Wettability of an electroactive membrane in surfactant-containing brine for conductive heating membrane distillation

Abstract

Membrane distillation (MD) is a technology that has proven to be highly efficient in desalination. However, the occurrence of membrane wetting can lead to the failure of the process. Given this, we developed an electroactive membrane (RC-M) using carbon nanotubes and reduced graphene oxide. The wettability of RC-M was then examined after treatment with cationic or anionic surfactants in brines during the conductive heating membrane distillation process. Results indicated that the RC-M had an abundance of charged functional groups and multiple defects in the graphene structure. Using 0.3 mol/L NaCl and 30 mg/L sodium dodecylbenzenesulfonate (SDBS), the RC-M worked for 600 mins with 97.2 % rejection. While, in a feed with hexadecyltrimethylammonium bromide, rejection dropped to 93.6 % in 350 minutes. When a potential was applied to the RC-M, the SDBS displayed electrostatic repulsion when interacting with the membrane, thereby preventing its adsorption. Moreover, the interaction between the feed and the charged RC-M caused electrolysis, and the resultant bubbles helped reduce wetting. Additionally, the RC-M itself possessed a hydrophilic layer that aided in mitigating wetting. The findings of this research offer valuable understanding regarding the durability of MD membranes and techniques to postpone membrane wetting.