Water contaminated with low concentrations of pollutants is more difficult to clean up than that with high pollutant content levels. Membrane separation provides a solution for removing low pollutant content from water. However, membranes are prone to fouling, losing separation performances over time. Here we synthesized neutral (IM-NH2) and positively charged (IL-NH2) imidazole derivatives to chemically functionalize membranes. With distinct properties, these imidazole grafts could tailor membrane physicochemical properties and structures to benefit forward osmosis (FO) processes for the removal of 20-100 ppm of Safranin O dye-a common dye employed in the textile industry. The water fluxes produced by IM-NH2- and IL-NH2-modified membranes increased by 67% and 122%, respectively, with DI water as the feed compared to that with the nascent membrane. A 39% flux increment with complete dye retention (∼100%) was achieved for the IL-NH2-modified membrane against 100 ppm of Safranin O dye. Regardless of the dye concentration, the IL-NH2-modified membrane exhibited steadily higher permeation performance than the original membrane in long-term experiments. Reproducible experimental results were obtained with the IL-NH2-modified membrane after cleaning with DI water, demonstrating the good antifouling properties and renewability of the newly developed membrane.
Keywords: FO membrane; dye removal; forward osmosis; imidazole derivatives; membrane modification.