite,and2)chemisorptionofCu2+caused 213 byvalenceforcesontotheperlitesurfacethroughspontaneousformationofchemicalbonds.In 214 particular,theadsorbedM2+(Cu2+orFe2+)ontotheperlitesurfacecanbeexplainedbythe 215 followingreactionsthatsuggestanincreasedpositivesurfacechargeastheamountofadsorbed 216 cationsincreases[15]: 217 –SiOH+M2+⇌SiO–M++H+Eq.1 218 SiOH+M2++H2O⇌SiO–MOH0+2H+Eq.2 219 2SiOH+M2+⇌(SiO)2M0+2H+Eq.3 220 AsforthesolidironFe(s),itsinteractionwiththecoppersaltdissolvedinthemedium, 221 andtheconsequentialdeposition(precipitation)ofcopper,canbeexplainedthroughthe 222 followingequations[27]: 223 Fe()+ᦙ䁤4(()→R䁤4(()+ᦙ() Eq.4 224 ½R()→½R2+(()+R−Eq.5 225 ½ᦙ+(()+R−→½ᦙ() Eq.6 226 ThenegativechargeoftheperlitesurfaceduetotheOH–maydecreasewithincreasing 227 ionicstrengthinthemediumasthelatteraffectstheactivitycoefficientsforOH°,leadingto 228 lessadsorbableCu2+ontotheperlitesurface[15].Theironhastwopossibilities:thefirstis 229 oxidationanddisplacementofCu2+asexplainedinEqs.4-5,andthesecondwillfollowthe 230 8pathwayasinEqs.1-3;however,whenFe2+andCu2+coexistinthemediumtheFe2+willbe 231 preferablyadsorbedontothesurfaceoftheperlitebecauseironismorereactivethancopper 232 accordingtothereactivityseries[27].Putdifferently,thefateoftheCu2+,whetheritis 233 displacement(Eqs.4and6)oradsorption(Eqs.1-3),orboth,willbedependentonthemanner 234 ofthespatialaswellasthetemporalapplicationofiron(copper-displacingmetal)andperlite 235 (theadsorbent),possibleinterferenceorsynergybetweenthetwoprocesses,andother 236 propertiesoftheinvolvedsubstancesandsolutions(e.g.concentrations,pH,kinetics,and 237 saturation). 238 3.2.Sim1vsSim2 239 Thebreakthroughpoint(53%)fortheAds-Fe(Sim1)wasrecordedat300min,whileit 240 reached(71%)at120minforAds-Fe(Sim2),andthroughoutCu2+removalunder(Sim2)was 241 alwaysbetterthanwhatwasachievedunder(Sim1)overtime.Apossibleexplanationisthat 242 theapplicationofperliteandironasco-occurringseparatepouchesin(Sim2)ledtomore 243 surfaceareacontactbetweentheperlite(highlyporousadsorbingsubstance)andtheironFe(s) 244 (thedisplacer),FigureS1.However,theadsorptionofheavymetalionshasbeenshownto 245 increasegraduallyfollowingthefirstminutesofcontactandreachesanequilibriumovertime 246 [28]. 247 3.3.Seq1vsSeq2 248 BothAds-Fe(Seq1)(perliteapplied40minaftertheironapplication)andAds-Fe(Seq2) 249 (ironapplied40minaftertheperliteapplication)resultedinagradualincreaseinCu2+removal 250 afterthesequentialapplicationat40min;theSeq1effectwasmorerapidandpronouncedat 251 120min(66%)comparedtothatoftheSeq2(43%).Thisisunderlainbytheiron 252 companionshipofperlitefor80minutesfollowingitssequentialadditiontotheperlite, 253 meaningthattheperformanceoftheperlite(Cu2+adsorption)wasboostedaspertheironeffect 254 (Cu2+displacementandprecipitationasCu(s))byapproximately10%at120min.However,this 255 wasnotquitethecaseforSeq2asitrequiredmoretimefortheeffectofthesequentialaddition 256 ofperlitetoboosttheperformanceoftheremoval;Seq2slightlybestedSeq1at1380min 257 leadingtooverall78%ofCu2+removal(thehighestaccrualacrossalltreatments).Inother 258 words,intheshortrun,theapplicationofperlite,whenprecedingtheapplicationofiron, 259 appearstobemoreeffectiveinCu2+removal,theoppositemaybe,however,morebeneficialin 260 thelongrun,Figure1and(SupplementalInformationFigureS1).Inotherwords,theadvantage 261 ofaccompanyingperlitewithironresidesinthefastuptakeofthetargetpollutant,asinthe 262 9longruntheiron-perlitemixmayjustyieldsimilaroutcometotheapplicationoftheperlite 263 alone. 264 SimsvsSeqs 265 At120min,Sim2hadthebestresultofCu2+removal(71%),representinganotable 266 meanreductionofcopperfrom0.0176g/l(~9timeslargerthanthepermissiblelimitin 267 wastewaterof0.002g/l)to0.0051g/lthatisonly~2.6timeslargerthanthepermittedlevel 268 (0.002g/l)bytheWHO[29].ThiswasfollowedbySeq1(66%),whilstSim1(42%)andSeq2 269 (43%)werealmostidentical.Afterwards,at300min,Sim1copper-removalcapacityincreased 270 to53%,whileSim2(70%)andSeq1(67%)capacityremainedconsistent,butSeq2showeda 271 considerablecapacityincreasefrom43%(120min)to(70%)(300min).Thispatterncontinued, 272 withaclearboostofSeq2capacity(reached78%,0.0039g/lofcopperthatisonly~2times 273 largerthanthepermissiblelimit),bytheendoftheexperimentat1380min.Itcanbededuced 274 fromthefindingsthatthebestcombinationofperliteandiron,intermsoftimeandefficiency 275 ofCu2+removal,isSim2despitethateventuallySeq2(followedbyAds)mayleadtothe 276 highestlevelsofremoval.Thisisagainassignabletomorechanceforkineticsinthecaseof 277 Sim2(separatesimultaneouspouchesofperliteandiron)duetothecombinationoftwo 278 processes,i.e.,adsorptionandmetal-displacement,whichappearedtoworkthebestbetween 279 40minand120minasourresultssuggest.Thisimpliesthatthisefficiencyoftheperliteand 280 ironcombinationisnotonlytime-dependentbutalsocontingentontheway/mannertheperlite 281 existswiththeironinthemedium.Thismeritsfurtherresearchtounderstandtheunderlying 282 mechanismsfurtheracrossvariablecontexts,pHlevels,timeranges,andconcentrations.Itis 283 worthyofnotethattheICP-OESmeasurementsshowedthattheperliteemployedinthisstudy 284 wasincompatiblefortheremovalofsulphurastherewasanegligiblechangeinthe 285 concentrationofsulphurovertimeinthecontaminatedAquaduetothenegativechargesofthe 286 SO42-andSiO2-.Additionally,comparedtothenon-contaminatedAqua,therewerenegligible 287 changesinthepH(~6.63onaverage)andconductivity(~1.14onaverage)at300minand1380 288 min. 289 Further,inferentially,ourstatisticalmodelindicatedthatthetreatmentcombination,the 290 samplingtime,andtheirinteractionshighlysignificantlyaffectedCu2+removal(X2(4,51)=99.43, 291 P<0.0001),(X2(4,51)=196.53,P<0.0001),and(X2(20,51)=85.48,P<0.0001),respectively; 292 whereastheeffectofthe40-mintimelagwasmarginallysignificant(X2(1,51)=3.65,P=0.056). 293 Specifically,themodelsummaryrevealedthefollowinglevelstobesignificantintermsof 294 Cu2+removal:Ads-Fe(Sim1)(P=0.01),Ads-Fe(Sim2)(P=0.021),Seq1(P=0.001), 295 samplingtime1380min(P=0.004),samplingtime15min(P=0.0007),Ads-Fe(Sim2)x 296 101380min(P=0.033),Fex15min(P<0.0001),Ads-Fe(Seq2)x15min(P=0.011),Ads-Fe 297 (Sim1)x15min(P=0.001);whereasthefollowingweremarginallysignificant:the40-min 298 timelag(P=0.056),andAds-Fe(Seq2)x300min(P=0.064);see(SupplementalInformation 299 TableS1)forfurthermultiplepairwise-comparisons. 300 301 302 303 304 305 306 307 308 309 310 311 11 312 Figure1.PercentageofCu2+removedovertime.ThebarchartshowsthepercentageofCu2+removalfrompollutedAqua(Y-axis)ateach 313 samplingtime(X-axis).Therewere6treatmentcombinations(Ads:perlitealone,Fe:iron(coarsepowder)alone,Ads-Fe(Sim1):perliteandiron 314 areappliedsimultaneouslyasamixinasinglepouch,Ads-Fe(Sim2):perliteandironareappliedsimultaneouslyasseparatepouches,Ads-Fe 315 (Seq1):Asequentialapplicationwheretheironpouchwasappliedfirstthenfollowedbytheperlitepouch40minlater,Ads-Fe(Seq2):A 316 sequentialapplicationwheretheperlitepouchwasappliedfirstthenfollowedbytheironpouch40minlater.Therewere6treatmentsx3repeats 317 x5samplingtimes=90readings(duetotheomissionof8readingsthetotalwas82). 318 123.4.Supportivecharacterisationoftheperliteassociatedwithcopperadsorption 319 Theexternalsurfaceareaoftheperlitesamplesincreasedaftertreatmentfrom1.34m2/gto 320 1.3607m2/g;whereasthetotalsurfacearea(BET)hasdecreasedfrom1.16m2/gto1.03m2/g, 321 indicatingconsiderableadsorptionoftheheavymetalintotheporesofperlitesurface[30].The 322 mineralogicalanalysisofperlitedeterminedbyXRD(SupplementalInformation,FiguresS5and 323 S6),confirmedthattheperliteisamorphouswithnodistinctcrystallinephases.Thespectra 324 resemblethoseofglass-likematerials[31];theonlydetectablefeaturefromthespectrumisawide 325 curvethatischaracteristicofthemaincomponentsofperlitesuchasquartz(SiO2)[32].TheEDAX 326 analysisofthepost-treatmentperliteshowedcopperattachmenttotheperlitesurface(Supplemental 327 Information,FigureS2). 328 Additionally,accordingtotheFTIRanalysis,certainpeakshiftsforsurfacefunctional 329 groupsweredetectedintheperlitepostAdstreatment,namelySi-Oat1029cm-1(pre-treatment) 330 became1005cm-1(post-treatment),Al-Obondstretchingat789cm-1(pre-treatment)became 331 overlappedwithanewpeakat561.7cm-1(post-treatment),assignabletocopperadsorptiononthe 332 perlitesurface[32],andat445cm-1(pre-treatment)relatedtoSi-Obecame410cm-1(post-treatment) 333 alsoattributabletocopperbondingwithsilicate[33].Additionally,uniformpeaksweredetectedat 334 the–OH(hydroxyl)region(3351cm-1)indicatingadsorbedwater,andthe(1650cm-1)region 335 characterisedfreewater[33],(SupplementalInformation,FiguresS3andS4).Post-treatmentFTIR 336 spectraofthesimultaneousandsequentialAds-Fetreatmentsshowedsimilarchanges. 337 Thecombination(Sim2)showed,promisingCu2+removalintermsoftimeandquantity 338 (ICP-OESdata)andEDAXresultsindicatedaconsiderableamountofcapturedironontheperlite 339 surface,aswell(SupplementalInformation,FigureS2).TheoxidationoftheironintheFepouchin 340 contactwiththeaqueouscopperledtoanexcessofironions(Fe2+)thatwascapturedbytheperlite, 341 whilstaconsiderableamountofCu2+gainedelectronsfromtheoxidisedirontobecomereduced 342 anddepositedontheironsubstrateasCu(s).(SupplementalInformation,FigureS2) 343 344 4.Conclusions 345 TheeffectsofCu2+removalbyperliteandperlite-ironmixesovertimewereinvestigated 346 throughanovelintegrationofphysicochemicalprocesseswithsimultaneousorsequential 347 applications.Adsorptionasasolutiontomitigateheavymetalpollutionisadvantageouswhen 348 comparedtootherconventionalprocesses,fortechnicalandeconomicalreasonsandthereusability 349 ofadsorbents[34].Moreover,horticulturalgradeperlitebeinginert,stable,ultra-light,highly 350 water-retentive,andpHneutral[19]substantiatesandaddstotheadvantageoftheadsorption;the 351 additionofirontoperliteinourworkprovedtohaveanadditiveeffectontreatingcopperpollution 352 ofwater.Itisimportanttohighlightthatthiseffectoftheironcompanionshipofperliteappearedto 353 13beconsiderablyfunctionalandthusdesirableintheshortrunintermsofenhancingthespeedof 354 copperuptakeintheshortrun(120min),whentheironandperliteareconcurrentbutnotmixed, 355 thenwhentheironisappliedbelatedlyaftertheperliteintroduction.Thisappertainstoasynergistic 356 relationshipbetweenCu2+displacementbyironandadsorptionbyperlite.Thisworkextendstheuse 357 ofperlitebeyondagricultureandinsulation;ourresultsencouragefurtherresearchtotestthe 358 processesandmechanismshighlightedusingdifferentclassesofadsorbents,reducingmetals,and 359 contaminants. 360 361 Acknowledgements 362 OurthanksgotoDrDesmondDooceyandMs.ShahlaKhanofCEAS,andDrJohnWatersofthe 363 DepartmentofEarthandEnvironmentalScience,UoM,fortheirhelpandsupport. 364 365 Funding 366 Thisresearchdidnotreceiveanyspecificgrantfromfundingagenciesinthepublic,commercial,or 367 not-for-profitsectors. 368 369 Datarepository 370 Khudr,M.S.,MohamedElhassanIbrahim,Y.,Garforth,A.,Alfutimie,A.Oncopperremovalfrom 371 aquaticmediausingsimultaneousandsequentialiron-perlitecomposites.Figshare.2020. 372 https://figshare.com/s/08588380b86b73aee41f 373 374 375 376 377 378 379 380 381 382 383 14