title: Reduction removal of hexavalent chromium by zinc-substituted magnetite coupled with aqueous Fe(II) at neutral pH value.
abstract: In this study, Cr(VI) removal by Zn-substituted magnetite coupled with aqueous Fe(II) through adsorption and reduction was investigated. A series of Zn-substituted magnetites (Fe3-xZnxO4, x=0, 0.25, 0.49, 0.74 and 0.99) were synthesized by a coprecipitation method, followed by systematic characterization, e.g., X-ray diffraction (XRD), thermogravimetry (TG), specific surface area and surface acid/base titration. The characterization results show that all samples had a spinel structure without an obvious alternation by Zn substitution. The BET surface area and surface site density gradually increased with Zn substitution. During Cr removal under neutral pH value, Cr(VI) was first adsorbed on the magnetite surface and then reduced to Cr(III) by Fe3-xZnxO4and adsorbed Fe(II); finally, it was immobilized on the Fe3-xZnxO4surface, which was verified via X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge spectroscopy (XANES) analyses and desorption experiment. With the increase in the Zn content in magnetite, the Cr removal efficiency initially decreased; then, it improved, which was ascribed to the decreasing Cr(VI) reduction and increasing Cr(VI) adsorption. This variation in activity by Zn substitution was discussed in terms of the reaction mechanism as well as the cationic microstructure and surface properties of Fe3-xZnxO4.
authors.affiliation: Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, PR China.
authors.forename: Jinhua
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, PR China; CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
authors.forename: Caihua
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Guangdong Institute of Eco-environmental Science & Technology, Guangzhou 510650, PR China.
authors.forename: Gaoling
authors.initials: G
authors.lastname: Wei
authors.affiliation: CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong; CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China. Electronic address: liangxl@gig.ac.cn.
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Liang
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong. Electronic address: cewchu@polyu.edu.hk.
authors.forename: Wei
authors.initials: W
authors.lastname: Chu
authors.affiliation: CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
authors.forename: Hongping
authors.initials: H
authors.lastname: He
authors.affiliation: Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Guangdong Institute of Eco-environmental Science & Technology, Guangzhou 510650, PR China.
authors.forename: Deyin
authors.initials: D
authors.lastname: Huang
authors.affiliation: CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
authors.forename: Jianxi
authors.initials: J
authors.lastname: Zhu
authors.affiliation: CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
authors.forename: Runliang
authors.initials: R
authors.lastname: Zhu
keywords: Aqueous Fe(II); Cr(VI); Reduction; XPS; Zn-substituted magnetite