Surface engineering with ionic polymers on membranes for boron removal

Removal of boric acid from seawater and wastewater using reverse osmosis membrane technologies is imperative and yet remains inadequately addressed by current commercial membranes. Existing research efforts performed post-modification of reverse osmosis membranes to enhance boron rejection, which is usually accompanied by substantial sacrifice in water permeability. This study delves into the surface engineering of low-pressure reverse osmosis membranes, aiming to elevate boron removal efficiency while maintaining optimal salt rejection and water permeability. Membranes were modified by the self-polymerization and co-deposition of dopamine and polystyrene sulfonate at varying ratios and concentrations. The surfaces became smoother and more hydrophilic after modification. The optimum membrane exhibited a water permeability of 9.2 ± 0.1 L·m⁻²·h⁻¹·bar⁻¹, NaCl rejection of 95.8% ± 0.3%, and boron rejection of 49.7% ± 0.1% and 99.6% ± 0.3% at neutral and alkaline pH, respectively. The water permeability is reduced by less than 15%, while the boron rejection is 3.7 times higher compared to the blank membrane. This research provides a promising avenue for enhancing boron removal in reverse osmosis membranes and addressing water quality concerns in the desalination process.