title: ZrO2-functionalized magnetic mesoporous SiO2 as effective phosphate adsorbent.
abstract: Phosphate pollution may cause eutrophication of the aquatic environment. In the present study, magnetic mesoporous SiO2 (denoted as MMS) and ZrO2-functionalized magnetic mesoporous SiO2 (denoted as ZrO2-MMS) were prepared and phosphate adsorption over the materials was investigated. The adsorbents were characterized by X-ray diffraction, transition electron microscopy, vibration sample magnetometer, N2 adsorption/desorption, zeta-potential measurement, and X-ray photoelectron spectroscopy. The results showed that MMS consisted of magnetite with particle sizes of 10-20 nm and ordered mesoporous SiO2 with the most probable pore diameter of 2.0 nm. The adsorbents could be readily separated and recovered under external magnetic field. The surface grafting of ZrO2 onto MMS led to an increase in surface zeta potential due to the formation of covalently linked ZrO2 functionality on the surface of MMS. Moreover, ZrO2 functionalization resulted in enhanced phosphate adsorption. Phosphate adsorption isotherms over the adsorbents could be well described by the Freundlich model. Phosphate adsorption kinetics followed the pseudo-second-order kinetics and the adsorption rate decreased with initial phosphate concentration. Additionally, increasing pH led to suppressed phosphate adsorption, and phosphate adsorption slightly increased with ionic strength.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, China.
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Wang
authors.forename: Juan
authors.initials: J
authors.lastname: Zhou
authors.forename: Dan
authors.initials: D
authors.lastname: Wei
authors.forename: Haiqin
authors.initials: H
authors.lastname: Wan
authors.forename: Shourong
authors.initials: S
authors.lastname: Zheng
authors.forename: Zhaoyi
authors.initials: Z
authors.lastname: Xu
authors.forename: Dongqiang
authors.initials: D
authors.lastname: Zhu
mesh_terms: D000327:Adsorption; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008280:Magnetics; D046529:Microscopy, Electron, Transmission; D009994:Osmolar Concentration; D010710:Phosphates / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D012822:Silicon Dioxide / Q000737:chemistry*; D013816:Thermodynamics; D014961:X-Ray Diffraction; D015040:Zirconium / Q000737:chemistry*
chemical_list: D010710:Phosphates; D012822:Silicon Dioxide; D015040:Zirconium; C028541:zirconium oxide
keywords: Magnetic adsorbent; Mesoporous SiO(2); Phosphate adsorption; ZrO(2) functionalization