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In this study, the perchlorate sorption behaviors of three various representative anion resins were systematically investigated with respect to sorption kinetics, equilibrium capacity, perchlorate selectivity, thermodynamics and isotherms. Results showed that the equilibrium capacity of the three investigated resins followed the order of Purolite A530E≈magnetic ion exchange resin > Purolite A532E due to the effect of structure type, while magnetic ion exchange resin (MIEX) reached the equilibrium much faster than Purolite A530E and Purolite A532E, which can be attributed to its smaller particle size and larger surface area. Furthermore, the two Purolite resins showed superior perchlorate selectivity than MIEX resin because of matrix and functional groups. The adsorption kinetics for each of three selected resins fitted best with the pseudo-second-order model, indicating the adsorption process was controlled by chemical sorption. While the fitting of intra-particle model implied that intra-particle diffusion was not the only rate-limiting step of the whole process. The isotherm data can be best described by the Freundlich isotherm and the value of intensity of adsorption was larger than 1, suggesting the process was heterogenous and favorable adsorption. The negative Δ G ° manifested that the adsorption of perchlorate by each of the three resins was a spontaneous process, and the positive indicated it was also an endothermic and entropy driven process. Besides, the effects of independent variables on the perchlorate sorption of the three resins were also evaluated completely. Results suggested that the removal of perchlorate increased with the increase of resin dosage and temperature for each of the three resins, and the sorption process was nearly independent of solution pH in a wide range of 4–10 for each of the resins. [ABSTRACT FROM AUTHOR]

Abstract: The reduced graphene oxide/magnetite composites (RGO-M), synthesized by an in situ reaction, have been investigated for the adsorption of fluoroquinolone, ciprofloxacin (CIP) and norfloxacin (NOR). The composites were characterized by Transmission electron microscope (TEM), Scanning electron microscope (SEM), Energy dispersive X-ray (EDX), Vibrating sample magnetometer (VSM), X-ray diffraction (XRD). The high saturation magnetization (12.0emug−1) made them easier and faster to be separated under an external magnetic field. Batch adsorption tests indicated that RGO-M exhibited adsorption affinity to CIP or NOR with a maximum adsorption capacity of 18.22 or 22.20mgg−1, respectively. Langmuir, Freundlich and Temkin model were used to fit the equilibrium data on RGO-M at 298K. The results showed that the adsorption equilibrium could be well fitted by Langmuir and Temkin model. CIP and NOR adsorption on RGO-M could be well described by the pseudo-second order kinetics model. Adsorption of CIP and NOR on RGO-M was found to be strongly dependent on pH. The thermodynamic parameters indicated that the adsorption process was a spontaneous and exothermic process in nature. This study proved that RGO-M could be utilized as an efficient and magnetically separable adsorbent for fluoroquinolone antibiotics. [Copyright &y& Elsevier]

Abstract: The adsorption characteristics of perchlorate on MIEX resin were investigated using batch experiments. Effects of contact time, agitation speed, pH, coexisting anions and organic matter were determined. The kinetics data indicated that the perchlorate adsorption process reached equilibrium within 30min. In an experimental pH of 4.0 to 9.0, perchlorate removal was above 98%. Major anions reduced perchlorate adsorption in the order of SO4 2− >PO4 3− >CO3 2− >NO3 −. However, humic acid had not obvious effect on perchlorate removal. Langmuir, Freundlich, and Temkin isotherms were used to fit the perchlorate adsorption equilibrium at 298K. The results were shown that the adsorption equilibrium could be well fitted by Freundlich isotherm. The pseudo first-order and second-order kinetics models were used to fit the kinetics process of perchlorate adsorption on MIEX resin. The results demonstrated the adsorption kinetics agreed with the pseudo second-order model, indicating that the adsorption of perchlorate on MIEX was chemical sorption. The negative ΔG 0 values indicated that the adsorption of perchlorate on MIEX resin was thermodynamically feasible and was a spontaneous process. The values of ΔH 0and ΔS 0 showed that the adsorption was an exothermic process in nature and the randomness degree at the solid/liquid interface increases after adsorption. [Copyright &y& Elsevier]

Abstract: Fe3O4@mesoporous SiO2 core–shell composite microspheres (MS), synthesized by a typical solvothermal reaction and PEI functionalized MS (MS-PEI), have been investigated for humic acid (HA) adsorption. The structure of microspheres was characterized using scanning electron microscope, transmission electron microscope, energy dispersive X-ray, N2 adsorption–desorption, zeta potential measurements, X-ray diffraction and vibrating sample magnetometer. The high saturation magnetization (31.9emu/g) made them easier and faster to be separated from water under an external magnetic field. Batch adsorption tests indicated that MS-PEI exhibited high adsorption affinity to aqueous HA with a maximum adsorption capacity of 128.64mg/g. The Freundlich model could fit the adsorption isotherm of HA on MS and MS-PEI very well, implying that adsorption processes are heterogeneous. HA adsorption on MS and MS-PEI could be well described by the pseudo-second-order kinetics. Adsorption of HA on the adsorbents was found to be strongly dependent on pH. HA loaded MS-PEI can be effectively desorbed in 0.1M NaOH, and the regenerated microspheres can be recycled. So, it can be used as a promising adsorbent for the adsorptive HA removal in water treatment process. [Copyright &y& Elsevier]

Abstract: The adsorption characteristics of fluoride on activated alumina (AA) were studied using batch methods. Effects of reaction time, pH, ionic strength, and coexisting anions were determined. Kinetics data indicated that the fluoride adsorption process reached equilibrium within 10h. In an experimental pH range of 5–10.5, fluoride uptake decreased with the increase of pH. Ionic strength did not impact fluoride adsorption in the entire experimental pH range. However, major anions reduced fluoride adsorption in the order of HPO4 2− >HCO3 − >SO4 2− >Cl−. Other toxic elements that might coexist with fluoride in groundwater, such as arsenic and selenium, also reduced fluoride adsorption through competition for the same surface sites. A speciation-based model was used to quantify the fluoride adsorption on activated alumina as functions of pH, with and without competing toxic elements. This model simulated fluoride adsorption well over a broad pH range of 5–10.5, and a wide surface loading range of 1–10mg-F/g adsorbent. [Copyright &y& Elsevier]