INSOLUBILIZATION OF HEAVY METALS IN VOLCANIC DEPOSIT WITH MAGNESIUM OXIDE INSOLUBILIZER

Abstract

 To evaluate of the effect of MgO on insolubilizaiton of heavy metals in volcanic deposit, the raw deposit sampled from five points in Akako River in Miyazaki prefecture, Japan was treated with MgO, and leaching test, pH dependence test and sequential extraction test were performed. B and As were leached from the raw deposit and the concentrations exceeded the Environmental Quality Standards for soil. By adding MgO of 6% into the raw deposit, leaching concentrations of As, B, Cd, F and Pb satisfied the Environmental Quality Standards for soil. The results of pH dependence test indicated that MgO treatment could be highly effective at a pH of 2 for Cd and F; however, it was much less effective less than a pH of 7 for B, As, T-Cr and Pb. It was suggested that As and B could be adsorbed on MgO, Mg(OH)₂ and Fe(OH)₃ to be insolubilized.