Biosurfactant Mediated Remediation Process Evaluation on a Mixture of Heavy Metal Spiked Topsoil Using Soil Column and Batch Washing Methods

This study investigated the effects of biosurfactant produced by a mangrove isolate on a heavy metal spiked soil remediation using two different methods of biosurfactant addition (pretreatment and direct application) at different concentrations (0.5%–5%) for 10 days employing column and batch method of washings. The FT-IR spectral and biochemical analysis confirmed the chemical nature of biosurfactant as a glycolipid. Pre-addition of biosurfactant at 0.5% concentrations and further incubation for a month resulted in better chromium removal than the direct biosurfactant washing method. A maximum recovery of lead (99.77%), nickel (98.23%), copper (99.62%), and cadmium (99.71%) were achieved with column washing method at 1% biosurfactant concentration. Release of 26% soluble fractions of nickel (pre-addition with biosurfactant) and 40% copper (direct application) were achieved by column washing method at 1.0% concentration of biosurfactant. A total of 0.034 mg/10 g of lead, 0.157 mg/10 g of nickel, 0.022 mg/10 g of copper, 0.025 mg/10 g of cadmium, and 0.538 mg/10 g of chromium were found to remain in the spiked soil after column washing with 1.0% biosurfactant solution. However, pre-addition of 0.5% biosurfactant treatment helps in maximum removal of chromium metal leaving a residual concentration of 0.426 mg/10 g of soil, suggesting effective removal at very low concentration. The average extraction concentration of metals in batch washings was between 93–100%, irrespective of the concentration of biosurfactant studied. In this study, the percentage removal of copper, cadmium, chromium, nickel, and lead from spiked soils by column washing was comparatively lower than batch washing.