INFLUENCE OF WEAK MAGNETIC FIELD ON HEAVY METAL CATIONS REMOVAL BY ZERO VALENT IRON

Weak magnetic field (WMF) was proposed to enhance heavy metals sequestration by ZVI in this study. The WMF influence on the kinetics of Cu(II) removal by ZVI was investigated at pH 4.0 as functions of initial Cu(II) concentrations and Fe(0) dosages. The removal efficiencies of various heavy metals including Cu(II), Zn(II), Ni(II), Cd(II), Pb(II), Co(II), by ZVI at pH 5.0-7.0 with or without WMF were also determined. The results showed that WMF significantly enhanced Cu(II) sequestration by ZVI at different ZVI dosages and the reaction could be accelerated by over 10-fold to achieve over 95% Cu(II) removal efficiency at various Fe(0) dosages due to WMF. The Cu(II) removal efficiencies were improved from 85%, 12% to 96%, 98%, respectively at pH 5.0 and pH 6.0. WMF caused a more markedly drop in ORP and more rapid generation of Fe(II), which resulted in dramatically accelerated sequestration rate of Cu(II) by ZVI. The disappearance rate of Cu(II) by ZVI reduced markedly with increasing initial Cu(II) concentration without WMF but the removal rates of Cu(II) were similar at different initial Cu(II) concentrations with WMF. The removal efficiencies of heavy metals by ZVI at pH 5.0-7.0 follow this order: Cu(II) > Pb(II) > Zn(II) > Ni(II) > Cd(II) approximate to Co(II) without WMF. Coupling ZVI with WMF was only efficient for Cu(II) and Pb(II) removal but not for Zn(II), Ni(II), Cd(II), and Co(II), indicating the outstanding advantage of WMF in improving ZVI reactivity. Employing WMF to enhance contaminants removal by ZVI is considered to be a promising technique in future water treatment since it does not need extra energy input and costly reagents.