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 pH 4.0-5.5. 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.
P. Feng et al., "Weak Magnetic Field Accelerates Chromate Removal by Zero-Valent Iron," Journal of Environmental Sciences (China), vol. 31, pp. 175 - 183, Chinese Academy of Sciences, May 2015.
The definitive version is available at https://doi.org/10.1016/j.jes.2014.10.017
Civil, Architectural and Environmental Engineering
Keywords and Phrases
Activation energy; Chemical activation; Corrosion; Impurities; Iron; Magnetic devices; Magnetic fields; Magnetic storage; Magnetism; Reduction; Apparent activation energy; Iron corrosion; Magnetic memory; Positive correlations; Two-stage process; Weak magnetic fields; Zero-valent iron; Zerovalent irons; Chromium compounds; Chromate; Concentration (composition); Corrosion; Iron; Magnetic field; Magnetization; Reaction kinetics; Reduction; Remediation; Waste management; Chromic acid; Iron; Water pollutant; Chemistry; Magnetic field; pH; Precipitation; Scanning electron microscopy; Water pollutant; Chemical Precipitation; Chromates; Hydrogen-Ion Concentration; Iron; Magnetic Fields; Microscopy; Electron; Scanning; Water Pollutants; Chemical; Fe2+ release
International Standard Serial Number (ISSN)
Article - Journal
© 2015 Chinese Academy of Sciences, All rights reserved.
01 May 2015
This work was supported by the National Natural Science Foundation of China (Nos. 21277095, 51478329), the Specialized Research Fund for the Doctoral Program of Higher Education (20130072110026), and the Tongji University Open Funding for Materials Characterization (No. 2013080).