通讯作者：Quan, X (reprint author), Dalian Univ Technol, Minist Educ, Sch Environm Sci & Technol, Key Lab Ind Ecol & Environm Engn, Dalian 116024, Peoples R China.
合写作者：Quan, Xie,Fan, Xinfei,Yi, Gang,Chen, Shuo,Yu, Hongtao,Chen, Yongsheng
发表刊物：ENVIRONMENTAL SCIENCE & TECHNOLOGY
关键字：Charge density; Desalination; Ions; Microfiltration; Nanofiltration; Nanofiltration membranes; Sodium chloride; Sodium sulfate; Surface charge; Water treatment, Bulk solutions; Donnan potential; Enhanced surface charge; External voltages; High permeability; Monovalent ions; Rejection rates; Seawater desalination, Sulfur compounds
摘要：Nanofiltration (NF) is considered a promising candidate for brackish and seawater desalination. NF exhibits high multivalent ion rejection, but the rejection rate for monovalent ions is relatively low. Besides, great challenges remain for conventional NF membranes to achieve high ion rejection without sacrificing water flux. This work presents an effective strategy for improving the ion rejection of conductive NF membrane without decreasing the permeability through electrically assisted enhancement of surface charge density. When external voltage is increased from 0 to 2.5 V, the surface charge density of the membrane increases from 11.9 to 73.0 mC m(-2), which is 6.1X higher than that without external voltage. Correspondingly, the rejection rate for Na2SO4 increases from 81.6 to 93.0% and that for NaCl improves from 53.9 to 82.4%; meanwhile, the membrane retains high permeabilities of 14.0 L m(-2) h(-1) bar(-1) for Na2SO4 filtration and 14.5 L m(-2) h(-1) bar(-1) for NaCl filtration. The Donnan steric pore model analysis suggests that the Donnan potential difference between the membrane and bulk solution is increased under electrical assistance, leading to increased ion transfer resistance for improved ion rejection. This work provides new insight into the development of advanced NF technologies for desalination and water treatment.