Efficient Fluoride Removal and Dye Degradation of Contaminated

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Article Cite This: ACS Omega 2019, 4, 9686−9696

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Efficient Fluoride Removal and Dye Degradation of Contaminated Water Using Fe/Al/Ti Oxide Nanocomposite Arnab Mukherjee,† Mrinal K. Adak,† Sudipta Upadhyay,† Julekha Khatun,† Prasanta Dhak,‡ Sadhana Khawas,† Uttam Kumar Ghorai,§ and Debasis Dhak*,† †

Nanomaterials Research Lab, Department of Chemistry, Sidho-Kanho-Birsha University, Purulia 723104, India Department of Chemistry, Techno India University, Kolkata 700091, India § Department of Industrial Chemistry, Ramakrishna Mission Vidyamandira, Belur Math, Howrah 711202, India Downloaded via 46.161.58.152 on July 18, 2019 at 08:44:55 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

‡

S Supporting Information *

ABSTRACT: The trimetallic Fe/Al/Ti (1:1:1) nanocomposite (FAT), synthesized by an adaptable tuned chemical route, offers a new approach for water treatment, for example, the de-fluoridation and photodegradation soluble dye methylene blue (MB) at pH 7. FAT acted as a good fluoride scavenger in the presence of other co-ions and within a widespread pH range (pH 2−11). The photodegradation efficiencies were >90% for different concentrations of MB solutions. The characterization of FAT includes thermogravimetric analysis, X-ray diffraction, Fourier transform-infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and ζ-potential analysis. Furthermore, the regeneration efficiencies of both the water treatments were checked, where the removal efficiency was not hampered significantly even after five batches. Spectroscopic techniques were adopted to perform the kinetic studies and to propose the probable mechanistic paths.

1. INTRODUCTION

Ahmed et al. were able to degrade MB photo-catalytically using Fe2O3/TiO2 nanoparticles.24 Among the adsorbents for fluoride removal, activated alumina is the most used as it is commonly available and inexpensive,26 but its high adsorption is exhibited at low pH ranges, which eventually promotes dissolution of aluminum.27 In this communication, the 3d transition metal oxides (Fe2O3 and TiO2) were modified with the Al3+ trivalent cation to form 1:1:1 trimetallic oxide for the de-fluoridation and photodegradation process as Al3+ enhances the efficiencies of Fe3+ and Ti4+ in bimetallic systems.28,29 Various techniques for the development of metal oxides were applied, such as the impregnation method,30 solid-state dispersion, sol−gel method,31 hydrothermal method,32 mechanical mixing method, coprecipitation method, flame spray pyrolysis, photo-deposition method, and so forth. 33 These methods have some disadvantages, for example, prolonged reaction time, difficult procedures, high temperature, specialized instruments, toxic reagents, external additives, and so forth. Among the various preparation ways, solution combustion synthesis is an efficient, economically favored, and homogeneous method for preparing various metal oxides.34 A simple chemical method to synthesize nanoparticles is the formation of a precursor mass

Industrial activities contaminate water reservoirs with hazardous chemicals, like heavy metals (Pb2+, Cd2+),1 dyes,2 fluoride, and so forth.3 Fluoride (F−) contamination of drinking water is becoming a global problem for the modern world4 besides the release of carcinogenic dyes from textile industries also affecting human and aquatic life.5 The World Health Organization (WHO) made a guideline of 1.5 mg/L fluoride level for drinking water as intake of excess fluoride-containing drinking water affects human health5 and one-third of the 1.26 billion Indian population is in danger of fluorosis (>2 mg/L).6 Several techniques have been developed for de-fluoridation, such as precipitation,7 membrane-based electrodialysis processes,8 adsorption,9 and so forth, among which adsorption is the most promising.10 Previously activated alumina,11 activated carbon,12 and bone char13 were used. Various metal oxides have been confirmed to have an excellent affinity to fluoride adsorption, such as the oxides of Fe,14 Ti,15 Al,16 Zr,17 Mg,18 and their bimetallic compositions.19,20 For the purpose of detoxification of industrial colored wastes, several techniques like adsorption,21 precipitation, sedimentation, ion-exchange processes,22 and biological treatments23 were adopted; however, photocatalytic degradation with nanoparticles is a well accepted process.24 V-doped Mn3O4 nanoparticles were able to degrade methylene blue (MB) in the presence of H2O2 at pH 10 photo-catalytically.25 © 2019 American Chemical Society

Received: January 28, 2019 Accepted: March 27, 2019 Published: June 3, 2019 9686

DOI: 10.1021/acsomega.9b00252 ACS Omega 2019, 4, 9686−9696

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through solution combustion synthesis using a fuel (urea, glycine, oxalyl dihydrate)33 with the constituent metal nitrates. This process has some advantages, for example, self-sustained reaction in homogeneous solution, simple equipment, time and energy consuming, and molecular level mixing, and also the product composition can be tuned.35,36 The efficient trimetallic Fe/Al/Ti (1:1:1) nano-oxide (abbreviated as FAT) was synthesized by a simple solution combustion method using the chelating ligand triethanolamine for the fluoride removal and photocatalytic degradation of MB (C16H18ClN3S), IUPAC name: 3,7-bis(dimethylamino)-phenothiazin-5-ium chloride, at neutral pH medium for the first time. Herein, the investigation of fluoride adsorption with different initial F− concentrations, adsorbent dose in different time intervals along with the photodegradation of different concentrations of MB with their kinetic, thermodynamic, and mechanistic studies, was done. The pH effects and interfering co-anions on the F− adsorption process and the reuse abilities were also examined. We investigated in order to confirm that this work is a novel cost-effective method and has recycling ability for waste water treatment.

Figure 1. Synthetic procedure of nanosized FAT.

2. EXPERIMENTAL SECTION 2.1. Materials Required. Chemicals used during this work were NaF, Fe(NO3)3·9H2O, Al(NO3)3·9H2O, TiO2, HF, triethanolamine (abbreviated as TEA), tartaric acid, MB, HNO3 and double distilled water. All the chemicals were bought from Merck Specialties Limited, Mumbai, India. 2.2. Material Synthesis. 2.2.1. Preparation of 0.05 M Solution of Fe(NO3)3·9H2O, Al(NO3)3·9H2O, Ti-Tartarate Solution. The 0.05 (M) solutions of Fe(NO3)3·9H2O and Al(NO3)3·9H2O were prepared by dissolving the required amount of corresponding metal salts into 1000 mL volumetric flasks using double distilled water, and to prepare the Titartarate solution [0.05 (M)], the standard process was adopted.37 2.2.2. Synthesis of FAT. All the required chemicals were taken in a 1000 mL beaker in equimolar ratio, and the standard procedure was adopted to prepare the precursor mass.35 After mechanical grinding, the precursor carbonaceous mass was calcined at 900 °C for 4 h, nano-powders of FAT were obtained as shown in the flow chart in Figure 1 and the mechanism of the formation of the precursor mass is discussed in Figure S1.35 2.3. Analytical Measurements. The concentration of fluoride, pH studies, and other physical parameters was done using Thermo Scientific (Orion Versa star Pro) Advance Electrochemistry Meter (Software Revision: r4.06, serial number: V11855). The thermogravimetric analysis (TGA) for the precursor sample was done using PerkinElmer STA 6000 at N2 atmosphere. UV−vis spectrophotometer (PerkinElmer, LAMBDA 35) was used to measure the degradation of MB and also for the UV−vis DRS study (diffused reflection spectra) of FAT. The nano-powder was characterized by X-ray diffraction (Bruker D8 ADVANCE eco), Cu Kα radiation (λ = 1.5406 Å) with scanning speed 2° 2θ/min and identified by standard JCPDS file (76-1157). Fourier transform-infrared spectroscopy (FTIR) (PerkinElmer Spectrum model L1600300) was recorded in the range of 4000−450 cm−1 by the KBr pellet method (Merck Spectra grade, Merck India Private Limited) for the characterization. Transmission electron microscope (TEM) (JEM-ARM300F, USA, Inc.) was used for powdered sample characterization. Scanning

electron microscope (SEM) (Model JSM 5800 JEOL, Tokyo, Japan) was used for the surface morphology and other topographic information. The ζ -potential investigation was done using Malvern Zetasizer Nano ZS90 (United Kingdom). 2.4. Determination of Fluoride Ion Concentration. The ion-selective electrode was used to determine F− level. TISAB(III) (Orion 940911) was used to minimize the ionic strength variation in the samples, and the cyclohexane diamine tetraacetic acid buffer was used to mask the other interfering ions in aqueous medium. A calibration curve was obtained using NaF standard solutions (Orion 940907) with different F− concentrations of 1−10 ppm, which were mixed with TISAB(III) in 10:1 volumetric ratio. The results were plotted as F− as a function of concentration (ppm) versus potential (mV) to obtain the calibration curve. 2.5. Preparation of Fluoride and Dye Solutions. Standard fluoride solution (1000 mL of 1000 ppm) was prepared by dissolving the requisite amount of anhydrous NaF with double distilled water, and from that, 3, 5, and 10 ppm fluoride solutions were prepared and stock solutions of 1000 mL 10−5 (M) and 10−4 (M) MB were prepared by dissolving the appropriate amount of the dye using double distilled water, and the physical parameters were measured by the Thermo Scientific (Orion Versa star Pro) Advance Electrochemistry Meter, as described in Table 1. For different F− solutions (3, 5, and 10 ppm), different adsorbent doses (0.05, 0.1, and 0.2 g/100 mL) were varied and Table 1. Physical Parameters of the Fluoride Solutions and MB Solution at 30 °C Initiallya initial conc.

initial pH

conductance (μS cm−1)

salinity (psu)

resistivity (κΩ cm)

TDS (ppm)

3 ppm 5 ppm 10 ppm 10−5 (M) 10−4 (M)

6.80 6.44 6.24 7.26 7.11

5.63 17.74 31.16 24.91 161.5

0.014 0.017 0.022 0.020 0.075

45.46 57.62 31.97 39.44 6.193

58.33 8.682 15.30 12.32 79.13

a

Fluoride concentrations are expressed in ppm, and MB concentrations are expressed in molar (M) unit.

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Figure 2. (A) TGA curve for the synthesized precursor FAT, (B) XRD studies of FAT, (C) FTIR studies of FAT: (a) as calcined, (b) fluoride adsorbed, and (c) regenerated. (D) magnified FTIR studies of FAT. All samples for (B,C) are produced after calcining at 900 °C, 4 h.

Figure 3. (a) TEM morphology, (b) particle size distribution, and (c) SEM image of FAT calcined at 900 °C for 4 h.

shaken as per the standard procedure38 by varying the contact times from 30 to 60 min at 30 °C, pH 7. For the photodegradation, the MB solutions were irradiated in sunlight with 1 mmol of FAT with 100 mL stock solution taken in a 250 mL beaker with occasional stirring. The experiments were performed under ambient condition between 11 am and 11:30 am (month of April, Purulia, West Bengal, India) at a latitude and longitude of 23.3613° N, 86.3399° E, respectively, with average solar intensity 6.08 kW h m−2.39 The photocatalytic experiments were conducted simultaneously to avoid the error arising because of the solar light fluctuation. Dye solutions (3 mL) were taken in regular intervals, arresting the mixture for the kinetic studies up to 20 min (1200 s) and detected under UV−vis spectrophotometer. A set without catalyst was also exposed to sunlight irradiation to ensure the role of the photocatalyst.

3. RESULTS AND DISCUSSION 3.1. Characterization. TGA analysis for the precursor sample was studied from 50 to 900 °C with heating rate of 10 °C/min, as shown in Figure 2A. The thermal degradation of the prepared black mass occurred in three stages, with a total mass loss of 68.19%. In Stage I, the weight loss was because of physically and chemically adsorbed water, which occurred up to ∼300 °C with 12.60% of mass loss. The second weight loss with 49.50% happened between 330 and 670 °C, with the evolution of CO2, NH3, and nitrogenous oxide in Stage II, as described in Figure S1. In the final Stage III, that is, at >670 °C, there was a gradual weight decrease, which indicated complete volatilization of all the substances as mentioned in the previous stages, the sample tended to reach its calcination temperature, and the mass loss was 5.79%. It could be decided that the TG graph tended to be parallel with the x-axis above 9688


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adsorbents were fit for batch studies without any adverse effect, as indicated in Figure 2C(c). TEM studies showed mostly spherical morphology with uniform distribution of the particles, as indicated in Figure 3a. The black and white spots indicate focused particles. The diameter of the particles ranged between 35 and 55 nm (Figure 3b), and the average diameter was found to be 42.00 ± 0.50 nm with 30% polydispersity, which was calculated by a UTI image tool software (version 3.0). The morphology of FAT was observed by SEM, as shown in Figure 3c. The topology was very porous in nature, with average grain size 155 nm using UTI image tool software (version 3.0). Larger grains are visible with porosity indicated by the darker part of the micrograph. 3.2. Analytical Studies for Fluoride Adsorption. 3.2.1. Fluoride Removal Efficiency. The whole experiment was performed as described in Section 2.5, and the percentage of fluoride removal was calculated using eq 1; the results are enlisted in Table 2.

Table 2. Effect of Fluoride Removal as a Function of Dose and Time at 30 °C, pH 7 % of fluoride removal time (min)

adsorbent dose (g/100 mL)

3 ppm

5 ppm

10 ppm

30

0.05 0.10 0.20 0.05 0.10 0.20 0.05 0.10 0.20

53.27 54.00 63.58 65.92 95.00 99.00 48.01 60.65 65.86

50.88 80.38 99.00 67.81 77.60 85.65 59.90 60.96 71.53

82.95 83.49 85.14 92.09 95.26 98.40 92.26 94.55 96.58

45

60

800 °C. Thus, calcination was performed at 900 °C to get the desired phase. X-ray diffraction (XRD) patterns of FAT calcined at 900 °C for 4 h is shown in Figure 2B. The XRD patterns were verified with the JCPDS data file no. 76-1157. All of the diffraction peaks of FAT indicated orthorhombic with Cmcm (63) S.G with a = 3.37 Å, b = 9.15 Å, and c = 10.58 Å and the unit cell volume was 326 Å3. The heating rate and calcination time were carefully monitored. The crystallite size was obtained as 30 nm using Scherrer’s method.38 The FTIR spectra of FAT calcined powder, F− adsorbed powder, and F− regenerated powder are shown in Figure 2C(a−c), respectively. The broad peak observed at 3426 cm−1 is for the vibration of −OH groups, hydrogen bonded with intermolecular water molecules or the surface absorbed moisture.40 The peaks around 1630 cm−1 are designated for the metal carbonyl stretching vibrations present in the samples.38 It was reported that the peaks observed from 1150 to 1170 cm−1 were those for mixed metal oxides M− OH.41 The peaks observed at 617 and 1076 cm−1 were for the stretching vibrations of Ti−O or O−Ti−O bond41 and Al−O bond,40 respectively, as shown clearly in Figure 2D. After adsorption, the −OH group peak was shifted and the intensity of the peak was slightly decreased. This was because of the involvement of the fluoride adsorption. The peak intensity decreased after fluoride adsorption, but after regeneration, it almost merged with the pure sample, which indicated that the regeneration process was done properly and assured that the

% Fluoride removal =

C0 − Cf × 100 C0

(1)

where C0 and Cf (ppm) are the F− concentration of the initial and the final state, respectively. The effects of change in adsorbent dose at various fluoride concentrations at different contact times are illustrated in Figures S2−S4. It was observed that with increasing concentration of pollutant (here F−), the percentage removal efficiency of the pollutant increased, which seemed to be opposite to the general trend. However, in this case, on increasing F− concentration, more and more F− were available for adsorption onto the adsorbent competing with OH− ions in solution. Similar types of observations were previously reported elsewhere.6,9,47,48 From Table 2, it can be concluded that the use of 0.2 g/100 mL of adsorbent dose gave the most satisfactory results for all of the sets of fluoride solutions. A maximum of 99.00% F− removal capacity was observed after 30 min of shaking with the adsorbent dose 0.2 g/100 mL at 5 ppm initial F− concentration. Thus, further studies were done using the adsorbent dose 0.2 g/100 mL, and the kinetic studies of 3, 5, and 10 ppm F− solutions were performed at contact time from 5 to 300 min. The variation of other parameters, such as pH, conductance, salinity, resistivity, and TDS (total

Figure 4. (A) Influence of pH of fluoride adsorption of FAT at 10 ppm F− solution, with inset plot showing the ζ-potential of FAT vs pH, (B) effect of % of fluoride removal in the presence of other co-ions onto 0.2 g/100 mL FAT (concentrations of NaCl, Na2SO4, NaNO3, Na3PO4, and NaHCO3 were 500, 500, 50, 500, and 250 mg/L) in 10 ppm F− solution. 9689


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Figure 5. (A) Adsorption kinetics of fluoride, (B) pseudo-1st-order fitting, (C) pseudo-2nd-order fitting, (D) Langmuir isotherm of fluoride adsorption for 0.2 g/100 mL FAT at pH 7, 30 °C.

Table 4. Thermodynamic Parameters for F− Adsorption in 10 ppm Fluoride Solution at 0.2 g/100 mL Adsorption Dose onto FAT Composite

Table 3. Pseudo-2nd-Order Kinetics Data of FAT (0.2 g/ 100 mL) Compared to Previous Results on Fluoride Removal C0 (mg/L) 20 50 10 11 3p, 5q, 10r

adsorbent Fe3O4@Al(OH)3 Mg−Al−CO3 layered double hydroxides polypyrrole/TiO2 bionanomaterial scaffolds FAT

k2 (g min/mg)

R2

refs

3.142 × 10−2 4.4846 × 10−3

0.9997 0.99

48 45

3.9 × 10−2 1.9 × 10−3

0.998 0.997

9 6

1.20 × 10−1p, 1.97 × 10−1q, 2.40 × 10−2r

0.999p,q,r

this work

T (K)

ΔG0 (kJ/mol)

ΔH0 (kJ/mol)

ΔS0 (J/mol)

303 318 328

−52.19 −50.23 −50.00

−79.97

−92.20

Figure 7. Photographs of the vials (a) 10−5 (M) MB, (b) 10, (c) 120 s (d) 10−4 (M) MB, (e) 10, (f) 120, and (g) 300 s with 1 mmol FAT after photocatalytic experiment.

dissolved solid), before and after the adsorption process is mentioned in Tables 1 and S1, respectively. The fluoride adsorption was performed at different pH ranges from pH 2 to pH 11 for the adsorbent dose, as depicted in Figure 4A. The removal capacity was detected to be >80% throughout the pH range, and the optimum condition was found at pH 5. This trend could be elucidated based on the composition and the surface charge of FAT. As the metal centers are made up of hard materials, the adsorbent can scavenge the fluoride, overcoming the competition with OH−/ other anions. In the surface potential study, the ζ-potential (pHZPC) was observed at 5.72, as shown in Figure 4A (inset).

Figure 6. Van’t Hoff plot of F− adsorption onto 0.2 g/100 mL adsorbent dose of 10 ppm fluoride solution. 9690


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Figure 8. (A,B) UV−vis spectral absorbance of degradation of 10−5 and 10−4 (M) MB, respectively, and (C,D) variation of concentration of MB with irradiation time (s) (inset: pseudo-1st-order kinetic studies of 10−5 and 10−4 (M) MB), respectively, using 1 mmol FAT at pH 7.

Table 5. Kinetic Details and Percentage Degradation Data of MB in Different Concentrations Using 1 mmol FAT conc. of MB (M) −5

10 10−4

rate constant (s−1)

% of degradation

R2

90.90 98.40

1 0.93

−2

1.08 × 10 1.37 × 10−2

FAT showed positive superficial charge up to pH 5, which favored anion adsorption (F−),42 which can be correlated with the pH study given in Figure 4A. The details of variation of F− adsorption onto FAT at higher pH are discussed in the Supporting Information (Figure S5). Experiments were continued regarding the F− removal in the presence of different interfering co-ions with two sets of 10 ppm aqueous F− solutions, one containing Cl−, NO3−, and SO42− and another containing Cl−, NO3−, SO42−, PO43−, and HCO3− sodium salts, as per the allowed limit of WHO at 30 ± 2 °C43 with 0.2 g/100 mL FAT within the time intervals of 5−300 min (Figure 4B). The percentage of the fluoride removal got lowered in the presence of PO43− and HCO3− along with the other anions (Cl−, NO3−, SO42−), as shown in Figure 4B(b), as the fluoride

Figure 9. FTIR studies of photodegradation of MB using 1 mmol FAT.

adsorption affinity follows the order in the presence of the other co-ions, such as HCO3− < PO43− < Cl− ≈ SO42− < NO3−.44,45 This might be for the affinity of these anions toward

Table 6. Comparison of MB Degradation Using Other Metal-Based Nanocomposites Sample s. no

composite

amount

MB conc.

degradation (%)

degradation time

refs

1. 2. 3. 4. 5.

TiO2-graphene reduced graphene/manganese oxide (rGO/MnO2 hybrid) TiO2 Fe2O3/TiO2 FAT

30 mg 10 mg 6% w/w 1−7 wt % 1 mmol

0.01 g L−1 50 mg L−1 50 mg L−1 10−5 mol/L 10−5 (M) 10−4 (M)

90.0 66.0 79.0 60.0−79.0 90.9 98.4

150 min 5 min 90 h ∼60 min 2 min 10 min

51 52 53 5 this work

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≡MOH2 + + OH− ↔ ≡ MOH(s) + H 2O (neutralization) (5)

where MF is the surface-occupied site, MOH2+ represents the acidic active site, and MOH(s) represents surface OH− ions, which was neutral. 3.3. Analytical Studies. 3.3.1. Photodegradation of MB. The photodegradation process was performed as discussed in Section 2.5, and to find out the degradation efficiency, eq 6 was used. The kinetics was studied using spectroscopic studies, and a probable mechanism was also established. % degradation =

the adsorbent dependent on high charge density and pH effect.46 The fluoride removal process followed the two-step metal− ligand exchange mechanism, as shown in eqs 2 and 3, revealed from the FTIR studies, and to find out the reuse ability, the standard procedure was adopted.38 Eqs 4 and 5 represent the leaching out of adsorbent fluoride from the adsorbent, which was also supported by the FTIR analysis, as shown in Figure 2C. (2)

≡MOH2 + + F− ↔ MF + H 2O

(3)

(6)

where C0 and Ct (M) are the MB concentration of the initial and the final state, respectively. The percentage of degradation of different concentrations of MB is summarized in Tables 5 and 6. The photodegradation of different concentrations of MB were successfully illustrated by UV and FTIR studies, as shown in Figures 8A,B and 9. 3.3.2. Kinetic and Thermodynamic Studies of Fluoride Adsorption. In the kinetic investigation, the contact time varied from 5 to 300 min for the 3, 5, and 10 ppm F− solutions with an adsorbent dose of 0.2 g/100 mL at 30 °C at pH 7 (Figure 5A,C). For this study, both the pseudo-1st- and pseudo-2nd-order model were examined as shown in Figure 5B,C. In the case of the pseudo-1st-order model, that is, ln(qe − qt) = ln qe − k1t, where qt and qe represent the quantities of F− adsorbed (mg/g) at the given contact time and at equilibrium, respectively, and the pseudo-1st-order rate constant is k1 (min−1), the adsorption results were not fitted as shown in Figure 5B. The kinetic studies were illustrated and the changes in concentration of fluoride with adsorption time were monitored at various time intervals, and kinetic results were verified for the pseudo-2nd-order model (eq 7).

Figure 10. Mechanistic path of photodegradation of MB using 1 mmol FAT.

≡MOH(s) + H+ ↔ ≡ MOH2 +

(C0 − Ct ) × 100 C0

t 1 t = 2 + qt qe qe k 2

where M is the metal ion (Fe3+ or Al3+ or Ti4+), MOH (s) represents a surface OH− ion, and MF represents a surface site occupied by a fluoride ion. For the regeneration process, the probable mechanism can be drawn as

(7) −

where the qt and qe represent the amount of F adsorbed (mg/ g) at the given contact time and at equilibrium, respectively, and k2 is the rate constant of the pseudo-2nd-order reaction (g min/mg). The adsorption results fitted best to the pseudo2nd-order model (R2 > 0.99, Figure 5C) as chemisorption controlled the adsorption kinetics47 revealed from the FTIR study of the fluoride-adsorbed adsorbent (Figure 2C). Zhao et

≡MF + H3O+ ↔ ≡ MOH2 + + HF (leaching out of F−) (4)

Figure 11. Photodegradation of (a) 10−5 (M) and (b) 10−4 (M) MB using electron scavenger (AgNO3) over FAT under solar irradiation. 9692


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Figure 12. (a) Reusability of FAT at different adsorbent doses in fluoride adsorption; (b) reusability of FAT in the photodegradation process in different MB solutions.

al. (2010)48 and Chen et al. (2017)44 have studied Fe2O3@ Al(OH)3 nanoparticles and pyrrole/TiO2, which promoted pseudo-2nd-order reaction kinetics with k2 (g min/mg) 3.142 × 10−2 and 3.9 × 10−2 with R2 0.9997 and 0.998, respectively, when the initial fluoride concentrations were 20 and 10 ppm, respectively. However, Lv et al. (2006)45 and Kumar et al. (2017)3 have shown k2 (g min/mg) to be 4.4846 × 10−3 and 1.9 × 10−3 with R2 0.99 and 0.997 when the initial F− concentration was considered to be 50 and 11 ppm, respectively. In our study, k2 (g min/mg) was found to be of higher value on the order of 10−1 for 3 and 5 ppm initial F−concentration, whereas k2 was in the order of 10−2 for 10 ppm F− concentration with R2 value 0.999 in all the cases. The pseudo-2nd-order kinetic results of FAT are compared in Table 3. The adsorption capacities were studied with adsorbent dose 0.2 g/100 mL for the adsorption isotherm study, which was well fitted in Langmuir isotherm model,47 as shown in Figure 5D. Using the Langmuir isotherm further investigations, ΔH0 and ΔS0 were evaluated by using the Van’t Hoff plot,49 as shown in Figure 6 and data summarized in Table 4. The result revealed that FAT nano-adsorbent was able to adsorb the F− ions by electrostatic interaction as well as by chemisorption. The negative (−ve) value of ΔH0 indicated that the adsorption process was exothermic, and the (−ve) value of ΔS0 indicated that the adsorption process was reversible; that is, the adsorbent FAT could be reused for another batch studies. 3.3.3. Kinetics of the Dye Degradation under Visible Light. To describe the photodegradation process using 1 mmol FAT, experimental setups were done as stated in Section 2.5 and the color change with time of the arrested solutions is shown in Figure 7a−g. The change in concentration of MB with respect to the irradiation time was measured as shown in Figure 8. The kinetics results were best fitted to the Lindemann−Hinshelwood pseudo-1st-order kinetics50 for 10−5 and 10−4 (M) MB, respectively, and the rate constants were evaluated through −ln(C/C0) versus t plot, as shown in Figure 8C,D (inset) for the sets shown in Figure 8A,B. The percentage degradation of MB with FAT photocatalysts was calculated using eq 6. The kinetic details and percentage degradation data are mentioned in Table 5. The role of using the trimetallic nanocomposite FAT as a photocatalyst instead of the commercially available TiO2 (Merck Specialties Limited, Mumbai, India) is described in the Supporting Information (Figure S7a−d), and the

degradation efficiency with respect to time for FAT is compared with other metal-based nanocomposites in Table 6. 3.3.4. UV and FTIR Investigation of Photodegraded Products. The UV−visible spectrum of 10−5 (M) and 10−4 (M) MB (a typical thiazine dye) showed absorption (λmax) intensely at 293.4 and 663 nm,54 as shown in Figure 8A,B, respectively. The change from blue color to colorless aqueous solution of MB in the presence of FAT irradiated in sunlight indicated the chemical change in the aqueous solution. In UV analysis in Figure 8A,B, the peaks of MB gradually lowered as the irradiation time continued. The 663 nm peak disappeared and a peak generated at 246.8 nm, which represented the formation of leuco-MB (LMB) (C16H19N3S), the reduced product of MB.55 In FTIR studies, shown in Figure 9a characteristic peaks of MB were observed at 1600, 1356, 1144, and 1065 cm−1 for CC group, C−N(Me)2 group, C−N bending, and C−S−C stretching, respectively,56 and the band at 3425 cm−1 was for the O−H stretching. As the photodegradation process continued, the FTIR patterns changed, where signature peaks of MB57 disappeared. The presence of the peak around 1640 cm−1 in the products ensured the presence of the CC group and 1071 cm−1 also indicated the C−S−C stretching present in the product (Figure 9b-c). The bands around 3400 cm−1 got broadened and peaks around 580 cm−1 appeared in the degraded products, which indicated the presence of the N−H 2° amine group and N−H wagging. Thus, the FTIR study also revealed that MB got photodegraded in the presence of FAT and the aromatic rings did not break down, and the appearance of the 2° N−H amine group supported the formation of LMB after the degradation. 3.3.5. Photocatalytic Mechanism of MB. The UV and FTIR studies supported that MB was reduced to LMB in the photodegradation process. From the UV−vis DRS study, the band gap of FAT was found to be 1.72 eV (see Supporting Information, Figure S6a,b). On photoirradiation, FAT generate electrons (eCB−) in the conduction band (CB) and holes (hVB+) in the valance band (VB). The water molecules (H2O) in the reaction medium reacted with the holes (hVB+) in the VB to produce H+. Now the generated electrons in the CB and the H+ produced in the medium preformed the reduction of MB to LMB through the 2e−, 1H+ mechanism,58 as shown in Figure 10 representing the mechanism of degradation of MB using FAT. The proposed mechanism of the MB degradation was associated with the electrons formed in the CB of FAT. To 9693


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understand the key role of the CB electrons, the same degradation procedure was adopted using an electron scavenger (0.05 mM AgNO3),33 where the degradation (%) got lowered up to 30 and 35% for 10−5 and 10−4 (M) MB solutions, respectively, as shown in Figure 11a,b. Thus, it could be concluded that the electrons generated in the CB were solely responsible to carry out the photodegradation. 3.4. Recycling Study. Reusability of an adsorbent is the promising aspect of an adsorbent. In this communication, reuse sets were performed for the 10 ppm F− solution, with the 0.05, 0.1, and 0.2 g/100 mL adsorbent doses for 45 min contact time, discussed in Section 3.2.1, and to reuse FAT for the F− removal process, the standard process was adopted.38 To reuse, after the photodegradation process, FAT was washed with 0.1 (M) HCl and ethanol and deionized water until the adsorbents got neutral and filtered, and allowed to dry in oven at 110 °C. The regeneration efficiencies of both the water treatments were still at their higher value up to five cycles, as shown in Figure 12a,b.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected], debasisdhak@yahoo. co.in. ORCID

Debasis Dhak: 0000-0001-7792-2220 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Authors would like to thank the Department of Science and Technology, Government of West Bengal, vide project sanction no. 674(sanc )/ST/P/S&T/15G/5/2016 dated 09/ 11/2016 for financial support. M.K.A. is thankful to the Council of Scientific and Industrial Research (CSIR), Government of India, for the Senior Research Fellowship [sanction no. 09/1156(0004)/18-EMR-I].

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4. CONCLUSIONS

REFERENCES

(1) González, M. A.; Trócoli, R.; Pavlovic, I.; Barriga, C.; La Mantia, F. Capturing Cd(II) and Pb(II) from contaminated water sources by electro-deposition on hydrotalcite-like compounds. Phys. Chem. Chem. Phys. 2016, 18, 1838−1845. (2) Annamalai, S.; Santhanam, M.; Sudanthiramoorthy, S.; Pandian, K.; Pazos, M. Greener technology for organic reactive dye degradation in textile dye-contaminated field soil and in situ formation of ″electroactive species″ at the anode by electrokinetics. RSC Adv. 2016, 6, 3552−3560. (3) Kumar, A.; Paul, P.; Nataraj, S. K. Bionanomaterial Scaffolds for Effective Removal of Fluoride, Chromium, and Dye. ACS Sustainable Chem. Eng. 2017, 5, 895−903. (4) World Health Organization Press. Diarrhoea: Why children are still dying and what can be done, Geneva, Switzerland. 2009. (5) Ahmed, M. A.; El-Katori, E. E.; Gharni, Z. H. Photocatalytic degradation of methylene blue dye using Fe2O3/TiO2 nanoparticles prepared by sol−gel method. J. Alloys Compd. 2013, 553, 19−29. (6) Kumar, A.; Paul, P.; Nataraj, S. K. Bionanomaterial Scaffolds for Effective Removal of Fluoride, Chromium, and Dye. ACS Sustainable Chem. Eng. 2017, 5, 895−903. (7) Reardon, E. J.; Wang, Y. A limestone reactor for fluoride removal from wastewaters. Environ. Sci. Technol. 2000, 34, 3247−3253. (8) Arahman, N.; Mulyati, S.; Lubis, M. R.; Takagi, R.; Matsuyama, H. The removal of fluoride from water based on applied current anmembrane types in electrodialyis. J. Fluorine Chem. 2016, 191, 97− 102. (9) Chen, J.; Shu, C.; Wang, N.; Feng, J.; Ma, H.; Yan, W. Adsorbent synthesis of polypyrrole/TiO2 for effective fluoride removal from aqueous solution for drinking water purification: Adsorbent characterization and adsorption mechanism. J. Colloid Interface Sci. 2017, 495, 44−52. (10) Mohapatra, M.; Anand, S.; Mishra, B. K.; Giles, D. E.; Singh, P. Review of fluoride removal from drinking water. J. Environ. Manage. 2009, 91, 67−77. (11) Gong, W.-X.; Qu, J.-H.; Qu, R.-P.; Lan, H.-C. Adsorption of fluoride onto different types of aluminas. Chem. Eng. J. 2012, 189-190, 126−133. (12) Meenakshi; Maheshwari, R. C. Fluoride in drinking water and its removal. J. Hazard. Mater. 2006, 137, 456−463. (13) Nemade, P. D.; Vasudeva Rao, A.; Alappat, B. J. Removal of fluorides from water using low cost adsorbents. Water Sci. Technol.: Water Supply 2002, 2, 311−317. (14) Huang, Y. S.; Shih, Y.-J.; Chang, C. Adsorption of fluoride by waste iron oxide: the effects of solution pH, major coexisting anions, and adsorbent calcination temperature. J. Hazard. Mater. 2011, 186, 135.

In conclusion, the present study describes the preparation of trimetallic nanocomposite, FAT, by a tuned, fast, energyefficient chemical route as a useful material for contaminated or waste water treatment. The average particle size and grain size of FAT powder were estimated through TEM and SEM studies, which were 42 and 155 nm, respectively. XRD study of the synthesized nano-adsorbent FAT was orthorhombic with 326 Å3 unit cell volume. The results confirmed that the high fluoride removal capacity was found for the adsorbent dose 0.2 g/100 mL for all sets. The fluoride adsorption occurred through the chemisorption process following the pseudo-2ndorder kinetic model with rate constant values in between 10−1 and 10−2 g min/mg range via a two-step metal ligand exchange mechanism. FAT (1 mmol) can act as a photocatalyst for the detoxification of organic dye (MB) to LMB with greater than 90% degradation efficiencies for different MB concentrated solutions. The photodegradation was established through the UV and FTIR studies of the reaction solutions and a 2e−, 1H+ probable mechanistic path was also established. This photodegradation kinetics of MB obeyed the Lindemann−Hinshelwood pseudo-1st-order kinetic model, where the rate constants were in the range 10−2 s−1. FAT could be reusable at least up to five cycles for both the fluoride removal and the MB degradation process without hampering any other aspects. Thus, the use of this cost-effective material could be a solution to prevent the water contamination.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.9b00252. Figure showing the synthesis reaction mechanism, water analysis table, variation of adsorbent dose graphs, effect of pH on adsorbent, UV−vis diffuse reflectance spectra (UV−vis DRS) of FAT, photocatalytic efficiency of FAT with respect to commercial TiO2 (PDF) 9694


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(15) Chen, L.; He, S.; He, B.-Y.; Wang, T.-J.; Su, C.-L.; Zhang, C.; Jin, Y. Synthesis of Iron-Doped Titanium Oxide Nanoadsorbent and Its Adsorption Characteristics for Fluoride in Drinking Water. Ind. Eng. Chem. Res. 2012, 51, 13150. (16) Zhou, Q.; Lin, X.; Lin, B.; Luo, X. Fluoride adsorption from aqueous solution by aluminum alginate particles prepared via electrostatic spinning device. Chem. Eng. J. 2014, 256, 306. (17) Velazquez-Jimenez, L. H.; Hurt, R. H.; Matos, J.; RangelMendez, J. R. Zirconium-carbon hybrid sorbent for removal of fluoride from water: oxalic acid mediated Zr(IV) assembly and adsorption mechanism. Environ. Sci. Technol. 2014, 48, 1166. (18) Zhang, K.; Wu, S.; Wang, X.; He, J.; Sun, B.; Jia, Y.; Luo, T.; Meng, F.; Jin, Z.; Lin, D.; Shen, W.; Kong, L.; Liu, J. Wide pH range for fluoride removal from water by MHS-MgO/MgCO3 adsorbent: Kinetic, thermodynamic and mechanism studies. J. Colloid Interface Sci. 2015, 446, 194. (19) Deng, S.; Liu, H.; Zhou, W.; Huang, J.; Yu, G. Mn-Ce oxide as a high-capacity adsorbent for fluoride removal from water. J. Hazard. Mater. 2011, 186, 1360−1366. (20) Liu, H.; Deng, S.; Li, Z.; Yu, G.; Huang, J. Preparation of Al-Ce hybrid adsorbent and its application for defluoridation of drinking water. J. Hazard. Mater. 2010, 179, 424−430. (21) Ahmed, M. A.; Abou-Gamra, Z. M.; Salem, A. M. Photocatalytic degradation of methylene blue dye over novel spherical mesoporous Cr2O3/TiO2 nanoparticles prepared by sol-gel using octadecylamine template. J. Environ. Chem. Eng. 2017, 5, 4251. (22) Gupta, V. K.; Ali, I.; Saleh, T. A.; Nayak, A.; Agarwal, S. Chemical treatment technologies for waste-water recycling-an overview. RSC Adv. 2012, 2, 6380−6388. (23) Robinson, T.; McMullan, G.; Marchant, R.; Nigam, P. Remediation of dyes in textile effluent: a critical review on current treatment technologies with a proposed alternative. Bioresour. Technol. 2001, 77, 247−255. (24) Ahmed, M. A.; El-Katori, E. E.; Gharni, Z. H. Photocatalytic degradation of methylene blue dye using Fe2O3/TiO2 nanoparticles prepared by sol−gel method. J. Alloys Compd. 2013, 553, 19−29. (25) Ramezanpour, S.; Sheikhshoaie, I.; Khatamian, M. Synthesis, characterization and photocatalytic properties of V-doped Mn3O4 nanoparticles as a visible light-activated photocatalyst. J. Mol. Liq. 2017, 231, 64−71. (26) Chen, L.; Wu, H.-X.; Wang, T.-J.; Jin, Y.; Zhang, Y.; Dou, X.-M. Granulation of Fe-Al-Ce nano-adsorbent for fluoride removal from drinking water by spray coating on sand in a fluidized bed. Powder Technol. 2009, 193, 59−64. (27) Valdivieso, A. L.; Reyes Bahena, J. L.; Song, S.; Urbina, R. H. Temperature effect on the zeta potential and fluoride adsorption at the alpha-Al2O3/aqueous solution interface. J. Colloid Interface Sci. 2006, 298, 1−5. (28) Biswas, K.; Saha, S. K.; Ghosh, U. C. Adsorption of Fluoride from Aqueous Solution by a Synthetic Iron(III)−Aluminum(III) Mixed Oxide. Ind. Eng. Chem. Res. 2007, 46, 5346−5356. (29) Tsai, C.-Y.; Kuo, T.-H.; Hsi, H.-C. Fabrication of Al-Doped TiO2 Visible-Light Photocatalyst for Low-Concentration Mercury Removal. Int. J. Photoenergy 2012, 2012, 1. (30) Sathishkumar, P.; Sweena, R.; Wu, J. J.; Anandan, S. Synthesis of CuO-ZnO nanophotocatalyst for visible light assisted degradation of a textile dye in aqueous solution. J. Chem. Eng. 2011, 171, 136− 140. (31) Neppolian, B.; Wang, Q.; Yamashita, H.; Choi, H. Synthesis and characterization of ZrO2−TiO2 binary oxide semiconductor nanoparticles: application and interparticle electron transfer process. Appl. Catal., A 2007, 333, 264−271. (32) Liao, W.; Zheng, T.; Wang, P.; Tu, S.; Pan, W. Efficient microwave-assisted photocatalytic degradation of endocrine disruptor dimethyl phthalate over composite catalyst ZrOx/ZnO. J. Environ. Sci. 2010, 22, 1800−1806. (33) Renuka, L.; Anantharaju, K. S.; Vidya, Y. S.; Nagaswarupa, H. P.; Prashantha, S. C.; Sharma, S. C.; Nagabhushana, H.; Darshan, G. P. A simple combustion method for the synthesis of multi-functional

ZrO2/CuO nanocomposites: Excellent performance as Sunlight photocatalysts and enhanced latent fingerprint detection. Appl. Catal., B 2017, 210, 97−115. (34) Yang, L.; Xiao, Y.; Liu, S.; Li, Y.; Cai, Q.; Luo, S.; Zeng, G. Highly active WO3 semiconductor photocatalyst prepared from amorphous peroxo-tungstic acid for the degradation of various organic compounds. Appl. Catal., B 2010, 94, 142−149. (35) Dhak, D.; Pramanik, P. Particle Size Comparison of SoftChemically Prepared Transition Metal (Co, Ni, Cu, Zn) Aluminate Spinels. J. Am. Ceram. Soc. 2006, 89, 1014−1021. (36) Varma, A.; Mukasyan, A. S.; Rogachev, A. S.; Manukyan, K. V. Solution Combustion Synthesis of Nanoscale Materials. Chem. Rev. 2016, 116, 14493−14586. (37) Dhak, P.; Dhak, D.; Das, M.; Pramanik, K.; Pramanik, P. Impedence Spectroscopy study of LaMnO3 modified BaTiO3 ceramics. Mater. Sci. Eng., B 2009, 164, 165−171. (38) Adak, M. K.; Sen, A.; Mukherjee, A.; Sen, S.; Dhak, D. Removal of fluoride from drinking water using highly efficient nano-adsorbent, Al(III)-Fe(III)-La(III) trimetallic oxide prepared by chemical route. J. Alloys Compd. 2017, 719, 460−469. (39) http://www.synergyenviron.com/tools/solar-irradiance/india/ west-bengal/purulia (accessed April 18, 2018). (40) Sujana, M. G.; Anand, S. Iron and aluminium based mixed hydroxides: A novel sorbent for fluoride removal from aqueous solutions. Appl. Surf. Sci. 2010, 256, 6956−6962. (41) Chen, J.; Feng, J.; Yan, W. Facile Synthesis of polythiophene/ TiO2partical composite in aqueous medium and its adsorption performance for Pb (II). RSC Adv. 2015, 5, 86945−86953. (42) Mohan, D.; Sharma, R.; Singh, V. K.; Steele, P.; Pittman, C. U., Jr. Fluoride Removal from Water using Bio-Char, a Green Waste, Low-Cost Adsorbent: Equilibrium Uptake and Sorption Dynamics Modeling. Ind. Eng. Chem. Res. 2012, 51, 900−914. (43) Addendum, F. E. I. t. f. Guide for Drinking-Water Quality, 2017. (44) Chen, J.; Shu, C.; Wang, N.; Feng, J.; Ma, H.; Yan, W. Adsorbent synthesis of polypyrrole/TiO2 for effective fluoride removal from aqueous solution for drinking water purification: Adsorbent characterization and adsorption mechanism. J. Colloid Interface Sci. 2017, 495, 44−52. (45) Lv, L.; He, J.; Wei, M.; Evans, D.; Duan, X. Factors influencing the removal of fluoride from aqueous solution by calcined Mg-Al-CO3 layered double hydroxides. J. Hazard. Mater. 2006, 133, 119−128. (46) Kamble, S. P.; Jagtap, S.; Labhsetwar, N. K.; Thakare, D.; Godfrey, S.; Devotta, S.; Rayalu, S. S. Defluoridation of drinking water using chitin, chitosan and lanthanum-modified chitosan. Chem. Eng. J. 2007, 129, 173−180. (47) Zhang, K.; Wu, X.; Wang, X.; He, J.; Sun, B.; Jia, Y.; Luo, T.; Meng, F.; Jin, Z.; Lin, D.; Shen, W.; Kong, L.; Liu, J. Wide pH range for fluoride removal from water by MHS-MgO/MgCO3 adsorbent: Kinetic, thermodynamic and mechanism studies. J. Colloid Interface Sci. 2015, 446, 194. (48) Zhao, X.; Wang, J.; Wu, F.; Wang, T.; Cai, Y.; Shi, Y.; Jiang, G. Removal of fluoride from aqueous media by Fe3O4@Al(OH)3 magnetic nanoparticles. J. Hazard. Mater. 2010, 173, 102−109. (49) Daifullah, A.; Yakout, S.; Elreefy, S. Adsorption of fluoride in aqueous solutions using KMnO4-modified activated carbon derived from steam pyrolysis of rice straw. J. Hazard. Mater. 2007, 147, 633− 643. (50) Jafari, S.; Nezamzadeh-Ejhieh, A. Supporting of coupled silver halides onto clinoptilolite nanoparticles as simple method for increasing their photocatalytic activity in heterogeneous photodegradation of mixture of 4-methoxy aniline and 4-chloro-3-nitro aniline. J. Colloid Interface Sci. 2017, 490, 478−487. (51) Yang, N.; Liu, Y.; Wen, H.; Tang, Z.; Zhao, H.; Li, Y.; Wang, D. Photocatalytic Properties of Graphdiyne and Graphene Modified TiO2: From Theory to Experiment. ACS Nano 2013, 7, 1504−1512. (52) Qu, J.; Shi, L.; He, C.; Gao, F.; Li, B.; Zhou, Q.; Hu, H.; Shao, G.; Wang, X.; Qiu, J. Highly Efficient Synthesis Of Graphene/MnO2 Hybrids And Their Application For Ultrafast Oxidative Decomposition of Methylene Blue. Carbon 2014, 66, 485−492. 9695


ACS Omega

Article

(53) Sima, J.; Hasal, P. Photocatalytic Degradation of Textile Dyes in a TiO2/UV System. Chem. Eng. Trans. 2013, 32, 79−84. (54) Heger, D.; Jirkovský, J.; Klán, P. Aggregation of Methylene Blue in Frozen Aqueous Solutions Studied by Absorption Spectroscopy. J. Phys. Chem. A 2005, 109, 6702−6709. (55) Impert, O.; Katafias, A.; Kita, P.; Mills, A.; Pietkiewicz-Graczyk, A.; Wrzeszcz, G. Kinetics and mechanism of a fast leuco-Methylene Blue oxidation by copper(II)-halide species in acidic aqueous media. Dalton Trans. 2003, 348−353. (56) Singh, A.; Khare, P.; Verma, S.; Bhati, A.; Sonker, A. K.; Tripathi, K. M.; Sonkar, S. K. Pollutant Soot for Pollutant Dye Degradation: Soluble Graphene Nanosheets for Visible Light Induced Photodegradation of Methylene Blue. ACS Sustainable Chem. Eng. 2017, 5, 8860−8869. (57) Cabrera, L. I.; Martínez, M.; Reyman, D.; Crespo, P.; Morales, M. P.; Herrasti, P. One single-step synthesis of multifunctional methylene blue-coated magnetite nanoparticles. J. Nanopart. Res. 2011, 13, 6931−6939. (58) Hoffmann, A. A.; Dias, S. L. P.; Rodrigues, J. R.; Pavan, F. A.; Benvenutti, E. V.; Lima, E. C. Methylene blue immobilized on cellulose acetate with titanium dioxide: an application as sensor for ascorbic acid. J. Braz. Chem. Soc. 2008, 19, 943−949.

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Efficient Fluoride Removal and Dye Degradation of Contaminated

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