Treatment of hydrocarbon marine pollution with cloud point extraction

The release of hydrocarbons (HC) into the marine environment has serious consequences, both economically and ecologically. This work presents an efficient process to remove HC pollution from seawater: cloud point extraction (CPE), considered to be a reliable, inexpensive, and environmentally friendly method, using the readily biodegradable nonionic surfactants Lutensol ON30 and Tergitol 15-S-7. A real salt water sample with a high chemical oxygen demand (COD = 1700 mg O₂/L) was thus treated. First, the phase diagrams of the binary systems (water–surfactant), and the pseudo-binary systems (water–surfactant–HC), were determined. Second, after a 24 h settling time, considered as optimal, the extraction results, that is, residual soluble COD, residual percentage of surfactant in the dilute phase and volume fraction of coacervate at equilibrium, were expressed in terms of temperature and initial surfactant concentration. For each parameter, the results obtained were modeled using the response surface methodology and represented on three-dimensional diagrams. They show that the COD can be reduced to 10 and 15 mg O₂/L, using Lutensol ON30 and Tergitol 15-S-7, respectively, under seawater temperature conditions. Finally, it was shown that the surfactant can be recycled. The present work demonstrates that CPE can reduce the HC content of seawater on a laboratory scale.