Toluene removal from nonionic surfactant coacervate phase solutions by vacuum stripping

Cloud point extraction (CPE) has been demonstrated to remove volatile aromatic pollutants from wastewater by using a nonionic surfactant as a separating agent. To make this process economically feasible, the surfactant in the concentrated or coacervate phase containing most of the original pollutant must be recycled and reused. This work proposes a vacuum stripping process to strip the volatile pollutant from the coacervate, leaving the concentrated surfactant solution to be recycled to the CPE process. An acrylic column was packed with glass Raschig rings and operated under rough vacuum in co-current mode to remove toluene from the coacervate phase containing the t-octylphenolpolyethoxylate (OP(EO7)) nonionic surfactant. Co-current operation is necessary to avoid excessive foaming. In this study, although the apparent Henry's law constant of toluene was drastically reduced due to toluene solubilization in surfactant micelles, up to 90% of toluene was removed from 300 mM OP(EO)7 surfactant solution using a 30.5-cm long column. The packed column can be operated without flooding and plugging, despite the viscous nature of the coacervate. The toluene removal increases with decreasing liquid loading rate, and column pressure, but with increasing number of distributor holes. The overall liquid phase volumetric mass transfer coefficient is reported for this system.