고도선별과 토양세척을 이용한 중금속 비산 오염토양의 As, Pb 처리 특성

Abstract

The marginal soil has been seriously contaminated with heavy metals such as As, Pb and Cu due to smelting activity for such a long time. As these heavy metal contents exceeded both the worrisome level and countermeasure level for Region 1 under the Soil Environment Conservation Act of Korea. Farming activities have been restricted by the Korean Government. For this reason, studies on effective removal of the heavy metals from agricultural land contaminated with As and Pb are needed. To identify the characteristics of paddy soils and upland soils contaminated with AS and Pb, this study carried out physico-chemical analyses including soil classification, moisture content, organic content, cation exchange capacity and pH. Then, for investigation of the types of heavy metals in the contaminated soil with As and Pb, the sequential extraction experiment was carried out. The primary metal removal experiment determinated washing reagent, concentration of washing reagent, solid-liquid ratio, stirring speed, and duration time which would work for the optimal removal of As and Pb from the contaminated soils(refers to initial contaminated soil). As the optimum factors determined from these removal heavy metal experiments, 30% of As and 60% of Pb were only removed. Therefore, in order to increase the removal efficiency for As and Pb, the advanced separation method was applied to the initial contaminated soils. The initial contaminated soil was sampled and then it was classified into magnetic soil and non-magnetic soil through the particle size separation and the magnetic separation. The optimum factors elicited from the primary metal removal experiment were applied for the classified soil and a soil washing test was given to it. As the results of the advanced separation process, removal efficiency of As and Pb was 35.5% and that of the magnetic soil was 64.9%. In the non-magnetic soil, removal efficiency of As was 35.0% and that of Pb was 67.9%. The contents of heavy metal from the magnetic and non-magnetic soil were below the worrisome level for Region 1, but only the As content exceeded the worrisome level for Region 1. Therefore, to effectively remove As from the magnetic soil, the initial contaminated soil sample was again classified into +0.053 mm and -0.053 mm through the particle size separation. Five soil washing experiments were repeated on the classified samples with the optimal factors obtained from the primary metal removal experiments. The washing tests were carried out twice for the +0.053 mm soil sample and five times for the -0.053mm soil sample. As a result, it was discovered that the content of As was below the reference level of the Korean Soil Environment Conservation Act. Therefore, it is suggested that for effective removal of As and Pb from the contaminated soil, the soil washing is an economic and efficient disposal process.