Wastewater Pollution Prevention for volatile organic compounds (Benzene, Toluene, Ethylbenzene, and Xylene) using cloud point extraction and regeneration of surfactant by evaporation

The aim of this work was the cloud point extraction (CPE) of volatile organic compounds, namely benzene, toluene, ethylbenzene, and p -xylene (BTEX), from aqueous solutions using the readily biodegradable nonionic surfactant PONPE 7.5. Binary water/surfactant and pseudo-binary (in the presence of solute) phase diagrams were plotted. The extraction results for four quantities—Extraction efficiency ( E ), residual concentrations of solute and surfactant in the dilute phase ( X s,w and X t,w , respectively), and volume fraction of coacervate at equilibrium ( Ф c )—were expressed as functions of the wt.% surfactant and the temperature. The effect of sodium sulfate and cetyltrimethylammonium bromide (CTAB) addition was also studied, and the possibility of recycling the surfactant was demonstrated. The results obtained for each parameter upon applying CPE to remove BTEX were represented on three-dimensional diagrams using response surface methodology (RSM). We sought the optimal tradeoff between the parameters that govern CPE efficiency according to the initial concentration of surfactant and the temperature. E was found to increase with surfactant concentration and hydrocarbon alkylation degree in the following order: B < T < E < X , with respective maximum values of 75, 83, 90, and 95%, without the addition of sodium sulfate or CTAB. The concentration of the solute in the coacervate increased as the temperature, surfactant or additive concentration, and degree of alkylation of the aromatic solute increased.