Adsorption and chemical cleaning process of anionic and non-ionic surfactants on the membrane surface through the forward osmosis process: application for water reuse

Abstract

Forward osmosis (FO) process, an attractive membrane technologies, have been widely studied and applied in many fields to manufacture the clean water. This work, we focused on the fouling behavior and mechanisms of forward osmosis (FO) fouled by sodium dodecyl sulfate (SDS) as anionic surfactants and of nonylphenol ethoxylate (NPE, NP-40) as nonionic surfactant, including cleaning process to recover the system. FO process was run under different operating conditions (cross flow velocity, pH of feed solution, surfactant concentration). In addition, deionized-water (DI), 0.1 M NaCl, and alkaline solution (NaOH) were applied as agents for the cleaning process. The results revealed that the diffusion of water molecules increased with cross-flow velocity, feed solution pH, and surfactant increasing in both single surfactant and mixture surfactant. In addition, deposits of negative charge on the membrane surface induced the diffusion of water molecules, whereby increasing FO performance. Contrariwise, the diffusion in salt molecules decreased after adding the surfactant into the feed solution due to the surfactant layer performing as a resistance, resulting in the reduction of salt flux and increasing of reversal salt selectivity. In terms of cleaning process, the findings significantly indicated that the highest performance was increased when the FO system was operated at high pH (pH 11) of feed solution due to negatively charged promoted the increasing in diffusion of water molecules.