ADSORPTION OF HEAVY METAL POLLUTANTS BY LANDFILL SOILS

The leachate in landfill sites carries out highly concentrated inorganic and organic pollutants. Such pollutants can be intercepted by the adsorption of landfill soil and will proceed with a long-term stabilization-degradation reaction in the soil. Moreover, the possibility of groundwater pollution due to the leachate from landfill can be reduced through the intercepted adsorption by the soil. Simulated adsorption batch experiments were carried out in this study to investigate the adsorption removal of heavy metals by soils. The tested soils included red loam from the Taichung sanitary landfill site and six alluvial soils located over the most widespread area in Taiwan. The results indicated the following trend for the ability of heavy metal adsorption removal by such tested soils: Hsinying soil > Chunghsin Village soil > Chung Hsing University soil about = to Hsuehchia soil > Taichung sanitary landfill soil > Mashan soil > Tunghsiao soil. The adsorption removal of heavy metals followed Pb about = to Cu > Ni about = to Cd about = to Zn. The adsorption removal by red loam increased with Cd concentration; however, part of the Cd removal in the high-pH region for high Cd concentration was due to precipitation. Thus, consideration of the speciation distribution was necessary to determine the maximum probable precipitated amount and the minimum probable adsorbed amount. In addition, in the presence of organic ligand [ethylenediamine tetraacetic acid (EDTA)], the adsorption effect of Cd by red loam was suppressed because of the complexation with EDTA, and the adsorption decreased with increasing EDTA concentration.