Effect of Long-Term Operation on the Desalination Performance of Poly(Vinyl Alcohol)-Based Pervaporation Membranes

Herein, the long-term stability of poly(vinyl alcohol) (PVA)-based pervaporation membranes in desalinating seawater reverse osmosis (SWRO) brine was investigated. A commercial PVA/polyacrylonitrile (PAN) composite membrane was evaluated using synthetic seawater. During desalination, the water flux and permeate conductivity decreased and increased, respectively, with notable salt scaling observed within the membrane substrate. Similar trends were observed when treating real SWRO brine, although salt scaling within the substrate was more severe. To mitigate salt-scaling-induced deterioration in desalination performance, a hydrophobic polytetrafluoroethylene (PTFE) substrate was selected as the support layer for fabricating a PVA/PTFE composite membrane, which was then applied to SWRO brine desalination. Although the water flux decreased during operation, the permeate conductivity remained constant, with negligible scaling within the substrate. These findings demonstrated that the PVA/PTFE composite membrane exhibits better performance and longer-term stability than the commercial PVA/PAN composite membrane for treating SWRO brine.