Comparative study on washing effects of different washing agents and conditions on heavy metal contaminated soil

Abstract The soil washing technology of heavy metals in soil has the prospect of practical application. In this study, we screening out the best washing conditions for remediation of heavy metal contaminated soil and the conclusions are verified by pilot-scale field tests. Compared with citric acid (CA) and ethylene diamine teraacetic acid disodium salt (EDTA), Iron-based compounds (IC) has highest removal rate of heavy metals in soil. Heavy metals are mainly concentrated in soil with small particle size. Comprehensive cost consideration, the best washing concentration is 0.06 mol•L−1, the best solid liquid ratio is 1:5 and the best washing time is 30 min. CaO can precipitate heavy metals in washing waste liquor by increasing the pH of heavy metals in washing waste liquor, and the best precipitation time is 30 minutes considering the comprehensive cost. The results of pilot scale experiments show that the IC washing technology was shown to be an effective approach to rapidly reduce the Pb, Zn and As in contaminated soil.