title: Weak magnetic field accelerates chromate removal by zero-valent iron.
abstract: Weak magnetic field (WMF) was employed to improve the removal of Cr(VI) by zero-valent iron (ZVI) for the first time. The removal rate of Cr(VI) was elevated by a factor of 1.12-5.89 due to the application of a WMF, and the WMF-induced improvement was more remarkable at higher Cr(VI) concentration and higher pH. Fe2+ was not detected until Cr(VI) was exhausted, and there was a positive correlation between the WMF-induced promotion factor of Cr(VI) removal rate and that of Fe2+ release rate in the absence of Cr(VI) at pH4.0-5.5. These phenomena imply that ZVI corrosion with Fe2+ release was the limiting step in the process of Cr(VI) removal. The superimposed WMF had negligible influence on the apparent activation energy of Cr(VI) removal by ZVI, indicating that WMF accelerated Cr(VI) removal by ZVI but did not change the mechanism. The passive layer formed with WMF was much more porous than without WMF, thereby facilitating mass transport. Therefore, WMF could accelerate ZVI corrosion and alleviate the detrimental effects of the passive layer, resulting in more rapid removal of Cr(VI) by ZVI. Exploiting the magnetic memory of ZVI, a two-stage process consisting of a small reactor with WMF for ZVI magnetization and a large reactor for removing contaminants by magnetized ZVI can be employed as a new method of ZVI-mediated remediation.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.. Electronic address: pianpian1991@126.com.
authors.forename: Pian
authors.initials: P
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Guan
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
authors.forename: Yuankui
authors.initials: Y
authors.lastname: Sun
authors.affiliation: School of Environmental Science & Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea.
authors.forename: Wonyong
authors.initials: W
authors.lastname: Choi
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
authors.forename: Hejie
authors.initials: H
authors.lastname: Qin
authors.affiliation: Department of Civil, Architectural & Environmental Engineering, Missouri University of Science and Technology, 1870 Miner Circle, Rolla, MO 65409, USA.
authors.forename: Jianmin
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.. Electronic address: qiaoqiao@tongji.edu.cn.
authors.forename: Junlian
authors.initials: J
authors.lastname: Qiao
authors.affiliation: Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, China. Electronic address: lilina@sinap.ac.cn.
authors.forename: Lina
authors.initials: L
authors.lastname: Li
mesh_terms: D011232:Chemical Precipitation; D002840:Chromates / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D060526:Magnetic Fields; D008855:Microscopy, Electron, Scanning; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D002840:Chromates; D014874:Water Pollutants, Chemical; D007501:Iron
keywords: Activation energy; Fe(2+) release; Iron corrosion; Magnetic memory; Reduction