Efficient Dye Removal from Aqueous Solutions Using Rhamnolipid Biosurfactants by Foam Flotation

Methylene blue was efficiently removed from aqueous solution by foam flotation using a rhamnolipid biosurfactant as a dye collector. The effects of four parameters, namely, pH (1.5–11.5), frother concentration (5–65 ppm), aeration rate (2–6 L/min) and rhamnolipid to methylene blue weight ratio (0.5–6.5), on dye removal were studied and optimized using response surface methodology. Results showed that dye removal increases by increasing of all parameters; however, the nonlinear trend was observed for the effects of frother concentration and rhamnolipid to methylene blue ratio. Optimum removal conditions, resulting in about 93% dye removal, was achievedat pH value of 11.5, methyl isobutyl carbinol (MIBC) concentration of 35 ppm, airflow rate of 4 L/min, and rhamnolipid to methylene blue ratio of 3.5, after only 10 min flotation. Investigations also showed that the presence of electrolyte can significantly decrease the removal efficiency. Kinetics study revealed that the process follows the first-order model with a rate constant of about 0.288 sec- This study demonstrates that rhamnolipid could be considered as a potentially efficient and environment-friendly collector for the treatment of dye contaminated wastewater.