Selective and Efficient Removal of Anionic Dyes from Solution by

Article Cite This: J. Chem. Eng. Data 2019, 64, 791−799

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Selective and Efficient Removal of Anionic Dyes from Solution by Zirconium(IV) Hydroxide-Coated Magnetic Materials Yanyan Hu and Runping Han*

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College of Chemistry and Molecular Engineering, Zhengzhou University, No. 100 Kexue Road, Zhengzhou, 450001 P. R. China ABSTRACT: An effective adsorbent, a zirconium hydroxide coating on the surface of magnetic materials (Zr−Fe3O4), was successfully synthesized by a precipitation method to selectively adsorb Alizarin red (AR) from solution in batch mode. The characterizations of Zr−Fe3O4 were achieved by XRF, XRD, SEM, and XPS. Adsorption conditions of AR on Zr−Fe3O4, including the pH, contact time, concentration of the dye, and ionic strength of the aqueous solution, were optimized, and the maximum adsorption capacity from experiments was 83.7 mg·g−1 at 313 K. Common salts existing in solution were beneficial to AR adsorption. The analysis of adsorption isotherm data showed that the Redlich−Peterson model could better describe the adsorption procedure of AR on the magnetic adsorbent. The kinetic data could be fitted well by the Elovich equation. The adsorption process was spontaneous, endothermic, and entropy-produced according to the thermodynamic results. XPS analysis showed that there was interaction between Zr from the adsorbent and O from AR. In addition, adsorption in a single system was compared to competitive adsorption in the binary system between AR and acid chrome blue K (AK). It was concluded that the complexation was the main force between Zr−Fe3O4 and AR, while there was selective adsorption of AR from solution. Zr− Fe3O4 was selective and effective in the removal of AR from solution.

1. INTRODUCTION Dyes in bodies of water have created serious environmental problems and affect the health of human beings and aquatic biota.1 Dyes are discharged into wastewater from various industries, including dye manufacturing, textiles, paper, food coloring, leather, plastics, and cosmetics.2,3 It is found that more than 10 000 kinds of dyestuffs are used and synthesized every year, among which more than 10% existed in natural water.4,5 Because of the colors of dyes, the transparency of bodies of water has been reduced, leading to the hindrance of light penetration and the solubility of gas in aquatic bodies.6 Water-soluble Alizarin red (AR), a kind of anthraquinone dye utilized in many domains, has high durability, which results in the difficult degradation of this dye. There is the structure of catechol in AR. Therefore, it is essential to investigate a simple, efficient, and economic adsorbent for the safe removal of AR.7,8 There are many physicochemical methods that have been explored by scientists for the removal of dyes from water, including adsorption,9 photocatalytic degradation,10 oxidation, precipitation, fungal decolonization,11 flocculation, and membrane filtration.12 Because of their efficiency and simple operation, the adsorption procedures have been widely used. Besides, the application of magnetic particle to wastewater has received considerable attention because of the simple separation from the mixed systems by an external magnet, and this method is sustainable as an easy separation.13,14 There are many materials modified via zirconium oxide and hydroxide, elucidating good adsorption capacities for the contaminants in water,15,16 but little research has been © 2019 American Chemical Society

published using magnetic materials coated with zirconium oxide and hydroxide to adsorb dyes in aqueous solution. In this study, zirconium hydroxide was used to coat magnetic particles by a precipitation method in order to obtaining an effective adsorbent for AR adsorption. Factors such as the pH, contact time, initial concentration of AR, temperature, and ion strength were investigated to study the effect on the adsorption quantity in batch mode. The adsorption mechanism of AR on Zr− Fe3O4 was studied by the analysis of XPS, while isotherm and kinetic results and thermodynamic parameters were attained and competitive adsorption was performed.

2. MATERIALS AND METHODS 2.1. Instruments and Reagents. All of the reagents used in this study, including AR, acidic chrome blue K (AK), FeCl3· 6H2O, FeSO4·7H2O, and ZrOCl2·8H2O with analytical purity were purchased from Kermel (Tianjin, China). Stock solutions of AR and AK, 500 mg·L−1, were prepared by dissolving 250 mg of AR or AK in doubly distilled water to 500 mL. The working solution was simply prepared by daily dilution to a suitable concentration, of which the pH was adjusted using 0.01−0.1 mol·L−1 HCl and NaOH solutions. In this research, the pH of solutions was measured with a pH-mV meter (LeiCi PHS-3C, China) at room temperature. The adsorbent and AR solution mixed in a 50 mL conical flask Received: November 12, 2018 Accepted: January 15, 2019 Published: January 31, 2019 791

DOI: 10.1021/acs.jced.8b01063 J. Chem. Eng. Data 2019, 64, 791−799

Journal of Chemical & Engineering Data

Article

the volume of AR solution (L), and m is the mass of Zr−Fe3O4 (g). The competitive adsorption of AR and AK was carried out by fixing the concentration of one component and varying another to prepare the mixed solution. To distinguish the adsorption properties of the two dyes, it was investigated by a comparison of the changes in adsorption capacities from the mixed system. The total absorbance of the solution is the sum of absorbance from contribution of AR and AK in solution.

were agitated in an air bath shaker (GuoHua SHZ-82, China). The AR concentration remaining in the aqueous phase was analyzed using a UV spectrophotometer (Shimadzu Brand UV3000) at the wavelength of maximum absorbance (515 nm, at pH 8.0−9.8), and for acid chrome blue K (AK, anionic dye), the maximum absorbance is 544 nm. X-ray diffraction (XRD) analysis of Fe3O4 and Zr−Fe3O4 was performed with a PANalytical X’Pert PRO instrument (The Netherlands). The results of XRF were obtained via an X-ray fluorescence spectrometer (S4 PIONEER, Bruker, Germany). The configuration of the surface was received by a scanning electron microscope (SEM, Hitachi Su8020, Japan). The magnetization and BET surface area of materials used in this study were determined with a Squid-VSM and a Micromeritics ASAP2020, respectively. To prove the adsorption mechanism, X-ray photoelectron spectroscopy (XPS, Thermo Escalab 250Xi, England) was carried out. 2.2. Preparation of Adsorbent. The first step was to synthesize magnetic Fe3O4. Then 5.41 g of FeCl3·6H2O and 5.57 g of FeSO4·7H2O were dissolved in 0.5 mol·L−1 HCl in a 1000 mL beaker with magnetic stirring. Next, 300 mL of 1.25 mol·L−1 NaOH solution was added dropwise to the mixture under vigorous stirring at ambient temperature, along with the formation of black magnetic particles. After continuing to stir for 30 min, 25% HCl solution was used to achieve neutral pH in the mixture. The obtained dark precipitate (Fe3O4) was separated from the reaction system with a magnet and washed with doubly distilled water several times before being dried at 60 °C in an oven. The next step was to modify the magnetic materials via zirconium oxychloride. First, 0.5 g of obtained Fe3O4 and 0.2 g of ZrOCl2·8H2O were added to 100 mL of H2O. After shaking for 1 h at 303 K, 1.25 mol·L−1 NaOH was used to adjust the pH of the solution to approximately 10, and then the mixture stood for 4 h. The solid particles that were obtained were washed with doubly distilled water until the liquid supernatant was neutral. Finally, the product, a modified adsorbent, was dried in an oven at 80 °C for 4 h. 2.3. Adsorption of AR and Competitive Adsorption. All the batch adsorption experiments were conducted on a thermostated shaker (SHZ-82) at constant speed (120 rpm) in order to investigate the effect of adsorption parameters such as pH, contact time, temperature, ion strength, and initial AR concentration. For each adsorption suit, 10 mL of AR solution at various concentrations and pH values was mixed completely with adsorbent (0.010 g) and then shaken for different lengths of time. In this study, all variables were fixed and a variable affecting the adsorptive capacity for an appropriate range was changed, for the sake of the optimum conditions. After the reaction, the magnetic adsorbent was separated by magnetic separation and the dye concentration of solution was measured using on a UV/vis-3000 spectrophotometer (Shimadzu Brand UV-3000 with a 1 cm path length) according to the Beer− Lambert law at a wavelength of maximum absorbance of 515 nm. The quantity of AR adsorbed onto a unit weight of Zr− Fe3O4 (qt or qe, mg·g−1) was calculated from the following relationship q=

(c 0 − c )V m

A515 = kAR515cAR + kAK515cAK

(2)

A544 = kAR544cAR + kAK544cAK

(3)

Then, the concentrations of AR and AK in binary systems can be obtained from the following equations cAR =

kAK544A515 − kAK514A544 kAR515kAK544 − kAR544kAK 515

(4)

cAK =

kAR515A544 − kAR544A515 kAR515kAK544 − kAR544kAK515

(5)

where kAR515, kAK515, kAR544, and kAK544 are the absorption coefficients for AR and AK at wavelength of 515 and 544 nm. Values of the absorption coefficient can be obtained through the absorbance at 515 or 544 nm at known concentrations of dyes. A515 and A544 are the absorbances of mixed solution at wavelengths of 515 and 544 nm, respectively. The adsorption quantity of AR or AK can also be calculated according to eq 1. All adsorption experiments were carried out twice, and averages were recorded. The error in the measurement is less than 5%. 2.4. Desorption Study. The exhausted or spent adsorbent (dye-loaded Zr−Fe3O4) was obtained for the adsorption of 150 mg/L AR or AK at pH 5.8. Then, the spent adsorbent was washed with distilled water to remove any unabsorbed dye and was dried at 333 K. Dye-loaded Zr−Fe3O4 was desorbed by a 0.01 mol/L NaOH solution, and the regenerated adsorbent was reused under the same experimental conditions. The regeneration yield was obtained as the ratio of values of qe before and after regeneration.

3. RESULTS AND DISCUSSION 3.1. Characterization of Adsorbent. The XRD patterns of Fe3O4 and Zr−Fe3O4 are presented in Figure 1, suggesting that the main structure of Fe3O4 underwent no change after being modified by zirconium hydroxide. Compared to the standard atlas, the pattern was in good agreement with magnetic Fe2O3 at 30, 37, and 64°, which shows that the structure of the synthesized magnetic materials is mainly magnetic Fe3O4. The results of XRF analysis are 59.2% Fe for Fe3O4 and 54.1% Fe and 8.14% Zr for Zr−Fe3O4. It was clear that the content of zirconium obviously increased. On the basis of this result, it was postulated that the zirconium hydroxide was coated successfully onto the magnetic particles. FTIR analysis of Fe3O4 and Zr−Fe3O4 (not shown) showed that the absorption peak at 570 cm−1 from Fe3O4 was due to the Fe−O vibration while the peaks at 3435 and 1634 cm−1 from Zr−Fe3O4 were due to the stretching vibration and bending vibration of OH from ZrO(OH)2, respectively. SEM pictures of adsorbents of Fe3O4 and Zr−Fe3O4 are shown in Figure 2. It was known from Figure 2 that the particle

(1)

where c0 and c are the initial AR concentration and the concentration of AR at any time t, respectively (mg·L−1), V is 792



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Figure 3 showed the XPS of Zr−Fe3O4 before and after AR adsorption, and the binding energy of different elements was used to explore the chemical composition and combined forms of adsorbent and AR. Figure 3a is the full spectrum diagram of the magnetic adsorbent before and after dye uptake. It is obvious that the three peaks at 530.0, 531.8, and 532.5 eV are the characteristic peaks of O 1s, corresponding to O2−, OH/ O−Zr bonding, and H2O, respectively.17 From Figure 3b,c, it was concluded that the proportion of OH/O−Zr binding has a significant increase from 5.88 to 24.2%. This implied that the reaction mechanism of the adsorption process can be the complexation between Zr and −OH in AR. Meanwhile, the results of Zr 3d spectra in Figure 3d,e suggested that the peak intensity of Zr−O binding at 182.3 and 184.7 eV was greater for the adsorbed materials,18 which was consistent with the results of O 1s. 3.2. Adsorption Study. 3.2.1. Effect of Solution pH on Adsorption. The pH of the reaction system is a crucial parameter for the adsorption property because of the protonation and deprotonation of the functional groups on the surface of the adsorbent and adsorbate at different pH values. Protonation or deprotonation can influence the surface charges of adsorbents, leading to the electrostatic interactions between the adsorbent and adsorbate and the solubility of AR in water.19,20 The effect of initial AR solution pH on the adsorption capacity is shown in Figure 4, which shows that values of qe decreased with the increase in solution pH from 2 to 11. Obviously, at pH < pHpzc, the surface of the materials is positively charged and availed the uptake of AR due to the increased electrostatic force of attraction.21 It was evident that the adsorption capacity of AR increased when the pH decreased from 7 to 2. For the condition of pH > pHpzc, the negatively charged adsorbent could repel the AR molecules, resulting in the reduction of adsorption. Even at pH 8−10, the adsorption capacities were >40.0 mg·g−1, confirming that another interaction, such as complexation, is the primary interaction between Zr−Fe3O4 and AR. Considering the actual acidity of wastewater and the slight change before and after adsorption at solution pH 6 (data not shown), the original AR solution (pH 5.8) was not adjusted in the next experiments. 3.2.2. Effect of Contact Time. The effects of contact time on the uptake of AR onto Fe3O4 and Zr−Fe3O4 are shown in Figure 5. It was observed that the adsorbed quantity of AR increased with the increase in contact time. It was also seen that the adsorption quantity was significantly enhanced after the Zr coating, which showed that this adsorbent was a good prospect for the application for effluent disposal. It was found from Figure 5 that the time of adsorption equilibrium was nearly 6 h. 3.2.3. Effect of Common Salt Concentration. Figure 6 revealed the effect of coexisting common salts on the adsorption quantity. It was estimated that the adsorption quantity increased gradually with the increase in salt concentration (ionic strength) and finally tended to balance and attain adsorption saturation. The positive effect of ionic strength may be due to the fact that the reduction of the thickness of the double layer was beneficial to the combination of adsorbate with the active sites. If electrostatic attraction was the major role during the adsorption process, then the adsorption quantity often significantly decreased with the increase in salt concentration. Therefore, the results from

Figure 1. XRD patterns of Fe3O4 and Zr−Fe3O4.

Figure 2. SEM pictures of Fe3O4 (a, c, left) and Zr−Fe3O4 (b, d, right).

size of two adsorbents was more uniform and the surface was rough, which was beneficial to the adsorption. The BET surface areas were 65.3 and 87.9 m2·g−1 for the adsorbent before and after Zr loading, which implied that there was a larger specific surface area, which favored adsorption. The pHpzc of the modified material measured by the batch equilibration technique was 7.8. The magnetic properties of Fe3O4 and Zr−Fe3O4 were also analyzed using VSM. According to the hysteresis loop (figure not shown), the saturation magnetization values of Fe3O4 and Zr−Fe3O4 were 69.5 and 57.3 emu·g−1. The saturation magnetization of Zr−Fe3O4 declined by 17.6% as a result of the introduction of ZrO2 (as the antimagnetic and covering effect) onto the surface of Fe3O4. This change also showed that the surface of Fe3O4 was completely coated. The slight decrease in saturation magnetization might be due to the effect of a thinner surface-coated ZrO(OH)2 layer, so it was concluded that the material still had good magnetism for the separation from solid−liquid mixtures by an external magnet. 793



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Figure 3. Full spectrum diagram (a), O 1s (b, c), and Zr 3d (d, e) XPS spectra of Zr−Fe3O4 particles before and after AR adsorption.

3.2.5. Adsorption Isotherm Studies. The study of the isotherm models can reflect the interaction between adsorbents and adsorbents and provides a theoretical basis for predicting the reaction mechanism and adsorption capacity in the practical application.22 The adsorption isotherms of AR on the Zr−Fe3O4 are illustrated in Figure 8. The equilibrium adsorption data were analyzed by the Langmuir model, Freundlich model, and Redlich−Peterson model (Table 1). Nonlinear regression analysis was used to fit the data according to the smallest sum of squares difference between the calculated data and the experimental data. The corresponding isotherm parameters from the models are shown in Table 2. Fitted curves are also presented in Figure 8. It is seen from Table 2 that there were the highest values of R2 (>0.92) and the lowest values of SSE from the Redlich− Peterson model at three temperatures. Furthermore, fitted

experiments also confirmed that the electrostatic attraction was not the main action. This was an advantage of AR adsorption onto Zr−Fe3O4 in dye wastewater including salts. Herein, the 0.04 mol·L−1 concentration of sodium chloride was added in later experiments. 3.2.4. Effect of Initial Dye Concentration at Various Temperatures. The effects of initial AR concentrations on AR adsorption onto Zr−Fe3O4 were evaluated in the range from 20 to 250 mg·L−1 (Figure 7). It was found that the values of qe gradually increased with the increase in the initial AR concentration, and then reached the adsorption saturation. The initial dye concentration offered an important driving force for the transfer resistance of AR between the liquid and the solid phases.9 It was also observed that the adsorption quantity became larger with the increase in temperature, which confirmed that the process was endothermic. 794



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Figure 4. Effect of the initial pH on the adsorption quantity of the dye (T = 303 K, C0 = 100 mg·L−1, m = 0.01 g).

Figure 7. Equilibrium quantities of AR for various initial concentrations at different temperatures (m = 0.01 g, t = 6 h, CNaCl = 0.04 mol·L−1).

Figure 5. Effect of contact time on the adsorption process (T = 303 K, C0 = 100 mg·L−1, m = 0.01 g). Figure 8. Isotherm nonlinear fitting curves at different temperatures (m = 0.01 g, t = 6 h, CNaCl = 0.04 mol·L−1).

Peterson model was the best fit to the adsorption equilibrium data. The Langmuir model was better for describing the equilibrium data with higher values of R2 and lower values of SSE. Meanwhile, parameter g from the Redlich−Peterson model was close to 1, which indicated that the adsorption process of AR contained monolayer and multilayer chemical adsorption. Parameter 1/n from the Freundlich model was lower than 0.3, and this showed a favorable procedure.24 3.2.6. Adsorption Kinetics. Figure 9 presents the contact time for the adsorption quantity at three AR concentrations. The adsorption quantity became larger with the increase in AR concentration. To determine the controlling mechanism and the ratelimiting step,26,27 two kinetic models (Table 1) were employed to fit the kinetic experimental data, and the results are summarized in Table 3. Fitted curves from models are also presented in Figure 9. The consistency between the experimental data and model nonlinear regression analysis was studied by calculating the determined coefficients (R2 values, closer to 1 means more applicable).

Figure 6. Effect of NaCl and Na2SO4 concentrations on AR adsorption (T = 303 K, c0 = 100 mg·L−1, m = 0.01 g, t = 6 h).

curves from the Redlich−Peterson model were closer to the experimental curves, so it was postulated that the Redlich− 795



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Table 1. Adsorption Kinetics Models Used in the Study model

equation

parameters

Isotherm Models

qe =

Langmuir model

qmKLce

qe is the equilibrium adsorption quantity (mg·g−1), ce is the AR concentration at equilibrium (mg·L−1), KL is the Langmuir binding constant related to the free energy of adsorption (L·mg−1), qm is the maximum adsorption capacity (mg·g−1).23

1 + KLce

KF and 1/n are the Freundlich constants characteristic of the system, implying the adsorption capacity and the adsorption intensity.24

qe = KFce1/ n

Freundlich model Redlich−Peterson model

qe =

Ace 1 + Bce g

A, B, and g are the Redlich−Peterson parameters, and g indicates the degree of heterogeneity between 0 and 1. If the value of g is 1, then the equation is equal to Langmuir.25

Kinetic Models

k 2qe 2t

pseudo-secondorder kinetic model

qt =

Elovich equation

q1 = ln(αβ)β + ln tβ

1 + k 2qet

k2 is the rate constant of the equation (g·mg−1· min−1). a is the initial adsorption rate constant (mg·g−1· min−1); β is related to the extent of surface coverage and activation energy for chemisorption (g·mg−1)

Table 2. Adsorption Isotherm Parameters for AR Adsorption on Zr−Fe3O4a

Table 3. Parameters of Adsorption Kinetics for AR Adsorption on Zr−Fe3O4 (T = 303 K)

Langmuir

Pseudo-Second-Order Kinetic Model KL/(L·mg−1)

T/K

293 303 313 Freundlich T/K

0.173 0.245 0.243 KF

293 24.3 303 27.1 313 29.2 Redlich−Peterson

C0/ (mg·L−1)

qm(theo)/ (mg·g−1)

qe(exp)/ (mg·g−1)

R2

SSE

69.2 69.8 79.0

70.1 74.5 83.7

0.955 0.954 0.914

82.9 88.1 237

1/n

R2

SSE

C0/(mg·L−1)

α

β

R2

SSE

0.213 0.198 0.210

0.873 0.917 0.866

234 160 371

50 100 150

34.5 29.2 42.4

0.177 0.109 0.111

0.981 0.966 0.982

1.78 7.94 3.86

T/K

A

B

g

R2

SSE

293 303 313

14.8 29.3 26.5

0.279 0.648 0.483

0.945 0.908 0.921

0.956 0.985 0.921

67.7 23.9 183

qe(exp)/ (mg·g−1)

50 43.7 100 65.1 150 67.3 Elovich Equation

qe(theo)/ (mg·g−1)

k2×10−3

R2

SSE

42.4 64.2 66.7

2.72 1.20 1.37

0.915 0.853 0.927

7.99 34.1 16.1

attributed to the higher R2. This confirmed that the process was a heterogeneous diffusion process that contained chemical adsorption.28 Furthermore, the value of qe(exp) (from experiments) was close to qe(theo) (from the pseudo-second-order kinetic model), suggesting that the chemical adsorption is the speed control step, and this model can predict the equilibrium adsorption quantity.29 Overall, the adsorption procedure of AR on Zr−Fe3O4 was heterogeneous chemical adsorption. 3.3. Competitive Adsorption of AR and AK and Adsorption Selectivity. To discuss the selectivity of adsorbents to dye adsorption, research on the competitive adsorption of AR and AK was implemented. The results of competitive adsorption in binary systems are shown in Figure 10. It was seen from Figure 10a that the equilibrium adsorption capacity of AK decreased from 25.0 to 14.3 mg·g−1 when the AR concentration was 5 to 50 mg·L−1 (lower than 42.8%). To fix the AR concentration and change the AK concentration, the values of qe (AR) decreased from 41.0 to 36.1 mg·g−1 (only lower than 12.0%) in Figure 10b. Therefore, it was found that Zr−Fe3O4 was more likely to bind AR from a solution with higher selectivity. An adsorption study on a single system consisting of AR and AK was performed, and the values of qe/ce (partition coefficient) were obtained at various concentrations. The results are shown in Figure 11. It was clearly found that there were higher values of qe/ce near AR. This also indicated the uptake selectivity of AR onto Zr−Fe3O4. Although both AR and AK are anionic dyes, the quantities adsorbed onto Zr−Fe3O4 were significantly different. These results are due to the differences in dye structure (Appendix). Because there are two ortho hydroxyl groups in the benzene

SSE=∑ (q − qc)2 , and q and qc are the experimental value and calculated value according the model, respectively a

Figure 9. Adsorption kinetics nonlinear fitting curves with varying AR concentrations (T = 303 K, m = 0.01 g, t = 6 h, CNaCl = 0.04 mol·L−1).

It was concluded that the Elovich equation was better for describing the adsorption of AR on the magnetic materials 796



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and electrostatic attraction between Zr−Fe3O4 and AK may be the main role. In a comprehensive analysis of the results of this study, it was demonstrated that the forces between adsorbents and adsorbate molecules included electrostatic interaction and complexation. Figure 12 shows the major complexation process in which the complexation of two ortho hydroxyl groups on Alizarin red and zirconium formed a stable fivemembered ring.30

Figure 12. Diagram of the conjectural complexation mechanism.

Therefore, we referred to the specific selectivity for AR adsorption on Zr−Fe3O4. 3.4. Thermodynamic Analysis of Adsorption. Thermodynamic studies for the present adsorption of AR onto Zr− Fe3O4 were undertaken to exhibit the reaction mechanism. Thermodynamic parameters such as changes in the standard free energy (ΔG°, kJ·mol−1), enthalpy (ΔH°, kJ·mol−1), and entropy (ΔS°, J·mol−1·K−1) are defined as follows Kc = Figure 10. Competitive adsorption of AR and AK (T = 303 K and m = 0.01 g). (a) CAK = 50 mg·L−1, CAR = 5−50 mg·L−1. (b) CAR = 50 mg·L−1, CAK = 5−50 mg·L−1.

Cad,e Ce

(6)

where cad,e is the concentration of AR on the adsorbent at equilibrium (mg·L−1). An infinitely dilute value of Kc′ is obtained by calculating the apparent equilibrium constant (Kc) at different initial concentrations of AR and extrapolating to zero, and this value will give Kc′. In this study, the concentration was used instead of activity in order to obtain the standard thermodynamic equilibrium constant (Kc′) of the adsorption system. The value of Kc′ is selected to determine the Gibbs free energy of adsorption (ΔG°) according to the following equation: ΔGo = −RT ln Kc′

(7)

The constant is expressed in terms of the enthalpy change of adsorption (ΔH°) and the entropy change of adsorption (ΔS°) as a function of temperature. Values of ΔH° and ΔS° can be calculated according to the van’t Hoff equation: ΔGo = ΔH o − T ΔS o

(8) −1

−1

R is the universal gas constant, 8.314 J·mol ·K ; T is the solution temperature, K. The results calculated on the basis of equilibrium data are listed in Table 4, showing that ΔG° < 0, 0 < ΔH° < 84 kJ· mol−1, and ΔS° > 0. It was summarized that the uptake process of AR was spontaneous and endothermic with an increase in entropy and contained physical adsorption. Combined with the results of kinetic analysis, it was possible to speculate that the reaction in this research includes physical adsorption and chemisorption.

Figure 11. Comparison of qe/Ce between AR and AK (T = 303 K, m = 0.01 g).

rings for AR and Zr, it is easily to bind the two ortho hydroxyl groups to form a five-membered ring through complexation. However, for AK there are two hydroxyl groups in two benzene rings in one molecule, so complexation becomes weak 797



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that the interaction between adsorbents and adsorbents was dominated by complexation and contains electrostatic attraction and ion exchange. In addition, Zr−Fe3O4 had a distinctive selectivity for AR removal. The experimental results showed that the magnetic composite can be utilized as a magnetically separable and promising adsorbent for water system cleanup.

Table 4. Thermodynamic Parameters of AR Adsorption onto Zr−Fe3O4 ΔG/(kJ·mol−1) −1

−1

−1

ΔH/(kJ·mol )

ΔS/(J·mol ·K )

293 K

303 K

313 K

26.9

109

−4.88

−6.15

−7.05

■

3.5. Comparison of the Quantity Adsorbed with Other Adsorbents. The adsorption capacity and the best fit isotherm model in this work were compared with those of other adsorbents. The results are shown in Table 5. It was summarized that Zr−Fe3O4 showed satisfactory removal performance for AR and a good prospect for application. Furthermore, there was higher selective adsorption toward AR from solution, but a suitable model for fitting the equilibrium data was also different because the experimental conditions and characterization of adsorbents were different. Li prepared Fe3O4@ZrO2 core−shell microspheres to enhance the phosphopeptides, but its precursor is zirconium isopropoxide, which was eventually converted to zirconia by calcination. 35 However, in this study the method of preparation was simple and no organic compounds were used, so there is some competitive superiority with respect to the application of Fe3O4@ZrO2 obtained in this study. 3.6. Desorption Study. A desorption study is helpful for explaining the mechanism of adsorption and for making the process more economical.36,37 The desorption efficiency was 19.5% for AR adsorption and 36.2% for AK adsorption. This showed that AR bound more strongly onto the surface of the adsorbent. The regeneration efficiency of reuse was >60%, and there were some properties of recycling. This desorption result led to a similar conclusion from competitive adsorption between AR and AK, and there was selective for Zr−Fe3O4 to bind AR. The lower desorption efficiency also confirmed that the action between AR (orthotwo OH groups) and Zr existing on the surface of the adsorbent was coordination or complexation.

APPENDIX The chemical structure of Alizarin red is the following:

The chemical structure of acid chrome blue K is the following:

■

AUTHOR INFORMATION

Corresponding Author

*Tel: +86 371 67781757. Fax: +86 371 67781556. E-mail: [email protected]. ORCID

4. CONCLUSIONS Zr−Fe3O4 composites for the removal of AR from solution have been successfully prepared by chemical precipitation, exhibiting an extraordinary adsorption capacity and fast uptake rates. From the analysis of the surface properties of materials, it was found that zirconium had been commendably loaded onto the magnetic particle surface. Coexisting common salts favored AR adsorption. By investigating the fitting data of adsorption kinetics and isotherms, it was evident that the suitable fitting models were the Elovich equation and the Redlich−Peterson model, respectively. Combined with the results of competitive adsorption and XPS analysis, it was quite possible to conclude

Runping Han: 0000-0002-1585-4522 Funding

This work was supported by the National Natural Science Foundation of China for undergraduate cultivation in basic science (J0830412). Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Gregory, A. R.; Elliott, J.; Kluge, P. Ames testing of direct Black 38 parallels carcinogenicity testing. J. Appl. Toxicol. 1981, 1, 308−313.

Table 5. Comparison of the Quantity Adsorbed by Different Adsorbents for the Removal of AR adsorbents activated-carbon magnetic nanocomposite magnetic chitosan mustard husk gold nanoparticles olive stone byproduct modified nanosized silica Zr−Fe3O4

adsorption capacity (mg·g−1)

initial concentration of AR (mg·L−1)

adsorbent dosage (g)

108.69

70

0.01

Langmuir

9

40.12 1.97 123.4 16.1 200 65.1

100 25 35 125 250 100

0.1 0.5 0.015 5.0 0.15 0.01

Langmuir Freundlich Langmuir Redlich−Peterson Langmuir Redlich−Peterson

33 18 34 31 32 this work

798

suitable model

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(2) Yagub, M. T.; Sen, T. K.; Afroze, S.; Ang, H. M. Dye and its removal from aqueous solution by adsorption: A revie.Adv. Adv. Colloid Interface Sci. 2014, 209, 172−184. (3) Salleh, M. A. M.; Mahmoud, D. K.; Abdul Karim, W. A. W.; Idris, A. Cationic and anionic dye adsorption by agricultural solid wastes: A comprehensive review. Desalination 2011, 280, 1−13. (4) Xu, X.; Gao, B. Y.; Jin, B.; Yue, Q. Y. Removal of anionic pollutants from liquids by biomass materials: A review. J. Mol. Liq. 2016, 215, 565−595. (5) Lee, J. W.; Choi, S. P.; Thiruvenkatachari, R.; Shim, W. G.; Moon, H. Evaluation of the performance of adsorption and coagulation processes for the maximum removal of reactive dyes. Dyes Pigm. 2006, 69, 196−203. (6) Wang, S. B.; Li, H. T. Dye adsorption on unburned carbon: kinetics and equilibrium. J. Hazard. Mater. 2005, 126, 71−77. (7) Córdoba, A.; Magario, I.; Ferreira, M. L. Experimental design and MM2−PM6 molecular modelling of hematin as a peroxidase-like catalyst in Alizarin Red S degradatio. J. Mol. Catal. A: Chem. 2012, 355, 44−60. (8) Sun, J. R.; Lu, H. Y.; Du, L. L.; Lin, H. B.; Li, H. D. Anodic oxidation of anthraquinone dye Alizarin Red S at Ti/BDD electrodes. Appl. Surf. Sci. 2011, 257, 6667−6671. (9) Fayazi, M.; Ghanei-Motlagh, M.; Taher, M. A. The adsorption of basic dye (Alizarin red S) from aqueous solution onto activated carbon/γ-Fe2O3 nano-composite: Kinetic and equilibrium studies. Mater. Sci. Semicond. Process. 2015, 40, 35−43. (10) Gupta, V. K.; Jain, R.; Mittal, A.; Saleh, T. A.; Nayak, A.; Agarwal, S.; Sikarwar, S. Photo-catalytic degradation of toxic dye amaranth on TiO(2)/UV in aqueous suspensions. Mater. Sci. Eng., C 2012, 32, 12−17. (11) Khataee, A. R.; Vafaei, F.; Jannatkhah, M. Biosorption of three textile dyes from contaminated water by filamentous green algal Spirogyra sp.: Kinetic, isotherm and thermodynamic studies. Int. Biodeterior. Biodegrad. 2013, 83, 33−40. (12) Wang, H.; Yuan, X.; Zeng, G.; Leng, L.; Peng, X.; Liao, K.; Peng, L.; Xiao, Z. Removal of malachite green dye from wastewater by different organic acid-modified natural adsorbent: kinetics, equilibriums, mechanisms, practical application, and disposal of dye-loaded adsorbent. Environ. Sci. Pollut. Res. 2014, 21, 11552−11564. (13) Tang, S. C. N.; Lo, I. M. C. Magnetic nanoparticles: Essential factors for sustainable environmental applications. Water Res. 2013, 47, 2613−1632. (14) Giakisikli, G.; Anthemidis, A. N. Magnetic materials as sorbents for metal/metalloid preconcentration and/or separation, A review. Anal. Chim. Acta 2013, 789, 1−16. (15) Qiu, H.; Liang, C.; Zhang, X.; Chen, M.; Zhao, Y.; Tao, T.; Xu, Z.; Liu, G. Fabrication of a biomass-based hydrous zirconium oxide nanocomposite for preferable phosphate removal and recovery. ACS Appl. Mater. Interfaces 2015, 7, 20835−20844. (16) Zhan, Y. H.; Zhang, H. H.; Lin, J. W.; Zhang, Z.; Gao, J. Role of zeolite’s exchangeable cations in phosphate adsorption onto zirconium-modified zeolite. J. Mol. Liq. 2017, 243, 624−637. (17) Mallet, M.; Barthélémy, K.; Ruby, C.; Renard, A.; Naille, S. Investigation of phosphate adsorption onto ferrihydrite by X-ray Photoelectron Spectroscopy. J. Colloid Interface Sci. 2013, 407, 95− 101. (18) Fang, L. P.; Wu, B. L.; Lo, I. M. C. Fabrication of silica-free superparamagnetic ZrO2@Fe3O4 with enhanced phosphate recovery from sewage: Performance and adsorption mechanism. Chem. Eng. J. 2017, 319, 258−267. (19) Rong, Y. C.; Li, H.; Xiao, L. H.; Wang, Q.; Hu, Y. Y.; Zhang, S. S.; Han, R. P. Adsorption of malachite green dye from solution by magnetic activated carbon in batch mode. Desalin. Water. Treat. 2018, 106, 273−284. (20) Gautam, R. K.; Mudhoo, A.; Chattopadhyaya, M. C. Kinetic, equilibrium, thermodynamic studies and spectroscopic analysis of Alizarin Red S removal by mustard husk. J. Environ. Chem. Eng. 2013, 1, 1283−1291.

(21) Celekli, A.; Birecikligil, S. S.; Geyik, F.; Bozkurt, H. Prediction of removal efficiency of Lanaset Red G on walnut husk using artificial neural network mode. Bioresour. Technol. 2012, 103, 64−70. (22) Liu, R. C.; Zhang, B.; Mei, D. D.; Zhang, H. Q.; Liu, J. D. Adsorption of methyl violet from aqueous solution by halloysite nanotubes. Desalination 2011, 268, 111−116. (23) Hanafiah, M. A. K. M.; Ngah, W. S. W.; Zolkafly, S. H.; Teong, L. C.; Majid, Z. A. A. Acid Blue 25 adsorption on base treated Shorea dasyphylla sawdust: Kinetic, isotherm, thermodynamic and spectroscopic analysis. J. Environ. Sci. 2012, 24, 261−268. (24) Aksu, S. Determination of the equilibrium, kinetic and thermodynamic parameters of the batch biosorption of nickel(II) ions onto Chlorella vulgaris. Process Biochem. 2002, 38, 89−99. (25) Redlich, O.; Peterson, D. L. A useful adsorption isotherm. J. Phys. Chem. 1959, 63, 1024. (26) Asfaram, A.; Ghaedi, M.; Hajati, S.; Goudarzi, A. Ternary dye adsorption onto MnO2 nanoparticle-loaded activated carbon: derivative spectrophotometry and modeling. RSC Adv. 2015, 5, 72300−72320. (27) Asfaram, A.; Ghaedi, M.; Hajati, S.; Goudarzi, A.; Bazrafshan, A. A. Simultaneous ultrasound-assisted ternary adsorption of dyes onto copper-doped zinc sulfide nanoparticles loaded on activated carbon: optimization by response surface methodology. Spectrochim. Acta, Part A 2015, 145, 203−212. (28) Wu, Y. J.; Zhang, L. J.; Gao, C. L.; Ma, J. Y.; Ma, X. H.; Han, R. P. Adsorption of copper ions and Methylene Blue in a single and binary system on wheat straw. J. Chem. Eng. Data 2009, 54, 3229− 3234. (29) Zhang, R. D.; Zhang, J. H.; Zhang, X. N.; Dou, C. C.; Han, R. P. Adsorption of Congo red from aqueous solutions using cationic surfactant modified wheat straw in batch mode: Kinetic and equilibrium study. J. Taiwan Inst. Chem. Eng. 2014, 45, 2578−2583. (30) Fan, H.; Chen, P. H.; Wang, C. Z.; Wei, Y. M. Zirconiumdoped magnetic microspheres for the selective enrichment of cis-diolcontaining ribonucleosides. J. Chromatogr. A 2016, 1448, 20−31. (31) Albadarin, A.B.; Mangwandi, C. Mechanisms of Alizarin Red S and Methylene blue biosorption onto olive stone by-product: Isotherm study in single and binary systems. J. Environ. Manage. 2015, 164, 86−93. (32) Li, D. L.; Liu, Q.; Ma, S. L.; Chang, Z. X.; Zhang, L. Adsorption of Alizarin Red S onto nano-sized Silica modified with γ-aminopropyltriethoxysilane. Adsorpt. Sci. Technol. 2011, 29, 289−300. (33) Fan, L. L.; Zhang, Y.; Li, X. J.; Luo, C. N.; Lu, F. G.; Qiu, H. M. Removal of alizarin red from water environment using magnetic chitosan with Alizarin Red as imprinted molecules. Colloids Surf., B 2012, 91, 250−257. (34) Roosta, M.; Ghaedi, M.; Mohammadi, M. Removal of Alizarin Red S by gold nanoparticles loaded on activated carbon combined with ultrasound device: Optimization by experimental design methodology. Powder Technol. 2014, 267, 134−144. (35) Li, Y.; Leng, T. H.; Lin, H. Q.; Deng, C. H.; Xu, X. Q.; Yao, N.; Yang, P. Y.; Zhang, X. M. Preparation of Fe3O4@ZrO2 core-Shell microspheres as affinity probes for selective enrichment and direct determination of phosphopeptides using matrix-assisted laser desorption ionization mass spectrometry. J. Proteome Res. 2007, 6, 4498−4510. (36) Han, R. P.; Wang, Y.; Sun, Q.; Wang, L. L.; Song, J. Y.; He, X. T.; Dou, C. C. Malachite green adsorption onto natural zeolite and reuse by microwave irradiation. J. Hazard. Mater. 2010, 175, 1056− 1061. (37) Zhao, B. L.; Xiao, W.; Shang, Y.; Zhu, H. M.; Han, R. P. Adsorption of light green anionic dye using cationic surfactantmodified peanut husk in batch mode. Arabian J. Chem. 2017, 10, s3595−s3602.

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Selective and Efficient Removal of Anionic Dyes from Solution by

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