Use of aqueous two-phase PEG-salt systems for the removal of anionic surfactant from effluents

Linear alkylbenzene sulfonates (LAS) are synthetic anionic surfactants that are extensively used in many industries. As a result, large volumes of effluents containing high levels of these compounds are discharged into water bodies, causing risks to aquatic flora and fauna. Then, there is a need for environmentally safe and economically viable technologies for the removal of LAS from aqueous matrices. The present work evaluates the use of aqueous two-phase systems (ATPS) composed of PEG and sulfate salts for this purpose, considering the effects of tie line length (TLL), molar mass of polymer, and type of cation-forming salt on the partitioning behavior of LAS. All the LAS partition coefficient (K_LAS) values were greater than unity, and the LAS extraction efficiencies (%E_LAS) were higher than 97%. The system consisting of PEG 1500 + (NH₄)₂SO₄ + H₂O provided the highest K_LAS (1083.34) and %E_LAS (99.9%), indicating that the method provided good extraction of LAS to the top phase. This system was applied using a real effluent sample in laboratory-scale experiments as well as in bench-scale batch trials. The results obtained at the laboratory scale showed %E_LAS values greater than 98%, while the best K_LAS value obtained in the batch experiments was 8.50 (±1.75) (%E_LAS = 78.17%). These values demonstrated the potential of ATPS for the removal of LAS from industrial effluents.