Combining biodegradable surfactants and potassium inorganic salts for efficiently removing polycyclic aromatic hydrocarbons from aqueous effluents

Abstract

The use of aqueous solutions of non-ionic surfactants like Tergitol 15-S7 and Tergitol 15-S9 is proposed for the first time to ex-situ remediation of Phenanthrene, Pyrene and Benzo[a]anthracene polluted soils, thus generating aqueous Polycyclic Aromatic Hydrocarbons (PAH)-polluted effluents. The effectiveness of several potassium based-inorganic salts (K3PO4, K2HPO4, K2SO4, K2S2O3 and K2CO3) to act as PAHs extractants was evaluated. The immiscibility region of the aqueous solutions was determined at room temperature, correlated by three empirical equations and compared with other non-ionic surfactants belonging to Tween and Triton families. The segregation capacity of the salts was analyzed in the light of their water-structuring degree and molar Gibbs free energy of hydration (ΔhydG). Tie-line determination was the tool used to determine the more viable PAHs removal strategy. Thus, the efficiency of combining K3PO4 to salt out Tergitol 15-S9 aqueous solutions polluted with the selected PAHs was investigated. The extraction percentage of the pollutants was 75% of Benzo[a]anthracene, 72% of Phenanthrene and 60.5% of Pyrene. The process was simulated at real scale through SuperPro Designer v.8.5 for the treatment of 156,000 tons/year of PAH-polluted soil.