Development of a hybrid water treatment process using forward osmosis with thermal regeneration of a surfactant draw solution

Abstract

AbstractA hybrid process of forward osmosis (FO) in combination with thermal regeneration of the draw solution is proposed and investigated experimentally. On the side of the draw solution, a surfactant water emulsion is contacting the FO membrane. The solubility of non-ionic surfactants in water is exceptional in that it decreases at elevated temperatures. Depleted surfactant/water draw solution can thus easily be separated into an aqueous phase (product water) and a surfactant-rich phase (regenerated draw solution) by increasing temperature in order to induce liquid phase separation. The optimal choice of a surfactant as active draw agent will need to account for the surfactants performance in the thermal separation as well as in FO. In this work, 12 different surfactants were evaluated and discussed for their usability as draw solution. The surfactant L31 showed the best performance considering both criteria: high affinity toward water in FO and the lowest temperatures in thermal regeneration at 50°C. ...