Separation of polycyclic aromatic hydrocarbons from rhamnolipid solution by activated carbon adsorption

Separating hydrophobic organic contaminants from a surfactant solution facilitates the reuse of surfactants and reduces waste disposal costs. This study presented an investigation of selective adsorption of hydrophobic organic compounds in rhamnolipid solution by activated carbon as a means of recovering biosurfactants. Three polycyclic aromatic hydrocarbons (PAHs) were used as examples of hydrophobic organic compounds, along with rhamnolipid as biosurfactants. PAH solubility in the micelles increased linearly with increasing concentrations of rhamnolipid. Batch adsorption experiments on containing rhamnolipid and PAH solutions were performed using activated carbon. The adsorption behavior of rhamnolipid and PAH fitted the Freundlich isotherm model and pseudo-second-order kinetics model well. The selectivity value for PAH removal from the surfactant solution decreased with decreasing PAH hydrophobicity and increased with decreasing surfactant concentration. The sorption process was divided into four steps, and sorption schematics were proposed to elucidate the mechanism of sorption. Micelle adsorption was followed by surface solubilization. The findings demonstrate that activated carbon adsorption is an effective method for recovering biosurfactants.