Chitosan: polyvinyl alcohol based mixed matrix sustainable coatings for reusing composite membranes in water treatment: fouling characterization

Abstract

This work aims at studying the potential of modifying the surface of used polyamide (PA) reverse osmosis (RO) commercial membranes by coatings made of renewable and biodegradable polymers, chitosan (CS) and polyvinyl alcohol (PVA), filled with Cu-ion-exchange layered AM-4 titanosilicate and UZAR-S3 stannosilicate to provide antifouling properties and enlarging life time of thin-film composite (TFC) membranes. The water permeation and fouling ratios were evaluated as a function of active layer material in the presence of model organic (BSA) and inorganic (NaCl) foulants. The mixed matrix membrane (MMM) coatings added on the active surface of the PA commercial membranes generally decreased the flux decline and increased the permeate flow recovery rate. The CS:PVA based coatings promote the reversible and not the irreversible fouling, especially CuAM-4CS:PVA. Beside, ATR-FTIR confirms the reversible nature of the BSA fouling and the irreversible nature of the NaCl fouling. These results may in the future open the possibility of renewing the useful lifetime of commercial RO membranes by a simple coating method in the light of the circular economy.