Volatile organic compound removal from nonionic surfactant coacervate phase solutions by co-current vacuum stripping

Abstract

Cloud point extraction (CPE) has been demonstrated to remove volatile organic compounds (VOCs) from wastewater by using a nonionic surfactant as a separating agent. To make the CPE process economically feasible, the surfactant in the concentrated, or coacervate, phase must be recycled and reused. This work utilized a packed column operated under rough vacuum in co-current mode to remove the VOCs (benzene, toluene, ethylbenzene, 1,2 dichloroethane, trichloroethylene, and tetrachloroethylene) from the t-octylphenolpolyethoxylate (OP(E0₇)) coacervate solution. Despite the viscous nature of the coacervate solution, the co-current operation can effectively avoid plugging, excessive foaming, and flooding. The Henry’s law constants of the VOCs are substantially reduced up to 90% due to the solubilization of VOCs in the surfactant micelles. For continuous operation, more than 87% for all VOCs is removed from a 450 mM OP(EO) ₇ solution within a single stage operation. The VOC removal percentage decreases with increasing liquid loading rate, column pressure, surfactant concentration, and solute hydrophobicity, but it substantially increases with increasing number of distributor holes and temperature.