Effects of Rhamnolipid Biosurfactants on Removal of Phenanthrene from Soil

Abstract

Solubilizing agents may enhance remediation of soils contaminated with hydrophobic organic contaminants by diminishing sorption of the contaminants or increasing desorption rates. The effectiveness of rhamnolipid biosurfactants to enhance the removal of sorbed contaminants from soil was determined using column studies. Soil columns were contaminated with phenanthrene and subsequently eluted with electrolyte solution or with electrolyte solution containing 500 mg/L rhamnolipid. For the four soils studied, removal of 50% of the phenanthrene from the soil columns was accomplished in a 2-5-fold shorter time period, and the time required for 90% removal was reduced up to 3.5-fold when elution was performed with the rhamnolipid-containing solution as compared to the treatment without rhamnolipid. The effect of rhamnolipid on the removal of phenanthrene was satisfactorily simulated using independently obtained parameters with a two-component advective-dispersive model accounting for micellar solubilization and admicellar sorption. A more detailed analysis of the system showed that desorption rates of phenanthrene in the presence of 500 mg/L rhamnolipid were higher than predicted on the basis of desorption rate constants of phenanthrene determined in the absence of rhamnolipid. It is concluded that rhamnolipid enhanced the removal of phenanthrene mainly by micellar solubilization and also by influencing sorption kinetics.

Assessment of Bioavailability of Soil-Sorbed Atrazine

“…Mechanisms underlying the apparent availability of sorbed chemicals are complex due to the divergent properties of chemicals considered, the resultant sorption mechanisms, the metabolic diversity of microorganisms, and the heterogeneity of soils. Several microbially based mechanisms have been proposed for the apparent bioavailability of soil-sorbed organic chemicals: (i) production of biosurfactants (16,50); (ii) production of extracellular enzymes to degrade target compounds; (iii) microorganisms with high substrate affinity, which efficiently reduce concentrations of the substrate close to the cell surface (5); (iv) reduction of the distance between cells and substrate by adhesion to sorbents (5,26); and (v) reduction of the distance between cells and substrate by means of motility and chemotaxis (29).…”

Recent Advances in Petroleum Microbiology

“…The low-molecular-weight biosurfactants (glycolipids, lipopeptides) are more effective in lowering the interfacial and surface tensions, whereas the high-molecular-weight biosurfactants (amphipathic polysaccharides, proteins, lipopolysaccharides, and lipoproteins) are effective stabilizers of oil-in-water emulsions (41,97,149,384,401,525). Many studies have characterized the roles of biosurfactants in biodegradation by observing the effects of fractionated preparations (42,121,178,182,254,282,200,306,456,524,525,629,688,689). However, the successful application of biosurfactants in bioremediation of petroleum pollutants will require precise targeting to the physical and chemical nature of the pollutant-affecting areas.…”

Adsorption of a Multicomponent Rhamnolipid Surfactant to Soil

“…Therefore, we investigated the adsorption of the surfactant mixture and of the individual components to soil using batch adsorption and column experiments. Two frequently used representative sandy soils, the Borden material and Eustis soil, were selected for this study (5,(22)(23)(24).…”