nanoparticle beads of chitosan-ethylene glycol diglycidyl

Research ArticleNanoparticle Beads of Chitosan-Ethylene GlycolDiglycidyl EtherFe for the Removal of Aldrin

G Garcıa Rosales 1 P Avila-Perez1 JO Reza-Garcıa1 A Cabral-Prieto2

and EO Perez-Gomez1

1TECNMInstituto Tecnologico de Toluca Departamento de Posgrado Avenida Tecnologico 100 sn Colonia Agrıcola BellavistaLa Virgen Metepec 52149 Mexico2Instituto Nacional de Investigaciones Nucleares Carretera Mexico-Toluca SN La Marquesa Ocoyoacac CP 52750 Mexico

Correspondence should be addressed to G Garcıa Rosales gegaromxyahoocommx

Received 20 May 2020 Revised 25 January 2021 Accepted 4 February 2021 Published 18 February 2021

Academic Editor Andrea Penoni

Copyright copy 2021 G Garcıa Rosales et al is is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

is article reports on the preparation of iron nanoparticles (FeNPs) supported in chitosan beads (Chi-EDGE-Fe) for removingaldrin from aqueous solutionse FeNPs and Chi-EDGE-Fe beads were characterized by means of scanning electronmicroscopy(SEM) transmission electronmicroscopy (TEM) X-ray diffraction (XRD) Fourier transform infrared (FTIR) and theMossbauerspectroscopy (MS) techniques TEM XRD and MS showed that the FeNPs had core-shell structures consisting of a core of eitherFe0 or Fe2B and a shell of magnetite Furthermore SEM images showed that Chi-EDGE-Fe beads were spherical with irregularsurfaces and certain degrees of roughness and porosity whilst the sorbent mean pore size was 204 nm and the occluded ironnanoparticles in the chitosan material had diameters of 70 nm and formed agglomerates e sorbent beads consisted of carbonoxygen chlorine aluminum silicon and iron according to the SEM-EDS analysis Functional groups such as O-H C-H -CH2N-H C-O C-OH and Fe-OH were detected in the FTIR spectra In addition a characteristic band appeared at about 1700 cmminus 1

after the sorption process involving aldrin MS also showed that the iron nanoparticles in the beads probably oxidized into NPs ofα-Fe2O3 as a result of the supporting process e isotherm of the aldrin removal followed the LangmuirndashFreundlich model andpresented a maximum adsorption capacity of 7484mgg demonstrating that chitosan-Fe beads are promising sorbents for theremoval of toxic pollutants in aqueous solutions

1 Introduction

Organo-chlorine pesticides (OCPs) are used extensively inagriculture and are considered to be one of the most haz-ardous classes of environmental and persistent organicpollutants (POPs) [1 2] ey are toxic to many forms ofwildlife including aquatic organisms insects andmammalsand they persist in aquatic environments for many yearsafter their application [3] eir lipophilicity and persistencycan lead to their bioaccumulation and biomagnification inthe fatty tissues of biological organisms and food chains [4]As a result of the high levels found in organisms thesepollutants also produce adverse effects in humans [5 6]Aldrin as an OCP presents potential risks to health as an

endocrine disruptor and can damage blood kidneys theliver and the central nervous system [7 8] Several physicalbiological and chemical methods have been developed toremove OCPs such as bioremediation [9] photochemicaloxidation catalytic degradation [10] membrane filtration[11] and adsorption [12] Adsorption is the most popularand promising technique due to its low cost accessibilityexcellent performance and environmental friendliness [13]On the contrary in some systems FeNPs have been found tobe exceptional in the removal of contaminants as sorbents ordegradation moieties In recent years nanocomposites in-volving FeNPs have been used in POP removale constantsearch for materials that exhibit adequate properties forcertain applications and the development of new

HindawiJournal of ChemistryVolume 2021 Article ID 8421840 13 pageshttpsdoiorg10115520218421840

technological tools has given way to nanotechnology FeNPshave been studied for the removal of a broad variety ofcontaminants such as dyes nitrates heavy metals andchlorinated organic compounds [14 15] due to their sizerange larger specific surface areas and higher densities ofreactive surface sites Iron-oxide NPs are generally formedwhen FeNPs are exposed to contaminants and their removalprocess may consist on mechanisms such as degradationabsorption encapsulation and diffusion Pure FeNPshowever tend to agglomerate when their particle sizesovercome a critical size resulting in a decrease in theirspecific surface areas and active sites for the removal ofcontaminants Hence innovative and low-cost materialsincluding SBA-15 carbon resins clays and chitosan havebeen used to control FeNPsrsquo particle sizes and remediate thisdisadvantage Due to its high contents of amino and hy-droxyl functional groups chitosan has great potential for theabsorption of several compounds [16] Chitosan is adeacetylated form of chitin a well-known cationic poly-saccharide which is an abundantly available low-cost bio-polymer and the most widespread biopolymer in natureefree amino (NH2) and hydroxyl (OH-) groups in its mo-lecular structure can serve effectively as active adsorptiongroups Chitosan is nontoxic hydrophilic biocompatiblebiodegradable and antibacterial resulting in diverse ap-plications in the biomedical field cosmetics food textileindustries and the environment [17] A large number ofresearchers have confirmed the use of chitosan as a sorbentfor the removal of organic compounds from aqueous so-lutions since the physical-chemical properties of chitosancan be modified via the expansion of its polymer networkopenings Some studies performed with chitosan beads haveshown that it has high efficiency in sorption processesChitosan beads have also exhibited high adsorption ca-pacities in wastewater treatment studies [18] Additionallythe ease with which they can be separated from effluents andthe possibility of sorbent regeneration has made chitosanbeads one of the most prominent materials for sorptionapplications However chitosan beads exhibit instability insolutions with pH valueslt4 which results in the dissolutionof the material and drops in its adsorption capacity isproblem is however solved by a reaction of the chitosanwith a cross-linking agent which leads to the conservation ofthe biopolymer through the formation of bonds amongst thechitosan chains e objective of this research is to obtain anefficient chitosan-FeNPs composite material to be used as anadsorbent for the removal of aldrin e Langmuir andFreundlich equations were used to fit the equilibrium iso-therm data in order to understand and evaluate the inter-action mechanisms between the surface of the compositeand the contaminant

2 Materials and Methods

21 Synthesis of FeNPs e FeNPs were prepared via thesodium borohydride reduction method in which ferricchloride (FeCl36H2O from Merckreg) was dissolved in anethanol-water mixture (1 1V) and stirred for severalminutes In addition sodium borohydride (from Merckreg)

was dissolved in deionized water and subsequently addeddropwise to the iron-chloride solution using a burette ac-companied by vigorous hand stirring After the first drop ofsodium borohydride solution was added solid black par-ticles appeared immediately and the remaining sodiumborohydride was added to complete and accelerate the re-duction process Immediately afterward the reacting solu-tion was stirred for an additional 10minutes e vacuumfiltration technique was used to separate the black ironnanoparticles from the liquid phase Two sheets ofWhatmanfilter papers (40 mesh) were used in this process e solidparticles were washed three times with absolute ethanol toremove all the water content e synthesized NPs werefinally dried in an oven at 323K for 12 hours and were keptin a jar in an argon atmosphere to avoid further oxidation

22 Synthesis of Chitosan-FeNPs (Chi-EDGE-Fe)Chitosan medium molecular weight powder at 80 mesh(177 μm) with over a 90 degree of deacetylation and aceticacid of 998 purity fromAlimentos America and Fremontregwere used Sodium hydroxide (NaOH) with 97 purity fromChemical Reagents Meyerreg ethylene glycol diglycidyl ether(EGDE) from the Tokyo Chemical Industry and aldrin(C12H8Cl6) with 984 purity from Chem Servicereg were alsoused First 78 g of chitosan powder was placed in a 500mLbeaker and dissolved in 250mL of a 04M acetic acid so-lution Next the FeNPs were added to the mixture whichwas then subjected to ultrasonic shaking for 3minutesenwith the aid of a peristaltic bomb and a hypodermic needle(internal diameter 09mm) 100mL of NaOH solution(01M) was added dropwise to the previous solution and theresulting mixture was stirred for 2 hourse resulting beadswere washed with water until a pH 7-8 was reached In orderto carry out the material cross-linking process a 7mLchitosan bead solution plus 25mL of deionized water and01 g of EGDE were put into a two-necked flask and thedeionized was adjusted to pH 12 with the NaOH solution(01M)e resulting solution was heated at 70degC and stirredcontinuously at 125 rpm under an inert atmosphere of N2 for6 hours At the end of the reaction the beads were left to coolto 15degC and washed with deionized water until pH 7 wasreached After synthetizing the Chi-EDGE-Fe beads in thismanner they were subjected to a lyophilization process in aHeto PowerDryreg LL1500 apparatus at minus 60degC and 05mbarFinally these beads were placed inside 15mL vials andimmersed in liquid nitrogen for 2 minutese samples werethen placed in the equipment nozzles e total lyophili-zation process took around 24 hours

23 Characterization of the Materials SEM TEM and MSDRX and FTIR e morphological analysis was performedvia a scanning electron microscope JEOLreg JSM-5900LVe solid samples were sprinkled on a metallic disk andcovered with gold for 100 seconds using the AJAreg sputteringsystem ATC 1500 e chemical composition was deter-mined by means of the EDS system (Oxfordreg 7279) whichincluded the scanning electronmicroscope In order to studythe morphologies and sizes of the FeNPs supported in the

2 Journal of Chemistry

chitosan beads (Chi-EDGE-Fe) via transmission electronmicroscopy (TEM model JEOLreg 2010) a sample wasprepared by dispersing a small amount of Chi-EDGE-Fe inethanol using an ultrasonic bath with a few drops of sus-pension that were then placed on a carbon film supported ona copper substrate For the identification of the iron phasesin the FeNPs and Chi-EDGE-Fe materials approximately50mg of material was placed in a Lucite sample holder andMS studies were performed using a Wisselreg constant ac-celeration spectrometer with 57CoRh e reported isomershifts are referred to as those of metallic iron e crystalphases of FeNPs Chi-EGDE and Chi-EGDE-Fe were an-alyzed using a BRUKERreg (D8Discover) XRD diffractometerwith a copper anode X-ray tube (λ1543 A) the X-raydiffraction reflections were measured in a range from 4deg to70deg in 2θdeg scale utilizing a 002 step size and a scan speed of1degmin e FTIR spectra were obtained via a ScientificNicoletreg iS5 spectrometer and used to determine thefunctional groups in the composite material e recordedFTIR spectra ranged from 4000 cmminus 1 to 500 cmminus 1 over thecourse of 50 scans

24 Surface Characterization BET Active Site Density andIsoelectric Point e surface areas of the beads were de-termined by using the Multipoint BET Nitrogen Adsorptiontechnique and the BELPREP-flow II (BEL Japanreg Inc)device Prior to analysis the samples were degassed for1 hour at 30degC In order to determine the active site density30mL of NaClO4 solution (01M) was added to a 50mL testtube to be used as a reference or blank sample en 300mgof beads were added to another test tube containing anadditional 30mL of the blank sample e solutions werestirred for 24 hours at room temperature At the end of thisprocess the pH of the sample suspension was adjusted to apH 2 by means of a 01M solution of HClO4 en thesuspension was readjusted to a pH 12 via the dropwiseaddition of a 01M solution of NaOH with a micropipettee pH of the solution was measured using a HannaInstrumentsreg model HI3221 potentiometer Finally theactive site density was calculated using the equation de-veloped by Bell et al [19] In order to determine the iso-electric point ten samples of 001 g 002 g 004 g 006 g008 g 010 g 020 g 040 g and 050 g in 10mL of deionizedwater were placed in 15mL centrifuge tubes and centrifugedat 100 rpm for 24 hours at room temperature using theScorpion Scientificreg A50651 apparatus until achievingcomplete hydration Finally the pH of each supernatant wasmeasured via the Hanna Instrumentsreg model HI3221potentiometer

25 Sorption Study Sorption experiments were carried outat 20degC A standard stock solution of 1000mgL of aldrin wasfirstly prepared by dissolving the standard aldrin reagent(984 purity from Chem Servicereg) in acetone this solutionwas further diluted to the concentrations required for eachexperiment e sorption experiments were carried outusing a batch system at different concentrations (10mgL20mgL 30mgL 40mgL 50mgL 60mgL 80mgL

100mgL 120mgL 160mgL 180mgL and 200mgL)polypropylene tubes and a ratio of 001 g of sorbent to 001 Lof aqueous aldrin solution It is important to note that theexperiments were carried out in the dark in order to reducethe degradation process of the aldrin and favour the ad-sorption process Each sample was stirred at 120 rpm for 24hours subsequently the liquid phase was separated bycentrifugation 10mL of hexane was added and the solutionwas stirred manually for 10 minutes to extract the aldrinFinally the sample concentration was adjusted to 2mL inthe Buchireg R-300 rotary evaporator and later to 05 microL in theN2 atmosphere e analysis of the liquid phase was per-formed by gas chromatographymass spectrometry with anAgilentreg 6890N coupled to an Agilentreg 5973 with an HPreg190915-433 capillary column

3 Results and Discussion

31 Iron Nanoparticles (FeNPs) e original FeNPs con-sisted of black fine powder as observed in Figure 1(a) toavoid oxidation and the FeNPs were washed with degassedethanol several times and stored in an argon atmosphereese FeNPs reacted to an external magnetic field as shownin Figure 1(b) because of their ferromagnetic propertiesese particles exhibit cooperative spin behaviour ie thespins are oriented in the same direction within a section ofthe material called ldquothe domainrdquo By reducing nanoparticlesizes below a critical size super-paramagnetism (SP) isestablished in which the cooperative spin behaviour dis-appears and the thermal energy is enough to destroy anysuch cooperative effect

32 SEM and TEM Image Analyses of Materials Once theFeNPs were incorporated into the polymeric composite achange in colour was observed e Chi-EGDE-Fe beadswere tinted in yellow (Figure 2(a)) which can be attributedto the oxidation of the FeNPs In Figure 2(b) the averageparticle diameter of the composite was 264mm After thelyophilization process the composite exhibited sphericalparticles had a rough structure and presented small channelson its surface (see Figure 2(c)) Zooming in 500x reveals thatthe channels have an almost pentagonal arrangement that isrepeated forming a honeycomb with thick contours that areabout 10 μm thick with a diameter close to 40 μm (seeFigure 2(d)) In order to observe how the FeNPs weredistributed within the spheres a sphere was cut transversallyand observed at 50x (see Figure 2(e)) It is observed fromFigure 2(e) that the internal structure of a sphere has verysmall channels with an average diameter of 34 nm Fur-thermore they are for the most part distributed homo-geneously but make up agglomerates in some regions withsizes up to 42 μm Since the surfaces of these sphericalparticles are rough and porous there are favourable transfersof mass and energy flows between the contaminant and theadsorbent material e average pore diameter was 204 nmclassifying it as a macroporous material whilst the poreswith larger diameter were found on the surface above 25 μmin depth [20] Table 1 shows the elemental composition of a

Journal of Chemistry 3

1cm

(a)

1cm

(b)

Figure 1 e FeNPs in (a) absence and (b) presence of an external magnetic field

1cm

(a)

23 24 25 26 27 28 29

Freq

uenc

y

Diameter (mm)

264 mm

(b)

(c) (d)

Figure 2 Continued


Chi-EGDE-Fe bead e principal components are carbonand oxygen which arise mainly from the chitosan andethylene-glycol diglycidyl ether compounds e addition ofthese latter substances resulted in a relatively low chlorinecontent that can be attributed to the chitosan Small amountsof aluminum and silicon of unknown origin were alsoobserved Knidri et al [21] noted the presence of silicon inchitosan spectra but failed to speculate on its origin epresence of aluminum can be attributed to the sample holdersince this device was made of aluminum Finally the Chi-EGDE-Fe beads had a small percentage of iron content

TEM image processing was performed to measure theparticle sizes of the FeNPs Figure 3(a) shows spherical NPsforming long chains due to their strong magnetic nature themeasurements showed that the diameters were in the rangeof 10 nm to 50 nm with an average diameter of 28 nm (seethe inserted histogram in Figure 3(a)) When a close-up wasmade towards one of the nanoparticles (Figure 3(b)) a core-shell structure was observed with a core diameter of 17 nmand an external diameter of 25 nm with the shells ranging inthickness from 2nm to 4 nm ese core-shell particles arecharacteristic of FeNPs When the FeNPs within the chi-tosan spheres were analyzed it was observed that there weresome morphological differences relative to those of the pureFeNPs A thicker coveringmaterial surrounded these FeNPsmaking it impossible to observe the core-shell structureInside the spheres the particle diameters increased tosim70 nm According to Chaudhuri [22] and Kopanja et al[23] these types of clustered nanoparticles are typical afterthe stabilization process with chitosan has occurred

33 Mossbauer Spectroscopy (MS) Figure 4(a) shows theMossbauer spectrum for the FeNPs in which a superposi-tion of three Mossbauer hyperfine patterns can be observedtwo of magnetic and one of SP nature e six-line magneticpattern (green line) with a hyperfine magnetic field ofB 33 T is characteristic of metallic iron e broader six-line magnetic pattern (blue line) with a hyperfine magneticfield of B 26 T is characteristic of iron borides such as Fe2BFinally the two-line quadrupole doublet (magenta line) canbe associated with FeNPs having particle sizes below the10 nm range e hyperfine parameters of this quadrupoledoublet ie an isomer shift of δ 034mms a quadruplesplitting of ΔE2 075mms and broad line widths ofΓ 08mms are typical of nanometric FeNPs including theshell materials composed of maghemite or magnetite [24]When examining certain features of the Mossbauer spectrait is possible to make some inferences about the particle sizesof the FeNPs For example if the Mossbauer spectrum ofthese FeNPs were to consist of broad and poorly resolvedmagnetic patterns this pattern would be indicative ofparticles with sizes ranging between 12 nm and 15 nm onthe other hand if a singlet or a doublet pattern were to berecorded it would be indicative of particles withsizeslt10 nm and in possession of super-paramagneticproperties As the next section will show the presence ofmaghemitemagnetite is further confirmed by XRD mea-surements on the unsupported FeNPs On the other handFigure 4(b) shows the corresponding Mossbauer spectrumof the Chi-EDGE-Fe beads which exhibits a quadrupoledoublet only e isomer shift (δ) and quadrupole splitting(ΔE2) parameters shown in Figure 4(b) are related toparticles with sizes below the 10 nm range as previouslyindicated in this composite it was not possible to detect themagnetic component of the FeNPs In this particular casethe absence of magnetism may suggest that the FeNPs weretotally oxidized during the synthesis of the Chi-EDGE-Febeads e FeNPs may have transformed into α-Fe2O3particles of sizelt10 nm as a result of the synthesis of thecomposite as inferred from the pale-yellow colour of thebeads

(e) (f )

Figure 2 (a) Chi-EGDE-Fe (b) size of the bead (c d) SEM image of the external surface (e f ) SEM image of the internal surface

Table 1 Elemental analysis of Chi-EGDE-Fe beads

Element Chi-EGDE-Fe elementalC 6130O 3010Al 044Si 044Cl 216Fe 556


34 X-Ray Diffraction (XRD) e X-ray diffraction (XRD)analysis was conducted to investigate the crystalline struc-ture of the FeNPs Figure 5(a) shows the XRD patterns ofthese NPs where the main diffracted lines located at 35deg and45deg in the 2θdeg scale indicate the presence of magnetite andmetallic iron respectively Figures 5(b) and 5(c) show the

XRD patterns of the Chi-EGDE and Chi-EGDE-Fe mate-rials respectively with similar broad diffracted lines at sim10degand 20deg and low intensities and broad signals between 35degand 40deg on the 2θ scale e broad diffracted XRD lines ofhigher intensity are indicative of a low crystallization levelfor the chitosan which is due to the low degree of

10 15 20 25 30 35 40 45 50

Freq

uenc

y

Diameter (nm)

28 nm

(a)

(b) (c)

Figure 3 TEM (a) fine particles of FeNPs (b) ultrafine nanoparticles of FeNP core (c) ultrafine nanoparticles of Chi-EGDE-Fe


deacetylation [25] Ultrasmall hematite NPs could be sug-gested from the Mossbauer spectroscopy point of viewwhere the particlesrsquo size from 2 nm to 3 nm could be inferred[26] However neither the MS nor the XRD technique wasable to discern the presence of hematite unambiguously einference was made based on the pale-yellow colour of theChi-EGDE-Fe beads e pure Chi-EGDE material waswhite On the other hand the hyperfine parameters of thequadrupole doublet in the composite were lower than thosearising from the quadrupole doublet of the pure FeNPs

(Figure 4(a)) suggesting a different iron phase from thosepresent in the pure FeNPsmdashthe Fedeg and Fe2B and phases andSP particles of maghemitemagnetite e ambiguity indiscerning the nature of the FeNPs in the composite arisesfrom the fact that a very small amount of these FeNPs weremixed with the Chi-EGDEmaterial to form the composite Ablack or grey colour would be expected for the Chi-EGDE-Febeads if no oxidation were to take place when this compositewas produced Instead a pale-yellow colour was observed(Figure 2(a)) us at this point in the analysis the nature of

ndash10 ndash8 ndash6 ndash4 ndash2 0 2 4 6 8 10

59

I (n

u)

mms

α-Fe2O3Fe2B

Fe0

(a)

ndash10 ndash8 ndash6 ndash4 ndash2 0 2 4 6 8 10mms

δ = 0205ΔEQ = 0355Г= 042

11

I (n

u)(b)

Figure 4 Mossbauer spectra of (a) FeNPs and (b) Chi-EGDE-Fe

10 20 30 40 50 60 70 80

45

Card Fe2B

FeNPs

Inte

nsity

(au

)

Aacutengle 2θ

35

(a)

10 20 30 40 50 60 70 80

Chi-EGDE

Chi-EGDE-Fe

Card Chi

20

Inte

nsity

(au

)

Aacutengle 2θ

10

(b)

Figure 5 XRD patterns of (a) FeNPs and (b) Chi-EGDE and Chi-EGDE-Fe


the iron NPs in the composite remained uncertain To clearthis point up a 77KMossbauer spectrum would be requiredto search for the hyperfine magnetic field associated with thequadrupole doublet shown in Figure 4(b)

35 FTIR Analysis Figure 6 shows the FTIR spectra of thecross-linked Chi-EGDE-Fe beads e broad peak locatedthe ranges of 3600 cmminus 1 and 3100 cmminus 1 which corresponds tothe overlapping stretching vibrations of N-H andO-H bonds[27] e band at 2870 cmminus 1 can be assigned to symmetricand asymmetric stretching vibrations of the C-H bond of themethylene group CH2e band at 1647 cmminus 1 is the result ofthe flexion of the N-H bonds in the primary amino groupsand the band at 1424 cmminus 1 can be assigned to the flexuralvibration of the amino groups C-N and N-H Additionallythe band at 1376 cmminus 1 can be assigned to the C-O stretchingvibration of a primary alcohol group and the band at1065 cmminus 1 corresponds to the free amino group [28] Sathyaet al [29] reported that the peaks located at 610 cmminus 1 and560 cmminus 1 are due to the formation of iron-oxide nano-particles whereas Iovescua et al [30] reported that the peaksat 563 cmminus 1 and 461 cmminus 1 are characteristic of the stretchingmodes of Fe-O bonds in hematite Several changes areobserved in the FTIR spectrum after the sorption process inChi-EGDE-Fe-aldrın material and in the functional groupscorresponding to OH N-H C-N and Fe-O which indicatethat these changes are directly related to the absorption ofaldrin e small shifts and intensity changes observed atapproximately 1700 cmminus 1 to lower wavenumbers are prob-ably related to the interactions between the amino groupsand Cl ions of aldrin Also an interaction between the ironNPs and aldrin is noticeable in the 700 cmminus 1 and 500 cmminus 1

range

36 Surface Characterization e specific surface area(SBET) volume and pore diameter results for the Chi-EGDE-Fe beads and the FeNPs are shown in Table 2 eFeNPs have the greatest specific surface areas with an av-erage value of 44degm2gdegplusmn deg2m2g this value is similar to theone reported by Picasso et al [31] and lower than that re-ported by Akhgar et al [32] ese differences are attributedto the particle sizes of the FeNPs On the contrary the Chi-EGDE-Fe beads have a lower average specific surface areais difference in specific surface area can be attributed tothe FeNPs that are supported on the Chi-EGDE beads Asreported previously the Fe content in the Chi-EGDE-Febeads is only 556 and this Fe is probably in the formα-Fe2O3 differing from the original FeNPs It is important tonote that the other parameters namely the TPV and APDdo not change appreciably between samples (Table 2)

e measured active site density for the Chi-EGDE-Febeads was 28 sitesnm2 and the isoelectric point wasestablished at pH 7 Hence it is possible to infer that thesurface of the material is positively charged is conditionfavours the removal of molecules in a negatively chargedsolution At pHgt 692 and pH 7 the surfaces of the Chi-EGDE-Fe beads would be negatively charged in such a way

these materials would not be able to remove organiccompounds

37 Sorption Isotherm as a Function of Aldrin Concentratione sorption of aldrin by means of the Chi-EGDE-Fe beadsunder equilibrium conditions (qe) as a function of the aldrinconcentration (Ce) is presented belowe sorption processtook place at 20degC whilst using a contact time of 24 hours andseveral aldrin concentrations e experimental data werefitted to the mathematical models developed by LangmuirFreundlich and LangmuirndashFreundlich and the best fit wasobtained with the LangmuirndashFreundlich model e max-imum adsorption capacity of the beads reached 7484mggdegplusmn deg2mgg Figure 7 shows the fitted experimental datausing the LangmuirndashFreundlich model only which isexpressed in equation (1) below LangmuirndashFreundlichisotherm includes the knowledge of adsorption heteroge-neous surfaces It describes the distribution of adsorptionenergy onto heterogeneous surface of the adsorbent [33] Ata low adsorbate concentration this model becomes theFreundlich isotherm model whilst at a high adsorbateconcentration it becomes the Langmuir isotherm Lang-muirndashFreundlich isotherm can be expressed as follows

qe qMLF KLF Ce( 1113857

MLF

1 + KLF Ce( 1113857MLF

(1)

Here qe (mgg) is the amount of the sorbed adsorbateunder equilibrium conditions qMLF is the maximum ad-sorption capacity (mggminus 1) KLF is equilibrium constant forheterogeneous solid and MLF is heterogeneous parameterese parameters can be obtained by using the nonlinearregression techniques e calculated isothermal coefficientsare summarized in Table 3

38 Proposed Removal Mechanism e interaction be-tween the aldrin and the Chi-EDGE-Fe can occur in twopossible ways with the first way being a sorption process

4000 3500 3000 2500 2000 1500 1000 500

Fe-O

C-NC-O

N-HN-HC = OC-HO-HN-HTr

ansm

itanc

e (au

)

Wavenumber (cmndash1)

Chi-EGDE-Fe-aldrin

Chi-EGDE-Fe

Figure 6 FTIR spectra


and the second one involving a degradation process eadsorption mechanism can involve a physical entrap-ment or a chemical binding via weak Van der Waalsforces dipole-dipole and ion-dipole interactions cationexchanges strong covalent bonding and a phys-isorption which could take place in multiple layers[34 35] Figure 8 shows the proposed sorption mecha-nism for the interaction between Chi-EGDE-Fe and al-drin developed by the Avogadro Vision 120 software Inthe FTIR analysis it was possible to observe several activesites including hydroxyl (OH) and amino (NH) groupsas well as C-O and Fe-OH bonds on the surface of thecomposite all of which favour the adsorption of aldrine sorption of aldrin can be carried out via differentmechanisms one of which involves the C-OH sites and

aldrin-Cl bonds whilst another one involves the Fe-OHgroups and aldrin-Cl ions e FTIR analysis appears toindicate that all these interactions occur because severalfrequency shifts of these functional groups were ob-served is observation coincides with the sorptionisotherm fitted with the LangmuirndashFreundlich modelconsidering that in this work the sorption process iscarried out at high concentrations and the adsorbate issorbed at sites located in fixed positions and may bearranged in a monolayer form in this case all the sitesare energetically equivalent Is important to note that adiffusion of aldrin molecules into the primary porousstructure of the Chi-EDGE-Fe seems to be impossible soonly the active surface sites of the secondary porositystructure may be accessible for the diffusion and

Table 3 Adjustment parameters for Langmuir Freundlich and LangmuirndashFreundlich models

Model Equation Settings

Langmuir qe q0bc2(1 + bc2)

R2 097qo 9369mg gminus 1

b 004 L mgminus 1

Freundlich qe KFC1ne

R2 090KF 1004mg gminus 1

n 232

LangmuirndashFreundlich qe qMLF(KLFCe)MLF (1 + (KLFCe)

MLF )

R2 099qMLF 7484mg gminus 1

KLF 00047 L mgminus 1

MLF 186

Table 2 Specific surface area volume and pore size parameters of the studied materials

Material SBET (m2g) Total pore volume (TPV) (cm3g) Average pore diameter (APD) (nm)FeNPs 4420 019 1710Chi-EGDE-Fe 3891 017 1708

0 20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80

ExperimentalLangmuir

FreundlichLangmuirndashFreundlich

q e (m

gg)

Ce (mgL)

Figure 7 Fitting data of the isotherm points to Langmuir Freundlich and LangmuirndashFreundlich model


adsorption of the pesticide molecules us the degra-dation of aldrin cannot be ruled out given the presence ofiron-oxide NPs in this case hematite NPs are highlyreactive with crystal defects such as vacancies which areunstable electrostatic points and act on any substancehaving dipolar properties Using the present results it isnot possible to distinguish between a sorption anddegradation process for aldrin us both the sorptionand degradation of aldrin may occur e sorptionprocess may occur through electrostatic interactionscaused by the inductive effect of the chlorine atoms inaldrin and the functional groups in the composite mayinfluence the degradation process through the crystaldefects in the hematite NPs

However several studies support the degradation ofaldrin Shoiful et al [13] show that in the absence ofsunlight aldrin degradation occurs after 12 hours and thatthis process is strongly influenced by the dissociationenergy of C-Cl bonding within the structure [36] edegradation products of aldrin have not been identifiedexperimentally as of yet However these degradationproducts have been predicted with computation models[37] which indicate that aldrin undergoes degradation toform dieldrin and pentachlordieldrin Bandala et al [38]indicate however that the degradation process canproduce low yields due to the hydrophobic character ofaldrin Sayles et al [39] explain that the degradation ofaldrin with Fe0 NPs begins when iron-oxides form on thesurfaces of the nanoparticles in the aqueous phaseresulting in magnetite (Fe3O4) that contains Fe2+ groupswhich then initiate the degradation reaction that results in

the formation of free radicals [40] e reaction is de-scribed as follows

3 FeIIFe2III1113858 1113859O4(magnetite) + 1 2O2 + 2H

+

minus minus minus minus gt 4 Fe2III1113858 1113859O3(maghemite) + Fe(II) + H2O

R minus Cl + 2eminus

+ H+

minus minus minus minus gtR minus H + Clminus

(2)

According to Yamada [36] in this process the H+

plays an important role in the dissociation of magnetiteand reduction of aldrin In this particular case thismechanism is ruled out due to the absence of magnetitee results of the current study were compared with thedata concerning the sorption of aldrin on different ad-sorbents (Table 4) It was noted that our nanoparticlebeads of chitosan-Fe (Chi-EGDE-Fe beads) showed thebest results for the sorption of aldrin Furthermore Luet al [8] prepared a compound of chitosan beads usedthem for aldrin removal and reported a low sorptioncapacity compared to the present work Sprynsky et al[34] utilized clinoptilolite and reported 499 μgg of aldrinremoval Also Bakouri et al [41] reported 1954mgg ofaldrin removal using acid-treated olive stones as an ad-sorbent us nanoparticle beads of chitosan-Fe exhibi-ted an acceptable performance in comparison to theseother adsorbents is situation can be explained by theformation of surface sites and the specific area thatprovides the increase in the adsorption capacity to removealdrin in solution

EDGE

Chi

Chi-EDGE-Fe

Aldrin

Cl B C OFe H N

FeNPsRemovalof aldrin

Fe-Cl

C-ClB-Cl

O-Cl

N-Cl

Figure 8 Proposal mechanism between Chi-EGDE-Fe and the aldrin


4 Conclusion

In the present work FeNPs were synthesized bymeans of thechemical reduction method and were supported in chitosanbeads cross-linked with ethylene glycol diglycidyl ether(Chi-EGDE-Fe) e supporting strategy was used in orderto improve the handling and recovery of the FeNPs in thesorption of aldrin in aqueous media ree iron phasesnamely Fe0 Fe3O4 and Fe2B were identified in the un-supported black FeNPs e FeNPs had a core-shell typestructure with the core consisting of Fe0 or Fe2B and havinga diameter of sim28 nm and the shell of magnetite beingsim2ndash4 nm thick e chitosan-EGDE-supported FeNP beadswere pale-yellow in colour had a spherical form and were ofhigh roughness e iron in these beads was possibly inhematite form e FTIR spectrum showed a noticeabledifference in the interval from 500 cmminus 1 to 700 cmminus 1 due tothe interaction with Chi-EDGE-Fe-aldrin As a result of theanalysis of the aldrin sorption isotherms a maximumsorption capacity of 7484mggplusmn 2mgg was obtained forthe iron beads e experimental data fit the LangmuirndashFreundlich model better (with a correlation of 099) indi-cating that in the sorption process a single layer of thepollutant may be formed on the surface of the adsorbentmaterial e interactions between Chi-EGDE-Fe and aldrincould take place on the available active sites on the surfacesof the beads as such between C-OH and Cl and Fe-OH andCl e degradation process of aldrin may have occurredthrough a reductive process triggered by the crystal defectsin the hematite NPs

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Additional Points

(i) We obtained beads of chitosan-ethylene glycol diglycidylether combined with iron-nanoparticles(ii) To adsorb aldrinfrom aqueous effluents (iii) Depending on the concentra-tion the percentage of aldrin removed changes (iv) eLangmuirndashFreundlich model described the aldrin isother-mal sorption on the material

Conflicts of Interest

e authors declare that they have no conflicts of interest

Acknowledgments

e authors gratefully acknowledge DGEST from Tec-nologico Nacional de Mexico (TNM) for the partial financialsupport of this work

References

[1] K Deering E Spiegel C Quaisser et al ldquoExposure assess-ment of toxic metals and organochlorine pesticides amongemployees of a natural history museumrdquo EnvironmentalResearch vol 184 2020

[2] S N Khuman P G Vinod G Bharat Y S M Kumar andP Chakraborty ldquoSpatial distribution and compositionalprofiles of organochlorine pesticides in the surface soil fromthe agricultural coastal and backwater transects along thesouth-west coast of Indiardquo Chemosphere vol 254 2020

[3] G Shukla A Kumar M Bhanti P E Joseph and A TanejaldquoOrganochlorine pesticide contamination of ground water inthe city of Hyderabadrdquo Environment International vol 32no 2 pp 244ndash247 2006

[4] M Anand and A Taneja ldquoOrganochlorine pesticidesresidue in placenta and their influence on anthropometricmeasures of infantsrdquo Environmental Research vol 182pp 1ndash6 2020

[5] E A Moawed and A M Radwan ldquoApplication of acidmodified polyurethane foam surface for detection and re-moving of organochlorine pesticides from wastewaterrdquoJournal of Chromatography B vol 1044-1045 pp 95ndash1022017

[6] X Jin Y Liu X Qiao et al ldquoRisk assessment of organo-chlorine pesticides in drinking water source of the Yangtzeriverrdquo Ecotoxicology and Environmental Safety vol 182p 109390 2019

[7] C J Martyniuk A C Mehinto and N D Denslow ldquoOr-ganochlorine pesticides agrochemicals with potent endo-crine-disrupting properties in fishrdquo Molecular and CellularEndocrinology vol 507 p 110764 2020

[8] L C Lu C I Wang and W F Sye ldquoApplications of chitosanbeads and porous crab shell powder for the removal of 17organochlorine pesticides (OCPs) in water solutionrdquo Car-bohydrate Polymers vol 83 no 4 pp 1984ndash1989 2011

[9] M J Garcıa-Galan L S Monllor-Alcaraz C Postigo et alldquoMicroalgae-based bioremediation of water contaminated bypesticides in peri-urban agricultural areasrdquo EnvironmentalPollution vol 265 p 114579 2020

[10] C M Dominguez N Oturan A Romero A Santos andM A Oturan ldquoOptimization of electro-Fenton process foreffective degradation of organochlorine pesticide lindanerdquoCatalysis Today vol 313 pp 196ndash202 2018

[11] L A Abron and J O Osburn ldquoA transport mechanism inhollow nylon fiber reverse osmosis membranes for the

Table 4 Works with chitosan andor iron particles

Adsorbent material Pollutant Maximum removal capacity ReferencesClinoptilolite Aldrin 499 (μgg) [34]Acid-treated olive stones Aldrin 1954 (mgg) [41]Chitosan beads Aldrin 2 (ngg) [8]Bacterial cells Aldrin 20 (ngg) [42]Biomimetic absorbent Aldrin 089 (μgg) [43]Cellulose acetate (CA) embedded with triolein (CA-triolein) Aldrin 4 (mgg) [44]Q-Fe Aldrin 7484 (mgg) is work


removal of ddt and aldrin from waterrdquoWater Research vol 7no 3 pp 461ndash477 1973

[12] R A Farghali M Sobhi S E Gaber H Ibrahim andE A Elshehy ldquoAdsorption of organochlorine pesticides onmodified porous Al30bentonite kinetic and thermodynamicstudiesrdquo Arabian Journal of Chemistry vol 13 no 8pp 6730ndash6740 2020

[13] A Shoiful Y Ueda R Nugroho and K Honda ldquoDegradationof organochlorine pesticides (OCPs) in water by iron (Fe)-basedmaterialsrdquo Journal ofWater Process Engineering vol 11pp 110ndash117 2016

[14] M O Munyati A Mbozi and M N Siamwiza ldquoPolyanilinenanoparticles for the selective recognition of aldrin synthesischaracterization and adsorption propertiesrdquo SyntheticMetals vol 233 pp 79ndash85 2017

[15] I Diale A Galdames M L Alonso L Bartolome J L Vilasand R M Alonso ldquoEffect of coating on the environmentalapplications of zero valent iron nanoparticles the lindanecaserdquo Science of the Total Environment vol 565 pp 795ndash8032016

[16] W-C Tsai M D G de Luna H L P Bermillo-Arriesgadoet al ldquoCompetitive fixed-bed adsorption of Pb(ii) Cu(ii) andNi(ii) from aqueous solution using chitosan-coated benton-iterdquo International Journal of Polymer Science vol 2016pp 1ndash11 2016

[17] H E Ramırez-Guerra F J Castillo-Yantildeez E A Montantildeo-Cota et al ldquoProtective effect of an edible tomato plant extractchitosan coating on the quality and shelf life of sierra fishfilletsrdquo Journal of Chemistry vol 2018 pp 1ndash6 2018

[18] C Luk J Yip C Yuen C Kan and K Lam ldquoA compre-hensive study on adsorption behaviour of direct reactive andacid dyes on crosslinked and non-crosslinked chitosan beadsrdquoJournal of Fiber Bioengineering and Informatics vol 7 no 1pp 35ndash52 2014

[19] L C Bell A M Posner and J P Quirk ldquoe point of zerocharge of hydroxyapatite and fluorapatite in aqueous solu-tionsrdquo Journal of Colloid and Interface Science vol 42 no 2pp 250ndash261 1973

[20] D H Everett ldquoManual of symbols and terminology forphysicochemical quantities and units appendix II definitionsterminology and symbols in colloid and surface chemistryrdquoIUPAC Pure and Applied Chemistry vol 31 no 4 pp 577ndash638 1972

[21] H Knidri R Khalfaouy A Laajeb A Addaou and A LahsinildquoEco-friendly extraction and characterization of chitin andchitosan from the shrimp shell waste via microwave irradi-ationrdquo Process Safety and Environmental Protection vol 104pp 395ndash405 2016

[22] S Chaudhuri ldquoCoreshell nanoparticles classes propertiessynthesis mechanisms characterization and applicationsrdquoChemical Reviews vol 112 pp 2373ndash2433 2012

[23] L Kopanja S Kralj D Zunic B Loncar andM Tadic ldquoCore-shell superparamagnetic iron oxide nanoparticle (SPION)clusters TEM micrograph analysis particle design and shapeanalysisrdquo Ceramics International vol 42 no 9pp 10976ndash10984 2016

[24] M Siddique E Ahmed andNM Butt ldquoParticle size effect onMossbauer parameters in c-Fe2O3 nanoparticlesrdquo Physica BCondensed Matter vol 405 no 18 pp 3964ndash3967 2010

[25] H El Knidri J Dahmani A Addaou A Laajeb andA Lahsini ldquoRapid and efficient extraction of chitin andchitosan for scale-up production effect of process parameterson deacetylation degree and molecular weightrdquo International

Journal of Biological Macromolecules vol 139 pp 1092ndash11022019

[26] E M Kutashova A V Pyataev N F ShkodichA S Rogachev and Y B Scheck ldquoFe-B nanomaterials bymechanochemical synthesis a Mossbauer studyrdquo Journal ofMagnetism and Magnetic Materials vol 492 p 165663 2019

[27] T C Sunarti M I Febrian E Ruriani and I Yuliasih ldquoSomeproperties of chemical cross-linking biohydrogel from starchand chitosanrdquo International Journal of Biomaterials vol 2019pp 1ndash6 2019

[28] S Subramani and N inakaran ldquoIsotherm kinetic andthermodynamic studies on the adsorption behaviour of textiledyes onto chitosanrdquo Process Safety and Environmental Pro-tection vol 106 pp 1ndash10 2017

[29] K Sathya R Saravanathamizhan and G Baskar ldquoUltrasoundassisted phytosynthesis of iron oxide nanoparticlerdquo Ultra-sonics Sonochemistry vol 39 pp 446ndash451 2017

[30] A Iovescu G Stınga M E Maxim et al ldquoChitosan-poly-glycidol complexes to coating iron oxide particles for dyeadsorptionrdquo Carbohydrate Polymers vol 246 p 116571 2020

[31] G Picasso J Vega R Uzuriaga and G Ruiz ldquoPreparacion denanopartıculas de magnetita por los metodos sol-gel y pre-cipitacion estudio de la composicion quımica y estructurardquoRevista de la Sociedad Quımica del Peru vol 78 pp 170ndash1822012

[32] B N Akhgar and P Pourghahramani ldquoImplementation ofsonochemical leaching for preparation of nano zero-valentiron (NZVI) from natural pyrite mechanochemically reactedwith Alrdquo International Journal of Mineral Processing vol 164pp 1ndash5 2017

[33] N Ayawei A N Ebelegi and D Wankasi ldquoModelling andinterpretation of adsorption isothermsrdquo Journal of Chemistryvol 2017 pp 1ndash11 2017

[34] M Sprynsky T Ligor and B Buszewski ldquoClinoptilolite instudy of lindane and aldrin sorption processes from watersolutionrdquo Journal of Hazardous Materials vol 151 pp 570ndash577 2008

[35] M N Rashed ldquoAdsorption technique for the removal oforganic pollutants from water and wastewaterrdquo in OrganicPollutants Monitoring Risk and Treatment M N RashedEd IntechOpen London UK 2013

[36] S Yamada Y Naito M Funakawa S Nakai and M HosomildquoPhotodegradation fates of cis-chlordane trans-chlordaneand heptachlor in ethanolrdquo Chemosphere vol 70 no 9pp 1669ndash1675 2008

[37] U Schenker M Scheringer and K Hungerbuhler ldquoIncludingdegradation products of persistent organic pollutants in aglobal multi-media box modelrdquo Environmental Science Pol-lution Research vol 14 p 145 2007

[38] E R Bandala S Gelover M T Leal C Arancibia-BulnesA Jimenez and C A Estrada ldquoSolar photocatalytic degradationof aldrinrdquo Catalysis Today vol 76 no 2-4 pp 189ndash199 2002

[39] G D Sayles G You M Wang and M J Kupferle ldquoDDTDDD and DDE dechlorination by zero-valent ironrdquo Envi-ronmental Science amp Technology vol 31 no 12 pp 3448ndash3454 1997

[40] E M Rodrıguez G Fernandez P M Alvarez R Hernandezand F J Beltran ldquoPhotocatalytic degradation of organics inwater in the presence of iron oxides effects of pH and lightsourcerdquo Applied Catalysis B Environmental vol 102 no 3-4pp 572ndash583 2011

[41] H El Bakouri J Usero J Morillo and A Ouassini ldquoAdsorptivefeatures of acid-treated olive stones for drin pesticides


equilibrium kinetic and thermodynamic modeling studiesrdquoBioresource Technology vol 100 pp 4147ndash4155 2009

[42] I C Mac Rae ldquoRemoval of chlorinated hydrocarbons fromwater and wastewater by bacterial cells adsorbed to magne-titerdquo Water Research vol 20 no 9 pp 1149ndash1152 1986

[43] H Liu J Qu R Dai J Ru and Z Wang ldquoA biomimeticabsorbent for removal of trace level persistent organic pol-lutants from waterrdquo Environmental Pollution vol 147 no 2pp 337ndash342 2007

[44] H Liu J Ru J Qu R Dai Z Wang and C Hu ldquoRemoval ofpersistent organic pollutants from micro-polluted drinkingwater by triolein embedded absorbentrdquo Bioresource Tech-nology vol 100 no 12 pp 2995ndash3002 2009


technological tools has given way to nanotechnology FeNPshave been studied for the removal of a broad variety ofcontaminants such as dyes nitrates heavy metals andchlorinated organic compounds [14 15] due to their sizerange larger specific surface areas and higher densities ofreactive surface sites Iron-oxide NPs are generally formedwhen FeNPs are exposed to contaminants and their removalprocess may consist on mechanisms such as degradationabsorption encapsulation and diffusion Pure FeNPshowever tend to agglomerate when their particle sizesovercome a critical size resulting in a decrease in theirspecific surface areas and active sites for the removal ofcontaminants Hence innovative and low-cost materialsincluding SBA-15 carbon resins clays and chitosan havebeen used to control FeNPsrsquo particle sizes and remediate thisdisadvantage Due to its high contents of amino and hy-droxyl functional groups chitosan has great potential for theabsorption of several compounds [16] Chitosan is adeacetylated form of chitin a well-known cationic poly-saccharide which is an abundantly available low-cost bio-polymer and the most widespread biopolymer in natureefree amino (NH2) and hydroxyl (OH-) groups in its mo-lecular structure can serve effectively as active adsorptiongroups Chitosan is nontoxic hydrophilic biocompatiblebiodegradable and antibacterial resulting in diverse ap-plications in the biomedical field cosmetics food textileindustries and the environment [17] A large number ofresearchers have confirmed the use of chitosan as a sorbentfor the removal of organic compounds from aqueous so-lutions since the physical-chemical properties of chitosancan be modified via the expansion of its polymer networkopenings Some studies performed with chitosan beads haveshown that it has high efficiency in sorption processesChitosan beads have also exhibited high adsorption ca-pacities in wastewater treatment studies [18] Additionallythe ease with which they can be separated from effluents andthe possibility of sorbent regeneration has made chitosanbeads one of the most prominent materials for sorptionapplications However chitosan beads exhibit instability insolutions with pH valueslt4 which results in the dissolutionof the material and drops in its adsorption capacity isproblem is however solved by a reaction of the chitosanwith a cross-linking agent which leads to the conservation ofthe biopolymer through the formation of bonds amongst thechitosan chains e objective of this research is to obtain anefficient chitosan-FeNPs composite material to be used as anadsorbent for the removal of aldrin e Langmuir andFreundlich equations were used to fit the equilibrium iso-therm data in order to understand and evaluate the inter-action mechanisms between the surface of the compositeand the contaminant

2 Materials and Methods

21 Synthesis of FeNPs e FeNPs were prepared via thesodium borohydride reduction method in which ferricchloride (FeCl36H2O from Merckreg) was dissolved in anethanol-water mixture (1 1V) and stirred for severalminutes In addition sodium borohydride (from Merckreg)

was dissolved in deionized water and subsequently addeddropwise to the iron-chloride solution using a burette ac-companied by vigorous hand stirring After the first drop ofsodium borohydride solution was added solid black par-ticles appeared immediately and the remaining sodiumborohydride was added to complete and accelerate the re-duction process Immediately afterward the reacting solu-tion was stirred for an additional 10minutes e vacuumfiltration technique was used to separate the black ironnanoparticles from the liquid phase Two sheets ofWhatmanfilter papers (40 mesh) were used in this process e solidparticles were washed three times with absolute ethanol toremove all the water content e synthesized NPs werefinally dried in an oven at 323K for 12 hours and were keptin a jar in an argon atmosphere to avoid further oxidation

22 Synthesis of Chitosan-FeNPs (Chi-EDGE-Fe)Chitosan medium molecular weight powder at 80 mesh(177 μm) with over a 90 degree of deacetylation and aceticacid of 998 purity fromAlimentos America and Fremontregwere used Sodium hydroxide (NaOH) with 97 purity fromChemical Reagents Meyerreg ethylene glycol diglycidyl ether(EGDE) from the Tokyo Chemical Industry and aldrin(C12H8Cl6) with 984 purity from Chem Servicereg were alsoused First 78 g of chitosan powder was placed in a 500mLbeaker and dissolved in 250mL of a 04M acetic acid so-lution Next the FeNPs were added to the mixture whichwas then subjected to ultrasonic shaking for 3minutesenwith the aid of a peristaltic bomb and a hypodermic needle(internal diameter 09mm) 100mL of NaOH solution(01M) was added dropwise to the previous solution and theresulting mixture was stirred for 2 hourse resulting beadswere washed with water until a pH 7-8 was reached In orderto carry out the material cross-linking process a 7mLchitosan bead solution plus 25mL of deionized water and01 g of EGDE were put into a two-necked flask and thedeionized was adjusted to pH 12 with the NaOH solution(01M)e resulting solution was heated at 70degC and stirredcontinuously at 125 rpm under an inert atmosphere of N2 for6 hours At the end of the reaction the beads were left to coolto 15degC and washed with deionized water until pH 7 wasreached After synthetizing the Chi-EDGE-Fe beads in thismanner they were subjected to a lyophilization process in aHeto PowerDryreg LL1500 apparatus at minus 60degC and 05mbarFinally these beads were placed inside 15mL vials andimmersed in liquid nitrogen for 2 minutese samples werethen placed in the equipment nozzles e total lyophili-zation process took around 24 hours

23 Characterization of the Materials SEM TEM and MSDRX and FTIR e morphological analysis was performedvia a scanning electron microscope JEOLreg JSM-5900LVe solid samples were sprinkled on a metallic disk andcovered with gold for 100 seconds using the AJAreg sputteringsystem ATC 1500 e chemical composition was deter-mined by means of the EDS system (Oxfordreg 7279) whichincluded the scanning electronmicroscope In order to studythe morphologies and sizes of the FeNPs supported in the










1cm

(a)

1cm

(b)


1cm

(a)

23 24 25 26 27 28 29

Freq

uenc

y

Diameter (mm)

264 mm

(b)

(c) (d)

Figure 2 Continued





(e) (f )







10 15 20 25 30 35 40 45 50

Freq

uenc

y

Diameter (nm)

28 nm

(a)

(b) (c)






59

I (n

u)

mms

α-Fe2O3Fe2B

Fe0

(a)


δ = 0205ΔEQ = 0355Г= 042

11

I (n

u)(b)


10 20 30 40 50 60 70 80

45

Card Fe2B

FeNPs

Inte

nsity

(au

)

Aacutengle 2θ

35

(a)

10 20 30 40 50 60 70 80

Chi-EGDE

Chi-EGDE-Fe

Card Chi

20

Inte

nsity

(au

)

Aacutengle 2θ

10

(b)





range






MLF

1 + KLF Ce( 1113857MLF

(1)



4000 3500 3000 2500 2000 1500 1000 500

Fe-O

C-NC-O


ansm

itanc

e (au

)


Chi-EGDE-Fe-aldrin

Chi-EGDE-Fe









b 004 L mgminus 1



n 232


MLF )



MLF 186



0 20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80



q e (m

gg)

Ce (mgL)







+



+ H+


(2)



EDGE

Chi

Chi-EDGE-Fe

Aldrin

Cl B C OFe H N


Fe-Cl

C-ClB-Cl

O-Cl

N-Cl



4 Conclusion


Data Availability


Additional Points




Acknowledgments


References





























































1cm

(a)

1cm

(b)


1cm

(a)

23 24 25 26 27 28 29

Freq

uenc

y

Diameter (mm)

264 mm

(b)

(c) (d)

Figure 2 Continued





(e) (f )







10 15 20 25 30 35 40 45 50

Freq

uenc

y

Diameter (nm)

28 nm

(a)

(b) (c)






59

I (n

u)

mms

α-Fe2O3Fe2B

Fe0

(a)


δ = 0205ΔEQ = 0355Г= 042

11

I (n

u)(b)


10 20 30 40 50 60 70 80

45

Card Fe2B

FeNPs

Inte

nsity

(au

)

Aacutengle 2θ

35

(a)

10 20 30 40 50 60 70 80

Chi-EGDE

Chi-EGDE-Fe

Card Chi

20

Inte

nsity

(au

)

Aacutengle 2θ

10

(b)





range






MLF

1 + KLF Ce( 1113857MLF

(1)



4000 3500 3000 2500 2000 1500 1000 500

Fe-O

C-NC-O


ansm

itanc

e (au

)


Chi-EGDE-Fe-aldrin

Chi-EGDE-Fe









b 004 L mgminus 1



n 232


MLF )



MLF 186



0 20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80



q e (m

gg)

Ce (mgL)







+



+ H+


(2)



EDGE

Chi

Chi-EDGE-Fe

Aldrin

Cl B C OFe H N


Fe-Cl

C-ClB-Cl

O-Cl

N-Cl



4 Conclusion


Data Availability


Additional Points




Acknowledgments


References
























































(e) (f )







10 15 20 25 30 35 40 45 50

Freq

uenc

y

Diameter (nm)

28 nm

(a)

(b) (c)






59

I (n

u)

mms

α-Fe2O3Fe2B

Fe0

(a)


δ = 0205ΔEQ = 0355Г= 042

11

I (n

u)(b)


10 20 30 40 50 60 70 80

45

Card Fe2B

FeNPs

Inte

nsity

(au

)

Aacutengle 2θ

35

(a)

10 20 30 40 50 60 70 80

Chi-EGDE

Chi-EGDE-Fe

Card Chi

20

Inte

nsity

(au

)

Aacutengle 2θ

10

(b)





range






MLF

1 + KLF Ce( 1113857MLF

(1)



4000 3500 3000 2500 2000 1500 1000 500

Fe-O

C-NC-O


ansm

itanc

e (au

)


Chi-EGDE-Fe-aldrin

Chi-EGDE-Fe









b 004 L mgminus 1



n 232


MLF )



MLF 186



0 20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80



q e (m

gg)

Ce (mgL)







+



+ H+


(2)



EDGE

Chi

Chi-EDGE-Fe

Aldrin

Cl B C OFe H N


Fe-Cl

C-ClB-Cl

O-Cl

N-Cl



4 Conclusion


Data Availability


Additional Points




Acknowledgments


References























































10 15 20 25 30 35 40 45 50

Freq

uenc

y

Diameter (nm)

28 nm

(a)

(b) (c)






59

I (n

u)

mms

α-Fe2O3Fe2B

Fe0

(a)


δ = 0205ΔEQ = 0355Г= 042

11

I (n

u)(b)


10 20 30 40 50 60 70 80

45

Card Fe2B

FeNPs

Inte

nsity

(au

)

Aacutengle 2θ

35

(a)

10 20 30 40 50 60 70 80

Chi-EGDE

Chi-EGDE-Fe

Card Chi

20

Inte

nsity

(au

)

Aacutengle 2θ

10

(b)





range






MLF

1 + KLF Ce( 1113857MLF

(1)



4000 3500 3000 2500 2000 1500 1000 500

Fe-O

C-NC-O


ansm

itanc

e (au

)


Chi-EGDE-Fe-aldrin

Chi-EGDE-Fe









b 004 L mgminus 1



n 232


MLF )



MLF 186



0 20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80



q e (m

gg)

Ce (mgL)







+



+ H+


(2)



EDGE

Chi

Chi-EDGE-Fe

Aldrin

Cl B C OFe H N


Fe-Cl

C-ClB-Cl

O-Cl

N-Cl



4 Conclusion


Data Availability


Additional Points




Acknowledgments


References
























































59

I (n

u)

mms

α-Fe2O3Fe2B

Fe0

(a)


δ = 0205ΔEQ = 0355Г= 042

11

I (n

u)(b)


10 20 30 40 50 60 70 80

45

Card Fe2B

FeNPs

Inte

nsity

(au

)

Aacutengle 2θ

35

(a)

10 20 30 40 50 60 70 80

Chi-EGDE

Chi-EGDE-Fe

Card Chi

20

Inte

nsity

(au

)

Aacutengle 2θ

10

(b)





range






MLF

1 + KLF Ce( 1113857MLF

(1)



4000 3500 3000 2500 2000 1500 1000 500

Fe-O

C-NC-O


ansm

itanc

e (au

)


Chi-EGDE-Fe-aldrin

Chi-EGDE-Fe









b 004 L mgminus 1



n 232


MLF )



MLF 186



0 20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80



q e (m

gg)

Ce (mgL)







+



+ H+


(2)



EDGE

Chi

Chi-EDGE-Fe

Aldrin

Cl B C OFe H N


Fe-Cl

C-ClB-Cl

O-Cl

N-Cl



4 Conclusion


Data Availability


Additional Points




Acknowledgments


References























































range






MLF

1 + KLF Ce( 1113857MLF

(1)



4000 3500 3000 2500 2000 1500 1000 500

Fe-O

C-NC-O


ansm

itanc

e (au

)


Chi-EGDE-Fe-aldrin

Chi-EGDE-Fe









b 004 L mgminus 1



n 232


MLF )



MLF 186



0 20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80



q e (m

gg)

Ce (mgL)







+



+ H+


(2)



EDGE

Chi

Chi-EDGE-Fe

Aldrin

Cl B C OFe H N


Fe-Cl

C-ClB-Cl

O-Cl

N-Cl



4 Conclusion


Data Availability


Additional Points




Acknowledgments


References



























































b 004 L mgminus 1



n 232


MLF )



MLF 186



0 20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80



q e (m

gg)

Ce (mgL)







+



+ H+


(2)



EDGE

Chi

Chi-EDGE-Fe

Aldrin

Cl B C OFe H N


Fe-Cl

C-ClB-Cl

O-Cl

N-Cl



4 Conclusion


Data Availability


Additional Points




Acknowledgments


References

























































+



+ H+


(2)



EDGE

Chi

Chi-EDGE-Fe

Aldrin

Cl B C OFe H N


Fe-Cl

C-ClB-Cl

O-Cl

N-Cl



4 Conclusion


Data Availability


Additional Points




Acknowledgments


References





















































4 Conclusion


Data Availability


Additional Points




Acknowledgments


References





















































nanoparticle beads of chitosan-ethylene glycol diglycidyl

Documents