Removal of Glyphosate from Aqueous Solution Using Nanosized

Article pubs.acs.org/jced

Removal of Glyphosate from Aqueous Solution Using Nanosized Copper Hydroxide Modified Resin: Equilibrium Isotherms and Kinetics Changyin Zhou,†,‡ Dongmei Jia,*,‡ Min Liu,§ Xuewen Liu,‡ and Changhai Li‡ †

School of Chemical Engineering, Qingdao University of Science & Technology, Qingdao 266042, China School of Chemistry and Chemical Engineering, Binzhou University, Binzhou 256603, China § Department of Chemical Engineering, The University of Melbourne, Melbourne 3010, Australia ‡

S Supporting Information *

ABSTRACT: To remove glyphosate from water, nanosized copper hydroxide modified resin (D201Cu) was synthesized and characterized. The influence of NaCl concentration, temperature, pH, time, humid acid, and fulvic acid on glyphosate adsorption onto D201Cu resins were fully investigated. Glyphosate uptake on D201Cu was 113.7 mg/g in the presence 18% NaCl. The adsorption isotherms and kinetic data fitted well to the Langmuir model and pseudo-second-order model, respectively. In NaOH and NaCl mixed solution, the D201Cu regeneration efficiency can be 90% after five cycles. On the basis of the adsorption results, the schematic diagrams of adsorption mechanism of glyphosate onto D201Cu resins were proposed.

1. INTRODUCTION As one of the most effective and affordable agricultural herbicides, N-(phosphonomethyl) glycine (glyphosate, C3H8NO5P, CAS number 1071-83-6) is widely used in agricultural crops.1,2 Glyphosate is strong polar, water-soluble, and low volatile. It can inhibit the plant enzyme from being involved in the synthesis of the aromatic amino acids.3 Due to the different manufacturing processes and application methods, a significant amount of glyphosate reaches the surface water, groundwater, and soil. Glyphosate can cause widespread and persistent contamination because of its complexation with heavy metals.4 In addition, it has been found that glyphosate can disrupt the digestive, reproductive, and respiratory system and increase health risks.5−7 Moreover, the phosphorus in effluent cannot be higher than 0.5 and 1.0 mg/L as stated in the phosphorus discharge standard of China (GB18918-2002) and EU (Water Framework Directive, 2000), respectively. In drinking water, the presence of glyphosate should be lower than 0.7 mg/L according to the USA National Primary Drinking Water Regulations (NPDWRs). Therefore, it is necessary to develop high efficient ways to remove the glyphosate from water. The conventional methods of removing glyphosate include chemical precipitation,8 advanced oxidation,9−12 membrane separation,13 biodegradation,14,15 and adsorption.16−19 Adsorption is one of the most feasible and environmentally friendly methods due to the advantages of high separation efficiency, economy, and no secondary pollution. Many materials including iron oxide/SBA-15,17 water industrial residual,18 ferric supported active carbon,19 and resins20,21 have been © 2017 American Chemical Society

used as adsorbents to remove glyphosate. However, there are still some disadvantages such as poor salinity resistance, a long adsorption time, and a low adsorption capacity, which limit their applications in glyphosate removal. Consequently, it is still of great importance to prepare efficient adsorbents for glyphosate removal with strong salinity resistance. Macroporous exchange resin such as D201 have been regarded as an excellent adsorbent to remove numerous organic pollutants due to their preferred pore structure, stable framework, and great adsorption capacity.22,23 Nevertheless, resins are not suitable for the removal of glyphosate when plenty of inorganic salts existing owing to low salinity resistance. It is well-known that nanosized copper hydroxides has high specific surface areas and lattice defects. The donor groups, including amine, carboxylate, and phosphonate of glyphosate, can chelate with copper(II). The chelate is extremely stable because of two five-membered chelate rings.24 As a result, a new adsorbent obtained by combining nanosized copper hydroxides on the surface of macroporous exchange resin may present excellent adsorption behavior and high salinity resistance toward glyphosate from aqueous solution. Herein, nanosized copper hydroxide modified D201 resins (D201Cu) were synthesized and employed to remove glyphosate. The main objectives of this study are to (1) characterize the synthesized adsorbent by a series of analytical Received: June 20, 2017 Accepted: August 4, 2017 Published: August 18, 2017 3585

DOI: 10.1021/acs.jced.7b00569 J. Chem. Eng. Data 2017, 62, 3585−3592

Journal of Chemical & Engineering Data

Article

7.0 before reused. All of the experiments were measured in triplicate, and the range of relative errors were from 0.5 to 1.5%. The concentration of glyphosate was determined by highperformance liquid chromatography (HPLC, Waters-2695), and the operation conditions of HPLC were described in ref 25.

methods, (2) investigate the adsorption behavior and salinity resistance of glyphosate by batch experiments, and (3) explore the interaction mechanism of glyphosate adsorption onto D201Cu resins.

2. MATERIALS AND METHODS 2.1. Materials. All of the chemical reagents purchased from Shanghai Reagent Station were analytical grade. Glyphosate (98%) was obtained from Qiaochang Chemistry Corporation in China. The D201 resins were supplied by Nankai Resin Corporation. 2.2. Synthesis of D201Cu Resins. In a typical synthesis of D201Cu resins, CuCl2 (0.03), NaCl (1 M), and HCl (2 M) were mixed in a 250 mL glass beaker and added 3 g of D201 resins afterward. The mixture was immersed in a thermostat for 24 h. Then, the modified resins were filtered and reacted with NaOH (2 M) at 298 K quickly. Finally, the modified resins were washed with ethanol and distilled water. D201Cu resins were obtained after dried at 303 K under vacuum for 24 h. The obtained resins were denoted as D201Cu-L.When adjusting the concentration of CuCl2 (0.07 or 0.2 M), the Cu content of D201Cu resins was changed accordingly. Correspondingly, the modified resins were named as D201Cu-M and D201Cu-H, respectively. The loaded Cu was determined by analyzing the composition of the acid washing solution on atomic absorption spectrophotometer (Thermo). The D201Cu (0.1 g) resin was put into 50 mL of HCl (5 M) and shaken for 48 h. The resulted solution was filtered before analyzing. 2.3. Characterization of the Resins. Fourier transform infrared spectroscopy (FR-IR) of the samples were recorded by a Nicolet 5700 (Thermo) spectrometer using a KBr method. The size and morphology were determined on Hitachi S4800N scanning electron microscopy (SEM) and JEM-1011 transmission electron microscopy (TEM). X-ray powder diffraction (XRD) patterns of all samples were recorded on a D8-advance diffractometer (Bruker) using Cu Kα radiation with an accelerating voltage of 40 kV and a generator current of 40 mA. The surface area, pore diameter distribution, and pore volume of D201Cu resins were measured on a Tristar 3000. Xray photoelectron spectra (XPS) spectral regions were determined with a 220i-XL spectrometer (VGESCALAB). 2.4. Adsorption and Desorption. A portion of 0.1 g of D201Cu resin was mixed with 100 mL of glyphosate aqueous solution at different concentrations in conical flasks. The pH was adjusted by NaOH (1 M). The coexisting ion effect was investigated with sodium chloride, humid acid, and fulvic acid. The flasks were then continuously shaken in a thermostatic oscillator at a desired temperature (288, 303, or 318 K) until the adsorption equilibrium was reached. The equilibrium glyphosate uptakes on the resin qe (mg/g) were determined as qe =

(C0 − Ce)V m

3. RESULTS AND DISCUSSION 3.1. Characterization of D201Cu. The SEM micrograph (Figure 1) revealed that the D201 surface was smooth and it

Figure 1. SEM images of D201, D201Cu-L, D201Cu-M, and D201Cu-H.

possessed superior specific areas. On the contrary, the D201Cu resins presented rough surface due to the loading of copper hydroxide particles with an irregular shape on D201. It enabled adsorbate ions diffused into the pores of D201Cu resins during the adsorption process. Moreover, it also can be seen that copper hydroxide particles are firmly immobilized on the D201 surface. The TEM images (Figure 2) indicated that the copper hydroxide nanoparticles on surface of D201Cu was around 100 nm.

(1) Figure 2. TEM images of D201, D201Cu-L, D201Cu-M, and D201Cu-H.

where Ce (mg/L) is the equilibrium concentration of glyphosate, C0 (mg/L) is the initial concentration, V (L) is the solution volume, and m (g) is the weight of the resin. Desorption experiments were performed by NaOH (1 M) and NaCl (1 M) mixed solution as a desorbent. After the adsorption experiments, the glyphosate loaded D201Cu resin was separated and subsequently added into 50 mL of NaOH and NaCl mixed solution for 3 h. The regenerated D201Cu resin were washed thoroughly with deionized water until a pH

The major properties of the D201 and D201Cu resins were characterized and summarized in Table 1. After modification, the specific surface area and pore size of D201Cu-L, D201CuM, and D201Cu-H were reduced. This may be attributed to the fact that the copper oxide particles partially narrowed the resin pores. 3586



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XPS provides useful information about surface functional groups of D201Cu. Figure 5a showed the Cu 2p, O 1s, N 1s, and C 1s peaks of D201Cu-H resin in the wide scanning spectrum. The peak at 394 eV was referred to the Cu 2p spectrum (Figure 5b). The peaks of Cu 2p1/2 and Cu 2p3/2 appeared at 933.3 and 953.2 eV, confirming the presence of Cu−O.28 The content of copper hydroxide groups in D201CuH indicated that the Cu(OH)2 was enriched on the external surface of the resins. As seen in Figure 5c, the O 1s spectra were divided into two peaks at 531.5 eV (−OH) and 535.6 eV (H2O), respectively,29 suggesting that Cu(OH)2 exist on the surface of D201Cu. The C 1s spectrum exhibits two components at 284.9 and 289.2 eV (Figure 5d). The dominant peak of sp2 CC at 284.9 eV was attributed to the aromatic structure. The small peaks of O−CO at 289.2 eV were assigned to carbon atoms attached to different oxygencontaining moieties.30 3.2. Effect of Coexisting NaCl. In water environment, glyphosate usually coexists with sodium chloride. Therefore, the key work of adsorption technique was to improve the resin selectivity. As shown in Figure 6, there were apparent effects on glyphosate adsorption with the increasing NaCl concentration. When the NaCl concentration increased from 3.0% to 18.0% (wt %), the adsorption capacity of D201Cu resins to glyphosate gradually increased. It was likely caused by the salting-out effect that the solubility of glyphosate decreased with increasing the NaCl concentration.31 With 18% NaCl coexisting, the adsorption capacity of D201Cu-L, D201Cu-M, and D201CuH to glyphosate was 113.7, 132.1, and 142.6 mg/g and had a relative increase of 190.1%, 254.3%, and 290.5% than that of D201, repectively. It meant that D201Cu resins had a better adsorption selectivity than D201. Therefore, D201Cu resins exhibits excellent salinity resistance. This result revealed the fact that glyphosate will be concentrated by the D201Cu resins efficiently in high salinity wastewater. 3.3. Effect of humic acid and fulvic acid. Humic acid (HA) and fulvic acid (FA) as water-soluble substances common in environment have been found to interact with nanomaterials in the environment.32 The HA interacted with nanomaterials may bring the changes in the surface properties and environmental behavior of these nanomaterials, a strong competitive adsorption effect to adsorbate.32,33 The adsorption capacity results of glyphosate onto D201Cu resins in the presence of HA and FA are investigated and presented in Figure 7. As shown in Figure 7, the presence of HA slightly decreased the adsorption capacity of D201Cu resins under the tested conditions. However, the FA effect on glyphosate adsorption was significant. The decrease in adsorption may be the coordination effect between copper and HA (or FA). Compared to HA, FA has a higher polarity, lower aromaticity, smaller molecular weight, more acidic property, and more hydrophilic property.32 The adsorption of glyphosate on D201Cu decreased more in the presence of FA, suggesting FA has a good complex ability with copper on the surface of D201Cu. Therefore, the FA occupied part of the adsorption sites on D201Cu surface and had negligible effects on the adsorption of glyphosate on D201Cu. 3.4. Adsorption Equilibrium Isotherms. Adsorption capacities of glyphosate with different D201Cu resins were shown in Figure 8a. D201Cu resins showed excellent adsorption ability for the glyphosate under a high Cu content. Copper hydroxide adopts a positive surface charge which favors the adsorption of anionic adsorbates.

Table 1. Physical Properties of D201 and D201Cu Resins adsorbent

SSABET (m2/g)

VP (cm3/g)

DDFT (nm)

Cu content (wt %)

D201 D201Cu-L D201Cu-M D201Cu-H

4.69 3.66 4.23 4.50

0.038 0.028 0.029 0.040

320.02 302.35 275.12 304.76

0 0.22 0.48 1.44

Figure 3 showed the FT-IR spectrum of D201, the prepared D201Cu, and glyphosate loaded D201Cu-H (D201Cu-H +

Figure 3. FTIR spectra of D201, D201Cu-L, D201Cu-M, D201Cu-H, and D201Cu-H + glyphosate.

glyphosate). The bands at 3440 and 1370 cm−1 represented the N−H and C−N stretching vibration, respectively. The bands at 1650 and 1530 cm−1 were attributed to the CC stretching vibration of aromatic rings and the asymmetric vibrations of the carboxyl groups, respectively. After glyphosate adsorption, the peak appeared at 1080 cm−1 corresponded to PO vibration from phosphonate group. The bands at 2840 and 560 cm−1 were due to the C−H and Cu−O stretching vibrations.26 As shown in Figure 4, the crystal structures of copper nanoparticles on the surface of D201Cu resins were ascertained using XRD. The XRD result of D201Cu-H confirmed the formation of Cu(OH)2 (Figure 4), which is in good agreement with the reported results.27

Figure 4. XRD patterns of D201, D201Cu-L, D201Cu-M, and D201Cu-H. 3587



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Figure 5. XPS spectra of D201Cu-H, including (a) survey spectrum of D201Cu-H, (b) the surface Cu 2p spectra of D201Cu-H, (c) the surface O 1s spectra of D201Cu-H, and (d) the surface C 1s spectra of D201Cu-H.

D201Cu-M, and D201Cu-H resins are shown in Figure 8b, c, and d. Langmuir and Freundlich isotherms were applied to analyze the adsorption process of glyphosate on D201Cu resins.34,35 The Langmuir isotherm is generally expressed as follows:

qe =

qmax bCe 1 + bCe

(2)

where qmax (mg/g) and b (L/mg) are the maximum adsorption capacity of adsorbent and the Langmuir constant, respectively. The Freundlich isotherm, the empirical model of heterogeneous systems, can be expressed as follows: qe = kCe1/ n

Figure 6. Effect of NaCl on the adsorption of glyphosate by D201 and D201Cu resins at 303 K and initial glyphosate 400 mg/L.

(3)

where k (mg/g) is the Freundlich constant represented an adsorption or distribution coefficient, and n is the constant represented the interaction between adsorbate and adsorbent. The fitted values of qmax, b, k, n, and the correlation coefficients (R2) are listed in Table 2. The values of qmax calculated from Langmuir model were close to experimental

Adsorption isotherms described the distribution of adsorbate molecules between the liquid phase and the solid phase and provided information about the capacity of the adsorbent. Adsorption isotherms of the glyphosate on D201Cu-L,

Figure 7. Effect of humic acid and fulvic acid on the adsorption of glyphosate by D201Cu resins at 303 K and initial glyphosate 400 mg/L. 3588



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Figure 8. Isotherms of glyphosate on D201Cu resins and nonlinear Langmuir isotherms, including (a) adsorption isotherms at 318 K, (b) Langmuir isotherms of D201Cu-L, (c) Langmuir isotherms of D201Cu-M, and (d) Langmuir isotherms of D201Cu-H.

Table 2. Isotherm Constants for Glyphosate Adsorption onto D201Cu Resins D201Cu-L isotherm model Langmuir

Freundlich

qmax (mg/g) b (L/mg) R2 k (mg/g) n R2

D201Cu-M

D201Cu-H

288 K

303 K

318 K

288 K

303 K

318 K

288 K

303 K

318 K

161.1 0.110 0.996 77.6 8.693 0.969

170.6 0.112 0.996 79.4 8.269 0.970

179.0 0.765 0.974 101.8 10.470 0.984

156.6 0.117 0.992 74.9 8.563 0.981

168.4 0.150 0.995 83.7 8.942 0.984

175.8 0.171 0.985 83.9 8.339 0.983

172.6 0.168 0.997 87.6 9.198 0.984

181.0 0.180 0.998 96.6 10.026 0.943

195.6 0.170 0.999 98.1 9.085 0.945

Figure 9. Effect of time on the adsorption of glyphosate onto D201Cu-L, D201Cu-M, and D201Cu-H (initial glyphosate concentration, 400 mg/L; agitation speed, 120 rpm; and adsorbent dose, 100 mg/(100 mL)).

data. The Langmuir model fitted the adsorption isotherms better than the Freundlich model, indicating that D201Cu resin adsorption to glyphosate was monolayer and its surface was homogeneous.36 With the increase of temperature, the qmax values increased, and adsorption was an endothermic process.37 3.5. Adsorption Kinetics. The glyphosate adsorption kinetics of D201Cu-L, D201Cu-M, and D201Cu-H were shown in Figure 9. It can be seen that adsorption was fast in 60 min for three adsorbents. The adsorption equilibrium reached within 200 min and showed a fairly fast kinetics rate.

With the glyphosate accumulating, the adsorption rate slowed down until equilibrium with glyphosate uptake of 157.4, 167.9, and 182.4 mg/g for D201Cu-L, D201Cu-M, and D201Cu-H, respectively. This was probably attributed to the larger specific surface areas of D201Cu resins and massive active adsorption sites. Pseudo-first-order and pseudo-second-order models were used to analyze the adsorption kinetics constants.38,39 The kinetic models could be expressed as follows: 3589



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Table 3. Parameters for Glyphosate Adsorption by D201Cu According to Different Kinetic Models kinetic parameters k1 (1/min) R2 qt (mg/g) t = 432 min qe (mg/g) k2 (g/(mg·min)) R2

pseudo-first-order pseudo-second-order

log(qe − qt ) = log qe − t 1 t = + 2 qt qe k 2qe

k1t 2.303

D201Cu-L

D201Cu-M

D201Cu-H

0.0484 0.9293 157.37

0.0203 0.7443 167.89

0.0350 0.8417 182.37

168.92 0.000327 0.9937

173.01 0.000629 0.9990

191.20 0.000429 0.9976

The fully deprotonated form of glyphosate (L3−) becomes protonated starts with one of the oxygen atoms in the phosphonate group (HL2−), then by amine group nitrogen atom (H2L−), and finally the carboxylate group oxygen atom (H3L).41 It is obvious that the solution pH will determine the major species of glyphosate and affect the adsorption capacity of D201Cu. The reported pKa1, pKa2, and pKa3 of glyphosate in aqueous solution was 2.20, 5.46, and 10.14.24 The mechanism of glyphosate adsorption onto D201Cu resins with pH 5−7 included two steps. Step 1, when the solution pH was increased from 5 to 7, the dominant species was H2L−, and the surface of D201Cu was positively charged via protonation (before adsorption). Step 2, the surface of the amino groups on the backbone of resins was protonated. Accordingly, H2L− was adsorbed on D201Cu by electrostatic interaction and ion exchange. Meanwhile, the coordinate bonding was nanosized copper hydroxide with high affinity toward ligands such as carboxylate and phosphonate. To further illuminate the adsorption mechanism of D201Cu-H to glyphosate, the Cu 2p changes of the D201Cu-H before and after adsorption were presented in Figure S1. From Figure S1, the peak changes of Cu 2p1/2 and Cu 2p3/2 further demonstrated that the complexes of glyphosate with copper formed during adsorption process. The active site amount of nanosized copper hydroxide may be much more than those of electrostatic interaction and ion exchange on the surface. Therefore, the D201Cu resins exhibited a high adsorption capacity and strong salinity resistance which was mainly due to the coordinate bonding between nanosized copper hydrous oxides and glyphosate. 3.7. Regeneration Study. It was important to evaluate the practical applications of the D201Cu by regeneration experiments. The regeneration efficiency Re can be calculated by eq 6. q R e = ei × 100% qe1 (6)

(4)

(5)

−1

where k1 (min ) and k2 (g/(mg·min)) represented the pseudo-first-order rate constant and the pseudo-second-order rate constant, respectively. t (min) means time, and qt (mg/g) is the adsorption capacity at time t. The results of adsorption kinetics were shown in Table 3. As shown in Table 3, the correlation coefficient R2 > 0.99 for the pseudo-second-order model was higher than that of the pseudo-first-order model. Meanwhile, the glyphosate adsorption capacity calculated from the pseudo-second-order model was fully consistent with experiment data. It suggested that the adsorption of glyphosate onto D201Cu fitted well to the pseudo-second-order kinetic model and chemisorption could be the rate-controlling step.40 3.6. Effect of pH. The formation of glyphosate complexes with metals depends on the pH of the conditions, that is, the degree of deprotonation of glyphosate.41 Therefore, using adsorption to remove glyphosate from aqueous solutions depends on the pH of the solution. To maximize remove glyphosate by the adsorbents, it is important to select an optimum pH. To study the pH effect, the solution pH was varied from 3 to 12 (Figure 10). It was apparent from the figure

where qei and qe1 (mg/g) are the adsorption capacity of regenerated adsorbent and the original adsorption capacity of virgin adsorbent, respectively. Figure 11 showed regeneration efficiency of D201Cu resins after five adsorption and desorption cycles. The adsorption capacity of D201Cu-L, D201Cu-M, and D201Cu-H decreased 3.5%, 4.3%, and 3.7% after the first cycle, respectively. The corresponding decrease was 9.4%, 9.8%, and 9.7% after five cycles. This decrease can be attributed to the loss of activated sites during each desorption step.42 The adsorption capacity of the regenerated D201Cu resins was still maintained at a level of above 90% at the fifth cycle.

Figure 10. Effect of pH on glyphosate adsorption by D201Cu resins.

that the glyphosate uptake was dependent on pH. Increasing the pH from 3 to 6, the glyphosate adsorption capacity by D201Cu-H resins dramatically increased from 50.1 mg/g to 179.1 mg/g. From pH about 4 to pH 10, D201Cu-L, D201CuM, and D201Cu-H resins showed a stable high adsorption capacity around 140 mg/g. This result indicated that D201CuL, D201Cu-M, and D201Cu-H resins had a wider adsorption pH range.

4. CONCLUSIONS Nanosized copper hydroxide modified resin was successfully prepared by D201. The physical-chemical properties were characterized by SEM, TEM, FT-IR, XRD, and XPS analysis. 3590



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(2) Carneiro, R. T.; Taketa, T. B.; Gomes Neto, R. J.; Oliveira, J. L.; Campos, E. V.; De Moraes, M. A.; da Silva, C. M.; Beppu, M. M.; Fraceto, L. F. Removal of glyphosate herbicide from water using biopolymer membranes. J. Environ. Manage. 2015, 151, 353−360. (3) Hao, C. Y.; Morse, D.; Morra, F.; Zhao, X. M.; Yang, P.; Nunn, B. Direct aqueous determination of glyphosate and related compounds by liquid chromatography/tandem mass spectrometry using reversedphase and weak anion-exchange mixed-mode column. J. Chromatogr. A 2011, 1218, 5638−5643. (4) Barja, B. C.; dos Santos Afonso, M. An ATR-FTIR study of glyphosate and its Fe(III) complex in aqueous solution. Environ. Sci. Technol. 1998, 32, 3331−3335. (5) De Roos, A. J.; Blair, A.; Rusiecki, J. A.; Hoppin, J. A.; Svec, M. Cancer Incidence among glyphosate-exposed pesticide applicators in the agricultural health study. Environ. Health Persp. 2004, 113, 49−54. (6) Benachour, N.; Séralini, G. E. Glyphosate formulations induce apoptosis and necrosis in human umbilical, embryonic, and placental cells. Chem. Res. Toxicol. 2009, 22, 97−105. (7) Slager, R. E.; Poole, J. A.; LeVan, T. D.; Hoppin, J. A. Rhinitis associated occupational rhinitis is associated with pesticide exposure among commercial pesticide applicators in the agricultural health study. Occup. Environ. Med. 2009, 66, 718−724. (8) Ni, F.; Liu, Z. Y.; Xu, Y. H. Experimental study on the treatment of glyphosate mother liquor by calcium precipitation. Ind. Water Treat. 2011, 31, 39−41. (9) Wang, M.; Zhang, G. L.; Qiu, G. N.; Cai, D. Q.; Wu, Z. Y. Degradation of herbicide (glyphosate) using sunlight-sensitive MnO2/ C catalyst immediately fabricated by high energy electron beam. Chem. Eng. J. 2016, 306, 693−703. (10) Lan, H. C.; He, W. J.; Wang, A. M.; Liu, R. P. An activated carbon fiber cathode for the degradation of glyphosate in aqueous solutions by the Electro-Fenton mode: Optimal operational conditions and the deposition of iron on cathode on electrode reusability. Water Res. 2016, 105, 575−582. (11) Wang, S.; Seiwert, B.; Kastner, M.; Miltner, A.; Schaffer, A.; Reemtsma, T.; Yang, Q.; Nowak, K. M. (Bio)degradation of glyphosate in water-sediment microcosms-A stable isotope co-labeling approach. Water Res. 2016, 99, 91−100. (12) Sandy, E. H.; Blake, R. E.; Chang, S. J.; Jun, Y.; Yu, C. Oxygen isotope signature of UV degradation of glyphosate and phosphonoacetate: Tracing sources and cycling of phosphonates. J. Hazard. Mater. 2013, 260, 947−954. (13) Song, J.; Li, X. M.; Figoli, A.; Huang, H.; Pan, C.; He, T.; Jiang, B. Composite hollow fiber nanofiltration membranes for recovery of glyphosate from saline wastewater. Water Res. 2013, 47, 2065−2074. (14) Nourouzi, M. M.; Chuah, T. G.; Choong, T. S. Y.; Rabiei, F. Modeling biodegradation and kinetics of glyphosate by artificial neural network. J. Environ. Sci. Health, Part B 2012, 47, 455−465. (15) Loperena, L.; Ferrari, M. D.; Saravia, V.; Murro, D.; Lima, C.; Ferrando, L.; Fernandez, A.; Lareo, C. Performance of a commercial inoculum for the aerobic biodegradation of a high fat content dairy wastewater. Bioresour. Technol. 2007, 98, 1045−1051. (16) Chen, F. X.; Zhou, C. R.; Li, G. P.; Peng, F. F. Thermodynamics and kinetics of glyphosate adsorption on resin D301. Arabian J. Chem. 2016, 9, 1665−1669. (17) Rivoira, L.; Appendini, M.; Fiorilli, S.; Onida, B.; Del Bubba, M.; Bruzzoniti, M. C. Functionalized iron oxide/SBA-15 sorbent: investigation of adsorption performance towards glyphosate herbicide. Environ. Sci. Pollut. Res. 2016, 23, 21682−21691. (18) Hu, Y. S.; Zhao, Y. Q.; Sorohan, B. Removal of glyphosate from aqueous environment by adsorption using water industrial residual. Desalination 2011, 271, 150−156. (19) Xie, M.; Xu, Y. H. Glyphosate adsorption by ferric supported active carbon. J. Environ. Sci-China 2011, 31, 239−244. (20) Xiao, G. Q.; Wen, R. M. Comparative adsorption of glyphosate from aqueous solution by 2-aminopyridine modified polystyrene resin, D301 resin and 330 resin: Influencing factors, salinity resistance and mechanism. Fluid Phase Equilib. 2016, 411, 1−6.

Figure 11. Regeneration efficiency of D201Cu resins to glyphosate in five cycles.

The adsorption capacity of D201Cu resins to glyphosate was measured. The order of adsorption capacity for D201Cu resins was D201Cu-H > D201Cu-M > D201Cu-L. The presence of HA and FA decreased the adsorption capacity of D201Cu to glyphosate. With the pH from 4 to 10, the D201Cu resins showed stable and high adsorption capacity around 140 mg/g. In high salinity wastewater, glyphosate can be concentrated by the D201Cu resins efficiently. The predominant mechanism for glyphosate adsorption on the D201Cu resins included coordinate bonding, electrostatic interaction, and ion exchange. Therefore, the D201Cu resins have a broad potential application prospect in environmental science and engineering.

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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/acs.jced.7b00569. Surface Cu 2p XPS spectra of D201Cu-H and D201CuH + glyphosate (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: +86-543-3190097. Fax: +86-543-3190097. ORCID

Dongmei Jia: 0000-0002-3880-7921 Funding

The research has been funded by the National Key R&D Program of China (2017YFC0505904), National Natural Science Foundation of China (51290282 and 21276027), Shandong key research and development program (2016GSF117021), and Shandong Province Higher Educational Science and Technology Program, China (J14LC05 and J15LD04). Notes

The authors declare no competing financial interest.

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REFERENCES

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