Removal of cadmium and lead from sediment by rhamnolipid

The potential of microbially-produced surfactant (rhamnolipid) to remove cadmium and lead from sediment was investigated. Batch washings were conducted on the sediment with different solution pH values and rhamnolipid concentrations. The speciation of heavy metals in the sediment before and after washing was analyzed by sequential extraction. The results show that rhamnolipid can remove cadmium and lead from sediment efficiently. The heavy metal removal efficiency is the best when the pH value of rhamnolipid solution is 10.0, and the removal ratio is the highest when the sorption of rhamnolipid on the sediment reaches a plateau. The speciation of the heavy metals has an effect on the removal efficiency, and the exchangeable and organic fractions can be removed efficiently. Four successive washings can remove 80.1% cadmium and 36.5% lead.