Removal of zinc and cadmium ions from contaminated soils with rhamnolipid biosurfactant produced by Pseudomonas aeruginosa S7PS5

Abstract

A soil treatment process using froth flotation technique involving anionic biosurfactant (rhamnolipids) using Sodium sulfide was studied. The supernatant produced by the strain Pseudomonas aeruginosa S7PS5 was tested for biosurfactants production, HPLC analysis showed the presence of L-rhamnosyl- β- hydroxydecanoyl- β-hydroxydecanoate (RL1) and L-rhamnosyl L-rhamnosyl- β-hydroxydecanoyl-β- hydroxydecanoate (RL2). The influence of the collector (rhamnolipid), pulp pH, a chemical activation step (sulfidization) and process time on metal removal efficiency has been investigated to recover Zn and Cd ions from a contaminated soil. An effective CMC of 35 mg/L was obtained. A perfect Zn and Cd removal efficiency was made at pH = 12 and 4 mg/g of Na₂S during the first 5 min of soil washing process, then a longer flotation time ( > 5 min) caused mechanical entrainment of Zn and Cd.

Keywords: Biosurfactants, flotation, Pseudomonas aeruginosa, rhamnolipids, soil washing