Renewable hybrid nanocatalyst from magnetite and cellulose for treatment of textile effluents

A hybrid catalyst was prepared using cellulose nanofibrils and magnetite to degrade organic compounds. Cellulose nanofibrils were isolated by mechanical defibrillation producing a suspension used as a matrix for magnetite particles.

jo u r n al h om ep a g e :w w w e l s e v i e r c o m / l o c a t e / c a r b p o l

Ana Carolina Cunha Arantesa, Crislaine das Grac¸ as Almeidaa,

Ligiane Carolina Leite Dauzackera, Maria Lucia Bianchia, Delilah F Woodb,∗,

Tina G Williamsb, William J Ortsb, Gustavo Henrique Denzin Tonolic

a Department of Chemistry, Federal University of Lavras, CP 3037 Lavras-MG, Brazil

b Bioproducts Research Unit, WRRC, ARS-USDA, 800 Buchanan St., Albany, CA 94710, USA

c Department of Forest Sciences, Federal University of Lavras, CP 3037 Lavras-MG, Brazil

Article history:

Received 17 November 2016

Received in revised form

27 December 2016

Accepted 4 January 2017

Available online 7 January 2017

Keywords:

Magnetite

Catalyst

Cellulose

Nanofibrils

Crystallite

a b s t r a c t

Ahybridcatalystwaspreparedusingcellulosenanofibrilsandmagnetitetodegradeorganiccompounds Cellulosenanofibrilswereisolatedbymechanicaldefibrillationproducingasuspensionusedasamatrix formagnetiteparticles.Thesolutionofnanofibrilsandmagnetitewasdriedandmilledresultingina catalystwitha1:1ratioofcelluloseandmagnetitethatwaschemicallyandphysicallycharacterized usinglight,scanningelectronandtransmissionelectronmicroscopies,specificsurfaceareaanalysis, vibratingsamplemagnetometry,thermogravimetricanalysis,Fouriertransforminfraredspectroscopy, X-raydiffraction,catalyticpotentialanddegradationkinetics.Resultsshowedgooddispersionoftheactive phase,magnetite,inthematofcellulosicnanofibrils.Leachingandre-usetestsshowedthatcatalytic activitywasnotlostoverseveralcycles.Thehybridmaterialproducedwastestedfordegradationof methylenebluedyeinFenton-likereactionsresultinginapotentialcatalystforuseindegradationof organiccompounds

PublishedbyElsevierLtd

1 Introduction

Cellulosehasbeenstudiedandappliedasaprecursorofnew

bio-engineeredmaterials(Oksmanetal.,2016;Rezaetal.,2015;Zhu

etal.,2015)andisorganizedatamacromolecularlevelintofibrils

consistingofglucoseunitsinalinearandcrystallinearrangement,

along with hemicelluloseand lignin (Fengel &Wegener, 1984;

Zugenmaier,2008).Cellulosefibersaremadeupofbasiccrystalline

building-blocksornanofibrilsthatcanformsuspensionsinwater

whenisolated(Chenetal.,2014)

Theisolationprocess,typicallybychemicalorphysical

meth-ods,canaffectthepropertiesoftheresultingcellulosenanofibrils

(Wang,Li,Yano,&Abe,2014).Mechanicaldefibrillationisaphysical

processwherecellulosefiberspassthroughamillthatreducestheir

∗ Corresponding author.

E-mail addresses: anacarolinacarantes@gmail.com

(A.C.C Arantes), crisalmeida@quimica.ufla.br (C.d.G Almeida),

ligiane.dauzacker@gmail.com (L.C.L Dauzacker), bianchi@dqi.ufla.br (M.L Bianchi),

de.wood@ars.usda.gov (D.F Wood), tina.williams@ars.usda.gov (T.G Williams),

bill.orts@ars.usda.gov (W.J Orts), gustavotonoli@dcf.ufla.br (G.H.D Tonoli).

dimensionsbyfriction.Atacertainsizerange,thenanofibrilsform

agel-likesuspension(Bufalinoetal.,2015;Fonsecaetal.,2016) Defibrillationisaphysicalmethodthatrequiresnochemicalsin theisolationofcellulosenanofibrils,thus,reducesprocessingsteps andpollution

Cellulosenanofibrilscanbeusedtoprepareamultitudeof use-ful commercialmaterials,suchasaerogels, xerogels,hydrogels, beadsandspecialtybiomaterials(includingmedicalgrafts)(Abe

&Yano,2011;Baetensetal.,2011;Chin,BintiRomainor,&Pang,

2014;Eichhornetal.,2010;Gerickeetal.,2013;Wan&Li,2015) Aerogelshavelowdensity,highstrengthandalargesurfacearea (Innerlohinger,Weber,&Kraft,2006)andareproducedby super-critical drying of cellulose nanofiber suspensions which allows themtomaintainastructuredgel(Heath&Thielemans,2010).Air dryingofnanofibersuspensionscausesthegelstructuretocollapse resultinginaxerogel(Baetensetal.,2011).Dependingonthefinal application,axerogelmayhavethesamebenefitsofanaerogel withoutthehighcostsofsupercriticaldrying

Aerogelsandxerogelsmadefromcellulosecanserveasfixed supportsforFeionsintheproductionofchemicalcatalysts(Small

&Johnston,2009).TheseFe-hybridizedaerogelscanbeexpected

http://dx.doi.org/10.1016/j.carbpol.2017.01.007

102 A.C.C Arantes et al / Carbohydrate Polymers 163 (2017) 101–107

tobeused ina number of industrial applicationsas theyhave

superparamagneticproperties, remarkablemechanical strength,

arelightweight,flexible,highlyporousand havealargesurface

areathatprovideahugenumberofreactivesites(Liu,Yan,Tao,Yu,

&Liu,2012).Inadditiontobeingproducedfromreadilyrenewable

resources,suchaswheatstraw,anagriculturalresidue,aerogels

maybe preparedusing green chemical methods which further

extendstheirusefulnessandacceptabilityasagreenproduct(Wan

&Li,2015).Olssonandcoworkersusedhighlyflexibleandporous

hybridaerogelsastemplatestoconstructsolidandstiff

nanocom-positesbycompaction(Olssonetal.,2010).Feionsmaybeused

tocatalyzeFenton-likereactionsforthegenerationof hydroxyl

radicals usingstrong oxidizing agents, suchas H2O2, as a

pre-cursor.Hydroxylradicalshave highoxidation potentialandcan

degradeorganicmolecules,suchasdyesgeneratedintextile

efflu-ents(Nogueira,Trovó,DaSilva,Villa,&DeOliveira,2007)

Theuseofiron-basedcatalystsystemsisadvantageousbecause

iron is a naturally-occurring,abundant compound that is

non-toxic,environmentallysafeandreadilyrenewableandsustainable

Someformsofironoxidehavemagneticpropertiesfacilitatingthe

removalof reactantssothattheycan bereadilyreused(Luo&

Zhang,2009).Magnetite,adarkcoloredironoxide,withthe

molec-ularformulaFe3O4,providesmagneticpropertiestomaterialsand

suppliesFeionstocatalyzeFenton-likereactions

Theaimofthisstudywastoevaluatethecatalyticefficiencyofa

magneticcatalystproducedbyimpregnatingcellulosenanofibrils

withmagnetiteandappliedtothedegradationofmethyleneblue

dyeinaFenton-likereactiveprocess

2 Materials and methods

2.1 Productionandcharacterizationofthecellulosesuspension

The fibers of commercial eucalyptus kraft pulp (Jacareí/SP,

Brazil)wereimmersedindistilledwaterfor48hat1%(w/w)

con-centrationbeforedefibrillation.Cellulosenanofibrilswereobtained

bymechanicaldefibrillationofthefibercellwallusinga

Super-MasscolloiderMKCA6-3,(MasukoSangyoCo.,LTD,Japan),operated

at1500rpm,witha0.01mmopeningbetweendisksand

apply-ing35 passages throughthedefibrillator (Bufalinoetal., 2015;

Tonoli et al., 2016) The resulting nanofibril suspensions were

characterizedmorphologicallyusingaNikonEclipseE200(Japan)

compoundmicroscopebyrandomlyselecting10areasonaslidefor

imageanalysis.Glassslideswerepreparedwith0.05mLofsample

mountedinglycerin

Scanningelectron microscopy(SEM) was performedusing a

Hitachi S4700 field emission SEM (Hitachi High-Technologies,

Japan).Thefreeze-driedsampleswereadheredtoaluminum

spec-imenstubsusingdouble-sidedadhesive-coatedcarbontabs(Ted

Pella,Inc., Redding,CA) Thesamples werethensputter-coated

with gold-palladium in a Denton Desk II sputter coating unit

(Moorestown,NJ).SEMimageswerecapturedata resolutionof

2650×1920pixels

Transmissionelectronmicroscopy(TEM)wasusedtovisualize

thecellulosenanofibrilsbymixingthesuspended sampleswith

uranylacetatetomakethecellulose particleselectrondensein

ordertoprovidecontrastintheTEM.Adropofthenanofibril

sus-pensionwasplaced onto a400-meshcarbon-formvar grid(Ted

Pella,Inc.,Redding,CA)heldattheedgewithdouble-adhesivetape

Thegridswereallowedtoair-dryandthenwereobservedand

pho-tographedina FEITecnai12 TEM(FEICompany,Hillsboro, OR)

operatedat120kV.Theaveragediameterofthemicro/nanofibrils

wasdeterminedbydigitalimageanalyses(ImageJ1.48v,National

InstitutesofHealth,USA)onTEMmicrographs.Aminimumof100

measurementswerecollectedforanalyses

2.2 Productionandcharacterizationofthemagnetichybrids Thesynthesisofmagneticmaterialwasperformedusingthe methodologyadaptedfromSchwertmann&Cornell(2000).Fe2+

andFe3+salts(6.314gFeCl3 and2.343gFeCl2)weredissolvedin

200mLof anaqueoussuspensionof cellulosenanofibrilsunder nitrogen flow NH4OH wasadded until pH11 wasattained to precipitatebothmagnetiteandcellulosefromsolution.The pre-cipitatewaswashedwithwateruntilpH∼7,oven-driedat60◦C, andmilledinaballmill.Themassratioofcellulose:magnetitewas 1:1(cel:mag) Toobtaintheratio,theexperimentalsamplewas comparedtoasampleofpuremagnetite(magnetite)preparedby

asimilarmethod

SurfaceareasweredeterminedviaN2 adsorptionat −196◦C

in anAutosorb-1Quantachrome system(Quantachrome Instru-ments,BoyntonBeach,FL).Thesampleswerepreviouslydegassed

at 110◦C for 10h, and the specific area was calculated using the Brunauer-Emmett-Teller (BET) model Magnetic properties

of the materials were measured by vibrating sample magne-tometry(VSM)usinganADE/DMSModel 880Vibrating Sample Magnetometer(MicroSense,LLC,Lowell,MA).Thermogravimetric analysis(TGA)wasperformedusingaShimadzuDTG-60AHTGA (Shimadzu Corporation, Kyoto, Japan) Samples (approximately

10mg)wereheatedundersyntheticairatmosphereintherange

of25–800◦Cwithaheatingrateof10◦Cmin−1andagasflowrate

of30mLmin−1.Fouriertransforminfraredspectroscopy(FTIR)was performedusingaShimadzuspectrophotometerIRAffinitysystem, withKBrpelletscontaining1% sample,in thespectralrange of 400–4000cm−1,4cm−1resolutionwith32scans.X-raydiffraction (XRD)wasperformedusingaShimadzuXRD-6000equippedwith

agraphitecrystalasmonochromatortocollimateCu-K␣1radiation

at␭=1.5406Åwithastepof0.02◦s−1andanangularrange(2␪)of

4◦–70◦ 2.3 Catalytictests AssaysofthecatalyticdecompositionofH2O2bycel:magwere performed,understirring,using30mgofthecel:magcatalyst,5mL

ofwaterand2mLofH2O2.Thevolumeofoxygenproducedwas monitoredbydisplacementofwaterinacolumnover30min.A comparativereactionwasalsorunusing30mgofcatalyst,5mL

ofmethyleneblue(50ppm)and2mLofH2O2.Forleachingtests,

60mgofthecel:magcatalystwerestirredwith10mLofwaterfor

180min;then,decompositionofH2O2wasmeasuredusing5mLof thesupernatant.Forthedyetests,catalyticpropertieswereassayed viakineticdegradationofmethylenebluedyeusing10mgofthe cel:magcatalyst,9.9mLof50ppmmethylenebluesolutionand 0.1mLofH2O2.Reactionsweremonitoredbyspectrophotometryin UV–visat665nmat0,15,30,60,90,120and180min.Alltestswere performedusingeitherthecel:magorthemagnetitecatalytic for-mulations.Moreover,thedegradationkineticswerealsoperformed forpurecellulose

3 Results and discussion

3.1 Morphologyofthecellulosenanofibrils Onefeaturethatdeterminesthepresenceofnanofibrilsisthe formationofanincreasinglygel-likesuspensionwithsuccessive passagesthroughthedefibrillator(Nakagaito&Yano,2004).When thesolutioncontainingcellulosefiberspassesthroughthe defib-rillator,disintegrationofthecellwallsoccur,thusmodifyingthe dimensionsand surface structure ofthefibers Structural mod-ification results in viscosity changes due to the breaking and reformationofchemicalbonds.Thecrystallinityindexanddegree

Fig 1. Optical microscopy images of cellulose pulp fibers before defibrillation (a) and cellulose nanofibrils obtained by mechanical defibrillation of cellulose fibers (b); transmission electron microscopy (TEM) micrograph showing the nanofibrils after defibrillation (c); accumulated diameter distribution of the nanofibrils after measurements using TEM micrographs (d).

of polymerization are also changed with consecutive passages

(Uetani&Yano,2011).Lightmicroscopyimages(Fig.1a,b)present

thecellulosefibersbeforeandafterpassagesthroughthe

defibril-lator(35cycles),andthesizechangesinthenanofibrilsmaybe

clearlyobserved.Fig.1cshowsatransmissionelectronmicrograph

(TEM)ofthenanofibrilsobtainedbymechanicaldefibrillationof

thestartingcellulosepulpfibers.Defibrillationdecreasesthe

aver-agefiberlengthsignificantlyandincreasestheswellingcapacity

byfracturingthefibrils,resultinginaconsiderableincreasein

sur-facearea(Tonoli,Fuenteetal.,2009;Tonolietal.,2016;Tonoli,

RodriguesFilhoetal.,2009).Highshearappliedtofibersduring

defibrillationefficientlydisintegratedfibersintosmallfragments

and,tosomeextent,separatedindividualnanofibrils.The

accumu-latednanofibrildiameterdistributionispresentedinFig.1d.The

averagediameterofnanofibrilswas50±41nm,withroughly55%

ofthenanofibrilsatadiameteroflessthan40nm

Thepresenceoffiberslargerthanthenanoscalecanbeobserved

inthesuspension(contentlargerthan100nminFig.1d),although

thisdidnotprecludeformationofcatalystssincethesuspensions

remainedstableandwell-dispersedwithnoseparationofthe

cel-lulosenanofibrils(Fig.2a).Theminimizationofstepsinthemilling

protocolwillreducetheproductioncostsofcatalysts,an

impor-tantadvantageinlarge-scaleproduction.Theproductionofcatalyst

withcellulosewithoutpassingthroughthedefibrillatorwasalso

testedasacontrolexperiment,butthesecellulosefiberstendedto

clusteranddidnotformastablesuspension(Fig.2b).Therefore,the

synthesisofcatalystswithoutdefibrillationproducedan

inhomo-geneoussolutionwheretheactivephasewasnotwelldispersed,

formingmagnetiteclusterswithlongfibersofcellulose

3.2 Propertiesofthehybridsmagneticmaterials

Ahomogeneousmagneticmaterialwasproduced(cel:mag)that couldbeclassifiedasaxerogelsinceitsslowoven-dryingwould resultinalossofmicroporosity.Thecel:magmaterialwasmilledto reducetheparticlesizeandtoincreasethesurfacearea,an impor-tantcharacteristicofacatalyst.Thefinalmassyieldforthesynthesis was94%resultinginamaterialwithamphiphilic(Fig.2c)and mag-netic(Fig.2d)properties.Bothpropertiesincreasetheapplication possibilitiesindifferentreactionmediaandfacilitatethereuseof thematerial

Magnetiteonitsowngenerallyformsclustersinaqueous solu-tionsleadingtoalossofactivityinFenton-likeprocessesbecause thesurfaceareaisreducedtherebyreducingaccesstoreactiveFe ions.Toimprovetheefficiencyofthecatalyst,themagnetitewas synthesizedinassociationwithcellulose nanofibrils.Nanofibrils maintainalargesurfaceareaandsincecellulosedoesnotdissolve

inwaterororganicsolvents,itwashypothesizedthatmagnetite dispersedin cellulosewouldforma stablesolution.Sucha dis-persedmatrixwithalargesurfaceareawouldincreaseaccessto catalyticsites,thuspromotinglongercatalyticlife

Toverify thehypothesis of anincreasednumber of reactive sites,specificsurfaceareaanalysesofthematerials(cel:magand magnetite)andtheisothermsofN2(g)adsorption-desorptionwere performed(Fig.3a).TheisothermspresentahysteresistypeIV typi-calofmesoporousmaterialsshownasporesizedistribution(Fig.3a, insert)withstrong adsorbent-adsorbateinteractions (Thommes

etal.,2015).Thespecificsurfaceareascalculatedare30m2g−1and

112m2g−1formagnetiteandcel:mag,respectively.Theincrease

insurfaceareademonstratestheadvantageofusingmagnetiteon cellulosenanofibrils

104 A.C.C Arantes et al / Carbohydrate Polymers 163 (2017) 101–107

Fig 2.Cellulose fibers after (a) and before (b) mechanical defibrillation Note the uneven dispersion of fibers in (b) and the stable and well-dispersed suspension in (a) The amphiphilic property of the hybrid catalyst demonstrated when the catalyst remains in the interface of organic phase and aqueous mixture (c) magnetic property demonstrated when the hybrid catalyst is attracted by a magnet (d).

Fig 3.(a) N 2(g) adsorption-desorption isotherms (the insert shows the pore size distribution) and (b) hysteresis cycles (the insert shows the initial magnetization curve as a function of applied magnetic field) of the hybrid catalyst synthetized with cellulose nanofibrils and magnetite (Cel:Mag) and pure magnetite (Magnetite).

Themagneticproperties werestudiedby performinga VSM

analysisandFig.3 exhibitsthehysteresisloopofthematerials.The

hysteresisandcoercivityofsamplesarecharacteristicof

superpara-magneticmaterials.Thesaturationmagnetization ofcel:mag at

29.74emu/giscomparabletothatofpuremagnetiteat31.58emu/g

indicatingthatthecellulosematrixdoesn’taffectthe

superparam-agneticpropertyofthemagnetite

Interactionsand dispersionsof magnetite and cel:mag were

observed via SEM and image analysis (Fig 4) Pure magnetite

formsclusters(Fig.4a)thatdonotdisperseinaqueousmedia.The

cel:magalsoformsclusters;however,themagnetiteclustersare

distributedinawebofcellulosenanofibrils(Fig.4b).Thecel:mag

clustershaveanincreasedsurfaceareaoverthemagnetiteclusters

whichincreasestheaccesstocatalyticsitesinthecel:mag

mate-rial.Sincecelluloseiswaterinsoluble,thesystemremainsstable,

withmaterialswell-dispersedinthereactionmedium.Recoveryof

themagneticmaterialfromthestablematrixismuchfasterthan

fromtheunstablematrix(magnetitealone)thus,makingitmuch

easiertore-usethenanofibrilcatalystthanitistorecoverthepure

magnetite

TEMimagesalsoshowthedispersionofmagnetitewithinthe

webofcellulosenanofibrils(Fig.4c,d).Cellulosedoesstainslightly

withuranylacetate,thuscelluloseregionsarelesselectrondense

thanthemagnetiteregions,whichareelectrondenseduetotheir

metallicnature.Thus,inFigs.4cand4d,celluloseisrelatively

light-coloredwhilemagnetiteisrevealedasdarkspotsdispersedinthe

matrix

Thermogravimetricanalysis(TGA)revealssomemasslossat

about100◦C related tolossof adsorbedwater(Fig.5).The

dif-ferentialthermogravimetric(DTG)curveshowsthetemperature

atwhichthemaximumdegradationweightlossoccurs.Athigher

temperatures,themasslossesarerelatedtophasechanges,

mate-rial degradation and loss of structural water Above ∼300◦C

cellulosenanofibrilsrapidlylosemassdue totheirrapid degra-dationtoCO2andH2O,withstabilization(neartotaldegradation withapproximately98%ofmass loss)seenat∼530◦C (Fig.5a).

Formagnetite,asmallmasslossoccursataround200◦Crelated

toadsorbedwater.Afterthis,nomasslossisseen;however,an exothermiceventisobservedintheDTGcurve(Fig.5b)relatedto conversionofmagnetitetomaghemite.Magnetitecanalsoconvert directlytohematitebutthisconversiondoesnotappearintheDTG curve(CornellandSchwertmann,2003).Themaghemite(␥-Fe2O3) andhematite(Fe2O3)areironoxidessuchasmagnetite,butwith differentcompositionsandmoleculararrangements.Asexpected, forthe1:1cel:maghybridsproducedhere(Fig.5c),a50%mass lossrelatedtodegradationofcellulosenanofibrilswasconfirmed withachangeinDTGcurveataround∼300◦Ccorrespondingto

energyrelease.Theother50%ofthemassismagnetite,whichis notexpectedtodegradewithinthistemperaturerange

Fig 6a shows the FTIR spectra of the samples For cellu-losenanofibrils,bandsareobservedcorrespondingtoOHgroups

at around 3600 and 3200cm−1; stretching of the CH bond at

2900cm−1;deformationofprimaryandsecondaryOHgroupsat

1640cm−1and1400cm−1region;stretchedCOgroupat1100cm−1 andbandsrelatedtoalcoholgroupsbelow1000cm−1(Silverstein& Webster,1997).Formagnetite,thecharacteristicbandsarebelow

600cm−1anditispossibletoidentifyabandat590cm−1related

toFeOinteractions(Cornell&Schwertmann,2003).Forcel:mag, characteristicbandsrelatedtocellulosewereseen,andthebandof FeOthatisinterestingtocatalysis,showingthatFeisavailablein thematerial

Fig.6 showstheX-raydiffractogramswithsomecharacteristic andwell-definedpeaks,ataround18◦and22◦(Zugenmaier,2008) correspondingtocellulosenanofibrilsindicativeofthepresenceof

Fig 4.Typical electron micrographs of a cluster of synthetized pure magnetite (a) and the hybrid catalyst (cel:mag) synthetized with cellulose nanofibrils and magnetite showing the magnetite dispersed into the web of the cellulose nanofibrils (b) viewed by scanning electron microscopy (SEM) The hybrid catalyst (cel:mag) synthetized with cellulose nanofibrils and magnetite showing the magnetite dispersed into the web of the cellulose nanofibrils (c, d) viewed by transmission electron microscopy (TEM).

Fig 5.Typical thermograms of thermogravimetric analysis (TGA) and differential thermogravimetric (DTG) curves of cellulose nanofibrils obtained with mechanical defibrillation (a); synthetized pure magnetite (b); and the hybrid catalyst (cel:mag) obtained with cellulose nanofibrils and magnetite (c).

crystallinephasesandagreeingwiththefindingsof

Vivekanand-hanformicrocrystallinecellulose.Well-definedpeaksareobserved

formagnetitealsoindicatingitscrystallinecharacter(shownwith

anenlargedscalesincetheintensityismuch lowerthanthatof

purecellulose)(Vivekanandhan,Christensen,Misra,&Mohanty,

2012)andconfirming theefficiencyof thesynthesis The

mag-netite diffractogram, according to the JCPDS data library (card

number88–315formagnetite)referstoanironoxidewithacubic

crystallinephase(Sasaki,1997).Forcel:mag,thediffractogramis

practicallyidenticaltopuremagnetite,withnearperfectoverlap,

indicatingthatmagnetiteiswell-dispersedwithinthematrix

mate-rial

3.3 Catalyticproperties

Catalyticpotentialofmaterialscouldbeverifiedbyperforminga

decompositionofH O becausethisreaction,inconsecutivesteps,

generatesfree radicals,highlyreactivespecies thatattack most organicmolecules(Munoz,dePedro,Casas,&Rodriguez,2015) Thereactionismonitoredbymeasuringtheformationofoxygen thatisproportionaltothedecompositionofperoxideaccordingthe reactionH2O2→H2O+½O2.Theresultsforcel:magandpure mag-netite(Fig.7)showthatbothmaterialsdecomposeH2O2whichis evidencedbytheincreaseinoxygenevolutionovertime.Magnetite generatesalargervolumeofoxygenthancel:magundersimilar conditionsperhapsduetothepresenceoftwicetheamountofFe

inpuremagnetitecomparedtocel:mag.Cel:magcontainsa 1:1 ratioofcelluloseandmagnetite

AFenton-likeprocessisacomplexreactionandtheexact mech-anismisdifficulttopredictinheterogeneoussystems.Moredetails aboutthepossibleFentondegradationmechanismswerereported elsewhere(He,Yang, Men,&Wang,2016; Munozet al.,2015) ThereisevidencethatFe2+andFe3+catalyzethegenerationoffree hydroxylradicalsthatdegrademostorganiccompounds(Heetal.,

106 A.C.C Arantes et al / Carbohydrate Polymers 163 (2017) 101–107

0

20

40

60

80

100

120

500 1500

2500 3500

Wavenumber (cm-1)

Fourier transform infrared (FTIR) spectroscopy

Cellulose Magnetite Cel:Mag (a)

0 400 800 1200 1600 2000

0 2000 4000 6000 8000

Cell ulose

Magn etite

Cel:Mag

2Θ

X-ray Diffraction (XRD) Patterns (Intensity)

Cell ulose Magnetite Cel:Mag (b)

Fig 6.(a) Typical Fourier transform infrared (FTIR) spectra of cellulose nanofibrils obtained with mechanical defibrillation ( Cellulose), synthetized pure magnetite ( Magnetite), and the hybrid catalyst obtained with cellulose nanofibrils and magnetite ( Cel:Mag) and (b) X-ray diffraction (XRD) patterns of cellulose nanofibrils obtained with mechanical defibrillation ( Cellulose) using the scale on the left; and synthetized pure magnetite ( Magnetite) and the hybrid catalyst obtained with cellulose nanofibrils and magnetite ( Cel:Mag) using the scale on the right.

0

2

4

6

8

10

Time (min)

Oxygen Evolution Over Time Cel:Mag

Cel:Mag Leached Magnetite Magnetite Leached

Fig 7.Oxygen evolution over time in reactions of H 2 O 2 decomposition using the

hybrid catalyst obtained with cellulose nanofibrils and magnetite ( Cel:Mag),

pure magnetite ( Magnetite), the leached hybrid catalyst ( Cel:Mag

Leached) and leached pure magnetite ( Magnetite Leached) as catalysts.

2016;Munozetal.,2015;Nidheesh,Gandhimathi,&Ramesh,2013;

Pouran,Raman,&Daud,2014).Therefore,inordertomaintain

cat-alyticactivityandre-usethematerialformultiplecycles,Feions

shouldbeavailableonthesurfaceofthecatalystandshouldnot

leachoutwithtime.Leachingtests,usingthesupernatantofwater

andcatalysts(cel:magleachedandmagnetiteleached),were

per-formedtodetermineifFewaslostfromthecatalysttothereaction

medium,resultinginalossofcatalyticactivity.IfFeleaches,H2O2is

decomposedbyahomogeneouscatalysisusingthesupernatantof

acatalystsolution.Fig.7showstheresultsofH2O2decomposition usingtheleachedmaterialsandshowsthatnosignificantevolution

ofoxygenwasobserved,indicatingthatmagnetiteandcel:magare notlosingcatalyticactivity

Themaintenanceof catalyticactivitywasconfirmedover 10 consecutivecyclesof methylene blue decomposition (9.9mLat

50ppm,for180min)usingthesamecatalystsamplewith>95% dis-colorationforall10cycles(Fig.8a).Catalyticpotentialofcel:mag andmagnetitewasevaluatedbydegradationkineticsusing methy-leneblueastheorganiccompound(Fig.8b).Thedegradationwas monitoredbymeasuringthediscolorationofthesolution spectro-scopicallyat665nm(Dhar,Kumar, &Katiyar,2015).Methylene blueisadyeusedasamodelforde-activatingapollutantandthe effectivenessofthisdegradationreactionindicatesthatthecel:mag catalystcouldbeusedintreatmentofeffluentsthatgeneratelarge quantitiesoforganicwaste

In 180min, complete and 90% discoloration of methylene bluesolution wasobserved following exposureto cel:mag and magnetite, respectively, indicating degradation of the organic compound.Degradationkineticsissimilarforboth cel:magand magnetite.However,cel:mag containshalftheamountof mag-netiteaspuremagnetitesincehalfofthemassiscellulose;i.e.,a1:1 cel:maghas5mgofmagnetitecomparedto10mgforpure mag-netite.ThepositiveresultsseeninFig.8 arelikelyduetothefact thatFeionsweremoreavailableinthecel:maghybridthaninthe magnetite,leadingtosimilarreactionrateswiththehalfamount

ofmagnetite.Thedegradationkineticsperformedwithpure

cellu-Fig 8.Catalytic potential in consecutive cycles reusing the same amount of hybrid catalyst (cel:mag) obtained with cellulose nanofibrils and magnetite (a) and degradation kinetics using the hybrid catalyst ( Cel:Mag), pure magnetite ( Magnetite) and pure cellulose ( Cellulose) as catalysts (b) demonstrated in measures of

necessaryforcatalysisandthatdiscolorationofthesolutionisnot

duetheabsorptionofdyebythecellulose

4 Conclusions

Arenewablehybridcatalyst wassuccessfully producedfrom

magnetiteandcellulosenanofibrils.Thematerialhaspotentialtobe

usedinFenton-likereactionstodegradeorganiccompound

pollu-tants.Feionspresentinmagnetitecatalyzedthegeneration,from

H2O2,ofhydroxylradicalsthat degradedmethylene-bluedye,a

compoundpresentintextileeffluents.Cellulosenanofibrilswere

producedbymechanicaldefibrillation,resultinginasuspension

ofnanofibrilswithanaveragediameterof50±41nm;55%ofthe

nanofibrilshaddiameters<40nm.Thesynthesisofthehybrid

cat-alyst,cel:mag,wasverifiedbyperformingSEM,TEM,surfacearea

measurements,VSM,TGA,FTIRandXRDanalysesandtheresults

showedgood dispersionofthemagnetiteoncellulosic surfaces

Leachingandre-usetestsofthecatalyticmaterialsshowedthat

theydidnotlosecatalyticactivityandcanbeusedformultiple

cycles Degradationkineticsof H2O2 and methylene blueshow

complete(100%)and90%discolorationwithin180minwiththe

cel:maghybridandmagnetite,respectively.Resultsshowedthat

the magnetite (active phase), when dispersed in the cellulosic

matrix,degradesmethylenebluedye,amodelorganicpollutant,

atthesameratewithlesscatalyst

Acknowledgments

Theauthorsthank:theNationalCouncilforScientificand

Tech-nologicalDevelopment(CNPq),CoordinationfortheImprovement

of Higher LevelPersonnel (CAPES) and The MinasGerais State

Research Foundation (FAPEMIG) for financial support;

Depart-mentsofChemistry andForestry Sciencesat FederalUniversity

of Lavras for their outstanding infrastructure support; USDA,

BioproductsfromAgriculturalFeedstocks,ProjectNumber:

2030-41000-058-00-D; Ron Weiss (Arkival Technology Corporation,

Nashua,NH)forcollectingthemagnetometrymeasurementson

thesamplesandforprovidinginformationforinterpretationofthe

data;andLuizCarlosA.Oliveiraforsurfaceareasanalysis

References

Abe, K., & Yano, H (2011) Formation of hydrogels from cellulose nanofibers.

Carbohydrate Polymers, 85(4), 733–737.

Baetens, R., Jelle, B P., & Gustavsen, A (2011) Aerogel insulation for building

applications: A state-of-the-art review Energy and Buildings, 43(4), 761–769.

Bufalino, L., de Sena Neto, A R., Tonoli, G H D., de Souza Fonseca, A., Costa, T G.,

Marconcini, J M., & Mendes, L M (2015) How the chemical nature of Brazilian

hardwoods affects nanofibrillation of cellulose fibers and film optical quality.

Cellulose, 22(6), 3657–3672.

Chen, W., Abe, K., Uetani, K., Yu, H., Liu, Y., & Yano, H (2014) Individual cotton

cellulose nanofibers: Pretreatment and fibrillation technique Cellulose, 21(3),

1517–1528.

Chin, S F., Binti Romainor, A N., & Pang, S C (2014) Fabrication of hydrophobic

and magnetic cellulose aerogel with high oil absorption capacity Materials

Letters, 115, 241–243.

Cornell, R M., & Schwertmann, U (2003) Introduction to the iron oxides In R M.

Cornell, & U Schwertmann (Eds.), The iron oxides: Structure, properties,

reactions, occurences and uses (2nd ed., pp 1–7) Weinheim, FRG: Wiley-VCH

Verlag GmbH & Co KGaA.

Dhar, P., Kumar, A., & Katiyar, V (2015) Fabrication of cellulose nanocrystal

supported stable Fe(0) nanoparticles: A sustainable catalyst for dye reduction,

organic conversion and chemo-magnetic propulsion Cellulose, 22(6),

3755–3771.

Eichhorn, S J., Dufresne, A., Aranguren, M., Marcovich, N E., Capadona, J R., Rowan,

S J., & Peijs, T (2010) Review: Current international research into cellulose

nanofibres and nanocomposites Journal of Materials Science, 45(1), 1–33.

Fengel, D., & Wegener, G (1984) Wood: Chemistry, ultrastructure, reactions Berlin:

Walter de Gruyter.

Fonseca, C S., da Silva, T F., Silva, M F., Oliveira, I R C., Mendes, R F., Hein, P R G.,

& Tonoli, G H D (2016) Eucalyptus cellulose micro/nanofibrils in extruded

Gericke, M., Trygg, J., & Fardim, P (2013) Functional cellulose beads: Preparation, characterization, and applications Chemical Reviews, 113(7), 4812–4836.

He, J., Yang, X., Men, B., & Wang, D (2016) Interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials: A review Journal of Environmental Sciences (China), 39, 97–109.

Heath, L., & Thielemans, W (2010) Cellulose nanowhisker aerogels Green Chemistry, 12(8), 1448–1453.

Innerlohinger, J., Weber, H K., & Kraft, G (2006) Aerocellulose: Aerogels and aerogel-like materials made from cellulose Macromolecular Symposia, 244, 126–135.

Liu, S., Yan, Q., Tao, D., Yu, T., & Liu, X (2012) Highly flexible magnetic composite aerogels prepared by using cellulose nanofibril networks as templates Carbohydrate Polymers, 89(2), 551–557.

Luo, X., & Zhang, L (2009) High effective adsorption of organic dyes on magnetic cellulose beads entrapping activated carbon Journal of Hazardous Materials, 171(1–3), 340–347.

Munoz, M., de Pedro, Z M., Casas, J A., & Rodriguez, J J (2015) Preparation of magnetite-based catalysts and their application in heterogeneous Fenton oxidation – A review Applied Catalysis B: Environmental, 176–177, 249–265 Nakagaito, A N., & Yano, H (2004) The effect of morphological changes from pulp fiber towards nano-scale fibrillated cellulose on the mechanical properties of high-strength plant fiber based composites Applied Physics A: Materials Science and Processing, 78(4), 547–552.

Nidheesh, P V., Gandhimathi, R., & Ramesh, S T (2013) Degradation of dyes from aqueous solution by Fenton processes: A review Environmental Science and Pollution Research, 20(4), 2099–2132.

Nogueira, R F., Trovó, A G., Da Silva, M R A., Villa, R D., & De Oliveira, M C (2007) Fundaments and environmental applications of Fenton and photo-Fenton processes Quimica Nova, 30(2), 400–408.

Oksman, K., Aitomäki, Y., Mathew, A P., Siqueira, G., Zhou, Q., Butylina, S., & Hooshmand, S (2016) Review of the recent developments in cellulose nanocomposite processing Composites Part A: Applied Science and Manufacturing, 83, 2–18.

Olsson, R T., Azizi Samir, M A S., Salazar Alvarez, G., Belova, L., Strom, V., Berglund,

L A., & Gedde, U W (2010) Making flexible magnetic aerogels and stiff magnetic nanopaper using cellulose nanofibrils as templates Nature Nanotechnology, 5(8), 584–588.

Pouran, S R., Raman, A A A., & Daud, W (2014) Review on the application of modified iron oxides as heterogeneous catalysts in Fenton reactions Journal of Cleaner Production, 64, 24–35.

Reza, M T., Rottler, E., Tölle, R., Werner, M., Ramm, P., & Mumme, J (2015) Production, characterization and biogas application of magnetic hydrochar from cellulose Bioresource Technology, 186, 34–43.

Sasaki, S (1997) Radial distribution of electron density in magnetite, Fe3O4 Acta Crystallographica Section B: Structural Science, 53(5), 762–766.

Schwertmann, U., & Cornell, R M (2000) Iron oxides in the laboratory: Preparation and characterization (2nd ed.) Weinheim: Wiley-VCH Verlag GmBH Silverstein, R M., & Webster, F X (1997) Spectrometric identification of organic compounds (6th ed.) London: John Wiley & Sons.

Small, A C., & Johnston, J H (2009) Novel hybrid materials of magnetic nanoparticles and cellulose fibers Journal of Colloid and Interface Science, 331(1), 122–126.

Thommes, M., Kaneko, K., Neimark, A V., Olivier, J P., Rodriguez-Reinoso, F., Rouquerol, J., & Sing, K S W (2015) Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report) Pure and Applied Chemistry, 87(9-10), 1051–1069 Tonoli, G H D., Fuente, E., Monte, C., Savastano Jr, H., Lahr, F A R., & Blanco, A (2009) Effect of fibre morphology on flocculation of fibre-cement suspensions Cement and Concrete Research, 39(11), 1017–1022.

Tonoli, G H D., Rodrigues Filho, U P., Savastano Jr, H., Bras, J., Belgacem, M N., & Rocco Lahr, F A (2009) Cellulose modified fibres in cement based composites Composites Part A: Applied Science and Manufacturing, 40(12), 2046–2053 Tonoli, G H D., Holtman, K M., Glenn, G., Fonseca, A S., Wood, D., Williams, T., & Orts, W J (2016) Properties of cellulose micro/nanofibers obtained from eucalyptus pulp fiber treated with anaerobic digestate and high shear mixing Cellulose, 23, 1239–1256.

Uetani, K., & Yano, H (2011) Nanofibrillation of wood pulp using a high-speed blender Biomacromolecules, 12(2), 348–353.

Vivekanandhan, S., Christensen, L., Misra, M., & Mohanty, A K (2012) Green process for impregnation of silver nanoparticles into microcrystalline cellulose and their antimicrobial bionanocomposite films Journal of Biomaterials and Nanobiotechnology, 3, 371–376.

Wan, C., & Li, J (2015) Synthesis of well-dispersed magnetic CoFe2O4 nanoparticles in cellulose aerogels via a facile oxidative co-precipitation method Carbohydrate Polymers, 134, 144–150.

Wang, H., Li, D., Yano, H., & Abe, K (2014) Preparation of tough cellulose II nanofibers with high thermal stability from wood Cellulose, 21(3), 1505–1515 Zhu, W., Ma, W., Li, C., Pan, J., & Dai, X (2015) Well-designed multihollow magnetic imprinted microspheres based on cellulose nanocrystals (CNCs) stabilized Pickering double emulsion polymerization for selective adsorption

of bifenthrin Chemical Engineering Journal, 276, 249–260.

Zugenmaier, P (2008) Crystalline cellulose and derivatives (1st ed.) Berlin: Springer.