Effects of particle size on the metal extraction with citrate in contaminated soils

Abstract

The contamination of toxic metals in soil has been a serious environmental problem due to their toxicity and environmental risk. Among various remediation technologies for metal contaminated soils, soil washing is considered as a more powerful and convenience technology because of easy operation and permanent removal of metals from soil. To find optimum extraction conditions for target metals such as Cu, Cr, Pb, and Zn in soil washing process, we investigated the metal extraction potential of citrate according to soil particle size, solution pH, and concentrations of citrate using liquid-solid partitioning as a function of extractant pH with parallel batch extraction procedures. The extraction kinetics was also tested with three different particle sizes of soil. The metal extraction was significantly affected by the extractant pH and the soil particle sizes. The metal fractionation in soil was analyzed using sequential extraction procedure before and after citrate extractions. The extracted fraction of metals was varied by the characteristics of each metal. These results imply both the physical-chemical characteristics of soils and the fractionation and speciation of metals in soils and extract solutions should be considered in soil washing process.