STABILIZATION OF ARSENIC-CONTAMINATED SOIL IN A REALGAR MINING AREA

In the present study quicklime, zero-valent iron (ZVI) and quicklime-ZVI mixture were used as stabilizing agents to treat arsenic in contaminated soils collected from a realgar mining area. Leaching concentration and the change of arsenic fractionation were analyzed to investigate the effects of three stabilizing agents on arsenic stabilization. The results indicate that both quicklime and ZVI exhibited excel lent stabilization effects for arsenic-contaminated soils. The arsenic leaching concentrations after stabilization in both cases were lower than the standard arsenic leaching concentration-China (5.0 mg L-1), with a stabilization rate of over 90%. At pH of 7.5-8.0, the Fe/As molar ratios of 25-100, the addition of ZVI was beneficial for arsenic stabilization. However, after the addition of quicklime to ZVI stabilized soils, the arsenic leaching concentrations increased. Before treatment, the arsenic contents in various fractions were in the sequence of calcium-bound arsenic (Ca-As) > aluminum-bound arsenic (Al-As) > iron-bound arsenic (Fe-As) > residual arsenic (O-As) > exchangeable arsenic (AE-As). Arsenic in the Ca-As form was the highest in the soil both before and after the stabilization. The addition of ZVI and quicklime increased the Fe-As and Ca-As contents, respectively, and both decreased the AE-As contents in the soil.