Remediation of chromium contaminated soil by soil washing using EDTA and N-acetyl-L-cysteine as the chelating agents

Abstract

The use of chelating agents in soil washing has been known to be an efficient, eco–friendly, and inexpensive treatment process for the removal of heavy metal contamination. In this study, statistically designed lab-scale soil washing experiments were carried out using two chelating agents i.e., ethylene diamine tetraacetic acid (EDTA) and N-acetyl-L-cysteine (NAC). The effects of pH, contact time and dosage of wash solution on chromium (Cr+6) removal efficiency (RE) was investigated and optimized using response surface methodology (RSM). The ANOVA analysis of the experimental design for both the chelating agents revealed that pH is the key influencing parameter in Cr+6 removal. The optimum conditions were found to be: pH - 5.5, contact time - 216 h, dosage of EDTA - 4128 mg/kg and dosage of NAC - 300 mg/kg. The projected Cr+6 RE under these optimum conditions was 14.3% and 65.7%, for EDTA and NAC, respectively. The results from this investigation indicated that soil washing with NAC could be a better alternative to EDTA for Cr+6 removal from soil.