Multi‐dimensional parametric study for enhancing Brackish Water Reverse Osmosis membrane performance suited for desalination of low salinity feeds

Abstract Reverse osmosis (RO) effectively provides clean drinking water. Different RO membrane types are tailored to treat saline water feeds with varying characteristics. In the context of low brackish water feeds, the objective is to remove only a minimal excess of salinity through the membrane. Our study introduces a method of membrane post‐treatments capable of achieving controlled salt rejection while concurrently enhancing permeate flux, which is vital for achieving effective and energy‐efficient desalination of low brackish water. The post‐treatments were conducted on our in‐house‐developed membranes using aqueous solutions of N,N‐Dimethylformamide and glycerol for different drying times at the coupon level. The process was scaled up at the module level, allowing us to assess its potential for commercial application. At the coupon level, the permeate flux increased significantly from 3.7 ± 0.9 to 10.6 ± 0.2 L/m 2 ·h·bar, while the salt rejection decreased from 95.6 ± 1% to 70.5 ± 1% when measured with a feed of 2,000 ppm NaCl concentration. At the module level, we observed a higher flux of 12.8 L/m 2 ·h·bar, alongside a salt rejection of 55.5% with a similar feed. Varying post‐treatment parameters at the coupon level allowed us to attain the desired salt rejection and permeate flux values. Physical changes in both pristine and post‐treated membranes, including polymer swelling, were observed without chemical alterations, enhancing our understanding of the post‐treatment effect and its potential for broader commercial use. Practitioner Points Post‐treatment of RO membranes enhances flux. Physical structuring through polymer swelling was observed with the chemical structure unaltered. Post‐treatment of RO opens doors for broader energy‐efficient desalination application.