Sorption and transport behaviours of heavy metals of landfill leachate in soil at Kham Bon village, Muang district, Khon Kaen province, Northeast Thailand

Abstract

This study aimed to investigate the behaviors of sorption and transport of heavy metals contaminated in landfill leachate affected by the physical and chemical characteristics of soil at Kham Bon landfill site and its vicinity. The study methodology consisted of landfill characterization, sorption and transport of heavy metals by batch (adsorption and desorption) and column experiment as well as Selective Sequential Extraction (SSE). Landfill site characterization included the analysis of leachate, soil, groundwater and surface water. The studied heavy metals were Pb, Zn, Cd, Cr and Cu. Soil used in this study was taken from the landfill site, of which the property of silty clay loam, sand and loamy sand. Actual leachate and synthetic leachate with monometal and mixed metals were conducted. The results of the heavy metals sorption in soil, both actual leachate and synthetic leachate mostly exhibited the sequence of adsorption as Pb > Zn > Cr > Cd > Cu for both batch (indicated by Linear, Freundlich and Langmuir isotherms) and column tests. Desorption test indicates Cd was easier extracted than other heavy metals, followed by Cu, Cr, Zn and Pb. SSE representing the heavy metals bounded to soil showed that cadmium was observed as an exchangeable fraction. The adsorption capacity from synthetic leachate was more effective than the adsorption capacity from actual leachate. The physicochemical properties soil (cation exchange capacity, clay content, and organic matter) reflected the behavior of heavy metals adsorption. Evidently, the organic and inorganic substances containing in landfill leachate play an important role in promoting the mobility of heavy metals in soil. Other factors influencing adsorption are pH and alkalinity. These factors induced precipitation in adsorption process. In summary, the study indicates that Pb and Zn were potentially accumulated in soil profile while Cr, Cd and Cu were possibly released to the groundwater and surface water. From the heavy metals sorption behavior, it is feasible to remediate contaminated soil accordingly.