Ultrafiltration membrane microreactor (MMR) for simultaneous removal of nitrate and phosphate from water

Removing low-concentration nitrate and phosphate from water is desirable because they may cause eutrophication when discharged, but it is challenging using current technologies. Although ultrafiltration (UF) membranes have higher permeability than nanofiltration and reverse osmosis membranes, they cannot remove nitrate and phosphate from water because of their low selectivity. It is the first time for a work to develop a novel UF membrane microreactor (MMR) simultaneously removing nitrate and phosphate with high capacity and selectivity. The UF MMR was fabricated by blending amorphous zirconium hydroxide and quaternary ammonium powder with poly(vinylidene fluoride) and had structure and pore size typical of conventional UF membranes. The MMR adsorption capacities for nitrate and phosphate were 9.66 mg-N/g and 15.58 mg-P/g, respectively. Adsorption followed pseudo second order rate law and was dominated by chemical adsorption. Coexisting sulfate ions usually compete strongly with nitrate and phosphate, but had little influence on removal using the UF MMR. The UF MMR had high permeability (500 LMH/MPa) and maintained excellent removal of nitrate and phosphate after regeneration with NaCl solution, making it a promising technology for water and wastewater treatment.