Wen Zhang, Jianbing Li, Guohe Huang, Wei Li, Ling Wang, and Shanshan Li
Bio-surfactant, contaminated soil, diesel, solubilization, sorption
This study was aimed to investigate the influence of pH and salinity on the surface property of a bio-surfactant called rhamnolipid. Its solubilization ability on diesel and its sorption onto different soils were also examined. Measurements of surface tensions of rhamnolipid solutions over a wide range of pH indicated that pH value of 4 can lead to a decrease of surface tension from 33 to 17 mN/m, but other pH values showed no obvious effect on surface tension change. The results illustrated that salinity had a positive effect on changing surface tension. However, the pH and salinity didn’t affect the critical micelle concentration (CMC) of bio-surfactant solution. In terms of solubilization effect, the lower concentration of rhamnolipid solution had a negligible effect on solubilization of diesel oil compounds, but there was a considerable increase in solubilization of diesel when rhamnolipid concentration was greater than 0.004%, and the molar solubilization ratio (MSR) of rhamnolipid was found as 1.5284. The sorption loss of rhamnolipid was calculated as 75%, 66.7%, and 50% for loam, sandy loam, and sand, respectively, indicating that soil properties such as particle size and organic matter had significant impact on bio-surfactant sorption which may generate negative effect on remediating oil contaminated soil.
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