Efficacy evaluation of different treatments involved in the washing of a multi-element contaminated soil using Taguchi optimization

Abstract

A laboratory trial was conducted to evaluate the effectiveness of different treatments on the soil washing of Zn, Cd, Pb, and Ni using Taguchi optimization. Results showed that the first rank belongs to DTPA for Zn, Cd, and Ni and EDTA for Pb. The second rank belongs to LMWOAs for Ni, and Pb and SSR for Cd, and Zn. The optimal level of SSR for Zn, Cd, and Ni was 10, while for Pb was 2.5. The role of biological treatment was negligible. The patterns of the time-dependent release of the four elements were well fitted to pseudo-second order and power function models. The highest removal percentage of Ni, Cd, Zn, and Pb after 24 h were 60.8, 60.1, 75.3, and 93.2%, respectively. It can be concluded that co-application of CHAs and LMWOA with a SSR of 10:1 can be considered as a proposed guideline for metals soil washing. • Chelating agent was the most effective factor in washing remediation of metals. • Optimum soil to solution ratio for Ni, Cd, and Zn was 10, while for Pb was 2.5. • The role of biological treatments in metals washing was minimal. • Co-application of chelating agents and organic acids was effective in metals washing.