The refurbishing of used salt water reverse osmosis composite membranes

This work presents the potential to repair used and dysfunctional reverse osmosis (RO) composite membranes. Under constant use, polyamide-based RO membranes exhibit a timely deterioration in salt rejection and water permeability from the values purported by their manufacturer. Manufacturers typically anticipate a 5%–7% decline of both characteristics. These changes are caused by an accumulation of various phenomena, including membrane matrix aging, fouling, and mechanical or chemical deterioration. The present work aims to allow the reuse of damaged RO membranes, which present a reduction in salt rejection together with an increase in flux, due to the deterioration of the polyamide barrier layer on their upper surface. Deficient membranes taken from desalination plants were cleaned, followed by the repair of the thermoset polyamide layer via interfacial repolymerization with trimesoyl chloride through a simple refurbishing process. Membranes were tested using a laboratory-scale crossflow RO test unit. It was found that while plant-used, defect membrane, exhibited a poor performance (salt rejection of 81% with a flux of 83 L/m2/h), once repaired, the membranes exhibited a substantial increase in salt rejection capacity (95%) and reduction in flux (36 L/m2/h), These results were in par with virgin membranes (salt rejection of 95% and flux of 42 L/m2/h) The repolymerization refurbishing technique and its resulting membrane physiochemical characteristics are described in detail.