Temperature and pH sensitive composite for rapid and effective removal of sulfonylurea herbicides in aqueous solution

Environmental Pollution 255 (2019) 113150

Contents lists available at ScienceDirect

Environmental Pollution journal homepage: www.elsevier.com/locate/envpol

Temperature and pH sensitive composite for rapid and effective removal of sulfonylurea herbicides in aqueous solution* Changsheng Li a, Nan Zhang b, Jixiao Chen a, Jiawen Ji a, Xue Liu c, Jianli Wang a, Jianhui Zhu a, Yongqiang Ma a, * a b c

Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, 100193, China The Institute for the Control of Agrochemicals, Ministry of Agriculture and Rural Affairs of the People's Republic of China, Beijing, 100125, China Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, 266101, China

a r t i c l e i n f o

a b s t r a c t

Article history: Received 15 April 2019 Received in revised form 29 August 2019 Accepted 30 August 2019 Available online 11 September 2019

Excessive pesticide residues in the environment have caused more and more serious social problems. In this article, the polymer materials and graphene oxide were smoothly grafted together through surfaceinitiated atom-transfer radical polymerization. A temperature and pH dual-sensitive adsorbent was successfully obtained, which was used for the removal of six sulfonylurea herbicides in the aquatic environment. Experiment results showed that the adsorbent could efficiently remove the tested pesticides in aqueous solution rapidly (only 1 min). The adsorption process was in consist with the pseudosecond-order kinetics equation and Freundlich model, and the thermodynamic parameters were also calculated. Furthermore, the mechanism for removal performance was judged as n-p, p-p, hydrogen bonding, hydrophobic and electrostatic interaction verdict. Exhilaratingly, the material showed no significant toxicity to Daphnia magna on risk assessment. © 2019 Elsevier Ltd. All rights reserved.

Keywords: Dual-sensitive material Removal Sulfonylurea herbicide Risk assessment

1. Introduction Pesticide has been an effective tool for agricultural diseases, insects and weeds control (Bapat et al., 2016; Cara et al., 2017;  et al., 2014; Wu et al., 2010). Herbicides Mandal et al., 2017; Masia account for more than 50% of the pesticides market (Kapsi et al., 2019). In 1982, the DuPont Corporation commercialized the first sulfonylurea herbicide (SUH): chlorsulfuron. Since then the SUHs have been globally used as one of the mainstream herbicides for their low application amount and low mammalian toxicity (Tranel and Wright, 2002; Sarmah and Sabadie, 2002; Russell et al., 2002; Brown, 1990), sales of SUHs reached $2.019 billion in 2015. However, lots of these herbicides are usually abused greater dosage than actual pesticide dose required. Because SUHs are water-soluble, high mobile and difficult to degrade (Benzi et al., 2011), the superfluous pesticides can be transferred to non-target surface water and groundwater by rainwash (Weston et al., 2005), runoff and leaching (Alvarez et al., 2008; Matouq et al., 2008). So SUHs can be

* This paper has been recommended for acceptance by Jung-Hwan Kwon. * Corresponding author. E-mail address: [email protected] (Y. Ma).

https://doi.org/10.1016/j.envpol.2019.113150 0269-7491/© 2019 Elsevier Ltd. All rights reserved.

often detected in the environment. For example, the Federal Geological Survey detected large residues of SUHs in surface and groundwater in the Midwestern as early as 1998 (Battaglin et al., 2000), and it also has been reported that SUHs was detected in soil, rivers and surface water (Sabadie, 2002; Zhou et al., 2006; Zhu et al., 2002). Meanwhile, some studies indicate that SUHs is toxic to aquatic organisms (Ding et al., 2010; Leboulanger et al., 2001; Joly et al., 2013). Such as iodosulfuron-methyl sodium is high-toxic to mammals (Ahmad, 2019; Baghestani et al., 2008; Leonard et al., 2017), and rimsulfuron and its metabolites have adverse effects on aquatic plants (Rosenbom et al., 2010). So the residual SUHs in the aquatic ecological environment often have a negative effect on non-target organisms, following crops, human health (Leboulanger et al., 2001; Ding et al., 2010; Pierre et al., 2013). SUHs have been proved a potential source of contamination for the aquatic environment through laboratory exposure tests (Fairchild et al., 1997; Coyner et al., 2001; Michael, 2003). At present, water pollution is a priority environmental issue (Mohamed et al., 2009; Herrerondez et al., 2017). So it is urgent to remove pesticides from Herna the water environment. A variety of methods have been recommended for the removal of SUHs in the environment, such as biodegradation (Zhao et al., 2018), photodegradation (Dugand zic et al., 2017), oxidative

2

C. Li et al. / Environmental Pollution 255 (2019) 113150

degradation (Zají cek et al., 2015), electrochemical oxidation (Souza et al., 2017) and physical adsorption. Many of these methods have some drawbacks, such as high cost, time consuming and incomplete removal. Among the aforementioned methods, physical adsorption is a competitive and attractive means on account of its low cost, simplicity, high efficiency, eco-friendly and broad application range (Cara et al., 2015; Alsbaiee et al., 2016). For example, activated carbon is widely used as an adsorbent for contaminated soil-water purification (Cara et al., 2017). Although it has high adsorption capacity, the slow adsorption rate and harsh regeneration condition still restrain its development and further use. Therefore, it is necessary to develop new materials with excellent adsorption performance. Since the 1980s, nanomaterials have played a special role in the fields of light, electricity, adsorption, catalysis and biological activity etc. Graphene has been one of the most widely used 2D materials among various nanomaterials. Compared to graphene, graphite oxide (GO) possesses numerous surface oxygen functional groups, such as hydroxyl, carboxyl and epoxy groups. These hydrophilic groups make GO an excellent substrate to gain new properties through esterification and amination derivative reactions. GO or modified GO is currently used to remove toxic and harmful pollutants from contaminated water environment (Gao et al., 2012). The dispersion of GO can be enhanced by functionalizing with the polymer to improve its adsorption performance (Bak et al., 2011; Liu et al., 2008). As a typical thermosensitive material, the hydrogen bond of poly N-isopropylacrylamide (PNIPAM) will contract or relax with the change of temperature. Wang et al. (2014) have used GO and PNIPAM composite materials for organic dyes removal. Gong et al. (2016) have studied GO grafted with PNIPAM by Surface-initiated atom-transfer radical polymerization (Si-ATRP) and selectively adsorb phenols. In recent years, due to the diversity of the molecular structure and different properties of environmental pollutants, in order to enhance the removal efficiency of specific pollutants, different types of sensitive adsorbents have been developed according to the different properties of waste, such as thermo-, pHsensitive adsorbent, and even “on-off switch” products (Li et al., 2018; Zheng et al., 2019; Zhang et al., 2018). Till now, sensitive materials have been extensively studied for their unique properties and are considered to have broad application prospects (Kim et al., 2015; Shi et al., 2015a,b). In addition, modified GO by PNIPAM or pH-sensitive GO nanocomposite as adsorbent has also been discovered in some literatures. Tabrizian et al. (2019) synthesized the pH-sensitive and magnetically separable GO@Fe/Cu bimetallic nanocomposite and applied to efficiently remove tetracycline. However, up to now, there are few reports on the use of temperature and pH dual-sensitive with GO and PNIPAM smart composite for SUHs removal in water. Environmental exposure and risk assessment is a new hot field, mainly through the toxicity test of model organisms to evaluate the impact of the target on the environmental ecosystem, to make up for the lack of understanding of its behavior in the environment. Daphnia magna (D. magna), a primary consumer in the aquatic food chain is an important feeder for fish, one of the most important invertebrate species in the aquatic environment. And it is also an internationally recognized model organism to assess the risk of toxicity of chemicals in aquatic organisms (Cui et al., 2017). Its advantages are short life cycle, easy to breed and sensitive for chemicals (Toumi et al., 2015). Guo et al. (2013) estimated the environmental risk of radio-labeled graphene using D. magna. At present, many international organizations, including Organization for Economic Co-operation and Development (OECD), International Standardization Organization (ISO) and United States Environmental Protection Agency (USEPA), have developed standard

toxicological methods for D. magna. Herein, the thermal and pH dual-sensitive polymer material (TPGO) was synthesized successfully by Si-ATRP method under mild conditions. Then, six representative SUHs (mesosulfuronmethyl, rimsulfuron, flazasulfuron, iodosulfuron-methyl sodium, pyrazosulfuron and ethoxysulfuron) were selected for the adsorption and removal test of TPGO in water. Finally, the aquatic environmental risk to D. magna was preliminarily assessed. The experiments mainly include: (1) TPGO was synthesized and the surface properties of GO and TPGO were studied; (2) the adsorbent dosage and adsorption time were optimized; (3) the effects of different pH and water on the adsorption properties of the materials were studied; (4) the adsorption kinetics and isotherms curves were determined and matched with different models; (5) thermodynamic parameters were measured and calculation; (6) based on the above results, the possible adsorption mechanism was discussed; (7) toxicity tests of the materials to D. magna were performed. 2. Material and methods 2.1. Materials and reagents Copper (I) bromide (CuBr), 2, 20 -Bipyridine (Bpy), N-isopropylacrylamide (NIPAM) and Hydroxyethyl methacrylate (HEMA) were purchased from Ouhe Technology Co., Ltd. (Beijing, China). 3-aminopropyltriethoxysilane (APTES) and triethanolamine were obtained from Energy Chemical (Shanghai, China). 2bromoisobutyryl bromide (BMPB) and extra dry tetrahydrofuran (THF) were supplied by J&K Chemicals (Beijing, China). Other organic solvents and reagents were obtained by Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). All chemical reagents were used directly in this experiment without further purification. Deionized water, mineral water (Evian, Aqua d’Or, and Ganten), tap water and seawater were used in all the course of removal test. Detailed information about water was shown in Table S1. All herbicides used in the experiment were supplied by the College of Science, China Agricultural University (purity98%, Beijing, China). Key physicochemical properties of investigated SUHs were shown in Table S2. D. magna was originally purchased from the Chinese Center for Disease Control and Prevention. Dechlorinated tap water contained 250 ± 50 mg kg1 CaCO3 and >5.8 mg kg1 dissolved oxygen at pH 7.5 ± 1.0. Incubator condition was at 21 ± 1  C, 16 h of light and 8 h of darkness for a photoperiod. 2.2. Fabricated procedure Fabricated process of TPGO was shown in Scheme 1. 2.2.1. Synthesis of (GO) GO used in this experiment was synthesized from a modified Hummers' method (Offeman et al., 1958). The specific operation steps we have reported in our previous work (Liu et al., 2013). 2.2.2. Synthesis of amino-functionalized (GO-NH2) Amino-functionalized GO was synthesized based on the previously reported paper (Li et al., 2018). Briefly, 30 g of GO and 7.5 mL of triethanolamine were mixed in 300 mL of ethanol, and the suspension mixture was evenly dispersed by ultrasound, and heated to 60  C by oil bath. After that 3 mL of ammonium hydroxide, 50 mL of deionized water were added to the reaction vessel, kept dribbling 35 mL of APTES (0.149 mol) gradually. The solution was stirred at 60  C overnight and cooled to room temperature. It was centrifuged

C. Li et al. / Environmental Pollution 255 (2019) 113150

3

Scheme 1. The preparation process of TPGO.

at 8000 rpm and the supernatant was discarded. Next, the precipitate was ultrasonically re-dispersed with ethanol and centrifuged again. The above purification operation was performed quintic to eliminate the excess APTES completely. Product was dried at 70  C under vacuum overnight. 2.2.3. Synthesis of 2-bromoisobutyrate-functionalized (GO-Br) Macroinitiator of Si-ATRP was performed following the procedure described in the literature (Li et al., 2018). Firstly, 20 g of GONH2 was homogenized dispersed with 300 mL of anhydrous THF by ultrasound, then 1.7 g of DMAP (0.014 mol) and 35 mL of TEA (0.253 mol) were added into mixture system. The mixture was cooled to 0  C by ice-water bath and kept this condition, added BMPB dropwise into the reaction system. The system was continued stirring for 2 h and returned to room temperature for 24 h. The purification process of the product was similar to the purified operation of GO-NH2. The obtained product was finally dried in vacuum at 70  C overnight. 2.2.4. Synthesis of TPGO Thermal and pH dual-sensitive material was synthesized via SiATRP method in accordance to previously report (Lv et al., 2015). NIPAM and HEMA were used as the monomers. 21 g of GO-Br was sonicated to the homogeneous mixture in methanol/H2O (300 mL/ 35 mL) under nitrogen atmosphere, added 12.44 g of NIPAM and 1.4 g of HEMA. Stirred 0.5 h at indoor temperature, then affiliated 2 g of CuBr and 7 g of Bpy. The reaction was heated at 50  C for 12 h under nitrogen condition and then cooled down approximately room temperature, washed with ethanol for quartic, water for thrice and ethanol for twice successively. At last, TPGO was desiccated in vacuum at 70  C for 24 h. 2.3. Characterization Scanning electron microscopy (SEM) photographs were used to capture insight into the microstructure and morphology by a Hitachi SU8020 microscope. Fourier transform infrared (FT-IR) spectra was analyzed by PerkinElmer Spectrum 100 FT-IR spectrometer in the range from 400 to 4000 cm1. The lower critical solution temperature (LCST) of TPGO was measured by TA DSC250 with differential scanning calorimetry (DSC). Meanwhile, X-ray

diffraction (XRD, Brucker D8 Advance) was carried out with Cu/Ka radiation measurements. The surface chemical composition of GO and TPGO was recorded by X-ray photoelectron spectroscopy (XPS) on Thermo Escalab 250Xi. Zeta potential of TPGO was measured by a Malvern Zetasizer Nano ZS. Carbon, hydrogen, nitrogen, and oxygen contents were determined by elementary analysis (EA) on Germany Elementar Vario EL cube. 2.4. Adsorption experiments Different TPGO dosages (25e250 mg) were studied to confirm the optimal dose of the adsorbent for SUHs removal. In order to optimize the adsorption time, 100 mg TPGO was added to the newly prepared SUHs solution (10 mL, 2 mg L1). The samples were swirled for 0 (shaking 5 times by hand), 0.5, 1, 1.5, 2, 2.5, 3, 5, 7, 10 and 15 min with the vortex tester, respectively. The removal rate of SUHs under different pH (3e11) values was tested with 100 mg of TPGO dosage and 1 min of the contact time. In the adsorption isotherm experiment, 100 mg TPGO was added to different initial concentration (0.1e50 mg L1) of iodosulfuron-methyl sodium (10 mL) solution and temperature (25, 35 and 45  C). The adsorption capacity equation was described in Equation S(1). 2.5. Analytical methods All samples were analyzed by an Agilent 1200 HPLC series and an Agilent 6410B triple-quadrupole mass spectrometer equipped with an electrospray ionization (ESI) interface (Agilent Technologies, USA). Eclipse plus C18 column (3.5 mm  2.1 mm  50 mm) from Agilent Technologies was employed at 25  C. The mobile phase was acetonitrile and H2OeHCOOH (0.1%) on the ratio of 70:30 with a flow rate of 0.2 mL min1. The triple-quadrupole mass spectrometer was used in MRM after selected ion monitoring had been performed. MRM data acquisition parameters of LC-MS/MS and the limit of detection for the all SUHs selected were shown in Table S3. 2.6. Aquatic environmental risk assessment experiment D. magna acute toxicity was conducted with reference to OECD guideline 202 and USEPA standard operating procedure 2024

4

C. Li et al. / Environmental Pollution 255 (2019) 113150

(Hassan et al., 2018; Cui et al., 2017). Different experimental concentrations (0.1, 1, 10, 100, 150, 200 and 500 mg L1) were selected, and blank control was set at the same time. Each 50 mL beaker was used to contain 30 mL of the test solution, and 10 homogeneous neonates (6e24 h) were attached to each beaker. Three replicates were set for each treatment and control. Do not feed or replace the test solution during the experiment. Immobilization and mortality of D. magna were observed and recorded after 24 h and 48 h. The daphnias that cannot swim for 15 s after mild agitation were indicated as immobilization. Immobilization status and mortality were analyzed by the probit method of analysis in SPSS software. 3. Results and discussion 3.1. Characterization of materials The surface morphology of the product composites were observed by SEM and shown in Fig. S1. The product has a smooth surface with typical wrinkles of GO in Fig. S1a, indicating that GO has been successfully synthesized. In contrast, after amino functionalization of GO, the surface appears broken slags while folds reduce (Fig. S1b). Fig. S1c shows that the GO surface becomes rougher, with fewer folds and deeper fragmentation, indicating that the initiator has been successfully fixed on GO. Fig. S1d shows that the surface roughness of TPGO is further deepened after SiATRP grafting. At the same time, wrinkled edges of the product appear to be coated with a film. As indicated in Fig. 1, for the GO, the characteristic peaks at 1732 and 1615 cm1 are ascribed to the C]O and C]C stretching vibrations (Liu et al., 2013). After functionalized with BMPB, the adsorption bands for GO-Br at the peak of 1708 cm1 is corresponding to the C]O stretching vibrations of in BMPB. For the TPGO, the appearance of new bands at 1600 and 1043 cm1 are attributed to the NeH and C]O in amide, respectively. Furthermore, the peak at 1457 cm1 is assigned to the CeN group. From the above results, NIPAM, HEMA and GO were successfully grafted by Si-ATRP. Furthermore, the LCST of TPGO was analyzed by differential scanning calorimetry (DSC). In Fig. S2, with the increase of temperature from 20 to 60  C, the distinct endothermic peak appears in 41.5  C. Compared to the LCST of NIPAM is 32  C, the possible reason

Fig. 1. FT-IR spectra of GO (a), GO-NH2 (b), GO-Br (c), TPGO (d).

for LCST enhancement was the increase of hydrophilic groups in the structure after recombined with HEMA and GO together (Lv et al., 2015). GO and TPGO surface structures were qualitatively investigated by XRD as shown in Fig. S3. According to the graph of GO, at about 2q ¼ 10.7, the existence of GO typical sharp diffraction peak (002) can be found. The broad peak at around 2q ¼ 23 suggests amorphous silicon is contained in the structure of TPGO, while slash of the major characteristic peak was indicated the success of polymers surface coating. To further confirm the chemical structure information of nanocomposite, the GO and TPGO were analyzed by X-ray photoelectron spectroscopy (XPS). The wide scan spectrum for GO and TPGO are displayed in Fig. 2. According to Fig. 2a, GO mainly contains carbon (C1s, 284.88 eV) and oxygen (O1s, 532.71 eV), while TPGO sample respectively involves carbon (C), nitrogen (N), oxygen (O), silicon (Si) and bromine (Br). The binding energies center of the five elements were located at 284.90 eV, 399.89 eV, 532.39 eV, 102.55 eV and 68.37 eV. The C1s spectrum (2b) of GO was divided into four peaks: 284.8 (CeC), 286.89 (CeO), 287.66 (C]O) and 288.89 eV (OeC]O). Compared with GO, two new peaks of CeN (286.62 eV) and NeC]O (287.48 eV) were observed in TPGO (2c) and confirmed the successful modification of the composite. In addition, binding energies at 398.9, 399.9 and 401.6 eV in N1s spectrum (2d) correspond to CeN and NeH groups respectively. Fig. S4 showed the zeta potential of TPGO at different pH values. It can be seen zeta potential changes from positive to negative within the range of pH from 3 to 11. The isoelectric point of TPGO is about at pH 4. When pH > 4, the material has a negative charge. 3.2. Screening of the best adsorption conditions In the adsorption test, the amount of adsorbent, adsorption time and pH of the solution were optimized as the factors affecting the adsorption performance. And removal rates in different types of water were also discussed. 3.2.1. Optimization of adsorbent dosage Different adsorbent dosages in the range of 25e250 mg (25, 50, 75, 100, 125, 150, 175, 200, 225 and 250) were added to six sulfonylurea herbicides mixture solution with the initial concentration of 2 mg L1. As shown in Fig. 3, with the increase of adsorption dose, the removal efficiency of SUHs were gradually increased. When the adsorption dose was 100 mg, the removal rate was above 80%. Therefore, considering the cost, the adsorbent in this experiment was selected as 100 mg as the optimal dosage. Hydrophobicity is also considered as one of the forces that affect the adsorption capacity of organic material. (Wei et al., 2012). In general, the logP value of the hydrophobic constant is positively correlated with the hydrophobic performance (Sierra et al., 2011). According to the relationship between the adsorbent rate of SUHs and the hydrophobic constant of the adsorbate, rimsulfuron with lowest hydrophobic constant had the worst adsorption effect. The hydrophobic constant of idosulfuron-methyl sodium is small, but the removal effect can reach more than 90%, which can be attributed to the fact that it is a sodium salt. It is easier to ionize and form hydrogen bonds with TPGO in the solution state, so as to achieve a better removal effect. 3.2.2. Effect of adsorptive time The adsorption time is one of the important parameters affecting the adsorption efficiency. In the experiment, to obtain better removal efficiency, 100 mg TPGO was added to several 10 mL mixture solutions respectively, and then the vortex was rotated at different times. It can be seen from Fig. 4, that the adsorption effect

C. Li et al. / Environmental Pollution 255 (2019) 113150

5

Fig. 2. XPS spectra of TPGO.

Fig. 3. Effect of adsorbent dosage for removal capacity. Other experimental conditions: the initial concentration of SUHs C0 ¼ 2 mg kg1; shock for 2 h; pH ¼ 7; T ¼ 25  C.

of TPGO was very obvious. The adsorption equilibrium has been reached within 1 min of the vortex, and the removal rate is higher than 80%. Hence, vortex adsorption for 1 min was used as the optimal contact time.

Fig. 4. The change of removal rate with different vortexing time (0(shake hand quintic), 0.5, 1, 1.5, 2, 2.5, 3, 5, 7, 10, 15 min); the initial concentration of SUHs C0 ¼ 2 mg kg1; pH ¼ 7; T ¼ 25  C.

3.2.3. Effect of pH in the system In this study, the solution showed different pH values (3, 4, 5, 6, 7, 8, 9, 10 and 11) by adjusting the concentration of HCl and NaOH. When the adsorption dose was 100 mg and the contact time was 1 min by eddying, the removal efficiency of the solution under different pH conditions was compared. However, during the

6

C. Li et al. / Environmental Pollution 255 (2019) 113150

experiment, it was found that the tested sulfonylureas were destabilized and degraded before the addition of adsorbent TPGO when pH was 3, 4, 5, 6 namely the system were acidic. Figs. S5eS10 were the response values of SUHs measured by LC-MS/MS at different pH (3, 5 and 7), which proved that SUHs were unstable in acid solution. In order to understand the morphological and structural changes of TPGO at high pH, TPGO was placed in solutions with different pH (7, 9 and 11). The change of element content in the material was determined by EA. The results are shown in Table S4. It can be seen that when the solution is basic, the content of oxygen and hydrogen gradually rises with the increase of pH value. At the same time, it was found that the pH of the solution decreased. This indicated that the surface of the material contains a large number of groups that can form hydrogen bonds with the hydroxyl group in basic solution, which leads to the decrease of pH of the solution and the increase of the content of oxygen and hydrogen. As the pKa of the studied herbicides range from 3.22 to 5.28, they all exist in the form of SUHs when the solution is nonacid. According to the zeta potential test results, the zeta potential values of TPGO are all negative when the pH of the system is more than 7. It indicates that the material surface is negatively charged. Therefore, electrostatic interaction exists between TPGO and SUHs, and the force increases gradually with the gradual increase of pH value. However, hydroxyl group forms hydrogen bond with the surface of the material and competes for the active site with the increase of OH concentration. The adsorption of the material to SUHs is inhibited, and the removal rate is reduced. Therefore, the adsorption property was best at pH 7 and decreased with the increase of pH in Fig. 5.

3.2.4. Effect of different types of water Considering that the natural water environment contains a variety of organic compounds and salts, different types of water were selected instead of deionized water for the adsorption test. The experimental results indicate that TPGO can effectively remove SUHs from mineral water and tap water, while its ability to remove SUHs in seawater is inhibited (Fig. S11). This is because there are a large number of salts and ions in the seawater, they can form electrostatic interaction with the negative charge on the surface of the material to reduce the adsorption property of the material.

Fig. 5. Effect of pH for removal capacity. Experimental conditions: the initial concentration of SUHs C0 ¼ 2 mg kg1; vortex time ¼ 1 min; T ¼ 25  C.

3.3. Adsorption kinetics study The removal rate and equilibrium time are very significant to analyze the adsorption mechanism. In order to further confirm the adsorption mechanism, the adsorption experimental data of flazasulfuron was fitted with two kinetic models (as shown in Equation S(2)), respectively. Compared with the pseudo-first-order kinetic model, the kinetic data of flazasulfuron was more consistent with the pseudosecond-order kinetic model with R2 > 0.99. The kinetic parameters of flazasulfuron were revealed in Table S5, and the linear fitting results are plotted in Fig. S12. Therefore, it was also demonstrated that the adsorption of TPGO on SUHs belongs to the specific interaction between the adsorbent and the adsorbed substance, and the adsorption effectiveness determined the level of adsorption power rather than the concentration of the adsorbate (Kica and Ronka, 2014). 3.4. Adsorption isotherms In order to obtain the adsorption isotherm data, iodosulfuronmethyl sodiumm was selected as the experimental pesticide, the initial concentration and experimental temperature were formulated in the range of 0.1e50 mg kg1 and 25  C, 35  C and 45  C, respectively. The experiment was conducted under the optimized conditions and different adsorption isotherms were drawn according to the data results. As shown in Fig. 6a, it reflected the correlation between equilibrium adsorption capacity (qe) and equilibrium concentration (Ce) at different temperatures. Meanwhile, three commonly used isotherm models (Langmuir, Freundlich, and Temkin models) were selected to evaluate the data. Isotherm models were shown in Equation S(3). If the adsorption process conforms to the Langmuir model, it indicates that the monomolecular layer is adsorbed. The Freundlich model is mainly used to fit the adsorption of multilayer heterogeneous surfaces. The strength of electrostatic interaction between charge and adsorption is consistent with Temkin model. The fitting graphs of the three evaluation models and calculation results of related parameters were described in Fig. 6bed and Table S6, respectively. It is well-known that the internal shrinkage hydrogen bond of the material becomes hydrophobic when the temperature is higher than the LCST, otherwise, the molecular chain becomes hydrophilic (Shi et al., 2015a,b). In this study, the LCST (41.5  C) of the product was measured by DSC. Therefore, when the temperature of the solution was close to or exceeded LCST, TPGO will shrink due to the enhanced intramolecular hydrogen bond, and the adsorption capacity will decrease. So the removal efficiency of TPGO is highest at 25  C. From the perspective of structure, TPGO not only interacts with SUHs, but also with its own molecules such as hydrogen bonding. Hence, we speculated that the adsorption process of SUHs was more about physical adsorbing heterogeneous surfaces. Meanwhile, compared with the results of Langmuir model and Temkin model, all R2 values after Freundlich model fitting were greater than 0.9 and the index 1/n were also >1 at 25  C, 35  C and 45  C. As a whole, the adsorption process conforms to the Freundlich model. Nevertheless, because of the strong electrostatic interaction between the adsorbent and the adsorbate, it is more consistent with the Temkin model at 25  C. However, when the adsorption temperature (35 and 45  C) of the adsorption system gradually approaches or exceeds the LCST (41.5  C) of TPGO, the hydrogen bond of the adsorbent itself is enhanced, and the adsorption effect on SUHs is weakened. Here the adsorption system is closer to homogeneous adsorption, which is more consistent with the Langmuir isothermal equation, and R2 is the highest.

C. Li et al. / Environmental Pollution 255 (2019) 113150

7

Fig. 6. Adsorption isotherms of for iodosulfuron-methyl sodium adsorption a); Langmuir model b); Freundlich model c); Temkin model d) at 25, 35 and 45  C, respectively.

3.5. Adsorption thermodynamics The corresponding thermodynamic parameters of adsorption were calculated by Van't Hoff equation such as energy change (DG0), enthalpy change (DH0), and entropy change (DS0) (Zhu et al., 2017; Li et al., 2016). The equation information was shown in Equation S(4). In the adsorption isotherm experiments at various temperatures, it can be found that the adsorption capacity decreases with the increase of temperature, which implies that the adsorption is an exothermic reaction. The calculated enthalpy change (DH0) also turns out that it is physical adsorption, because the value of 15.87 kJ mol1 conforms to the range of physical adsorption (20 < n < 0 kJ mol1) (Liu and Zhang, 2009). Therefore the negative DG0 implied that the adsorption is a spontaneous and feasible process. As shown in Table S7, the entropy change (DS0>0) indicates the interface between solid and liquid increases in disorder in the adsorption process.

3.6. Possible adsorption mechanism The possible adsorption mechanism for TPGO adsorption process was shown in Fig. 7. From the perspective of the prepared TPGO structure, firstly, p electron-deficient GO group can combine with the p electron-rich aromatic ring of SUHs structure to form pp interaction. Moreover, the surface of GO after modification is filled with abundant hydroxyl groups, amide bonds and carboxyl groups, while electronegative atoms like N and O etc. existed in the adsorbate SHUs. Therefore, it is suspected that there are n-p

interaction and hydrogen-bond interaction during the adsorption process (Shah et al., 2018). In addition, the hydrophobic effect of SUHs plays an important role in the adsorption process. And the existence of electrostatic interaction and hydrogen bonding between the adsorbent and SUHs were confirmed by the zeta potential measurement data of TPGO and effect test of pH value. In summary, the possible adsorption mechanism of TPGO is determined by p-p, n-p, hydrogen bonding, hydrophobic and electrostatic interaction together. 3.7. Risk assessment results Risk assessment is one of the important factors to determine whether new materials can be applied for water treatment (Hassan et al., 2018). In this paper, the aquatic environmental risk of TPGO was assessed by immobilization and mortality in D. magna. Table S8 showed D. magna immobilization and mortality with different concentrations of TPGO after 24 and 48 h. It can be seen different concentrations of materials showed no obvious inhibition and toxicity to D. magna after exposure 24 and 48 h. 4. Conclusions In short, the grafted composite with temperature and pH dualsensitive had been successfully synthesized by Si-ATPR method. SEM, FT-IR, DSC, XRD and XPS technical means were used for characterization. More importantly, the material can effectively adsorb SUHs in freshwater within 1 min. The study of adsorption kinetics accorded with pseudo-second-order kinetics and the

8

C. Li et al. / Environmental Pollution 255 (2019) 113150

Fig. 7. The possible adsorption mechanism for TPGO adsorption process.

adsorption isotherm was more consistent with the Freundlich model. The most likely adsorption mechanism is the combined effects of p-p, n-p, hydrogen bonding, hydrophobic and electrostatic interaction. Toxicity assessment test showed no significant toxicity to D. magna. The results show that TPGO may be applied in the field of freshwater management. Declaration of interest The authors declare that they have no conflict of interest. Acknowledgments This study was financially supported by the National Key Research and Development Program of China (2016YFD0201203) and the National Innovative Training Program for College Students of China (201910019188). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.envpol.2019.113150. References Ahmad, K.S., 2019. Adsorption evaluation of herbicide iodosulfuron followed by cedrus deodora sawdust-derived activated carbon removal. Soil Sediment Contam. 28, 65e80. Alsbaiee, A., Smith, B.J., Xiao, L.L., Ling, Y.H., Helbling, D.E., Dichtel, W.R., 2016. Rapid removal of organic micropollutants from water by a porous b-cyclodextrin polymer. Nature 529, 190e194. Alvarez, M.F., Llompart, M., Lamas, J.P., Lores, M., Jares, C.G., Cela, R., Dagnac, T., 2008. Simultaneous determination of traces of pyrethroids, organochlorines and other main plant protection agents in agricultural soils by headspace solidphase microextraction-gas chromatography. J. Chromatogr. A 1188, 154e163. Baghestani, M.A., Zand, E., Soufizadeh, S., Beheshtian, M., Haghighi, A., Barjasteh, A., Deihimfard, R., 2008. Study on the efficacy of weed control in wheat (Triticum aestivum L.) with tank mixtures of grass herbicides with broadleaved herbicides. Crop Protect. 27 (1), 104e111. Bak, J.M., Lee, T., Seo, E., Lee, Y., Jeong, H.N., Kim, B.S., Lee, H., 2011. Thermo responsive graphene nanosheets by functionalization with polymer brushes. Polymer 2, 316e323. Bapat, G., Labade, C., Chaudhari, A., Zinjarde, S., 2016. Silica nanoparticle based techniques for extraction, detection, and degradation of pesticides. Adv. Colloid. Interface 237, 1e14.

Battaglin, W., Furlong, E., Burkhardt, M., Peter, C., 2000. Occurrence of sulfonylurea, sulfonamide, imidazolinone, and other herbicides in rivers, reservoirs and ground water in theMidwestern United States, 1998. Sci. Total Environ. 248, 123e133. Benzi, M., Robotti, E., Gianotti, V., 2011. HPLCeDADeMSn to investigate the photodegradation pathway of nicosulfuron in aqueous solution. Anal. Bioanal. Chem. 399, 1705e1714. Brown, H.M., 1990. Mode of action, crop selectivity and soil relations of the sulfonylurea herbicides. Pestic. Sci. 29, 263e281. Cara, I.G., Trincǎ, L.C., Trofin, A.E., Cazacu, A., Topa, D., Peptu, C.A., Jitǎreanua, G., 2015. Assessment of some straw derived materials for reducing the leaching potential of Metribuzin residues in the soil. Appl. Surf. Sci. 358, 586e594. Cara, I.G., Rusu, B.G., Raus, L., Jitareanu, G., 2017. Sorption potential of alkaline treated straw and a soil for sulfonylurea herbicide removal from aqueous solutions: an environmental management strategy. Chemosphere 186, 360e366. Coyner, A., Gupta, G., Jones, T., 2001. Effect of chlorsulfuron on growth of submergedaquatic macrophyte Potamogeton pectinatus (sago pondweed). J. Environ. Pollut. 111, 453e455. Cui, F., Chai, T.T., Liu, X.Y., Wang, C.J., 2017. Toxicity of three strobilurins (kresoximmethyl, pyraclostrobin and trifloxystrobin) on Daphnia magna. Environ. Toxicol. Chem. 36, 182e189. Ding, F., Liu, W., Li, N., Zhang, L., Sun, Y., 2010. Complex of nicosulfuron with human serum albumin: a biophysical study. J. Mol. Struct. 975, 256e264.   Mijin, D.Z.,  Dugand zic, A.M., Tomasevic, A.V., Radisic, M.M., Sekuljica, N.Z., Petrovic, S.D., 2017. Effect of inorganic ions, photosensitisers and scavengers on the photocatalytic degradation of nicosulfuron. J. Photochem. Photobiol., A 336, 146e155. Fairchild, J.F., Ruessler, D.S., Haverland, P.S., Carlson, A.R., 1997. Comparative sensitivity of selenastrum capricornutum and lemna minor to sixteen herbicides. Arch. Environ. Contam. Toxicol. 32, 353e357. Gao, Y., Li, Y., Zhang, L., Huang, H., Hu, J.J., Shah, S.M., Su, X.G., 2012. Adsorption and removal of tetracycline antibiotics from aqueous solution by graphene oxide. J. Colloid Interface Sci. 368, 540e546. Gong, Z.L., Li, S.J., Han, W.F., Wang, J.P., Ma, J., Zhang, X.D., 2016. Recyclable graphene oxide grafted with poly(N-isopropylacrylamide) and its enhanced selective adsorption for phenols. Appl. Surf. Sci. 362, 459e468. Guo, X.K., Dong, S.P., Petersen, E.J., Gao, S.X., Huang, Q.G., Mao, L., 2013. Biological uptake and depuration of radio-labeled graphene by Daphnia magna. Environ. Sci. Technol. 47, 12524e12531. Hassan, A., Tayebeh, E.K., Simin, N., Ramin, N., Mohammad, K., 2018. Hexavalent chromium removal from aqueous solution using functionalized chitosan as a novel nano-adsorbent: modeling and optimization, kinetic, isotherm, and thermodynamic studies, and toxicity testing, 25, pp. 20154e20168. nchez-Gonz Herrero-Hern andez, E., Rodríguez-Cruz, M.S., Pose-Juan, E., Sa alez, S., nchez-Martín, M.J., 2017. Seasonal distribution of herbicide Andrades, M.S., Sa and insecticide residues in the water resources of the vineyard region of La Rioja (Spain). Sci. Total Environ. 609, 161e171. Joly, P., Bonnemoy, F., Charvy, J.C., Bohatier, J., Mallet, C., 2013. Toxicity assessment of the maize herbicides S-metolachlor, benoxacor, mesotrione and nicosulfuron, and their corresponding commercial formulations, alone and in mixtures, using the Microtox (R) test. Chemosphere 93, 2444e2450. Kapsi, M., Tsoutsi, C., Paschalidou, A., Albanis, T., 2019. Environmental monitoring and risk assessment of pesticide residues in surface waters of the Louros River

C. Li et al. / Environmental Pollution 255 (2019) 113150 (N.W. Greece). Sci. Total Environ. 650, 2188e2198. Kica, M., Ronka, S., 2014. The removal of atrazine from water using specific polymeric adsorbent. Separ. Sci. Technol. 49, 1634e1642. Kim, Y., Kim, D., Jang, G., Kim, J., Lee, T.S., 2015. Fluorescent, stimuli-responsive, crosslinked PNIPAM-based microgel. Sens. Actuators, B 207, 623e630. Leboulanger, C., Rimet, F., Lacotte, M.H., Berard, A., 2001. Effects of atrazine and nicosulfuron on freshwater microalgae. Environ. Int. 26, 131e135. Leonard, C.E., Hennessy, S., Han, X., Siscovick, D.S., Flory, J.H., Deo, R., 2017. Pro-and antiarrhythmic actions of sulfonylureas: mechanistic and clinical evidence. Trends Endocrinol. Metab. 28, 561e586. Li, H.Z., Sun, Z.B., Zhang, L., Tian, Y.X., Cui, G.J., Yan, S.Q., 2016. A cost-effective porous carbon derived from pomelo peel for the removal of methyl orange from aqueous solution. Colloids Surf., A 489, 191e199. Li, J., Zhou, Q.X., Wu, Y.L., Yuan, Y.Y., Liu, Y.L., 2018. Investigation of nanoscale zerovalent iron-based magnetic and thermal dual-responsive composite materials for the removal and detection of phenols. Chemosphere 195, 472e482. Liu, Z., Robinson, J.T., Sun, X.M., Dai, H.J., 2008. PEGylated nanographene oxide for delivery of water-insoluble cancer drugs. J. Am. Chem. Soc. 130, 10876e10877. Liu, Z.G., Zhang, F.S., 2009. Removal of lead from water using biochars prepared from hydrothermal liquefaction of biomass. J. Hazard Mater. 167, 933e939. Liu, X.T., Zhang, H.Y., Ma, Y.Q., Wu, X.L., Meng, L.X., Guo, Y.L., Yu, G., Liu, Y.Q., 2013. Graphene-coated silica as a highly efficient sorbent for residual organophosphorus pesticides in water. J. Mater. Chem. 1, 1875e1884. Lv, S.N., Cheng, C.J., Song, Y.Y., Zhao, Z.G., 2015. Temperature-switched controlled release nanosystems based on molecular recognition and polymer phase transition. RSC Adv. 5, 3248e3259. Mandal, A., Singh, N., Purakayastha, T.J., 2017. Characterization of pesticide sorption behaviour of slow pyrolysisbiochars as low cost adsorbent for atrazine and imidacloprid removal. Sci. Total Environ. 577, 376e385. , A., Blasco, C., Pico , Y., 2014. Last trends in pesticide residue determination by Masia liquid chromatography-mass spectrometry. Trends Environ. Anal. Chem. 2, 11e24. Matouq, M.A., Al-Anber, Z.A., Tagawa, T., Aljbour, S., Al-Shannag, M., 2008. Degradation of dissolved diazinon pesticide in water using the high frequency of ultrasound wave. Ultrason. Sonochem. 15, 869e874. Michael, J.L., 2003. Environmental fate and impacts of sulfometuron on watersheds in the southern United States. J. Environ. Qual. 32, 456e465. Mohamed, K.A., Basfar, A.A., Al-Shahrani, A.A., 2009. Gamma-ray induced degradation of diazinon and atrazine in natural groundwaters. J. Hazard Mater. 166, 810e814. Offeman, R.E., Hummers, J.R., William, S., 1958. Preparation of graphitic oxide. J. Am. Chem. Soc. 80, 1339. de rique, B., Charvy, J.C., Bohatier, J., Clarisse, M., 2013. Toxicity assessPierre, J., Fre ment of the maize herbicides S-metolachlor, benoxacor, mesotrione and nicosulfuron, and their corresponding commercial formulations, alone and in mixtures, using the Microtoxtest. Chemosphere 93, 2444e2450. Rosenbom, A.E., Kjær, J., Olsen, P., 2010. Long-term leaching of rimsulfuron degradation products through sandy agricultural soils. Chemosphere 79, 830e838. Russell, M.H., Saladini, J.L., Lichtner, F., 2002. Sulfonylurea herbicides. Pestic. Outlook 13, 166e173. Sabadie, J., 2002. Nicosulfuron: alcoholysis, chemical hydrolysis, and degradation on various minerals. J. Agric. Food Chem. 50, 526e531. Sarmah, A.K., Sabadie, J., 2002. Hydrolysis of sulfonylurea herbicides in soils andaqueous solutions: a review. J. Agric. Food Chem. 50, 53e62. Shah, J., Jan, M.R., Tasmia, 2018. Magnetic chitosan graphene oxide composite for solid phase extraction of phenylurea herbicides. Carbohydr. Polym. 199, 461e472.

9

Shi, Y., Ma, C.B., Peng, L.L., Yu, G.H., 2015a. Conductive “smart” hybrid hydrogels with PNIPAM and nanostructured conductive polymers. Adv. Funct. Mater. 25, 1219e1225. Shi, Y.G., Liu, M.Y., Wang, K., Deng, F.J., Wan, Q., Huang, Q., Fu, L.H., Zhang, X.Y., Wei, Y., 2015b. Bioinspired preparation of thermo-responsive graphene oxide nanocomposites in aqueous solution. Polym. Chem. 6, 5876e5883. Sierra, S., Ramos, M.C., Molina, P., Esteo, C., Vazquez, J.A., Burgos, J.S., 2011. Statins as neuroprotectants: a comparative in vitro study of lipophilicity, blood-brainbarrier penetration, lowering of brain cholesterol, and decrease of neuron cell death. J. Alzheimer's Dis. 23, 307e318.  izares, P., Rodrigo, M.A., 2017. Souza, F., Quijorna, S., Lanza, M.R.V., S aez, C., Can Applicability of electrochemical oxidation using diamond anodes to the treatment of a sulfonylurea herbicide. Catal. Today 280, 192e198. Tabrizian, P., Ma, W., Bakr, A., Rahaman, M.S., 2019. pH-sensitive and magnetically separable Fe/Cu bimetallic nanoparticles supported by graphene oxide (GO) for high-efficiency removal of tetracyclines. J. Colloid Interface Sci. 534, 549e562. Toumi, H., Boumaiza, M., Millet, M., Radetski, C.M., Felten, V., Ferard, J.F., 2015. Is acetylcholinesterase a biomarker of susceptibility in Daphnia magna (Crustacea, Cladocera) after deltamethrin exposure? Chemosphere 120, 351e356. Tranel, P.J., Wright, T.R., 2002. Resistance of weeds to ALS-inhibiting herbicide: what we have learned? Weed Sci. 50, 700e712. Wang, L., Jiang, L., Su, D., Sun, C., Chen, M.F., Goh, K.L., Chen, Y., 2014. Non-covalent synthesis of thermo-responsive graphene oxideeperylene bisimidescontaining poly(N-isopropylacrylamide) hybrid for organic pigment removal. J. Colloid Interface Sci. 430, 121e128. Wei, H., Yang, W.S., Xi, Q., Chen, X., 2012. Preparation of Fe3O4@graphene oxide core-shell magnetic particles for use in protein adsorption. Mater. Lett. 82, 224e226. Weston, D.P., Holmes, R.W., You, J., Lydy, M.J., 2005. Aquatic toxicity due to residential use of pyrethroid insecticides. Environ. Sci. Technol. 39, 9778e9784. Wu, J., Lu, J., Wilson, C., Lin, Y.J., Lu, H., 2010. Effective liquid-liquid extraction method for analysis of pyrethroid and phenylpyrazole pesticides in emulsionprone surface water samples. J. Chromatogr. A 1217, 6327e6333. r, M., Prucek, R., Ranc, V., Bedna r, P., Varma, R.S., Sharma, V.K., Zají cek, P., Kola Zboril, R., 2015. Oxidative degradation of triazine- and sulfonylurea-based herbicides using Fe(VI): the case study of atrazine and iodosulfuron with kinetics and degradation products. Sep. Purif. Technol. 156, 1041e1046. Zhang, M., Li, Y., Yang, Q.L., Huang, L.L., Chen, L.H., Ni, Y.H., Xiao, H.N., 2018. Temperature and pH responsive cellulose filament/poly (NIPAM-co-AAc) hybrids as novel adsorbent towards Pb(II) removal. Carbohydr. Polym. 195, 495e504. Zhao, H.Y., Zhu, J.Y., Liu, S.N., Zhou, X.G., 2018. Kinetics study of nicosulfuron degradation by a Pseudomonas nitroreducens strain NSA02. Biodegradation 29, 271e283. Zheng, M.X., Lian, F.L., Zhu, Y.J., Zhang, Y., Liu, B., Zhang, L.T., Zheng, B.D., 2019. pHresponsive poly (xanthan gum-g-acrylamide-g-acrylic acid) hydrogel: preparation, characterization, and application. Carbohydr. Polym. 210, 38e46. Zhou, Q., Wang, W., Xiao, J., 2006. Preconcentration and determination of nicosulfuron, thifensulfuron-methyl and metsulfuron-methyl in water samples using carbon nanotubes packed cartridge in combination with high performance liquid chromatography. Anal. Chim. Acta 559, 200e206. Zhu, G.T., Xing, X.J., Wang, J.Q., Zhang, X.W., 2017. Effect of acid and hydrothermal treatments on the dye adsorption properties of biomass-derived activated carbon. J. Mater. Sci. 52, 7664e7676. Zhu, Q., DeGelmann, P., Niessner, R., Knopp, D., 2002. Selective trace analysis of sulfonylurea herbicides in water and soil samples based on solid-phase extraction using a molecularly imprinted polymer. Environ. Sci. Technol. 36, 5411e5420.