Comparison of polyethersulfone and polyamide nanofiltration membranes for uranium removal from aqueous solution

Abstract

Dead-end filtration equipment was operated to evaluate the performance of polyethersulfone (PES-2) and polyamide (NF-1 and NF-2) membranes in terms of rejection and permeate flux for treatment of high-concentration uranium solutions under a variety of operational conditions. The optimum pH for uranium rejection using PES-2 was determined 6 while the rejection increased significantly in polyamide membranes with increase of pH. The permeate flux of all membranes increased as the pressure increased from 5 to 20 bar while the uranium rejection by these membranes changed differently. As the feed concentration increased from 7.5 to 238 mg/l, the uranium rejection by PES-2 decreased. On the contrary, the rejection by NF-1 and NF-2 increased from 57 to 79% and 62 to 98%, respectively. Also, the permeate flux of PES-2 was relatively constant whereas the permeate flux of polyamide membranes declined due to a decrease in the effective membrane pore size and an increase in osmotic pressure. The results showed that the nanofiltration process can be effectively employed for uranium removal from aqueous solutions.