Evaluation of enhanced soil washing process with tea saponin in a peanut oil–water solvent system for the extraction of PBDEs/PCBs/PAHs and heavy metals from an electronic waste site followed by vetiver grass phytoremediation

Abstract

AbstractBACKGROUNDProblems associated with PBDEs/PCBs/PAHs and heavy metals mixed contaminated sites have received wide attention. To address the associated environmental concerns, innovative remediation techniques are urgently needed.RESULTS5.0 mL L−1 peanut oil and 5.0 g L−1 tea saponin were found to be effective in extracting 94.6%, 97.1%, 95.1%, 83.5%, and 87.1% of PBDEs, PCBs, PAHs, Pb, and Ni, respectively, after two successive washing cycles. Cultivation of vetiver grass and addition of nutrients for 4 months further degraded 45.1%, 36.2%, and 40.2% of the residual PBDEs, PCBs and PAHs, respectively. Pb and Ni removal efficiencies by phytoextraction were 4.1% and 2.0%, respectively. The combined treatment partially restored the microbiological functions of washed soil, as indicated by a significant increase in the number, biomass C, N, and functioning diversity of soil microorganisms (P < 0.05). After treatment, the residual organic pollutants and heavy metals mainly existed as very slowly desorbing fractions and residual fractions, as evaluated by Tenax extraction combined with a first‐three‐compartment model and sequential extraction. The secondary environmental risk of residual mixed pollutants in the remediated soil was limited.CONCLUSIONThe proposed combined cleanup strategy proved to be effective and environmentally friendly. © 2014 Society of Chemical Industry