Enhanced washing of HCB and Zn from aged sediments by TX-100 and EDTA mixed solutions

Abstract

Soils and sediments contaminated with both organics and heavy metals are commonly found, but it is difficult to achieve successful remediation. This study investigated the simultaneous washing of hexachlorobenzene (HCB) and Zn from aged contaminated sediments with TritonX-100 (TX-100) and ethylenediaminetetraacetic acid (EDTA). The maximal removals of 41.5% and 30.0% were achieved for HCB and Zn with the mixed solution containing 5 mM EDTA and 15 mM TX-100, respectively. The removed fraction of Zn was mostly those exchangeable and bounded to Fe/Mn oxide. With TX-100 and EDTA mixed solution, HCB removal was slightly inhibited (< 2%) compared to TX-100 alone, while Zn removal was increased by 2% to 5% compared to EDTA alone. Negligible interaction between TX-100 and Zn–EDTA was found. Scanning electron microscope analysis revealed the increased dispersion of sediment particles in the presence of TX-100. The increased removal of Zn in the presence of TX-100 and EDTA mixed solution was suggested to result from the increased dispersion of sediment particles, which made entrapped Zn exposed. It was concluded that mixed solutions of TX-100 and EDTA were effective for the simultaneous washing of HCB and Zn from contaminated subsurface.