Removal of Pb and Hg from marine intertidal sediment by using rhamnolipid biosurfactant produced by a Pseudomonas aeruginosa strain

Abstract

Abstract The removal of heavy metal contaminants in marine intertidal sediments is an urgent issue. Heavy metal decontamination with rhamnolipid biosurfactant (RB) is a feasible way of solving this problem. In this paper, two heavy metals, lead (Pb) and mercury (Hg), in marine intertidal sediment were removed by prepared RB in laboratory scale. The results showed that Pb and Hg could be efficiently removed from the intertidal sediment in marine environment by using RB produced by a pseudomonas aeruginosa strain. At a critical micelle concentration of 43.73 mg L−1, 62.50% Pb and 50.20% Hg were removed from the marine intertidal sediment sample containing 520.32 mg ⋅ kg −1 of Pb and 13.15 mg ⋅ kg −1 of Hg (dry weight). The pH affected the Pb and Hg removal by RB, and the alkaline eluent medium was favorable for their removal. A major fraction of removed contaminants comprised organic bound to Pb and Hg during RB solution leaching. The content of exchangeable Pb after leaching treatment in the sediment increased followed by the increase of pH of the RB leaching solution. The removal efficiency increased rapidly during the first two days of leaching process. RB performed better than sodium dodecyl sulfate in terms of Pb and Hg removal. Scanning electron microscopy, zeta potential, and surface tension analysis indicated that leaching by RB solution changed the surface characters of sediment grains and led to high Pb and Hg removal efficiencies from the sediment.