Aluminum Substituted Cobalt Ferrite (CoâAlâFe) Nano Adsorbent for

Subscriber access provided by University of Newcastle, Australia

Article

Aluminum substituted cobalt ferrite (Co–Al–Fe) nano adsorbent for arsenic adsorption in aqueous systems and detailed redox behavior study with XPS Yaswanth Kumar Penke, Ganapathi Anantharaman, Janakarajan Ramkumar, and Kamal K Kar ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b16414 • Publication Date (Web): 03 Mar 2017 Downloaded from http://pubs.acs.org on March 5, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Aluminum substituted cobalt ferrite (Co–Al–Fe) nano adsorbent for arsenic adsorption in aqueous systems and detailed redox behavior study with XPS Yaswanth K. Penkea, Ganapathi Anantharamanb, Janakarajan Ramkumara,c*, Kamal K. Kara,c [a] Materials Science Programme , [b] Department of Chemistry, [c] Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur-208016, INDIA. * Tel.: +91-512-259-7546, Fax: +91-512-259-7408, *E-mail address: [email protected] KEYWORDS .Arsenic [As(III) and As(V)], Adsorption, aluminum-substituted cobalt ferrite (Co-Al-Fe ternary oxide), Raman and IR spectroscopy, XPS, ICP-OES. ABSTRACT: Arsenic [As(III) and As(V)] adsorption on aluminum substituted cobalt ferrite (Co-Al-Fe) ternary metal oxide adsorbent is reported by means of qualitative and quantitative spectroscopy tools. IR and Raman active signals were observed around 810-920 cm-1 band indicate different As-OHcomplexed and As-Ouncomplexed stretching vibrations on to the adsorbent. The adsorption behavior of arsenic (III and V) on to these adsorbents is studied as a function of contact time, different concentrations and pH conditions. The kinetics study on adsorption were performed to understand nature of adsorption which supports the Pseudo Second Order (PSO) model. The adsorption isotherm study indicates Freundlich type of adsorption. The maximum adsorption capacity of Co-Al-Fe adsorbent is observed around 130 and 76 mg g-1 for As(III) and As(V) systems respectively. Detailed XPS study of As 3d, Fe 2p, Co 2p and O 1s spectra has been reported in explaining the redox behavior and ligand exchange reactions in supporting arsenic adsorption mechanism.

1 INTRODUCTION Arsenic (As) exists as a carcinogenic element formed from natural and anthropogenic activity of different industries.1 Exposure (i.e. inhalation, ingestion) towards arsenic related systems [both organic and inorganic forms]gives several health disorder to mammals.2-4Thus the studies on removal of arsenic became one of the prime area of research for the past two decades. Among the arsenic salts, As(III) containing compounds are highly mobile and toxic as compared to As(V) systems. At present, different remediation processes like electro-coagulation/precipitation, adsorption, ion exchange (IX), reverse osmosis (RO) and bioremediation are in usage. Thus it is necessary to find a suitable method for remedia-

tion of arsenic. Adsorption is considered to be one of the efficient processes based on the factors like ease in operation and installation cost which encourages its usage.5-7 Organic and inorganic adsorbents varying from activated carbons (AC) and carbon nanotubes (CNT) to different metal oxide based adsorbents are in usage for arsenic remediation.1, 8-9 Even hybrid structural [i.e. MOF structures]based adsorbents were also verified for better arsenic removal e.g. iron impregnated CNT and graphene 3D structures.10 Among them, metal oxide adsorbents are found to be better adsorbents due to high crystallinity, large selective surface area [SSA], multiple oxidation states, huge number of adsorption sites, and high pHPZC [point zero charge] values.11In addition 1

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 17

2 they are considered to be environment benign materials which would add an advantage for long term development of sustainable materials for arsenic adsorption. Thus recently, different metal oxides, hydroxides or oxy-hydroxides of monoor hetero-metallic oxides were studied for the removal of arsenic species.12-23 Compared to the monometallic oxides of iron (Fe), aluminum (Al), nickel (Ni), the heterometallic oxides were observed for better arsenic mitigation abilities.24-28 The synergetic effects like pH withstand ability, pHPZC, dense adsorption sites, and mesoporous structures are some of the reasons in better arsenic removal ability.2931 Besides the presence of redox active containing metal could impart in the adsorption or removal of toxic arsenic species. Few metal oxide based adsorbents supports improvement in sorption of arsenic via oxidation like for example, oxidation of As(III) ions to As(V), and surface adhesion. Alternatively, the reduction reaction supported adsorption was also observed with adsorbents containing Fe(0) such as using zero valent iron (ZVI) and nano zero valent iron (nZVI) emphasizing the arsenic remediation. These redox natured adsorbents were reported with an ability in transforming soluble arsenic species [As(III) and As(V)] to insoluble zero valent arsenic element [As(0)]in aqueous solution which allows for easier separation by simple filtration techniques.32-35 Keeping this in view it is necessary to develop and study the metal oxides containing redox active metal centers for arsenic adsorption. Moreover, the presence of aluminum was found to increase the arsenic adsorption. Earlier we have shown that nickel based ternary metal oxide adsorbent (i.e. Ni-Al-Fe) was observed with better arsenic adsorption mainly for As(III) species as compared to pure nickel ferrite (i.e. NiFe2O4) adsorbent.36 In comparison to nickel based systems, the cobalt containing compounds of metal oxides are found to be a better choice due to variable oxidation states of cobalt atoms which may enhance the oxidative based surface adsorption of arsenic37. Recently, cobalt ferrite (i.e. CoFe2O4) has been used as adsorbents for different environmental remediation applications.31Also transitional metal oxide ad-

sorbents were earlier reported with an added advantage of magnetic separation [i.e. low field separation] because of their intrinsic magnetic behavior.12Moreover to the best of our knowledge cobalt based ternary metal oxide as adsorbents for arsenic adsorption remain unexplored. Here, a cobalt based ternary metal oxide adsorbent, aluminum substituted cobalt ferrite(i.e.Co0.9Al0.2Fe1.7O4 here after given as CoAl-Fe) is used to mitigate arsenic (III and V) from artificial aqueous systems under different experimental parametric conditions like pH, time (t) and concentration. Arsenic remediation study was analyzed with help of qualitative (Raman, FT-IR), semi-qualitative (XPS) and quantitative (ICP) studies. 2. EXPERIMENTAL SECTION 2.1 Materials Chemicals such as HCl and Co(NO3)2.6H2O [LobaChemiepvt Ltd, India], Al(NO3)3.9H2O [Merck,India], Fe(NO3)3.9H2O and ammonium hydroxide [Qualigens Fine Chemicals], citric acid [Samir Tech-ChemPvt Ltd, India], sodium arsenite (NaAsO2), and sodium arsenate hepta hydrate (NaH2AsO4·7H2O) systems, NaOH [Fisher Scientific, India] (S.D fine - chemicals Ltd, India)of laboratory grade were procured and used as received. All syntheses and experimental procedures were performed under standard atmospheric conditions using double distilled (D.D) water. Arsenite [As(III)] and arsenate [As(V)] standard stock solutions of different concentrations were prepared using sodium arsenite (NaAsO2) and sodium arsenate hepta hydrate (NaH2AsO4·7H2O) salts respectively. Standard acid and basic mediums were prepared freshly with 1 M HCl and 1 M NaOH solutions for pH adjustment. 2.2 Characterization tools for adsorbent powders and batch experiments aliquots XRD [P-XRD] pattern was observed in 10-90º range using X-ray diffractometer [PANalytical] using Cu-kα anode with an incident wavelength of 1.54 Å. Morphological study was


Page 3 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3 done using a field emission scanning electron microscope (FE-SEM) [JEOL FESEM - JSM7100F] and high resolution transmission electron microscopy (HR-TEM) (FEI Titan G2 60 - 300 TEM). BET-surface area analyzer (Autosorb-I; Quatachrome Corp) studies were performed in obtaining surface area parameters. Point zero charge (pHPZC) values were determined using a zeta potential meter (Nano-zeta sizer; Malvern). Raman spectra of the adsorbents were obtained using LabRam (Horiba scientific) spectrograph. A PerkinElmer model FTIR (PerkinElmer-Spectrum two) was used to collect IR of different adsorbent samples. X-ray photoelectron spectroscopy (XPS) studies were performed using XPS microprobe (PHI 5000 versa probe-ULVAC-PHI Inc). Individual step sizes and other process parameters were provided in detail in the supporting data [S 1.1]. The Raman and XPS data were base line corrected and curve fitted using Origin Pro 8.5 and XPSPEAK 41 software. The pH of the solutions was measured using microprocessor based digital pH meter. The arsenic and other metal ion concentrations in the supernatant solutions were determined using inductively coupled plasma optical emission spectroscopy (ICP-OES) instrument (iCAP 6000 series, ICP spectrometer, Thermo Scientific). 2.3 Preparation of adsorbent Aluminum substituted cobalt ferrite (i.e. Co-Al-Fe) adsorbent was synthesized by the selfignition method reported in the literature which is briefed in the supporting information Table S1.38 Batch studies were performed for different parametric conditions as detailed below. 2.4 Sample preparation for arsenic adsorption studies Qualitative studies IR, RAMAN and XPS study: Samples for these techniques have been prepared by the following procedure. Aliquots of arsenic solutions [100 mL , 57.6 ppm for As(III) and 24 ppm for As(V)] were dispersed with Co-Al-Fe adsorbent (0.1 g) and stirred for 24 h. The supernatant solutions

were vacuum filtered using membrane filters to collect adsorbent powder. The extracted adsorbent particles were dried in air and then kept overnight in the desiccator filled with silica gel prior to different spectroscopic (i.e. Qualitative) studies. Quantitative studies Kinetics study (ICP-OES): Adsorption kinetics study was carried out using the individual arsenite (250 mL, 57.6 ppm) and arsenate (250 mL, 24 ppm) solutions in pH 7.0 ± 0.1 dispersed with Co-Al-Fe adsorbent (0.25 g). The arsenic systems were agitated and samples were collected at various intervals like, 2, 5, 10, 15, 30, 60, 120, 180, 240, and 300 min. Adsorption Isotherms study (ICP-OES): The different concentrations (0.1, 0.5, 1, 5, 10, 25, 50, 100 and 150 ppm) of arsenite and arsenate solutions (50 mL aliquots) were prepared for Isotherms study. The Co-Al-Fe adsorbent (0.025 g) was dispersed in each of these prepared solution and the pH was adjusted to 7.0 ± 0.1 using standard HCl and/or NaOH solutions. The mixture was agitated for 24 h and the solution was filtered. The amount of remaining arsenic in the filtrate was determined using ICP-OES. pH study (ICP-OES): The pH variation studies were performed with arsenite (50 mL, 10 ppm) and arsenate solutions (50 mL, 10 ppm) dispersed with Co-Al-Fe adsorbent (0.025 g) at different pH conditions and agitated for 24 h. In all quantitative studies all adsorbent and solution systems were filtered and aliquot samples were proceeded to ICP-OES analysis. The adsorption capacity (Qe) of the adsorbent was calculated by using the following equation = (

−

) /

(1)

Where Co (mg L-1) is initial arsenic concentration, Ce is equilibrium concentration of arsenic, v (L) is the volume of solution, and m (g) is the mass of the adsorbent in the solution.



4 JCPDS No:22-1086 Additional signal

(533)

(440)

(511)

(422)

(400)

3000

(220)

4000

(111)

2000

(222)

3. RESULTS AND DISCUSSION 3.1 Characterization of the adsorbent Co-Al-Fe Fe adsorbent was synthesized uusing self-ignition method38 and the crystalline nnature was studied using PXRD. X-ray ray diffraction pattern of Co-Al-Fe adsorbent is shown in Figure 1a.. It is observed with intense peaks around 30º, 36º, 43º, 57º and 63º corresponding to (220), (311), (400), (511) and (440) lattice planes which are in good agreement with the cobalt ferrite standard (JCPDS file No: 22-1086) 1086) indicating the 38-39 formation of single phase. Inter planar spa spacing (d) of 2.5 Å and crystallite size of 12 12-13 nm were evaluated for the peak corresponding to (311) plane using Bragg's law and Scherer's fo formula. The additional peak shifting and broade broadening behavior observed in high inten intense peaks in the Co-Al-Fe Fe adsorbent as compared to pure ccobalt ferrite [CoFe2O4] are due to the substitution of Al3+ ions (r = 53 pm) for Fe3+ ions (r = 67 pm).40-42FESEM image shows the better aggl agglomerationn behavior as observed in Fig 11b. The particular TEM M observation conferred the nano dimension of adsorbent, Figure 2a.. TEM studies revealed the average particle size of the adsorbent is around 20 nm. The corresponding elemental compositions (Wt %) of individual elements were observed in EDX mapping as Fe (~ ~34.27 %), Co (~29.97 %), Al (~3.15 %), Oxygen ((~32.61%) respectively (refer supporting ting data Figure S1 and Table S2).. Individual fringe pattern in Figure 2b indicated the inter-planar planar spacing (d) of 0.22 nm. The selected area diffraction tion pattern (SADP)in Figure 2c confirmed the better crystalline nature of the adsorbent. The selective surface area (SSA) obtained from BET of Co-Al--Fe adsorbent is 79.64 m2 g-1, pore size of 16 nm and total pore volume of 0.32 cc g-1.Also the pHPZC value of Co-Al-Fe adsorbentss is around 6.8. 6.8.The substitution and near surface presence of Al3+in place of Fe3+ was analyzed qualitatively, using vibrational (IR and Raman) and XPS spectroscopy tools. The FT-IR IR and Raman spectra of freshly prepared Co CoAl-Fe adsorbent particles are illustrated ustrated in Figure 3. The IR active signals observed around 581 ((ν1) and 412 (ν2) cm-1 correspond to the frequency of absorption for tetrahedral and octahedral sites

(a)

(311)

5000

Normalized intensity (a.u)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 17

1000

0

10

20

30

40

50

60

70

80

90

2 θ (degrees) degrees)

Co adsorFigure 1. (a) XRD plot (b) FESEM image of Co-Al-Fe bent.

of ferrite structure (Fe-O), O), respectively. respectively A shifting behavior observed in IR signals comco pared to pure cobalt ferrite systems (ν ( 1,ν2) is attributed to the substitution of Al3+ ions for Fe3+ ions in various lattice sites leading to change in

Figure 2. (a) TEM image (b) Fringe pattern (c) SAD pattern pa of Co-Al-Fe adsorbent.


Page 5 of 17

0

Fe 2p

O 1s C1s

Al 2p

Intensity (a.u)

the bond length (M-O) and the mass differences in the crystal lattice structure.43 Raman spectroscopy signals for Fe-O (around 470 and 680 cm-1) and Co-O (around 550 and 630 cm-1) were due to the phonon modes of M-O bonds which are similar to that of the pure cobalt ferrite inverse spinel compound.44-45A similar shifting behavior is also observed in Raman peaks around 470 and 680 cm-1 corresponding to Fe-O lattice peaks compared to pure cobalt ferrite. This behavior is due to the formation of new phase where Fe3+ ions were substituted by Al3+ ions. An extra Raman signal of medium strong intensity observed around 730 cm-1 corresponds to the Al-O symmetric stretching vibrations.46 To further verify the near surface presence of Al3+ions in the present adsorbent XPS study was performed. The wide scan XPS spectrum of CoAl-Fe adsorbent is shown in Figure 4. The binding energy (B.E) signals observed around 280, 532, 709.8 and 780 eV are accounted for C 1s, O 1s, Fe 2p3/2 and Co 2p3/2elements, respectively.47 In addition to that extra peak found around 73.4 eV corresponds to the Al 2p signal. Thus, XPS also authenticates the presence of Al3+ in the present Co-Al-Fe adsorbent.

Co 2p

5

200

400

600

800

1000

1200

Binding energy (eV)

Figure 4. XPS wide scan spectrum of Co-Al-Fe adsorbent.

The composition of present adsorbent was determined as Co0.9Al0.2Fe1.7O4 by trace metal acid digestion technique using ICP-OES tool. 3.2 Arsenic adsorption over Co-Al-Fe adsorbent in pH 7 systems The adsorption behavior of Co-Al-Fe adsorbent is evaluated using microscopy and different spectroscopy tools. Previous studies were performed using different spectroscopy tools to understand surface coordination chemistry and related arsenic stretching vibrations (e.g. As-O/As-OH).48-56

Intensity (a.u)

412 581

(a)

0

500

1000

1500

2000

2500

3000

3500

4000

Wavenumbers (cm-1)

(b) T2g

Fe(III)-O T2g

Eg

Normalized intensity (a.u)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


200

Co(II)-O

A1g

Al-O

700

800

T2g

300

400

500

600

Raman shift (cm-1)

900

Figure 3. (a) IR and (b) Raman spectra of Co-Al-Fe adsorbent.

3.2.1 Analysis by FESEM: The FESEM images of arsenic (III and V) [Co= 100 ppm, t = 24 h] adsorbed Co-Al-Fe samples in pH 7 condition are shown in Figure 6. Upon arsenic adsorption, agglomeration and flocculation over the adsorbent particles are observed as shown in Figure 5a and 5b. This flocculent behavior may be due to the formation of surface hydroxyl groups after reacting with arsenic species [i.e. As-OH] to form immobilized structures.57 Further discussions on oxygen functional groups (i.e. M-O and M-OH) near the adsorbent surface is detailed in the XPS section. The weight percentage of arsenic on to the adsorbent is around 0.6 % and 1.1 % for As(III) and As(V) systems in the EDS spectra. The individual EDS spectra of pure and arsenic adsorbed samples were provided in the Supporting Information Figure S2.



6 As(V) As(III)

28 24 20

qt (mg g-1)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 17

16 12 8 4 0 0

50

100

150

200

250

300

t (min) Figure 6.. Adsorption kinetics of As(III) and As(V) on Co-AlCo Fe adsorbent {As(III) [Co = 57.6 ppm], As(V) [Co = 24 ppm], -1 pH ~ 7 ± 0.1, Adsorbent loading = 1 g L }.

k1 (g/mg. min), k2(g /mg.min): Related adsorpadsor tion rate constants.

Figure 5.. FESEM of (a) As(III) and (b) As(V) adsorbed Co Co-AlFe adsorbent in pH 7.0 condition [Co:: 100 ppm, adsorbent -1 loading: 1 g L , duration: 24 h].

3.2.3 Quantitative study of arsenic adsorption Adsorption kinetics: The rate of arsenic adsorption onto the Co Co-AlFe adsorbent is investigated by adsorption kine kinetics at pH 7 condition as shown in Figure 66. The pseudo-first first order (PFO), pseudo second order (PSO) models were used to describe the adsor adsorption kinetics. The mathematical representations of these kinetics models are given in the following equations, respectively.36 log(

−

) = log

−

∗

.

(2)

It is observed that the kinetics process is almost saturated with in few mins. after initiating the adsorption reaction which is due to the availabiliavailabil ty of large number of adsorption sites on this nan no dimensional adsorbent. In considering considerin PFO and PSO the present data is better fitted with PSO model indicating rate limiting step, which implies that the adsorption process is due to the chemichem sorption and physisorption phenomenon involvinvol ing valence forces by electrons sharing between adsorbent and adsorbate. The charge transfer phenomenon is dealt in XPS S section later in this paper. The corresponding rate parameters ded duced from the PSO model are listed in Table 1. The corresponding PSO (t/qt versus t) plots and related data were provided in the supporting data Figure S3 and Table S3. Table 1. Adsorption rate parameters for adsorption kinetics obtained from PSO model. As

=

-1

(g mg .min 1 )

(mg g )

As(III)

0.011

25.5

0.996

26.01

As(V)

0.038

10.36

0.997

10.62


-1

, &'

-

! (3)

qe: Adsorption capacities (mg g-1) on to the aadsorbent at equilibrium qt: Adsorption capacities (mg g-1) on to the aadsorbent at corresponding time 't' (min)

2

R

$

(mg/g)

Page 7 of 17

7 Ce (mg L-1): arsenic equilibrium concentration remained at the end of the experiment, KL and KF: The adsorbent adsorption site's affinity coefficient, n:heterogeneity factor related to the adsorption intensity of the adsorbent.

Adsorption isotherms: The adsorption capacities of As(III) and As(V) systems onto Co-Al-Fe ternary oxide adsorbent in pH 7 condition were evaluated using adsorption isotherms as given in Figure 7.The As(III) systems were observed with increment in the adsorbent loading (qe) with an increment in equilibrium concentrations of arsenic (Ce). The adsorbent exhibits better adsorption behavior for As(III) systems whereas in the case of As(V) systems the arsenic loading ability is saturated at higher equilibrium concentrations. Maximum adsorbent loading capacities of 130 and 76 mg g1 were observed for As(III) and As(V) systems. Both Langmuir and Freundlich isotherm models were used to study the adsorption isotherms, which were given in the following equations, respectively.36

=

()&

1!

. */

/0

The higher regression coefficients (R2 ~ 0.9) for both the systems suggest that Freundlich model is most suitable for both As(III) and As(V) adsorption studies. The adsorption parameters obtained from the Freundlich adsorption isotherms are given in Table 2. Freundlich isotherm suggests the multilayer adsorption or sorption onto a heterogeneous surface i.e. surface with multiple sorption sites of different active energies due to high SSA (refer BET results). This Freundlich model is valid for adsorption data over a confined range of arsenic equilibrium concentrations (Ce).31 The corresponding isotherm plots and related data were provided in the supporting data Figure S4 and Table S4. The low equilibrium concentrations of arsenic (Ce) of 7.9 ppb were observed for 100 ppb initial concentration of As(V) systems suggesting the probable usage of Co-Al-Fe adsorbent for drinking water applications which is as per WHO guidelines of permissible limit of less than 10 ppb.

*+ (4) *+ (5)

qe(mg g-1): amount of arsenic adsorbed onto the adsorbent at equilibrium condition, qe(mg g-1): amount of arsenic adsorbed onto the adsorbent at equilibrium condition, qmax (mg g-1): maximum adsorption capacity evaluated from Langmuir's equation,

Table 2. Adsorption isotherm related parameters obtained from Freundlich isotherm model.

As(V) As(III)

140

Arsenic

120 100

qe (mg g-1)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


KF (mg1-n Lng-1)

Freundlich

Experimental

n

2

R

Qexp (mg g )

-1

As(III)

2.43

1.1

0.92

130

As(V)

4.62

1.58

0.95

76

80 60 40 20 0 -20 0

20

40

60

80

100

Ce (ppm) Figure 7. Adsorption isotherms of As(III) and As(V) on Co-1 Al-Fe adsorbent (pH ~ 7 ± 0.1, t = 24 h, Adsorbent = 0.5 g L ).

120

3.2.4 Analysis by XPS studies: FT-IR and Raman spectra of arsenic adsorbed Co-Al-Fe adsorbent were recorded in solid (S 5).The variation in intensity of IR signals is not significant as compared to the pure adsorbed. A similar observation was noted in the Raman spectra wherein the arsenic adsorbed samples are almost same as that of pure adsorbent as shown in supporting information Figure S5 . XPS studies were performed on adsorbent samples



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 17

8 Table 3. As 3d XPS signals on to the adsorbent at pH 7 condition

(i) As(III) – pH 7 As(III) As(V)

System Binding Energy

As(0)

Area (%)

FWHM (eV)

Oxidation state

(eV)

46.0

45.0

44.0 43.0 42.0 41.0 Binding Energy (eV)

46.0

45.0

44.0 43.0 42.0 41.0 Binding Energy (eV)

0.258

As(0)

[As ]

pH 7

42.25

32.70

1.093

As(III)

43.04

36.76

1.023

As(III)

[H2AsO3] [H3AsO3]

43.81

22.43

1.120

As(V)

[HAsO4]

44.62

6.58

0.715

As(V)

[H2AsO4]

40.62

1.70

0.285

As(0)

[As ]

pH 7

40.0

Figure 8. As3d XPS spectra of arsenic adsorbed Co-Al-Fe adsorbent (i) As(III) (ii) As(V) in pH 7 condition.

prepared in pH 7 condition revealed the oxidation states of different elements. The As 3d XPS spectra of As (III/V) adsorbed Co-Fe-Al samples are observed with multiple As(III)) or broad shoulder like peak As(V) between 40 - 47 eV as shown in Figure 8. These peaks correspond to the oxidation of As(III) to As(V) in the As(III) adsorbed samples whereas the reduction of As(V) to As(III) was observed in the case of As(V) adsorbed samples. Besides that, in both cases a signal was observed at lower values of B.E around 40 eV, which could be assigned for the formation of traces of zero valent arsenic [i.e. As(0)] on the sample [1.5 % in As(III) systems and 1.7 % in As(V) systems)] were observed. No particular gray area in the spectra for As(III) and As(V)was observed as detailed in Table 3. Through this study it could be inferred that occurrence of redox reactions be attributable to the presence of redox active metal centers in the adsorbent.58-59 To ascertain further the redox behavior of metal ions and surface functional groups individual XPS spectra of Fe(2p), Co(2p)and O(1s) elements for pure and As (III) and As( V) adsorbed Co-Al-Fe samples were measured as

0

1.52

As(V)

As(0)

species

40.42

(ii) As(V)-pH 7 As(III)

arsenic

As(III)

40.0

As(V)

Probable

-

-2 -

o

41.94

18.53

2.033

As(III)

43.80

30.50

1.553

As(V)

[HAsO4]

[H3AsO3]

44.58

49.25

1.829

As(V)

[H2AsO4]

-2 -

shown in Figure 9. The main and satellite peaks correspond to Fe 2p3/2, Co 2p3/2 are shown in the same figure.47 The Co-Al-Fe adsorbent is observed with individual Fe(II) and Fe(III) peak signals of 34.15% and 61.56% intensity in Fe 2p3/2 individual spectrum. The intensity of peaks corresponding to Fe(II) is changed from 34.15% to 34.29% for As(III), 26.30% for As(V) loaded samples. The intensity of peaks correspond to Fe(III) is changed to 58.53 % and 67.96 % for As(III) and As(V) systems respectively. The increment in the peak intensity corresponding to Fe(III) signals in As(V) systems implies the electrons were transferred to arsenic systems for better reduction reactions, whereas Fe(III) peak intensity was reduced in As(III) indicates electron accepting behavior of iron centers which in turn supports the As(III) to As(V) oxidation reaction. The peak intensity corresponds to Co(II) is observed around 63.52 % for pure sample where as this is changed to 57.95 and 59.1 % for As(III) and As(V) loaded samples, respectively. Similarly, peak intensity corresponds to Co(III) is observed around 5.2 % for pure sample been changed to 7.15 and 5.56 % for As(III) and As(V) adsorbed systems. The increment in Co(III) signal intensity for both As(III) and As(V) systems indicates cobalt


Page 9 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


9

(i) Pure-Fe 2p Fe(III)

Satellite

Fe(II)

705.0

(i) Pure-Co 2p

Fe(II): 26.3 % Fe(III): 67.96 %

715.0 710.0 Binding Energy (eV)

720.0

705.0

Co(II)

Co(III)

Co(II): 63.52 % Co(III): 5.2 %

Satellite

Co(III)

Co(II)

775.0


790.0

775.0

M-O

532.0 531.0 530.0 529.0 528.0 Binding Energy (eV)

705.0

Co (II)

790.0

775.0


M-O

M-O

M-OH M-OH2

Co(III)

Satellite

(iii) As(V)- O1s

(ii) As(III)- O 1s

(i) Pure-O 1s


Co(II): 59.1 % Co(III): 5.85 %

Co(II): 57.97 % Co(III): 7.74 % 785.0 780.0 Binding Energy (eV)

720.0

(iii) As(V)-Co 2p

(ii)As(III)-Co 2p

Satellite

790.0

Fe(II)

Fe(II): 34.29% Fe(III): 58.53 %


Fe(III)

Satellite

Fe(III) Fe(II)

Satellite

Fe(II): 34.15 % Fe(III): 61.56 % 720.0

(iii) As(V)-Fe 2p

(ii) As(III)-Fe 2p

M-OH M-OH2


M-OH M-OH2


Figure 9. Fe 2p, Co 2p and O 1s XPS spectra of (i) Pure (ii) As(III) and (iii) As(V)adsorbed Co-Al-Fe adsorbent in pH 7 condition.



10 systems supported the arsenic reduction reactions. But, Co(II) signal was decreased for both As(III) and As(V) systems which clearly leads to oxidation reaction. The variations observed in Fe(II, III) and Co (II, III) intensities indicating the reduction and oxidation nature [i.e. better charge transfer] of the present adsorbent which in turn oxidizes and reduces the As(III) and As(V) species (i.e. redox reactions).The detailed XPS information of Fe2p and Co2p spectra is provided in the supporting data Table S5. The O 1s spectra is mainly divided into three zones corresponding to the lattice oxygen within the metal oxides (M-O), hydroxyl oxygen within the metal hydroxides (M-OH) and the O 1s adsorbed water group [M-OH2]. The intensities of M-O, M-OH, M-OH2 peaks for pure adsorbent were observed around 58.99, 36.09 and 4.89 % respectively as provided in the supporting data Table S6. The corresponding percentages of M-O peaks were decreased to 51.57 and 48.49 % for As(III) and As(V) loading systems, respectively. The decrease in surface based M-O functional groups supports the surface based redox behavior [i.e. Fe(II)-Fe(III) transformation in oxygen deficiency conditions60] reactions as earlier observed in Fe 2p spectra. Whereas, the M-OH intensities were increased to 44.52 and 46.89 % for As(III) and As(V) systems, respectively. The increment in the M-OH functional group validates the participation of hydroxyl (-OH) ligands and the formation of a monodentate surface complex structures during arsenic [As(V)] adsorption.61-63

3.3.1 Vibrational spectroscopy analysis: The FT-IR and Raman spectra of As(III) and As(V) adsorbed Co-Al-Fe samples were performed. The results of these spectra are similar to that of adsorbent and did not provide any significant information as provided in supporting information Figure S6, S7, S8, Table S7, except pH 9 [As(III)] and pH 2 [As(V)] systems. The As(III) systems in pH 9 condition are giving peaks around 840 and 920 cm-1 corresponding to symmetric and asymmetric stretching modes of As-O structures. Active peak observed around 920 cm-1 at pH 9 system indicates strong complexation behavior of As(III) species onto the adsorbent. Raman active signals of As(V) systems in pH 2 condition were observed around 750 and 843 cm1 assigned to νs(As-OH) and νs(As-O)uncomplexed. 3.3.2 Quantitative parameter effect: The effect of pH on arsenic adsorption in terms of Qt(mg g1 ) is shown in Figure 10. In case of As(V) systems the positive charge on adsorbent (pHPZC ~ 6.8) and pKa value of H3AsO4 (pKa1 ~ 2.1 ) caused better arsenic adsorption in pH 5 conditions (Qt~14.66 mg g-1). The repulsive forces between the arsenic anions and negatively charged adsorbent particles (pHPZC ~ 7.0) leading to unfavorable conditions for adsorption in basic systems. The better adsorption behavior of As(III) systems is observed in highly acidic and basic systems. 16

As(V) As(III)

14

12

3.3 Effect of pH on arsenic adsorption The influence of time and concentration on the arsenic adsorption in pH 7 condition were evaluated quantitatively. In order to verify the influence of pH parameter on the arsenic remediation process, few studies were performed under different pH conditions. Adsorbent powders collected from highly acidic to highly basic (pH: 2.0, 5.0, 7.0, 9.0, 12.0) systems are analyzed using IR, Raman and XPS tools whereas the filtrate samples were proceeded for ICP-OES analysis.

Qt (mg g-1)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 17

10

8

6

4 2

4

6

8

10

12

Initial pH Figure 10. Effect of pH on As(III) and As(V) adsorption by Co-Al-Fe adsorbent.


Page 11 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


11 The better adsorption of As(III) species in acidic systems (Qt~ 12.5 mg g-1) is attributed to the oxidation nature of arsenic species from +3 [As(III)] state to +5 [As(V)] state (i.e. nearly 70 %) as detailed in the XPS study (refer section 3.3.3). The high adsorption behavior of As(III) species in highly basic pH 12 systems (Qt~ 13.14 mg g-1) is attributed to the pKa1 [~9.2] and pKa2 [~ 12.1] value of H3AsO3. The data related to pH variation systems and pKa values corresponding to H3AsO3 and H3AsO4 were provided in the supporting data Table S8. The arsenic speciation behavior in various pH conditions is provided in the supporting information Figure S8.The affect of pH on adsorption behavior of the adsorbents is clearly evident from the different complexation results observed earlier.

11 %] also effecting the better adsorption of As(V) species [Qt ~ 14 mg g-1] over the pH 2 systems [Qt ~ 10 mg g-1].The absence of As(0) along with the repulsion between adsorbent and arsenic oxy-anions resulted in the very low As(V) adsorption ability in pH 12 conditions [Qt ~ 4 mg g1 ]. The high amount of noise observed in the highly basic [pH 12] As(V) system is because of low loading concentration of arsenic on top of the adsorbent. A difference in redox potential (Eo) values of adsorbent elements (i.e. Co, Al, Fe) and different arsenic (As) species resulted in the better electron transfer [i.e. redox] behavior which eventually resulted in the better arsenic remediation.37 Redox potentials (Eo) of various arsenic species in different systems are given in the supporting information Figure S9.

3.3.3 Adsorption mechanism using XPS tool The redox behavior of the present Co-Al-Fe adsorbent over the arsenic adsorption was earlier reported for pH 7 systems. The effect of pH on different arsenic oxidation states is reported over here for different pH systems (pH: 2, 5, 12).

The present Co-Al-Fe adsorbent arsenic adsorption behavior may be attributed to better crystalline nature, surface related properties mainly the redox behavior which resulted in the formation of As(0) species. Earlier studies reported ZVI adsorbent based redox assisted arsenic remediation in forming As(0) species to reduce toxicity and increased stability mainly in anoxic [i.e. N2 purging] conditions.64-65But in the present study the better adsorption ability was observed along with As(0) formation in normal atmospheric conditions using the Co-Al-Fe nano adsorbent. The adsorption capacities of different metal oxide adsorbents are provided in Table 5.From a recent study, cobalt ferrite (i.e. CoFe2O4) bimetal oxide adsorbent is observed with arsenic loading capacities of 100 and 74 mg g-1 for As(III) and As(V) systems in acidic (pH 3) and neutral (pH 7) conditions, respectively. Oxidation of As(III) into As(V) is observed with an influence of surface hydroxyl groups on arsenic remediation by adsorption.31 But reduction related reactions in forming zero valet arsenic [i.e. As(0)]on to the adsorbent were not observed over here. But, the present Co-Al-Fe ternary metal oxide adsorbent is showing maximum adsorption capacities of 130 and 76 mg g-1 for As(III) and As(V) systems [Co = 0.1 - 150 ppm]in near neutral(~ pH 7 )condition making it more suitable for drinking water

XPS spectra of individual As 3d in various pH condition are shown in Figure 11. As(III) systems are oxidized to As(V) state and simultaneously reduced to As(0) in highly acidic and highly basic [i.e. pH 2 and pH 12] systems. Whereas no significant reduction behavior was observed for As(III) systems in pH 5 condition. This can be seen in the ICP-OES studies where As(III) species were better adsorbed in pH2 and pH 12 systems [Qt ~ 12 - 13 mg g-1] compared to pH 5 systems. The occurrence of As(0) is causing better arsenic loading in case of As(III) systems. As(V) species are reduced to As(0) in low pH conditions [i.e. pH 2 and pH 5] due to better electrochemical reduction at low pH whereas no As(0) species were observed in pH 12 systems.64-65The corresponding B.E values and their corresponding oxidation states are given in Table 4. Apart from the pHPZC and pKa values even the high intensity of As(0) species in pH 5 systems [~



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 17

12

(ii) As(III)-pH 5

(i) As(III)-pH 2 As(III/V)

(iii) As(III)-pH 12 As(III/V)

As(III/V)

As(III)

As(III)

As(III)

As(V)

As(V) As(0)

As(V)

As(0)

47.0 46.0 45.0 44.0 43.0 42.0 41.0 40.0 47.0 46.0 45.0 44.0 43.0 42.0 41.0 40.0 47.0 46.0 45.0 44.0 43.0 42.0 41.0 40.0 Binding Energy (eV) Binding Energy (eV) Binding Energy (eV)

(vi) As(V) – pH 12

(v) As(V)-pH 5

(iv) As(V)-pH 2

As(III/V)

As(V) As(V)

As(V)

As(III/V)

As(III)

As(III)

As(0)

As(0)

47.0 46.0 45.0 44.0 43.0 42.0 41.0 40.0 47.0 46.0 45.0 44.0 43.0 42.0 41.0 40.0 48.0 47.0 46.0 45.0 44.0 43.0 42.0 41.0 40.0

Binding Energy (eV)

Binding Energy (eV)

Binding Energy (eV)

Figure 11. As 3d XPS spectra. (i) As(III)-pH 2 (ii) As(III)-pH 5 (iii) As(III)-pH 12 (iv) As(V)-pH 2 (v) As(V)-pH 5 (vi) As(V)-pH 12.

applications without any pre or post treatment processes. Interestingly the occurrence of simultaneous reduction and oxidation reactions (i.e. redox) helped in the formation of zero valent arsenic species [i.e. As(0)] as observed from XPS studies. Thus, the aluminum substitution effecting different surface reactions (i.e. ligand exchange)] and transitional metals centers (Co, Fe) in initiating electro chemical (i.e. redox) based reactions have resulted in the better arsenic adsorption of the present Co-Al-Fe ternary metal oxide adsorbent.

4 CONCLUSION The present aluminum substituted cobalt ferrite adsorbent (Co-Al-Fe) is evaluated for arsenic remediation from aqueous systems by qualitative and quantitative methods. Based on these results we conclude that inner sphere complex mechanism is indeed occurring for arsenic adsorption. The variation in intensities of XPS [O1s] spectra in different systems indicate the ligand (-OH) exchange mechanism supported adsorption phenomenon. Freundlich adsorption isotherms study revealed multilayer adsorption behavior on top of the adsorbent for both As(III) and As(V) species. Kinetics based study revealed the adsorption of


Page 13 of 17


1 2 Table 4. As 3d XPS spectra in different pH conditions 3 4 As Binding Area FWHM State Probable 5 Energy (%) (eV) arsenic 6 7 (eV) species 8 0 40.45 1.63 0.55 As(0) [As ] 9 As(III) pH 2 42.02 8.93 0.94 As(III) [H3AsO3] 10 42.79 25.41 0.93 As(III) [H3AsO3] 11 12 43.60 29.03 1.10 As(III/V) [H3AsO3]/[HAsO4]-2 13 43.84 5.38 1.54 As(V) [HAsO4]-2 14 44.43 15.52 1.29 As(V) [H2AsO4]15 46.00 14.1 2.18 As(V) [H2AsO4]16 17 0 18 As(V) 40.19 1.8 0.85 As(0) [As ] 19 pH 2 0 41.12 1.68 0.43 As(0) [As ] 20 43.45 27.86 2.24 As(III/V) [H3AsO3]/ [HAsO4]-2 21 [HAsO4]-2 43.74 9.63 1.27 As(V) 22 23 1.78 As(V) [HAsO4]-2 44.04 34.88 24 44.57 23.12 1.10 As(V) [H2AsO4]25 45.13 1.0 0.31 As(V) [H2AsO4]26 27 As(III) [H3AsO3] 1.03 42.05 23.93 28As(III) 29 pH 5 [H3AsO3] As(III) 42.68 24.97 0.97 30 1.02 As(III/V) [H3AsO3]/ [HAsO4]-2 43.26 19.58 31 [HAsO4]-2 1.43 As(V) 44.18 26.56 32 As(V) [H2AsO4]1.39 46.67 4.94 33 34 0 35 As(V) [As ] As(0) 1.25 40.87 10.82 36 pH 5 28.5 1.53 As(III) 42.93 [H3AsO3] 37 26.7 As(V) 1.06 43.94 [HAsO4]-2 38 9.64 As(V) 0.72 44.67 [H2AsO4]39 24.25 As(V) 2.11 44.76 [H2AsO4]40 41 42 0 As(III) 40.21 1.75 0.31 As(0) [As ] 43 pH 12 [HAsO3]-2 42.02 34.57 1.34 As(III) 44 [H2AsO3]42.85 27.43 0.88 As(III) 45 46 43.59 11.02 0.66 As(III/V) [H2AsO3]-/[AsO4]347 44.24 22.27 1.22 As(V) [HAsO4]-2 48 45.80 2.93 0.38 As(V) [H2AsO4]49 50 41.70 24.29 1.46 As(III) [H3AsO3] 51 As(V) 52 pH 12 42.71 24.0 1.28 As(III) [H3AsO3] 53 43.59 29.14 1.52 As(III/V) [H2AsO3]-/[AsO4]354 44.95 22.0 1.95 As(V) [HAsO4]-2/ [AsO4]355 56 57 58 59 60

13 Table 5. As(III) and As(V) adsorption capacities of various metal oxide adsorbents. Adsorbent

SSA

Co

(m g )

As(III) -1 (mg g )

[ppm]

23.32

16(pH 7)

0-190

52.47

40(pH 7)

179

As(V)

Co [ppm]

Ref

N/A

N/A

[66]

0-175

N/A

N/A

[66]

46(pH 7)

0-70

17 (pH 7)

0-50

[14]

CoFe2O4

101 100(pH 3)

0.5-50

74(pH 7)

0.5-50

[31]

Ni-Al-Fe

111 114(pH 7)

0.1-150 103(pH 7)

0.1-150

[36]

Co-Al-Fe

79.64 130(pH 7)

0.1-150

0.1-150

This study

2

α-Fe2O3 Al-doped α-Fe2O3 Fe3O4

-1

-1

(mg g )

76(pH 7)

arsenic through chemisorption phenomenon obeying PSO model.As(III) species were better adsorbed at pH 2 and pH 12 conditions whereas As(V) species were better adsorbed at pH 5 and pH 2 conditions. The detailed XPS studies of individual As 3d, Fe 2p and Co 2p spectra revealed the arsenic adsorption mechanism that electron transfer phenomenon. The simultaneous reduction and oxidation (i.e. redox) of As(III) and As(V) species resulted in formation of less toxic [i.e. As(V)] and more stable [i.e. As(0)]arsenic species onto the adsorbent. At low concentration of As(V) systems at pH7 condition indicates better arsenic adsorption (Ce < 10 ppb). Thus making the arsenic adsorption more efficient. Supporting Information: This material is available free of charge via the Internet at http://pubs.acs.org Supporting Information consisting information about adsorbent synthesis, IR and Raman spectra, XPS detailed peak analysis, adsorption kinetics, adsorption isotherm and pH based study related data were provided in the supporting data.

AUTHOR INFORMATION Corresponding Author: JanakarajanRamkumar*

E-mail address: [email protected] Tel.: +91-512-259-7546, Fax: +91-512-259-7408.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 17

14 Author Contributions: The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

13.

14.

Acknowledgements The authors would like to thank DST (Government of India) for their support to carry on this present research. The authors would also like to thank Prof. Goutam Deo [CHE, IIT Kanpur] for allowing to utilize Raman spectroscopy facility in his laboratory. Yaswanth. K. Penke would like to thank Mr. M. Siva Kumar (ACMS, IIT Kanpur) for his help in various characterization techniques. Yaswanth. K. Penke would also like to thank IIT Kanpur, MHRD(Government of India) for providing him the scholarship and other necessary support.

2.

3.

4.

5. 6.

7.

8.

9.

10.

11.

12.

16.

17.

REFERENCES 1.

15.

Mohan, D.; Pittman, C. U. Arsenic Removal from Water/wastewater Using Adsorbents-A Critical Review. J. Hazard. Mater.2007, 142 (1–2), 1–53. Singh, R.; Singh, S.; Parihar, P.; Singh, V. P.; Prasad, S. M. Arsenic Contamination, Consequences and Remediation Techniques: A Review. Ecotoxicol. Environ. Saf.2015, 112, 247–270. Jadhav, S. V; Bringas, E.; Yadav, G. D.; Rathod, V. K.; Ortiz, I.; Marathe, K. V. Arsenic and Fluoride Contaminated Groundwaters: A Review of Current Technologies for Contaminants Removal. J. Environ. Manage.2015, 162, 306–325. Gorchev, H. G.; Ozolins, G. WHO Guidelines for Drinking-Water Quality. WHO Chron.2011, 38 (3), 104– 108. Kartinen, E. O.; Martin, C. J. An Overview of Arsenic Removal Processes. Desalination1995, 103 (1–2), 79–88. Hashim, M. A.; Mukhopadhyay, S.; Sahu, J. N.; Sengupta, B. Remediation Technologies for Heavy Metal Contaminated Groundwater. J. Environ. Manage.2011, 92 (10), 2355–2388. Fu, F.; Wang, Q. Removal of Heavy Metal Ions from Wastewaters: A Review. J. Environ. Manage.2011, 92 (3), 407–418. Wang, J.; Xu, W.; Chen, L.; Huang, X.; Liu, J. Preparation and Evaluation of Magnetic Nanoparticles Impregnated Chitosan Beads for Arsenic Removal from Water. Chem. Eng. J.2014, 251, 25–34. Lata, S.; Samadder, S. R. Removal of Arsenic from Water Using Nano Adsorbents and Challenges: A Review. J. Environ. Manage.2016, 166, 387–406. Vadahanambi, S.; Lee, S.-H.; Kim, W.-J.; Oh, I.-K. Arsenic Removal from Contaminated Water Using ThreeDimensional Graphene-Carbon Nanotube-Iron Oxide Nanostructures. Environ. Sci. Technol.2013, 47, 10510– 10517. Giles, D. E.; Mohapatra, M.; Issa, T. B.; Anand, S.; Singh, P. Iron and Aluminium Based Adsorption Strategies for Removing Arsenic from Water. J. Environ. Manage.2011, 92 (12), 3011–3022. Yavuz, C. T.; Mayo, J. T.; Yu, W. W.; Prakash, A.; Falkner, J. C.; Yean, S.; Cong, L.; Shipley, H. J.; Kan, A.; Tomson, M.; Natelson, D.; Colvin, V. L. Low-

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

FieldMagnetic Separation of Monodisperse Fe3O4 Nanaocrystals. 2006, 314r, 964–968. Pierce, M. L.; Moore, C. B. Adsorption of Arsenite and Arsenate on Amorphous Iron Hydroxide. Water Res.1982, 16, 1247–1253. Feng, L.; Cao, M.; Ma, X.; Zhu, Y.; Hu, C. Superparamagnetic High-Surface-Area Fe3O4 Nanoparticles as Adsorbents for Arsenic Removal. J. Hazard. Mater.2012,217-218,439-446. Lin, S.; Lu, D.; Liu, Z. Removal of Arsenic Contaminants with Magnetic gamma (γ)-Fe2O3 Nanoparticles. Chem. Eng. J.2012, 211–212, 46–52. Han, C.; Pu, H.; Li, H.; Deng, L.; Huang, S.; He, S.; Luo, Y. The Optimization of As(V) Removal over Mesoporous Alumina by Using Response Surface Methodology and Adsorption Mechanism. J. Hazard. Mater.2013, 254–255 (1), 301–309. Anderson, M.; Ferguson, J. F.; Gavis, J. Arsenate Adsorption on Amorphous Aluminum Hydroxide. J. Colloid Interface Sci.1976, 54 (3), 391–399. Martinson, C. A.; Reddy, K. J. Adsorption of arsenic(III) and arsenic(V) by Cupric Oxide Nanoparticles. J. Colloid Interface Sci.2009, 336 (2), 406–411. Zhu, M.; Paul, K. W.; Kubicki, J. D.; Sparks, D. L. Quantum Chemical Study of Arsenic (III, V) Adsorption on Mn-Oxides: Implications for arsenic(III) Oxidation. Environ. Sci. Technol.2009, 43 (17), 6655–6661. Purwajanti, S.; Zhou, L.; Ahmad Nor, Y.; Zhang, J.; Zhang, H.; Huang, X.; Yu, C. Synthesis of Magnesium Oxide Hierarchical Microspheres: A Dual-Functional Material for Water Remediation. ACS Appl. Mater. Interfaces2015, 7 (38), 21278–21286. Setyono, D.; Valiyaveettil, S. Chemically Modified Sawdust as Renewable Adsorbent for Arsenic Removal from Water. ACS Sustain. Chem. Eng.2014, 2 (12), 2722–2729. Sharma, R.; Singh, N.; Gupta, A.; Tiwari, S.; Tiwari, S. K.; Dhakate, S. R. ElectrospunChitosan–polyvinyl Alcohol Composite Nanofibers Loaded with Cerium for Efficient Removal of Arsenic from Contaminated Water. J. Mater. Chem. A2014, 2 (39), 16669–16677. Pirilä, M.; Martikainen, M.; Ainassaari, K.; Kuokkanen, T.; Keiski, R. L. Removal of Aqueous As(III) and As(V) by Hydrous Titanium Dioxide. J. Colloid Interface Sci.2011, 353 (1), 257–262. Kong, S.; Wang, Y.; Hu, Q.; Olusegun, A. K. Magnetic Nanoscale Fe–Mn Binary Oxides Loaded Zeolite for Arsenic Removal from Synthetic Groundwater. Colloids Surfaces APhysicochem. Eng. Asp.2014, 457, 220–227. Chen, B.; Zhu, Z.; Guo, Y.; Qiu, Y.; Zhao, J. Facile Synthesis of Mesoporous Ce-Fe Bimetal Oxide and Its Enhanced Adsorption of Arsenate from Aqueous Solutions. J. Colloid Interface Sci.2013, 398, 142–151. Deng, S.; Li, Z.; Huang, J.; Yu, G. Preparation, Characterization and Application of a Ce-Ti Oxide Adsorbent for Enhanced Removal of Arsenate from Water. J. Hazard. Mater.2010, 179 (1–3), 1014–1021. Zhang, G.; Ren, Z.; Zhang, X.; Chen, J. Nanostructured iron(III)-copper(II) Binary Oxide: A Novel Adsorbent for Enhanced Arsenic Removal from Aqueous Solutions. Water Res.2013, 47 (12), 4022–4031. Gupta, K.; Ghosh, U. C. Arsenic Removal Using Hydrous Nanostructure iron(III)- titanium(IV)BinaryMixed


Page 15 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


15

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

41.

42.

Oxide from Aqueous Solution. J. Hazard. Mater.2009, 161, 884–892. Tu, Y. J.; You, C. F.; Chang, C. K.; Wang, S. L.; Chan, T. S. Arsenate Adsorption from Water Using a Novel Fabricated Copper Ferrite. Chem. Eng. J.2012, 198–199, 440–448. Liu, S.; Kang, S.; Wang, G.; Zhao, H.; Cai, W. Micro/nanostructured Porous Fe-Ni Binary Oxide and Its Enhanced Arsenic Adsorption Performances. J. Colloid Interface Sci.2015, 458, 94–102. Zhang, S.; Niu, H.; Cai, Y.; Zhao, X.; Shi, Y. Arsenite and Arsenate Adsorption on CoprecipitatedBimetal Oxide Magnetic Nanomaterials: MnFe2O4 and CoFe2O4. Chem. Eng. J.2010, 158 (3), 599–607. Farrell, J.; Wang, J.; O’Day, P.; Conklin, M. Electrochemical and Spectroscopic Study of Arsenate Removal from Water Using Zero-Valent Iron Media. Environ. Sci. Technol. 2001, 35 (10), 2026–2032. Bang, S.; Johnson, M. D.; Korfiatis, G. P.; Meng, X. Chemical Reactions between Arsenic and Zero-Valent Iron in Water. Water Res.2005, 39 (5), 763–770. Ramos, M. a V; Ramos, M. a V; Yan, W.; Yan, W.; Li, X.; Li, X.; Koel, B. E.; Koel, B. E.; Zhang, W.; Zhang, W. Simultaneous Oxidation and Reduction of Arsenic by Zero-Valent Iron Nanoparticles: Understanding the Significance of the Core-Shell Structure. J. Phys. Chem. C 2009, 113 (33), 14591–14594. Yan, W.; Ramos, M. a V; Koel, B. E.; Zhang, W.-X. Multi-Tiered Distributions of Arsenic in Iron Nanoparticles: Observation of Dual Redox Functionality Enabled by a Core-Shell Structure. Chem. Commun. (Camb).2010, 46 (37), 6995–6997. Penke, Y. K.; Anantharaman, G.; Ramkumar, J.; Kar, K. K. Aluminum Substituted Nickel Ferrite (Ni–Al–Fe): A Ternary Metal Oxide Adsorbent for Arsenic Adsorption in Aqueous Medium. RSC Adv.2016, 6 (60), 55608– 55617. Li, X.-Q.; Zhang, W.-X. Sequestration of Metal Cations with Zerovalent Iron Nanoparticles- A Study with High Resolution X-Ray Photoelectron Spectroscopy (HRXPS). J. Phys. Chem. C 2007, 111 (19), 6939–6946. Gul, I. H.; Maqsood, a. Structural, Magnetic and Electrical Properties of Cobalt Ferrites Prepared by the Sol-Gel Route. J. Alloys Compd.2008, 465, 227–231. Maaz, K.; Mumtaz, A.; Hasanain, S. K.; Ceylan, A. Synthesis and Magnetic Properties of Cobalt Ferrite (CoFe2O4) Nanoparticles Prepared by Wet Chemical Route. J. Magn. Magn. Mater.2007, 308 (2), 289–295. Singhal, S.; Barthwal, S. K.; Chandra, K. Structural, XRD, magnetic and Mo¨ ssbauer spectral studies of nano size aluminum substituted cobalt ferrites (CoAlxFe2-xO4). J. Magn. Magn. Mater.2006, 306, 233240. Aghav, P. S.; Dhage, V. N.; Mane, M. L.; Shengule, D. R.; Dorik, R. G.; Jadhav, K. M. Effect of Aluminum Substitution on the Structural and Magnetic Properties of Cobalt Ferrite Synthesized by Sol–gel Auto Combustion Process. Phys. B Condens. Matter 2011, 406 (23), 4350–4354. Sattar, a. a.; . El-Sayed, H. M.; El-Shokrofy,K. M.; ElTabey, M. M. E. Improvement of the Magnetic Properties of Mn-Ni-Zn Ferrite by the Non-Magnetic Al3+-Ion Substitution. J. Appl. Sci.2005, 5 (1), 162–168.

43. Philip, J.; Rana, S.; Raj, B. Micelle Based Synthesis of Cobalt Ferrite Nanoparticles and Its Characterization Using Fourier Transform Infrared Transmission Spectrometry and Thermogravimetry. Mater. Chem. Phys.2010, 124 (1), 264–269. 44. Shemer, G.; Tirosh, E.; Livneh, T.; Markovich, G. Tuning a Colloidal Synthesis to Control Co2+ Doping in Ferrite Nanocrystals. J. Phys. Chem. C2007, 111 (39), 14334–14338. 45. Jacintho, G. V. M.; Brolo, A. G.; Corio, P.; Suarez, P. a Z.; Rubim, J. C. Structural Investigation of MFe 2 O 4 (M = Fe, Co) Magnetic Fluids. J. Phys. Chem. C2009, 113(18), 7684–7691. 46. Saniger, J. M. Al-O Infrared Vibrational Frequencies of γ-Alumina. Mater. Lett.1995, 22 , 109–113. 47. Biesinger, M. C.; Payne, B. P.; Grosvenor, A. P.; Lau, L. W. M.; Gerson, A. R.; Smart, R. S. C. Resolving Surface Chemical States in XPS Analysis of First Row Transition Metals, Oxides and Hydroxides: Cr, Mn, Fe, Co and Ni. Appl. Surf. Sci.2011, 257 (7), 2717–2730. 48. Müller, K.; Ciminelli, V. S. T.; Dantas, M. S. S.; Willscher, S. A Comparative Study of As(III) and As(V) in Aqueous Solutions and Adsorbed on Iron OxyHydroxides by Raman Spectroscopy. Water Res.2010, 44, 5660–5672. 49. Goldberg, S.; Johnston, C. T. Mechanisms of Arsenic Adsorption on Amorphous Oxides Evaluated Using Macroscopic Measurements, Vibrational Spectroscopy, and Surface Complexation Modeling. J. Colloid Interface Sci.2001, 234 (1), 204–216. 50. Harrison, J.; Berkheiser, V. Anion Interactions with Freshly Prepared Hydrous Iron Oxides. Clays Clay Miner.1982, 30 (2), 97–102. 51. Parikh, S. J.; Lafferty, B. J.; Sparks, D. L. An ATR-FTIR Spectroscopic Approach for Measuring Rapid Kinetics at the Mineral/water Interface. J. Colloid Interface Sci.2008, 320 (1), 177–185. 52. Myneni, S. C. .; Traina, S. J.; Waychunas, G. A.; Logan, T. J. Experimental and Theoretical Vibrational Spectroscopic Evaluation of Arsenate Coordination in Aqueous Solutions, Solids, and at Mineral-Water Interfaces. Geochim. Cosmochim. Acta1998, 62(19–20), 3285–3300. 53. Loehr, T.M.; Plane, R.A. Raman spectra and structures of arsenious acid and arsenites in aqueous solution. Inorganic chemistry. J Inorg . Chem. 1968, 7(9), 17081714. 54. Vansant, F. K.; Van Der Veken, B. J.; Desseyn, H. O. Vibrational Analysis of Arsenic Acid and Its Anions. J. Mol. Struct.1973, 15 (3), 425–437. 55. Vansant, F. K.; Van Der Veken, B. J. Vibrational Analysis of Arsenic Acid and Its Anions. J. Mol. Struct.1973, 15 (3), 439–444. 56. Guan, X.-H.; Wang, J.; Chusuei, C. C. Removal of Arsenic from Water Using Granular Ferric Hydroxide: Macroscopic and Microscopic Studies. J. Hazard. Mater.2008, 156(1–3), 178–185. 57. Cheng, Z.; Fu, F.; Dionysiou, D. D.; Tang, B. Adsorption, Oxidation, and Reduction Behavior of Arsenic in the Removal of Aqueous As(III) by Mesoporous Fe/Al Bimetallic Particles. Water Res.2016, 96, 22–31. 58. Chowdhury, S. R.; Yanful, E. K.; Pratt, A. R. Chemical States in XPS and Raman Analysis during Removal of Cr(VI) from Contaminated Water by Mixed Maghe-



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 17

16 mite–magnetite Nanoparticles. J. Hazard. Mater.2012, 235–236, 246–256. 59. Chowdhury, S. R.; Yanful, E. K.; Pratt, A. R. Arsenic Removal from Aqueous Solutions by Mixed MagnetiteMaghemite Nanoparticles. Environ. Earth Sci.2011, 64, 411–423. 60. Shirsath, S. E.; Liu, X.; Yasukawa, Y.; Li, S.; Morisako, A. Switching of Magnetic Easy-Axis Using Crystal Orientation for Large Perpendicular Coercivity in CoFe2O4 Thin Film. Sci. Rep.2016, 6 (February), 30074. 61. Wang, Y.; Liu, W.; Wang, T.; Ni, J. Arsenate Adsorption onto Fe-TNTs Prepared by a Novel Water-Ethanol Hydrothermal Method: Mechanism and Synergistic Effect. J. Colloid Interface Sci.2015, 440, 253–262. 62. Liu, T.; Wu, K.; Xue, W.; Maa, C. Characteristics and Mechanisms of Arsenate Adsorption onto Manganese Oxide-Doped Aluminum Oxide. Environ. Prog. Sustainable Energy. 2015, 34 (4), 1009-1018.

63. Zhang, S.; Li, X.; Chen, J. P. An XPS Study for Mechanisms of Arsenate Adsorption onto a Magnetite-Doped Activated Carbon Fiber. J. Colloid Interface Sci.2010, 343 (1), 232–238. 64. Yan, W.; Ramos, M. A. V; Koel, B. E.; Zhang, W. X. As(III) Sequestration by Iron Nanoparticles: Study of Solid-Phase Redox Transformations with X-Ray Photoelectron Spectroscopy. J. Phys. Chem. C 2012, 116 (9), 5303–5311. 65. Sun, F.; Osseo-Asare, K. A.; Chen, Y.; Dempsey, B. A. Reduction of As(V) to As(III) by Commercial ZVI or As(0) with Acid-Treated ZVI. J. Hazard. Mater.2011, 196, 311–317. 66. Li, R.; Li, Q.; Gao, S.; Shang, J. K. Enhanced Arsenite Adsorption onto Litchi-like Al-Doped Iron Oxides. J. Am. Ceram. Soc.2011, 94 (2), 584–591.


17

Page 17 of 17

Table of Contents Graphic

16

846

140

As(III) As(V)

14

120

As(III) 100

12

817

80

Qt (mg g-1)

As(V)

qe (mg g-1)

Intensity (a.u)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


10

60

As(III)

40

8

As(V)

20

6

0 4

Pure

-20 100 200 300 400 500 600 700 800 900 1000 -1

Raman shift (cm )

0

20

40

60

Ce (ppm)

80

100

120


2

3

4

5

6

7

8

Initial pH

9

10

11

12

17

Aluminum Substituted Cobalt Ferrite (CoâAlâFe) Nano Adsorbent for

Recommend Documents

Aluminum Substituted Cobalt Ferrite (CoâAlâFe) Nano Adsorbent for