Adsorption Properties of Polyethersulfone-Modified Attapulgite Hybrid Microspheres for Bisphenol A and Sulfamethoxazole

In this paper, attapulgite purified by acid heat was employed, and millimeter polyethersulfone-modified attapulgite hybrid microspheres were prepared. The effects of mixed bisphenol A (BPA) and sulfamethoxazole (SMX) solution on the modified attapulgite doping ratio, initial solution pH, adsorbent dosage, contaminant concentration, and temperature were studied. The experimental results showed that BPA and SMX compete in the adsorption process, and the hybrid microspheres preferentially select the BPA molecules (anionic endocrine disruptors) compared to the SMX. The adsorption process in the mixed solution conforms to the quasi-secondary-order kinetic model. The adsorption of BPA and SMX by hybrid microspheres is more consistent with the extended Langmuir adsorption thermodynamic model, and the adsorption of BPA + SMX is more in line with the Langmuir adsorption thermodynamic model. At 25 °C, the maximum adsorption capacity of hybrid microspheres for BPA and SMX was 102.04 and 12.80 μmol·g−1, respectively, and the maximum adsorption of BPA + SMX was 112.36 μmol·g−1. After five regenerations, the removal effect of the hybrid microspheres on the endocrine disruptors remained above 95%.


Introduction
Endocrine-disrupting compounds (EDCs) are a class of hazardous substances that affect specific levels of endocrine (hormone) systems. Researchers, from the perspective of in vivo models and combined with clinical epidemiology, found that EDCs can cause diseases such as breast cancer and prostate cancer and affect human reproduction, thyroid, cardiovascular effects, and neuroendocrine systems [1]. In addition, EDCs can cause some metabolic diseases including obesity, diabetes, etc. EDCs can affect various functions of the body through different destruction pathways, for example, activation or inactivation of endocrine target receptors, disruption of hormone synthesis, activation of inactive hormones, etc. Studies showed that EDCs could affect the ability of hormone-metabolizing enzymes and affect the reactivity of nuclear receptors by altering hormone activity [2], change the normal course of estrogen and androgen action, inhibit or interfere with the synthesis of metabolic steroids [3], and influence estrogen and androgen receptors, promoting or inhibiting transcriptional or post-transcriptional synthesis mechanisms [4].
EDCs are usually organic pollutants or heavy metal substances. Most of the pesticides and stabilizers and plasticizers in plastics use endocrine disruptors, such as organochlorine pesticides, polychlorinated biphenyl (PCB), alkylphenol (AP), bisphenol A (BPA), alkylphenol ethoxylate (APE), and phthalate acid esters (PAE). EDCs come from a wide range of sources and can be discharged into natural water through certain channels, resulting in water pollution [5].

Preparation of PES-modified Attapulgite Hybrid Microspheres
Acid heat modification treatment: the purified attapulgite was immersed in 2 mol·L −1 hydrochloric acid in a water bath for 70 min, and the precipitate was taken out by suction filtration, then washed repeatedly with distilled water until neutral. After roasting for 2 h in a muffle furnace (200 • C), it was then sieved with a 100-mesh sieve to obtain an acid heat-modified attapulgite (AH-ATT).
Organic modification treatment: firstly, 5 g of CTMAB and 10 g of AH-ATT were dispersed into an ethanol/water (1000 mL/50 mL) mixed solution and stirred for 24 h. Then, the modified attapulgite was repeatedly resuspended, filtrated, and washed until the supernatant of the resuspension did not contain bromide ions. The organic acid heat-modified attapulgite (OAH-ATT) was obtained after drying and sieving (100 mesh).
Preparation of hybrid microspheres: PES was dissolved in DMAC and used to set up a solution with a mass fraction of 12%. OAH-ATT was added to the solution; then, the mixed solution was dropped into distilled water at a rate of 60 to 100 drops·min −1 at room temperature to prepare hybrid microspheres. The prepared microspheres were washed with distilled water, then washed with ethanol, and dried for use.

Calculation Method of Endocrine Disruptor
When the wavelengths of the spectrophotometer were 283 and 296 nm, the absorbances of the two endocrine disruptors of BPA and SMX in the solution did not interfere with each other based on the configured concentration of the mixed solution. Therefore, multiple linear regression methods can be used for analysis. In statistics, multiple linear regression is a method of fitting experimental data using linear equations to simulate the relationship between two or among more independent variables. Multiple linear regression can be expressed as follows [17]: where Y is the target value, and the data are the total absorbance of the mixed solution of the spectrophotometer at the selected wavelength; X n (n = 1, . . . , n) is the value of each independent variable, which is the absorbance of the two components of BPA and SMX at the selected wavelength; b n (n = 1, . . . , n) is the coefficient of the regression equation. In the experiment, the mixed solution was configured with ultrapure water, and there was no background interference to the total absorbance, while other coefficients were calculated using the experimentally prepared standard solution.
In order to study the adsorption kinetics, hybrid microspheres with a doping ratio of 1:2 were added to the mixed solution at 25 • C, 200 rpm, and pH 6. The total concentration of the mixed solution was 50, 100, 150, 200, or 250 µmol·L −1 . In order to study the adsorption thermodynamics, hybrid microspheres with a doping ratio of 1:2 were added to the mixed solution at a rotation speed of 200 rpm and pH 6 (the total concentration of the mixed solution was 50-500 µmol·L −1 ). The adsorption performance of hybrid microspheres at 25 • C, 40 • C, and 55 • C was investigated.
Considering that the concentrated liquid produced by acid-base regeneration is difficult to handle, pure ethanol was used as the regeneration liquid. Hybridized microspheres with a doping ratio of 2:1 were added to the mixed solution (20 mL, pH 6, 50 µmol·L −1 endocrine disrupting solution) and shaken for five days in a shaking incubator at 25 • C, 200 rpm. The adsorbed and equilibrated hybrid microspheres were placed into a 20-mL ethanol solution and regenerated in a shaking incubator at 25 • C, 200 rpm for one day. After that, it was washed repeatedly with ultrapure water at least three times and dried. The adsorption experiment was repeated again.
For the regeneration test, ethanol solution was utilized to regenerate the adsorbent. The adsorption amount (C) was detected after every regeneration process, and the initial adsorption amount was denoted as C 0 . The regeneration rate was equal to C/C 0 .
All of the above experiments were repeated three times, and the data were averaged.

Apparent Characteristics of Hybrid Microspheres
Diameter, porosity, and total pore volume of hybrid microspheres [18] were calculated according to Equations (2)-(4). Diameter: Porosity: Total pore volume: where W A is the mass of hybrid microspheres after drying (g), W B is the mass of hybrid microspheres before drying (g), ρ w is the density of water (ρ w = 1.0 g·cm −3 ), ρ p is the density of PES (ρ p = 1.43 g·cm −3 ), ρ c is the density of modified attapulgite (ρ c = 1.67 g cm −3 ), n is the number of weighed hybrid microspheres selected (n = 25), and C is the proportion of modified attapulgite in the hybrid microspheres (%). The calculation results of the diameter, surface area, porosity, and total pore volume of the hybrid microspheres are shown in Table 1. In Table 1, as the doping amount of the modified attapulgite increased, the porosity and total pore volume of the hybrid microspheres gradually decreased, but the specific surface area gradually increased. Figure 1 shows SEM images of hybrid microspheres. The characteristics of the hybrid microspheres in the figure were as follows: (1) pure PES microspheres formed an intermediate gap during the ball formation process, and the PES material wrapped the intermediate gap into a ball; (2) with the increase in doping amount of the modified attapulgite, the voids inside the hybrid microspheres were gradually reduced; (3) during the doping process of the modified attapulgite, the voids at the edge of the microspheres were preferentially filled, and the internal voids of the microspheres were gradually filled when increasing the doping amount; (4) by comparing PA4 and PA5, the macropores in the microspheres were filled when the doping amount continuously increased, and the modified attapulgite was filled in the small pores of the microspheres, thereby making the microspheres more compact. with the increase in doping amount of the modified attapulgite, the voids inside the hybrid microspheres were gradually reduced; (3) during the doping process of the modified attapulgite, the voids at the edge of the microspheres were preferentially filled, and the internal voids of the microspheres were gradually filled when increasing the doping amount; (4) by comparing PA4 and PA5, the macropores in the microspheres were filled when the doping amount continuously increased, and the modified attapulgite was filled in the small pores of the microspheres, thereby making the microspheres more compact.

Effect of Modified Attapulgite Doping Ratio
In Figure 2, when the doping ratio increased from 0:1 to 2:1, the adsorption amount of the hybridized microspheres to the BPA increased from 1.27 µmol·g −1 to 5.91 µmol·g −1 , and the adsorption amount of SMX increased to 3.13 µmol·g −1 from 0.27 µmol·g −1 . The removal rate of BPA + SMX increased from 11.62% to 67.85%. The pure PES microspheres had a poor adsorption effect on the endocrine disruptors BPA and SMX in the mixed solution, with only 1.27 µmol·g −1 and 0.27 µmol·g −1 . The modified attapulgite played a major role in the adsorption process of endocrine disruptors, while the PES acted as a skeleton to support the modification of the attapulgite particles. endocrine disruptors BPA and SMX in the mixed solution, with only 1.27 μmol·g and 0.27 μmol·g . The modified attapulgite played a major role in the adsorption process of endocrine disruptors, while the PES acted as a skeleton to support the modification of the attapulgite particles.
When the doping ratio of the hybrid microspheres increased from 0:1 to 1.5:1, the adsorption amount of the endocrine disruptors increased significantly by the hybrid microspheres, and the total adsorption amount increased from 1.55 μmol·g −1 to 8.45 μmol·g −1 . However, when the doping ratio increased from 1.5:1 to 2:1, the adsorption capacity of the hybrid microspheres to the endocrine disruptors slightly increased. The total adsorption increased from 8.45 μmol·g −1 to 9.05 μmol·g −1 . The adsorption active site increased in size due to an increase in specific surface area at a lower doping ratio, but further decreased in terms of porosity and total pore volume when the doping ratio of the hybrid microspheres was further increased. Thus, the increase in specific surface area did not effectively enlarge the adsorption active site. With the same doping ratio, the adsorption amount of BPA and SMX was lower when compared with the BPA in the single-component solution, but higher than with the SMX in the single-component solution. Overall, increasing the doping ratio could highly improve the adsorption amount of BPA and SMX.

Effect of the Initial pH of the Solution
In Figure 3, as the pH of the solution increased from 2 to 12, the adsorption amount of BPA by the hybrid microspheres increased from 5.65 μmol·g −1 to 6.75 μmol·g −1 , and the adsorption amount of hybrid microspheres to SMX increased from 1.00 μmol·g −1 to 4.81 μmol·g −1 . This suggests that the electrostatic force had little effect on the adsorption process under alkaline conditions. The effect of CTMAB on the surface of the attapulgite had a greater influence on the adsorption capacity of the hybrid microspheres. Hybrid microspheres had a stronger adsorption effect on anionic endocrine disruptors than cationic ones. The adsorption effect of the hybrid microspheres on BPA and SMX could be effectively enhanced due to the ionization. This is probably because the pKa of BPA (9.6, 10.2) is much higher than that of SMX (1.8, 5.7) [19]. A previous study also reported that the adsorption amount of BPA was only slightly varied whether in acidic or basic environment [20]. When the doping ratio of the hybrid microspheres increased from 0:1 to 1.5:1, the adsorption amount of the endocrine disruptors increased significantly by the hybrid microspheres, and the total adsorption amount increased from 1.55 µmol·g −1 to 8.45 µmol·g −1 . However, when the doping ratio increased from 1.5:1 to 2:1, the adsorption capacity of the hybrid microspheres to the endocrine disruptors slightly increased. The total adsorption increased from 8.45 µmol·g −1 to 9.05 µmol·g −1 . The adsorption active site increased in size due to an increase in specific surface area at a lower doping ratio, but further decreased in terms of porosity and total pore volume when the doping ratio of the hybrid microspheres was further increased. Thus, the increase in specific surface area did not effectively enlarge the adsorption active site. With the same doping ratio, the adsorption amount of BPA and SMX was lower when compared with the BPA in the single-component solution, but higher than with the SMX in the single-component solution. Overall, increasing the doping ratio could highly improve the adsorption amount of BPA and SMX.

Effect of the Initial pH of the Solution
In Figure 3, as the pH of the solution increased from 2 to 12, the adsorption amount of BPA by the hybrid microspheres increased from 5.65 µmol·g −1 to 6.75 µmol·g −1 , and the adsorption amount of hybrid microspheres to SMX increased from 1.00 µmol·g −1 to 4.81 µmol·g −1 . This suggests that the electrostatic force had little effect on the adsorption process under alkaline conditions. The effect of CTMAB on the surface of the attapulgite had a greater influence on the adsorption capacity of the hybrid microspheres. Hybrid microspheres had a stronger adsorption effect on anionic endocrine disruptors than cationic ones. The adsorption effect of the hybrid microspheres on BPA and SMX could be effectively enhanced due to the ionization. This is probably because the pKa of BPA (9.6, 10.2) is much higher than that of SMX (1.8, 5.7) [19]. A previous study also reported that the adsorption amount of BPA was only slightly varied whether in acidic or basic environment [20].

Effect of Adsorbent Dosage
In Figure 4, when the adsorbent dosage increased from 12.5 mg to 125 mg, the adsorption amount of the hybridized microspheres to the BPA decreased from 18.97 μmol·g −1 to 3.71 μmol·g −1 , and the adsorption amount of SMX decreased from 9.64 μmol·g −1 to 2.66 μmol·g −1 . The increase in adsorbent dosage could increase the effective active sites of the two endocrine disruptors, but the adsorption amount per gram decreased. Hybrid microspheres had a better affinity for hydrophobic endocrine disruptors, and the adsorption amount of BPA was higher than that of SMX. The lower adsorption amount of SMX was probably because the log Kow of SMX (0.9) is much lower than that of BPA (2.2) [21].

Effect of Initial Endocrine Disruptor Concentration
In Figure 5, when the initial concentration increased from 50 μmol·L −1 to 500 μmol·L −1 , the adsorption amount of the hybridized microspheres to the BPA increased from 3.13 μmol·g −1 to 11.04 μmol·g −1 , and the adsorption amount of SMX increased from 5.105 μmol·g −1 to 53.05 μmol·g −1 . Since the initial concentration of endocrine disruptors provides an important driving force to overcome the mass transfer resistance between the aqueous solution and the solid phase, the increase in endocrine disruptors concentration could increase the adsorption capacity of the adsorbent. However, since there is also a competition effect between the endocrine at the effective active sites, the removal effect of the hybrid microspheres deteriorated. The adsorption amount of the hybrid microspheres was

Effect of Adsorbent Dosage
In Figure 4, when the adsorbent dosage increased from 12.5 mg to 125 mg, the adsorption amount of the hybridized microspheres to the BPA decreased from 18.97 µmol·g −1 to 3.71 µmol·g −1 , and the adsorption amount of SMX decreased from 9.64 µmol·g −1 to 2.66 µmol·g −1 . The increase in adsorbent dosage could increase the effective active sites of the two endocrine disruptors, but the adsorption amount per gram decreased. Hybrid microspheres had a better affinity for hydrophobic endocrine disruptors, and the adsorption amount of BPA was higher than that of SMX. The lower adsorption amount of SMX was probably because the log K ow of SMX (0.9) is much lower than that of BPA (2.2) [21].

Effect of Adsorbent Dosage
In Figure 4, when the adsorbent dosage increased from 12.5 mg to 125 mg, the adsorption amount of the hybridized microspheres to the BPA decreased from 18.97 μmol·g −1 to 3.71 μmol·g −1 , and the adsorption amount of SMX decreased from 9.64 μmol·g −1 to 2.66 μmol·g −1 . The increase in adsorbent dosage could increase the effective active sites of the two endocrine disruptors, but the adsorption amount per gram decreased. Hybrid microspheres had a better affinity for hydrophobic endocrine disruptors, and the adsorption amount of BPA was higher than that of SMX. The lower adsorption amount of SMX was probably because the log Kow of SMX (0.9) is much lower than that of BPA (2.2) [21].

Effect of Initial Endocrine Disruptor Concentration
In Figure 5, when the initial concentration increased from 50 μmol·L −1 to 500 μmol·L −1 , the adsorption amount of the hybridized microspheres to the BPA increased from 3.13 μmol·g −1 to 11.04 μmol·g −1 , and the adsorption amount of SMX increased from 5.105 μmol·g −1 to 53.05 μmol·g −1 . Since the initial concentration of endocrine disruptors provides an important driving force to overcome the mass transfer resistance between the aqueous solution and the solid phase, the increase in endocrine disruptors concentration could increase the adsorption capacity of the adsorbent. However, since there is also a competition effect between the endocrine at the effective active sites, the removal effect of the hybrid microspheres deteriorated. The adsorption amount of the hybrid microspheres was

Effect of Initial Endocrine Disruptor Concentration
In Figure 5, when the initial concentration increased from 50 µmol·L −1 to 500 µmol·L −1 , the adsorption amount of the hybridized microspheres to the BPA increased from 3.13 µmol·g −1 to 11.04 µmol·g −1 , and the adsorption amount of SMX increased from 5.105 µmol·g −1 to 53.05 µmol·g −1 . Since the initial concentration of endocrine disruptors provides an important driving force to overcome the mass transfer resistance between the aqueous solution and the solid phase, the increase in endocrine disruptors concentration could increase the adsorption capacity of the adsorbent. However, since there is also a competition effect between the endocrine at the effective active sites, the removal effect of the hybrid microspheres deteriorated. The adsorption amount of the hybrid microspheres was lower than that in the unit system. This is due to the competitive relationship between BPA and SMX in the mixed system. By comparing the binary system and the unit system at the same concentration, the hybrid microspheres preferentially adsorbed BPA. The results are probably due to the higher negative charge of SMX than BPA, while some of the SMX adsorption sites were occupied by BPA molecules [22]. lower than that in the unit system. This is due to the competitive relationship between BPA and SMX in the mixed system. By comparing the binary system and the unit system at the same concentration, the hybrid microspheres preferentially adsorbed BPA. The results are probably due to the higher negative charge of SMX than BPA, while some of the SMX adsorption sites were occupied by BPA molecules [22].  Figure 6 shows the adsorption kinetics of BPA and SMX. With the increase in initial concentration of the mixed solution, the adsorption amount of the hybrid microspheres to BPA and SMX also increased. The initial concentration of the solution provides an important driving force to overcome its mass transfer resistance between the aqueous solution and the solid phase. Therefore, a higher initial concentration of the mixed solution led to a stronger adsorption effect, that is, a larger adsorption amount of the hybrid microspheres to BPA and SMX.

Adsorption Kinetics
The quasi-first-order kinetic model, quasi-second-order kinetic model, and intraparticle diffusion model were used to fit the process of adsorption of endocrine disruptors by hybrid microspheres. The results are shown in Tables 2 and 3. In Table 2, the quasi-second-order kinetic model had a higher correlation coefficient (R 2 > 0.996) relative to the quasi-first-order kinetic model (R 2 < 0.962), and the theoretically calculated adsorption amount agreed well with the experimental adsorption amount, indicating that the adsorption process conformed to the quasi-secondary kinetic model. The qe value increased with the initial concentration, while the rate constant (K2) decreased, due to the adsorption provided by a certain amount of adsorbent. The adsorption competition of endocrine disruptors on hybrid microspheres was less at lower concentrations, while the adsorption of endocrine disruptors at higher concentrations was more competitive.  Figure 6 shows the adsorption kinetics of BPA and SMX. With the increase in initial concentration of the mixed solution, the adsorption amount of the hybrid microspheres to BPA and SMX also increased. The initial concentration of the solution provides an important driving force to overcome its mass transfer resistance between the aqueous solution and the solid phase. Therefore, a higher initial concentration of the mixed solution led to a stronger adsorption effect, that is, a larger adsorption amount of the hybrid microspheres to BPA and SMX. The fitting results of the intraparticle diffusion model to the adsorption process showed that qt and t 0.5 exhibited multiple sets of linear relationships. The fitting data are shown in Table 3. The adsorption process could be divided into two stages. In phase I, the adsorption process was faster, and the removal rate of BPA + SMX accounted for about 60% of the total removal rate within 6 h. At this stage, macropore diffusion dominated. BPA and SMX were rapidly adsorbed onto the active sites at the outermost layer of the macropores. In phase II, the adsorption process proceeded slowly, and the hybrid microspheres reached the final adsorption equilibrium in about four days. BPA + SMX accounted for about 40% of the total removal rate. After the outer active site was saturated, the BPA and SMX molecules entered the active sites in the micropores, and intraparticle diffusion played a dominant role. The adsorption experiments were carried out at different stirring speeds, and it was found that the kp value of phase I did not change much, which proved that phase I was not affected by the diffusion of the boundary layer of the particles. Therefore, during the process of endocrine disruptors in the hybrid microsphere, phase I is a macroporous diffusion process and phase II is an intraparticle diffusion process. The quasi-first-order kinetic model, quasi-second-order kinetic model, and intraparticle diffusion model were used to fit the process of adsorption of endocrine disruptors by hybrid microspheres. The results are shown in Tables 2 and 3. In Table 2, the quasi-second-order kinetic model had a higher correlation coefficient (R 2 > 0.996) relative to the quasi-first-order kinetic model (R 2 < 0.962), and the theoretically calculated adsorption amount agreed well with the experimental adsorption amount, indicating that the adsorption process conformed to the quasi-secondary kinetic model. The q e value increased with the initial concentration, while the rate constant (K 2 ) decreased, due to the adsorption provided by a certain amount of adsorbent. The adsorption competition of endocrine disruptors on hybrid microspheres was less at lower concentrations, while the adsorption of endocrine disruptors at higher concentrations was more competitive. The fitting results of the intraparticle diffusion model to the adsorption process showed that q t and t 0.5 exhibited multiple sets of linear relationships. The fitting data are shown in Table 3. The adsorption process could be divided into two stages. In phase I, the adsorption process was faster, and the removal rate of BPA + SMX accounted for about 60% of the total removal rate within 6 h. At this stage, macropore diffusion dominated. BPA and SMX were rapidly adsorbed onto the active sites at the outermost layer of the macropores. In phase II, the adsorption process proceeded slowly, and the hybrid microspheres reached the final adsorption equilibrium in about four days. BPA + SMX accounted for about 40% of the total removal rate. After the outer active site was saturated, the BPA and SMX molecules entered the active sites in the micropores, and intraparticle diffusion played a dominant role. The adsorption experiments were carried out at different stirring speeds, and it was found that the k p value of phase I did not change much, which proved that phase I was not affected by the diffusion of the boundary layer of the particles. Therefore, during the process of endocrine disruptors in the hybrid microsphere, phase I is a macroporous diffusion process and phase II is an intraparticle diffusion process.

Adsorption Kinetics
In Tables 2 and 3, q e,exp is the equilibrium adsorption amount obtained in the experiment, and q e,cal is the calculated equilibrium adsorption amount. The separation factor defined by the Langmuir model was Rl = 1/(1 + KlC0), where C0 is the initial concentration of the solution, and the initial concentration of the mixed solution was 50-500 μmol·L −1 , calculated as 0 < Rl < 1.Therefore, the adsorption process of the endocrine disruptors in the mixed solution by the hybrid microspheres was a preferential adsorption process. According to the results of the Freundlich model fitting, it is known that 0 < 1/n < 1, indicating that the adsorption process was relatively easy to perform. The Langmuir and Freundlich thermodynamic fittings were applied to the adsorption isotherms of BPA, SMX, and BPA + SMX. Multiple linear regression analysis methods were used to extend the Langmuir thermodynamic fitting of the BPA + SMX adsorption isotherms. All parameters after fitting are shown in Table 4. According to the fitting results, the adsorption process of BPA and by hybrid microspheres was more consistent with the extended Langmuir adsorption thermodynamic model, and the adsorption process of BPA + SMX was more in line with the Langmuir adsorption thermodynamic model. The fitting results show that the adsorption process was uniform monolayer surface adsorption. The maximum adsorption capacities of hybrid microspheres in the mixed solution were 102.04 µmol·g −1 , 97.09 µmol·g −1 , and 90.91 µmol·g −1 under the conditions of 298 K, 313 K, and 328 K, respectively, while the maximum adsorption capacities of SMX were 12.80 µmol·g −1 , 10.73 µmol·g −1 , and 8.35 µmol·g −1 . The adsorption amount of the hybrid microspheres to the SMX was lower than that of the SMX in the single-component solution, but the adsorption amount of the BPA in the mixed solution was close to that of the single-component solution. This indicated that the adsorption of SMX by the hybrid microspheres was greatly affected by the BPA in the mixed solution, while the adsorption of BPA in the mixed solution was less affected by the SMX in the mixed solution. This may be due to the different solubilities of BPA and SMX in water. The active adsorption sites of hybrid microspheres were limited, and BPA molecules with lower solubility were preferentially selected in the mixed solution of BPA and SMX. This might be due to the lower log K ow of SMX.

Adsorption Thermodynamics
The separation factor defined by the Langmuir model was R l = 1/(1 + K l C 0 ), where C 0 is the initial concentration of the solution, and the initial concentration of the mixed solution was 50-500 µmol·L −1 , calculated as 0 < R l < 1.Therefore, the adsorption process of the endocrine disruptors in the mixed solution by the hybrid microspheres was a preferential adsorption process. According to the results of the Freundlich model fitting, it is known that 0 < 1/n < 1, indicating that the adsorption process was relatively easy to perform.
The ∆G 0 , ∆H 0 , and ∆S 0 in Langmuir thermodynamic fitting were calculated as shown in Table 5. It can be seen from Table 5 that the free energy of the hybrid microspheres in the adsorption process of endocrine disruptors was negative, and the value was about −21.5 kJ mol −1 , indicating that the whole adsorption was spontaneous, and the process of physical adsorption was the main process. Moreover, as the temperature increased, the absolute value of the free energy slightly increased, indicating that the temperature had little effect on the entire adsorption process. In Table 5, ∆H 0 was a negative value, indicating that the adsorption process was an exothermic reaction. ∆S 0 was a positive value, indicating that the endocrine disruptor in the hybrid microsphere adsorption mixed solution was a process with an entropy increase. This indicates that the hybrid microsphere preferentially adsorbed BPA in the mixed solution. Table 5. Thermodynamic parameters of binary mixed solution.

Regeneration
The hybrid microspheres after adsorption were regenerated with a pure ethanol solution, and the results are shown in Figure 8. After five regenerations, the removal effect of the hybrid microspheres on the endocrine disruptors remained above 95%. This is because the endocrine disruptors were not strong at the adsorption site, and they were easily resolved. This result suggests that the hybrid microspheres could be repeatedly used, thereby reducing the cost. Table 5. Thermodynamic parameters of binary mixed solution.

Regeneration
The hybrid microspheres after adsorption were regenerated with a pure ethanol solution, and the results are shown in Figure 8. After five regenerations, the removal effect of the hybrid microspheres on the endocrine disruptors remained above 95%. This is because the endocrine disruptors were not strong at the adsorption site, and they were easily resolved. This result suggests that the hybrid microspheres could be repeatedly used, thereby reducing the cost.

Conclusions
(1) The effects of hybrid microspheres on the adsorption of BPA and SMX were comprehensively investigated. The increase in doping ratio was beneficial for increasing the adsorption amount of hybrid microspheres to BPA and SMX. The modified attapulgite played a major role in the adsorption process of endocrine disruptors, while PSE acted as a skeleton support embedding modified bump. The increase in pH was beneficial for increasing the adsorption amount of hybrid microspheres to BPA and SMX in the mixed solution. The pH mainly affected the SMX adsorption but had little effect on the BPA adsorption. Hybrid microspheres had a stronger adsorption effect on anionic endocrine disruptors than cationic ones. The hybrid microsphere had a better affinity for the hydrophobic endocrine disruptor. When the initial concentration of endocrine disruptors increased, the amount of adsorption of the endocrine disruptors by the hybrid microspheres increased. Hybrid microspheres preferentially adsorbed BPA, since some of the SMX adsorption sites were occupied by BPA molecules.
(2) Adsorption kinetics studies showed that the endocrine disruption of hybrid microspheres reached equilibrium within four days. The adsorption process was more in line with the quasi-second-order kinetic model, and the theoretically calculated equilibrium adsorption amount was close to that obtained by the experimental equilibrium. The rate constant K 2 in the quasi-secondary kinetics decreased with the increase in initial concentration of endocrine disruptors due to the limited adsorption sites provided by a certain amount of hybrid microspheres. According to the results of the intraparticle diffusion model fitting, the adsorption process could be divided into two stages. Phase I was a macroporous diffusion process, which was completed in about 6 h, and the adsorption proceeded rapidly, whereas phase II was a diffusion process within the particle, and adsorption equilibrium was achieved around four days.
(3) The adsorption thermodynamic analysis showed that the adsorption process of BPA and SMX in the hybrid solution was more consistent with the extended Langmuir adsorption thermodynamic model. The process of hybrid microsphere adsorption of BPA + SMX was more consistent with the Langmuir adsorption thermodynamic model. Therefore, the adsorption process was uniform monolayer surface adsorption, and there was competitive adsorption. The maximum adsorption amount of the hybridized microspheres to the BPA was greater than the maximum adsorption amount to the SMX. It was a spontaneous, entropy-increasing, and exothermic reaction process based on