Adsorption of Hexavalent Chromium from an Aqueous Phase by

Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Adsorption of Hexavalent Chromium from an Aqueous Phase by Hydroxypropyl Methylcellulose Modified with Diethylenetriamine Haihong Huang, Deliang He,* Yining Tang, Yanni Guo, Ping Li, Wei Qv, Fan Deng, and Fuhui Lu

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College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China ABSTRACT: Modified hydroxypropyl methylcellulose was synthesized by hydroxypropyl methylcellulose (HPMC), epichlorohydrin, dimethylformamide (DMF) and diethylenetriamine. The chemical functional groups and morphology of the modified hydroxypropyl methylcellulose (MHPMC) were characterized by the Fourier transform infrared spectroscopy, and scanning electronic microscopy, and the crystal structure of MHPMC was studied by X-ray diffraction analyzer. Additionally, the element composition of the adsorbent was analyzed by the energy dispersive spectrometer, and the factors affecting the adsorption performance, such as time (15−240 min), the amount of adsorbent (0.1−0.8 g), initial concentration of ions (30−350 mg·L−1) and pH (4−7.5) were estimated. Results from the experimental data showed, under the optimum experimental parameters condition like adsorption time (110 min), adsorption quantity (0.4 g), initial ion concentration (100 mg·L−1), and pH (5.5), the adsorption removal rate reached 99.78%. In addition, the adsorption process is well consistent with the quasi-two-stage kinetic model and the Langmuir model, and the negative value of ΔG and the positive value of ΔH denote that the adsorption process of hexavalent chromium loaded on the MHPMC is endothermic and spontaneous. with heavy metal ions better.17−21 Thus, for the improvement of the adsorption capacity for cellulose material to adsorb heavy metal ions, chemically modified cellulose has been deeply explored by researchers. The amino group is an excellent ligand, which has a strong affinity with heavy metal ions due to Lewis acid−base interaction.22−24 Hydroxypropyl methylcellulose (HPMC), as a cellulose derivative material, was chosen as a raw material because of the hydroxyl groups on the surface and the low-cost. Few studies reported the new adsorbent obtained from the modified hydroxypropyl methylcellulose (MHPMC) for adsorbing hexavalent chromium. Therefore, the purpose of this article was to research the feasibility of removing toxic heavy metals by using the new adsorbent above. In this work, the MHPMC was obtained as a result of the HPMC modified with diethylenetriamine, and the factors affecting the adsorption experiment were utilized to find the maximum adsorption removal rate. Furthermore, the kinetics, isotherms, and thermodynamics in the adsorption process have been deeply studied for the sake of investigating the adsorption mechanism.

1. INTRODUCTION Hexavalent chromium, as an extremely toxic inhalant, is easily absorbed by the human body and causes kidney and liver damage, and it has a carcinogenic effect in the human body. There are three common valence states of chromium, namely Cr(II), Cr(III), and Cr(VI), which exist in the form of oxidation states in nature.1 In industrial wastewater, hexavalent chromium compounds (CrO42− and Cr2O72−) are more toxic, compared to the other oxidation states. Chromium contamination generally results from poor quality cosmetic raw materials, leather preparations, industrial dyes, electroplating and so on.2 Therefore, to solve the problem, various technologies were used to reduce the effect of hexavalent chromium on human life by decreasing the concentration, such as precipitation,3 adsorption,4,5 ion-exchange,6 membrane separation,7 filtration,8 chemical oxidation,9 electrochemistry,10 chelation, and reverse osmosis,11,12 etc. In these technologies, most of the methods require complex processes and expensive costs. However, adsorption, whether it is chemical adsorption or physical adsorption, is an undoubtedly simple and effective way to deal with heavy metal ions compared with other methods.13 Therefore, adsorption is a general choice to reduce heavy metal pollution. After years of research, researchers have found a wide variety of adsorbents and plenty of studies have been explored in cellulosic materials, especially in agricultural residues, such as straw, loquat skin, peanut shells, and bagasse, etc.14−16 Nevertheless, compared to the natural cellulose material, the modified cellulose containing the functional groups of hydroxyl group, carboxyl, amino group, and amide group can chelate © XXXX American Chemical Society

2. EXPERIMENTAL SECTION 2.1. Reagents and Instruments. Hydroxypropyl methylcellulose (HPMC) was purchased from Shijiazhuang NottingReceived: July 15, 2018 Accepted: November 28, 2018

A

DOI: 10.1021/acs.jced.8b00607 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

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ham Trading Co., Ltd. (Hebei, China). Potassium dichromate, epichlorohydrin, diethylenetriamine, and dimethylformamide (DMF) were obtained from the National Drug Group Chemical Reagents Co., Ltd. (Beijing, China). SHY-2A water bath constant temperature oscillator (Union Instrument Institute, Jiangsu) and PHS-3C acidometer (Yi Tian Precision Instrument Co., Ltd., Shanghai) were used. The UV-8100 ultraviolet spectrophotometer (Ling Yu Technology Co., Ltd., Beijing) was applied to determine the residual concentration of metal ions. The TENSOR27 Fourier infrared spectrometer (Brooke Company, Germany) and FEI Qu ANTA 200 scanning electron microscope (Czech, Czech) and Inca X-Max50 energy dispersive spectrometer (Oxford instrument Technology Co., Ltd., Shanghai) and X-ray diffraction analyzer (Rigaku, Japan) were utilized to characterize the new adsorbent. 2.2. Preparation of the New Adsorbent MHPMC. The HPMC was aminated with epichlorohydrin as the etherifying agent and diethylenetriamine as the cross-linking agent. The preparation process is as follows: 1 g of HPMC, 6 mL of epichlorohydrin, and 12 mL dimethylformamide were mixed in a flask with three necks and refluxed for 80 min at 100 °C, then 6 mL of diethylenetriamine was dripped into the flasks above at a rate of two drops per second, and after the reaction of 40 min, the yellow solid was obtained by washing with the absolute ethyl alcohol and distilled water for 2 to 3 times, respectively. Finally, the product was put into a vacuum drying oven and dried at 60 °C for 14 h to get the new adsorbent, MHPMC. The preparation process is shown in Figure 1.

detected by the energy dispersive spectrometer (EDS), and the surface functional groups of adsorbents were traced by Fourier infrared spectrometer (FT-IR). The X-ray diffraction analyzer (XRD) was applied to study the crystal structure of MHPMC and the ultraviolet spectrophotometer was utilized to determine the filtrate concentration of hexavalent chromium. The pH value corresponding to zero charge point (pHZPC) was used to evaluate the surface charge of the adsorbent. 2.4. Adsorption Studies. The experiments were performed in the tapered bottle at a pH value 6.0 by mixing 0.5 g of adsorbent with 100 mL of 100 mg·L−1 hexavalent chromium prepared from potassium dichromate solution and oscillated in the constant temperature water bath oscillator at a speed of 120 shakes min−1 at 293 K for 60 min in succession. Then the filtrate obtained was utilized to analyze the residual ion concentration by ultraviolet spectrometer at the wavelength of 540 nm as a result of the formation of the fuchsia compounds between hexavalent chromium and 1,5-diphenylcarbazide in an acid solution.25 Experimental operating parameters of time (15−240 min), amount of adsorbent (0.1−0.8 g), initial ion concentration (30−350 mg·L−1), pH (4−7.5), and temperature (293−323 K) were explored respectively, from which we can find the optimal adsorption. Equation 1 describes the loading capacity of the adsorption material, and eq 2 represents the removal rate of adsorbents.26 Q=

(C0 − Ce)V m

η% =

C0 − Ct 100 C0

(1)

(2)

where V (mL) indicates the volume of chromium ions solution, Ce and C0 (mg·L−1) demonstrate the concentration at equilibrium and initial concentration of chromium ions, respectively, m (g) refers to the adsorbent quality, Q (mg·g−1) represents the loading capacity of adsorbent, η (%) refers to the removal rate.

3. RESULTS AND DISCUSSION 3.1. Adsorption Material Characterization. 3.1.1. Morphological Features. The surface morphology of HPMC, MHPMC, and MHPMC loaded chromium were observed by the scanning electron microscope (SEM). It was found that the HPMC white powder displayed a smooth and compact cellulose tube structure in Figure 2a, while the MHPMC, a

Figure 1. Preparation schematic of MHPMC.

2.3. Adsorbent Characterization. The morphological of the HPMC and MHPMC were imaged by scanning electronic microscopy (SEM), the surface element of MHPMC was

Figure 2. SEM pictures of (a) HPMC, (b) MHPMC, and (c) MHPMC-loaded chromium. B



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Figure 3. EDS pictures of (a) MHPMC and (b) MHPMC-loaded chromium.

yellow solid, showed holes and folds in Figure 2b. A comparison of the two images shows that the change of morphology before and after modification is significant. Moreover, as shown in the Figure 2c, the modified adsorbent MHPMC after metal uptake presents a rougher surface. Generally, the wrinkle and rough morphology is conducive to the enhancement of adsorption capacity. 3.1.2. EDS and XRD Analysis of the HPMC and MHPMC. EDS is the useful method for detecting the elemental composition characteristics of materials. The EDS spectra of the modified adsorbent (MHPMC) is shown in Figure 3a. As demonstrated by the image, the modified adsorbent has an additional peak of N element compared to the raw material hydroxypropyl methylcellulose (HPMC), which reveals that the amino groups were successfully introduced. Moreover, as Figure 3b shows, the Cr(VI) signal appears in the EDS spectrum of the modified adsorbent MHPMC, indicating that Cr(VI) has been adsorbed on the adsorbent onto the modified adsorbent (MHPMC). The crystal structure of HPMC and MHPMC was examined by the X-ray diffraction analyzer. As Figure 4 shows, the patterns of the two XRD curves are very similar. The crystalline peaks of the HPMC exhibited at approximately 10.322°, 20.344°, and 36.423°. By contrast, the modified HPMC does

not show any reflection except the diffraction peaks at 21.425° and 37.577°, which signifies that the changes have taken placed in the crystal structure of the modified HPMC. Moreover, the intensity of the diffraction peak at 21.425° was decreased and widened, which enables us to state that the surface modification decreased the crystallinity of the HPMC and the chemical reaction is mainly implemented in the amorphous region. 3.1.3. Chemical Structure. It was observed that the infrared spectroscopy could be used to detect the surface functional groups of the adsorbent.27 Therefore, as Figure 5 shows, the

Figure 5. FTIR spectra of (a) HPMC, (b) MHPMC, and (c) MHPMC-loaded chromium.

functional groups of HPMC, MHPMC, and MHPMC-loaded Cr (VI) were characterized by the Fourier infrared spectrometer (FT-IR). The information conveyed from the diagram indicates that three infrared bands of MHPMC and HPMC both appear at 1643, 1452, and 1381 cm−1, but the band of MHPMC is stronger than that of HPMC. There is a large and broad band between 3700 and 3000 cm−1 in Figure 5b, which denotes that the amino and hydroxyl groups may be contained in the modified material,28 but a new band near 1096 cm−1 due to the C−N stretching and the stronger N−H

Figure 4. X-ray diffraction spectra of HPMC and the MHPMC. C



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deformation vibration around 1643 cm−1 ascertained the existence of amino groups. Besides, bands at 2902, 2966, 2824, 1452, and 1381 cm−1 in Figure 5a,b are considered to be the characteristic bands of saturated C−H vibration. Furthermore, after Cr(VI) adsorption, as depicted in Figure 5c, the strength of the O−H stretching vibration band of the chromium-loaded sample material is decreased, and its band position is redshifted from 3369 to 3387 cm−1, which can be assigned to complexation. In addition, the significant decreases in N−H deformation vibration peak’s intensity at 1655 cm−1 red-shifted to 1643 cm−1, suggesting that the amino group was involved in the adsorption process. A new band at 788 cm−1 in the IR spectrum of MHPMC-loaded chromium can be assigned to the Cr−O bond, indicating that Cr (VI) is adsorbed.29 On the basis of the above analysis, the amino groups have been successfully introduced into the modified cellulose material MHPMC and the adsorption of chromium was promoted to a large extent by the amino group and hydroxyl group due to the surface complexation, which is consistent with the result obtained from the elemental analysis. 3.1.4. The Zero Point Charge pH (pHZPC) Analysis. The pHzpc value plays a very important role in adsorption materials, which determines the net electric neutral pH value on the surface of the adsorbent.27,28 Generally, satisfying the pH < pHzpc inequality, the adsorbent surface is positively charged, which is favorable to the adsorption of the negatively charged chromium complex anions as a result of electrostatic attraction. On the contrary, at greater pH values (pH > pHzpc), the surface of the adsorbent is negative, which leads to a decrease in the adsorption of chromium anions by the adsorbent as a result of electrostatic repulsion. Figure 6 shows the zero point charge pH (pHzpc) curve of this new adsorbent, which displays that the pHzpc value of the new adsorbent is about 6.5.

Figure 7. Effect of shaking time on the removal rate for adsorbing Cr(VI).

surface of MHPMC; however, the adsorption rate slowed down until the platform of adsorption was reached due to the reduction of effective adsorption sites. It can be concluded from the diagram that the maximum adsorption removal rate occurs at the optimal time of 110 min which can be selected for the further experiments. 3.3. Effect of the Amount of MHPMC. The dosage of adsorbent exerts a significant impact on the adsorption efficiency for absorbing hexavalent chromium ions, and the proper adsorbent quantity is good for augmenting the adsorption sites for metal binding. Figure 8 displays the

Figure 8. Effect of the amount of MHPMC on removal rate for adsorbing Cr(VI). Figure 6. Curve of the zero charge point pH (pHZPC).

influence of new adsorbent on the removal rate of hexavalent chromium ions at different adsorption doses. The results denoted that the removal efficiency of chromium increased as the increases of adsorbent quantity during the initial stage (0.1−0.4 g), implying that an increase in the dosage of adsorbent may cause the increases in the adsorption sites and contact area. However, overlapping and aggregation of adsorbents for absorbing the hexavalent chromium may decrease the number of adsorption sites, hence, there is no significant increase in the adsorption rate when the amount of

3.2. Effect of Shaking Time. Shaking time plays a vital role in the process of heavy metal ion adsorption. Experiments were implemented to explore the effect of time on the adsorption of hexavalent chromium ions. As shown in Figure 7, It is apparent that the removal rate and adsorption capacity of Cr(VI) increase as the contact time increases. The adsorbent adsorbed hexavalent chromium at a fast rate in the initial adsorption stage because of the vacant adsorptive sites on the D



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this adsorption experiment is 5.5, which reveals that the adsorption removal rate of hexavalent chromium is nonnegligible at low pH value. The high adsorption removal rate at pH lower than pHzpc (6.5 for the MHPMC) can be assigned to the electrostatic attraction between negatively charged chromium anions and the amino protonation surface of the adsorbent, and the removal rate drops sharply when the pH increases from 6.5 to 7.5 as shown in the plot. This occurs because of the deprotonation of the functional amino groups at pH values greater than pHzpc as a result of an increase in the negative charge on the surface of the adsorbent thereby restraining the binding with hexavalent chromium which exists as anions in solution. 3.6. Adsorption Kinetics Model. The adsorption kinetic models were quoted to describe the adsorption rate and the adsorption mechanism of metal ions absorbed on the solid absorbent.32 The kinetic study of hexavalent chromium under the initial concentration of 100 mg/L was performed at different contact times (15−240 min). There are two dynamic models, eq 3 and eq 4, for describing the dynamic process of hexavalent chromium absorbed on the MHPMC. These are the quasi-primary dynamic and the quasi-secondary dynamic model, respectively.

adsorbent exceeds 0.4 g which is selected as the best adsorbent quantity in the subsequent experiments. 3.4. Effect of Initial Concentration. The optimal adsorbent dosage 0.4 g and the optimal time 110 min were used to adsorb different initial concentrations of hexavalent chromium ions. Figure 9 denotes the effect of initial chromium

Figure 9. Effect of initial concentration on removal rate for adsorbing Cr(VI)

ln(Q e − Q t ) = lnQ e − kt

(3)

t 1 t = + Qt Qe mQ e 2

(4)

−1

where Qt (mg·g ) indicates the adsorption capacity at time t and Qe (mg·g−1) denotes the equilibrium adsorption capacity; k (min−1) represents the quasi-primary dynamic rate constant, and m (mg·g−1·min−1) is quasi-secondary dynamic rate constant. Table 1 provides the value of R12 (0.8648), which suggests that the quasi-primary dynamic model is not in good accordance with the adsorption process. Therefore, the quasi-secondary dynamic model was introduced.33 The relationship of t/Qt to t is shown in Figure 11, which shows that the linear correlation coefficient of quasi-secondary dynamic model R22 (0.9994) is greater than R12 (0.8648). Furthermore, as Table 1 shows, the theoretical equilibrium adsorption capacity of hexavalent chromium calculated by the quasi-secondary dynamic model conforms to the adsorption capacity from the experiment, implying that the kinetic data coincides well with the quasi-secondary dynamic model, and the adsorption mechanism of hexavalent chromium on the modified adsorbent mainly occurred through chemical adsorption. 3.7. Adsorption Isotherms Model. The adsorption isotherms of hexavalent chromium ions on the modified adsorbent MHPMC were studied in the temperature range of 298 to 328 K at different initial hexavalent chromium ion concentrations (50−1200 mg/L) as shown in Figure 12. It was observed from the figure that the loading capacity of the adsorbent MHPMC increases in pace with the increase of equilibrium concentration until the platform of adsorption was reached, and the higher is the temperature, the greater is the adsorbent capacity within the scope of the experimental conditions. The adsorption process can be described by the following isotherm models. The Freundlich and the Langmuir isotherm were investigated to fit the isotherm data of heavy metal ions on the solid absorbent.34 The following two eqs 5 and 6 represent the two above models in turn.

solution concentration on the removal efficiency of hexavalent chromium. It was found that the removal rate of hexavalent chromium decreased with the increase of initial concentration, revealing that the decline of the removal rate is due to the steady of adsorbent dosage which cannot afford the increased ions concentration.30 Therefore, we can conclude that it is necessary to select a suitable concentration of the target pollutants so as to improve the removal efficiency. 3.5. Effect of pH. pH is a significant factor that needs to be studied in the process of adsorption.31 Figure 10 displays the effect of different pH values on the removal of hexavalent chromium by the MHPMC, and the appropriate pH value for

Figure 10. Effect of pH on removal rate of for adsorbing Cr(VI). E



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Table 1. Fitting Kinetics Parameters for Absorbing Hexavalent Chromium on the MHPMC quasi-primary dynamic

quasi-secondary dynamic

metal ion

Qe,exp (mg·g−1)

k (min−1)

Qe,cal (mg·g−1)

R12

m (mg·g−1·min−1)

Qe,cal (mg·g−1)

R22

Cr(VI)

24.95

0.0386

1.02

0.8648

0.0265

25.17

0.9994

Ce Ce 1 = + Qe Q maxb Q max

(6)

where KF and n denote the constant of Freundlich isotherm. Qe (mg·g−1) demonstrates the loading capacity of MHPMC at equilibrium, and Ce (mg·L−1) indicates the equilibrium concentration of hexavalent chromium ions. Qmax (mg·g−1) represents maximum adsorption capacity of MHPMC, and b indicates the Langmuir adsorption constant. The isotherms parameters shown in Table 2 were obtained from the equations above, and the isotherm data have a better fitting effect on the model of the Langmuir isotherm, compared to the Freundlich isotherm since the linear correlation coefficient RL2 is higher than RF2. The relationship of Ce/Qe to Ce is plotted to get the linear relationship as shown in Figure 13, where it is more obvious that the adsorption

Figure 11. Quasi-secondary dynamic model curve for Cr(VI) adsorption.

Figure 13. The Langmuir isotherm curve for Cr(VI).

process followed the Langmuir isotherm. The maximum loading capacity of the adsorbent MHPMC estimated by the Langmuir model reached 294.118 mg/g at 328 K and the intensity of the adsorption reaction can be reflected by the value of n.35 Generally, it is accepted that the adsorption conditions are favorable when n is greater than 1 and less than 10 thereby the conditions for the adsorption process discussed above are suitable because the value of n is greater than 1.36 Furthermore, the Langmuir isotherm model is applied to the

Figure 12. Adsorption isotherms of Cr(VI) at 298, 308, 318, and 328 K.

lnQ e = ln KF +

1 ln Ce n

(5)

Table 2. Fitting Isotherms Parameters for Absorbing Hexavalent Chromium on the MHPMC Langmuir isotherm metal ion Cr(VI)

T (K) 298 308 318 328

K K K K

Freundlich isotherm

b (L·mg−1)

Qmax (mg·g−1)

RL2

KF (mg·g−1)

n

RF2

0.0597 0.0407 0.0512 0.0654

187.27 253.17 273.97 294.12

0.9915 0.9853 0.9901 0.9956

35.2731 45.5686 34.5532 51.3364

3.06 3.13 2.45 2.86

0.9704 0.9850 0.9352 0.9221

F



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homogeneous adsorption and the monolayer adsorption layer, combining with the result of the kinetic studies, indicating that the adsorption mechanism of the new adsorbent is mainly dominated by the monolayer chemisorption. 3.8. Adsorption Thermodynamics. The effect of temperature on the adsorption process was studied by using the adsorption experiments at different temperatures.37−40 In this work, the batch thermodynamic experiments were studied between 298 and 328 K, and the following equations can be utilized to compute the thermodynamic parameters for adsorbing hexavalent chromium ions.

Kd =

Table 3. Thermodynamic Parameters for Absorbing Hexavalent Chromium on the MHPMC metal ion Cr(VI)

ln Kd =

−ΔH ΔS + RT R

ΔG = ΔH − T ΔS

298 308 318 328

K K K K

ΔG (kJ·mol−1)

ΔH (kJ·mol−1)

ΔS (J·mol−1·K−1)

R2

−0.468 −1.6671 −2.8671 −4.0671

35.292

120.0049

0.9926

3.9. Exploration of Adsorption Mechanism. The physical and chemical properties of MHPMC and the adsorption behavior of Cr(VI) were studied in this paper, and in order to explore the adsorption mechanism, the kinetic model and the isotherm model were deeply discussed. From the results of SEM-EDS and FT-IR, we can infer that the adsorption of chromium on the adsorbent surface is due to the complexation and electrostatic attraction.25 In addition, the adsorption process is in accordance with the quasi-secondorder kinetics, which implies that the adsorption of Cr(VI) by MHPMC is mainly controlled by chemisorption, which is consistent with the results obtained by the characterization.

Q ads Ce

T (K)

(7) (8) (9)

where Ce (mg·L−1) denotes the equilibrium concentration of hexavalent chromium ions. Kd represents the equilibrium constant and Qads (mg·g−1) is the loading capacity of MHPMC at equilibrium. R (J·mol−1·K−1) indicates the molar gas constant, and the values of ΔG (kJ·mol−1), ΔH (kJ·mol−1) and ΔS (J·mol−1·K−1) demonstrate the change of Gibbs free energy, enthalpy, and entropy, respectively. Figure 14 shows that the linear correlation coefficient of the thermodynamic adsorption process is 0.9926, indicating that

4. DESORPTION STUDY To further study the adsorption performance of the modified adsorbent MHPMC, the desorption experiments were carried out. The experimental process is as follows: 0.4 g of Cr(VI)loaded MHPMC mixed with 100 mL of 1 M NaOH in a 250 mL tapered bottle at a speed of 120 shakes min−1 at 293 K for 4 h. The mixture was filtered to obtain a filter residue, which was thoroughly washed by distilled water, and further introduced into the next desorption cycle. The desorption efficiency is calculated by the following equation: C2 η% = × 100 C0 − C1 (10) where η (%) indicates the desorption efficiency, C2 (mg·L−1) demonstrates desorption concentration of chromium, C1 and C0 represent the concentration at equilibrium and initial concentration of chromium ions, respectively. As shown in Figure 15, the desorption rate decreases with the increase of desorption cycles. After four cycles, the desorption efficiency η (%) can still reach more than 75%, which indicates that the adsorbent can be used repeatedly to remove chromium ions in aqueous solution. 4.1. Comparison with Different Adsorbents on the Removal Rate. In previous research, various adsorbents have been deeply discussed by the researchers. Table 4 shows the removal rate of different adsorbents. It was found that the adsorption removal rate of hexavalent chromium by the new adsorbent MHPMC is much higher when the concentration of hexavalent chromium reaches 100 mg/L, which reveals that the present work is of great significance for the treatment of hexavalent chromium in aqueous solution.

Figure 14. Thermodynamic model for absorbing Cr(VI) on the MHPMC.

the experimental data agree well with the thermodynamic adsorption model curve. Therefore, it is possible to evaluate the values of ΔG, ΔS, and ΔH through the linear relationship. The thermodynamic parameters (ΔG, ΔS, and ΔH) for absorbing hexavalent chromium were listed in Table 3. The negative value of ΔG indicates that the adsorption process of hexavalent chromium onto the MHPMC is spontaneous, and the positive values of ΔH and ΔS calculated by the slope and intercept of the plot (Figure 14) imply that the adsorption process of hexavalent chromium loaded on the modified adsorbent MHPMC is endothermic and irreversible.

5. CONCLUSION The new adsorbent MHPMC was studied in depth for the prominent adsorption capacity on hexavalent chromium. From the experimental results, it was found that the adsorption process of MHPMC for hexavalent chromium can be described well by the quasi-secondary dynamic model and the Langmuir model, indicating that the adsorption of hexavalent chromium by MHPMC is mainly controlled by chemisorption. G



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(3) Peng, H.; Guo, J.; Li, B.; Liu, Z.; Tao, C. High-efficient recovery of chromium (VI) with lead sulfate. J. Taiwan Inst. Chem. Eng. 2018, 85, 149−154. (4) Dong, L.; Jin, Y.; Song, T.; Liang, J.; Bai, X.; Yu, S.; Teng, C.; Wang, X.; Qu, J.; Huang, X. Removal of Cr(VI) by surfactant modified auricularia auricula spent substrate: biosorption condition and mechanism. Environ. Sci. Pollut. Res. 2017, 24, 17626−17641. (5) Yiğitoğlu, M.; Arslan, M. Adsorption of hexavalent chromium from aqueous solutions using 4-vinyl pyridine grafted poly (ethylene terephthalate) fibers. Polym. Bull. 2005, 55, 259−268. (6) Korak, J. A.; Huggins, R.; Arias-Paic, M. Regeneration of pilotscale ion exchange columns for hexavalent chromium removal. Water Res. 2017, 118, 141−151. (7) Saucedo-Rivalcoba, V.; Martínez-Hernández, A. L.; MartínezBarrera, G.; Velasco-Santos, C.; Rivera-Armenta, J. L.; Castaño, V. M. Removal of hexavalent chromium from water by polyurethane− keratin hybrid membranes. Water, Air, Soil Pollut. 2011, 218, 557− 571. (8) Desai, K.; Kit, K.; Li, J.; Davidson, P. M.; Zivanovic, S.; Meyer, H. Nanofibrous chitosan non-wovens for filtration applications. Polymer 2009, 50, 3661−3669. (9) Cheng, Q.; Wang, C.; Doudrick, K.; Chan, C. K. Hexavalent chromium removal using metal oxide photocatalysts. Appl. Catal., B 2015, 176, 740−748. (10) Li, D.; Sun, D.; Hu, S.; Hu, J.; Yuan, X. Conceptual design and experiments of electrochemistry-flushing technology for the remediation of historicall Cr(VI)-contaminated soil. Chemosphere 2016, 144, 1823−1830. (11) Dwivedi, A. D.; Permana, R.; Singh, J. P.; Yoon, H.; Chae, K. H.; Chang, Y. S.; Hwang, D. S. Tunichrome mimetic matrix, its perspective in abatement for carcinogenic hexavalent chromium and specific coordination behavior. Chem. Eng. J. 2017, 328, 629−638. (12) Bajpai, S.; Jha, M. K.; Gupta, S. K.; Gupta, A. Removal of hazardous hexavalent chromium from aqueous solution using divinylbenzene copolymer resin. Int. J. Environ. Sci. Technol. 2012, 9, 683−690. (13) Mahmoodulhassan, M.; Suthar, V.; Rafique, E.; Ahmad, R.; Yasin, M. Kinetics of cadmium, chromium, and lead sorption onto chemically modified sugarcane bagasse and wheat straw. Environ. Monit. Assess. 2015, 187, 1−11. (14) Ji, Z.; Feng, C.; Wu, X.; Li, Y.; Li, L.; Liu, X. Composite of biomass and lead resistent Aspergillus oryzae for highly efficient aqueous phase Pb(II) adsorption. Environ. Prog. Sustainable Energy 2017, 36, 1658−1666. (15) Zhong, L. X.; Peng, X. W.; Yang, D.; Sun, R. C. Adsorption of heavy metals by a porous bioadsorbent from lignocellulosic biomass reconstructed in an ionic liquid. J. Agric. Food Chem. 2012, 60, 5621− 5628. (16) Peng, X. W.; Zhong, L. X.; Ren, J. L.; Sun, R. C. Highly effective adsorption of heavy metal ions from aqueous solutions by macroporous xylan-rich hemicelluloses-based hydrogel. J. Agric. Food Chem. 2012, 60, 3909−3916. (17) Mahmoodulhassan, M.; Suthor, V.; Rafique, E.; Yasin, M. Removal of Cd, Cr, and Pb from aqueous solution by unmodified and modified agricultural wastes. Environ. Monit. Assess. 2015, 187, 1−8. (18) Deng, J.; Liu, Y.; Liu, S.; Zeng, G.; Tan, X.; Huang, B.; Tang, X.; Wang, S.; Hua, Q.; Yan, Z. Competitive adsorption of Pb(II), Cd(II) and Cu(II) onto chitosan-pyromellitic dianhydride modified biochar. J. Colloid Interface Sci. 2017, 506, 355−364. (19) Sun, C.; Ni, J. D.; Zhao, C. Z.; Du, J. M.; Zhou, C. G.; Wang, S. G.; Xu, C. H. Preparation of a cellulosic adsorbent by functionalization with pyridone diacid for removal of Pb(II) and Co(II) from aqueous solutions. Cellulose 2017, 24, 5615−5624. (20) He, S.; Zhang, F.; Cheng, S.; Wang, W. Synthesis of Sodium Acrylate and Acrylamide Copolymer/GO Hydrogels and Their Effective Adsorption for Pb2+ and Cd2+. ACS Sustainable Chem. Eng. 2016, 4, 3948−3959. (21) Thirumavalavan, M.; Lai, Y. L.; Lee, J. F. Fourier transform infrared spectroscopic analysis of fruit peels before and after the

Figure 15. Desorption study of Cr(VI) by MHPMC.

Table 4. Comparison of Hexavalent Chromium Removal Rate with Different Adsorbents metal ion Cr(VI)

adsorbent oleaster seed biochar and cherry stone biochar modified wheat bran sorghum stem powder MHPMC

removal rate (%) 84.2% and 81.3% 90% 63.75% 99.78%

ref 41 42 43 present work

Furthermore, the thermodynamic study in this adsorption process provides the inequality ΔG < 0 and the positive value of ΔH, denoting that the adsorption of hexavalent chromium by the new adsorbent is endothermic and spontaneous. Additionally, the MHPMC has an excellent adsorption capacity for hexavalent chromium compared with other adsorbents, indicating that it is a promising adsorbent for future application.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel: 0731-88822286. ORCID

Haihong Huang: 0000-0002-1149-1576 Funding

The work was supported by College of Chemistry and Chemical Engineering, Hunan University, Changsha City, China. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Pourfadakari, S.; Jorfi, S.; Ahmadi, M.; Takdastan, A. Experimental data on adsorption of Cr(VI) from aqueous solution using nanosized cellulose fibers obtained from rice husk. Data in Brief 2017, 15, 887−895. (2) Janik, P.; Zawisza, B.; Talik, E.; Sitko, R. Selective adsorption and determination of hexavalent chromium ions using graphene oxide modified with amino silanes. Microchim. Acta 2018, 185, 117−124. H



Article

adsorption of heavy metal ions from aqueous solution. J. Chem. Eng. Data 2011, 56, 2249−2255. (22) Wang, J.; Dang, M.; Duan, C.; Zhao, W.; Wang, K. Carboxymethylated cellulose fibers as Low-cost and Renewable Adsorbent Materials. Ind. Eng. Chem. Res. 2017, 56, 14940−14948. (23) Wang, S.; Wei, M.; Huang, Y. Biosorption of multifold toxic heavy metal ions from aqueous water onto food residue eggshell membrane functionalized with ammonium thioglycolate. J. Agric. Food Chem. 2013, 61, 4988−4996. (24) Chen, S.; Yue, Q.; Gao, B.; Li, Q.; Xu, X.; Fu, K. Adsorption of hexavalent chromium from aqueous solution by modified corn stalk: a fixed-bed column study. Bioresour. Technol. 2012, 113, 114−120. (25) Dupont, L.; Guillon, E. Removal of hexavalent chromium with a lignocellulosic substrate extracted from wheat bran. Environ. Sci. Technol. 2003, 37, 4235−4241. (26) Shaban, M.; Abukhadra, M. R.; Rabia, M.; Elkader, Y. A.; Mai, E. H. Investigation the adsorption properties of graphene oxide and polyaniline nano/micro structures for efficient removal of toxic Cr (VI) contaminants from aqueous solutions; kinetic and equilibrium studies. Rend. Lincei- Sci. Fis. 2018, 29, 141−154. (27) Lu, Y.; He, D.; Lei, H.; Hu, J.; Huang, H.; Ren, H. Adsorption of Cu (II) and Ni (II) from aqueous solutions by taro stalks chemically modified with diethylenetriamine. Environ. Sci. Pollut. Res. 2018, 25, 17425−17433. (28) Hokkanen, S.; Repo, E.; Suopajärvi, T.; Liimatainen, H.; Niinimaa, J.; Sillanpäa,̈ M. Adsorption of Ni (II), Cu (II) and Cd (II) from aqueous solutions by amino modified nanostructured microfibrillated cellulose. Cellulose 2014, 21, 1471−1487. (29) Singh, V.; Sharma, A. K.; Kumari, P.; Tiwari, S. Efficient chromium (VI) adsorption by Cassia marginata seed gum functionalized with poly(methylmethacrylate) using microwave irradiation. Ind. Eng. Chem. Res. 2008, 47, 5267−5276. (30) Abbas, A.; Hussain, M. A.; Sher, M.; Irfan, M. I.; Tahir, M. N.; Tremel, W.; Hussain, S. Z.; Hussain, I. Design, characterization and evaluation of hydroxyethylcellulose based novel regenerable supersorbent for heavy metal ions uptake and competitive adsorption. Int. J. Biol. Macromol. 2017, 102, 170−180. (31) Kebede, T. G.; Mengistie, A. A.; Dube, S.; Nkambule, T. T.; Nindi, M. M. Study on adsorption of some common metal ions present in industrial effluents by moringa stenopetala seed powder. J. Environ. Chem. Eng. 2018, 6, 1378−1389. (32) Esteves, B.; Cruz-Lopes, L.; Figueirinha, A.; de Lemos, L. T.; Ferreira, J.; Pereira, H.; Domingos, I. Heat-treated wood as chromium adsorption material. Eur. J. Wood. Wood. Prod. 2017, 75, 903−909. (33) Uzaşcı̧ , S.; Tezcan, F.; Erim, F. B. Removal of hexavalent chromium from aqueous solution by barium ion cross-linked alginate beads. Int. J. Environ. Sci. Technol. 2014, 11, 1861−1868. (34) Wang, J.; Yin, X.; Tang, W.; Ma, H. Combined adsorption and reduction of Cr(VI) from aqueous solution on polyaniline/multiwalled carbon nanotubes composite. Korean J. Chem. Eng. 2015, 32, 1889−1895. (35) Sharma, A.; Bhattacharyya, K. G. Adsorption of chromium (VI) on Azadirachta indica, (Neem) leaf powder. Adsorption 2005, 10, 327−338. (36) Ahmad, M.; Manzoor, K.; Ahmad, S.; Ikram, S. Preparation, Kinetics, Thermodynamics, and Mechanism Evaluation of Thiosemicarbazide Modified Green Carboxymethyl Cellulose as an Efficient Cu (II). J. Chem. Eng. Data 2018, 63, 1905−1916. (37) Duran, C.; Ozdes, D.; Gundogdu, A.; Senturk, H. B. Kinetics and isotherm analysis of basic dyes adsorption onto almond shell (Prunus dulcis) as a low cost adsorbent. J. Chem. Eng. Data 2011, 56, 2136−2147. (38) Gao, X.; Zhang, H.; Chen, K.; Zhou, J.; Liu, Q. Removal of heavy metal and sulfate ions by cellulose derivative-based biosorbents. Cellulose 2018, 25, 2531−2545. (39) Huang, D.; Li, B.; Wu, M.; Kuga, S.; Huang, Y. Graphene Oxide-Based Fe−Mg (Hydr)oxide Nanocomposite as Heavy Metals Adsorbent. J. Chem. Eng. Data 2018, 63, 2097−2105.

(40) El-Bahy, S. M. New Iminodiacetate Chelating Resin-Functionalized Fe3O4 Nanoparticles: Synthesis, Characterization, and Application for the Removal of Some Noxious Metal Ions from Wastewater. J. Chem. Eng. Data 2018, 63, 2299−2313. (41) Kahraman, H. T.; Pehlivan, E. Cr6+, removal using oleaster (Elaeagnus) seed and cherry (Prunus avium) stone biochar. Powder Technol. 2017, 306, 61−67. (42) Kaya, K.; Pehlivan, E.; Schmidt, C.; Bahadir, M. Use of modified wheat bran for the removal of chromium (VI) from aqueous solutions. Food Chem. 2014, 158, 112−117. (43) Prasanthi, M. R.; Jayasravanthi, M.; Nadh, R. V. Kinetic, thermodynamic and equilibrium studies on removal of hexavalent chromium from aqueous solutions using agro-waste biomaterials, casuarina equisetifolia L. and sorghum bicolor. Korean J. Chem. Eng. 2016, 33, 1−10.

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Adsorption of Hexavalent Chromium from an Aqueous Phase by

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