Extraction of high concentration of Cr(VI) in contaminated industrial soil using humic acid

Cr-contaminated soil is a serious threat to the ecological environment and human health because of its high toxicity of Cr(VI), and it needs to be treated properly. In this study, commercial humic acid (HA) was used as an extractant to treat high concentration of Cr contaminated soil (amorphous phase bound state), and the Cr(VI) removal rate was 90.55% under the optimal conditions (pH = 12, concentration 1 g/L, extraction time 24 h, liquid-solid ratio = 20:1). In this process, the remaining Cr species in the HA-treated soil was the most stable and the least mobile, with the highest retained native soil organic matter (SOM) compared to ethylenediaminetetraacetic acid (EDTA) and citric acid (CA). In addition, the economic cost advantage of HA was outstanding at only $55.3 per ton of soil contaminated with high concentrations of Cr(VI). Studies have shown that HA can be a "green" and more cost effective alternative to the traditional extractants EDTA and CA when targeting extraction treatments for high concentration Cr-contaminated soils and other Cr-containing wastes.