Abstract
This study investigated the performance of rhamnolipids-citric acid mixed agents in simultaneous desorption of lindane and heavy metals from soils. The capacity of the mixed agents to solubilize lindane, lead and cadmium in aqueous solution was also explored. The results showed that the presence of citric acid greatly enhanced the solubilization of lindane and cadmium by rhamnolipids. A combined effect of the mixed agents on lindane and heavy metals removal from soils was observed. The maximum desorption ratios for lindane, cadmium and lead were 85.4%, 76.4% and 28.1%, respectively, for the mixed agents containing 1% rhamnolipidsand 0.1 mol/L citric acid. The results also suggest that the removal efficiencies of lead and cadmium were strongly related to their speciations in soils, and metals in the exchangeable and carbonate forms were easier to be removed. Our study suggests that the combining use of rhamnolipids and citric acid is a promising alternative to simultaneously remove organochlorine pesticides and heavy metals from soils.
Highlights
Organic pollutants and heavy metals are often found together in contaminated soils
The purpose of this study was to investigate the performance of the rhamnolipids-citric acid combined agents for simultaneously removing organochlorine pesticides (OCPs) and heavy metals from simulated soils
Sequential extraction experiments revealed that both the combined effect of mixed agents on lead removal and the differentiated removal ratios between lead and cadmium were correlated with the fractionation of heavy metals
Summary
Organic pollutants and heavy metals are often found together in contaminated soils. 52% of National Priority List sites are co-contaminated by volatile organic compounds, semi-volatile organic compounds and heavy metals in the United States[1]. These contaminated soils are a threat to ecological security, and challenges for remediation projects. Existing methods, such as soil vapor extraction, thermal desorption, phytoremediation and solidification/stabilization are generally only suitable for the removal of either organic pollutants or heavy metals. The simultaneous removal of organics such as PLOS ONE | DOI:10.1371/journal.pone.0129978 June 18, 2015
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