A mixed-charge polyelectrolyte complex nanofiltration membrane: Preparation, performance and stability

Boosting the Performance of Nanofiltration Membranes in Removing Organic Micropollutants: Trade-Off Effect, Strategy Evaluation, and Prospective Development

“…Among the novel membranes of non-PA chemistry, the PEM-based membranes prepared via the LbL assembly technique displayed a higher potential to achieve superior and balanced performance in removing OMPs, for which the type of polyelectrolytes and number of layers need to be rationally designed. The probable swelling and deformation of polyelectrolyte layers induced by high salinity and pressure conditions are obstacles which need to be solved for the practical applications of PEM membranes. , Large-scale fabrication of these membranes also remains a challenge. Besides the commonly used modification methods and polymer-based novel chemistry of selective layers elaborated in detail in this review, other delicate strategies (e.g., capillary-assisted IP and amine modification , ) to regulate the formation of PA membranes and exploitation of two-dimensional nanomaterials (e.g., graphene oxide, molybdenum disulfide, MXene, , etc.)…”

“…In addition, it is suggested to pay more attention to the charge nonuniformity on and within the PA selective layer, , besides the overall charge property of membrane surface, in exploring PA membrane capabilities for salt/OMP separation. Development of the charge-mosaic (CM) membranes with unique ion rejection behaviors could potentially afford avenues for the enhancement of salt/OMP selectivity, though the efficient construction of an ideal CM structure with a proper pore size still remains a challenge. ,, Moreover, some latest insights into ion transport through membrane pores, − such as the transition state theory and the viewpoint that the energy barriers for ions in intrapore diffusion are larger than that for partitioning at the pore entrance, also provide implications for future tailored design of membranes with fit-for-purpose selectivity.…”

“…The probable swelling and deformation of polyelectrolyte layers induced by high salinity and pressure conditions are obstacles which need to be solved for the practical applications of PEM membranes. 150,151 Largescale fabrication of these membranes also remains a challenge. Besides the commonly used modification methods and polymer-based novel chemistry of selective layers elaborated in detail in this review, other delicate strategies (e.g., capillaryassisted IP 152 and amine modification 153,154 ) to regulate the formation of PA membranes and exploitation of twodimensional nanomaterials (e.g., graphene oxide, 155 molybdenum disulfide, 156 MXene, 157,158 etc.)…”

Planting Anion Channels in a Negatively Charged Polyamide Layer for Highly Selective Nanofiltration Separation

“…22 Zelner et al prepared a novel mix-charged NF membrane via two-step coating with Nafion and polyvinylamine. 23 Although the mixcharged membranes with a reinforced positively charged domain were obtained, they exhibited high rejection of Na 2 SO 4 (>70%) due to the unsatisfactory distribution of the positively charged domains. It is, therefore, the current positively charged membrane fabrication process that lacks control of the precise design of the charge and pore size distributions for achieving highspecification ion/solute selectivity.…”

“…Zhao et al added the positively charged amino-functionalized polyhedral oligomeric silsesquioxane (NH 2 -POSS) into a negatively charged PA matrix during IP, producing a PA membrane with more positively charged sites . Zelner et al prepared a novel mix-charged NF membrane via two-step coating with Nafion and polyvinylamine . Although the mix-charged membranes with a reinforced positively charged domain were obtained, they exhibited high rejection of Na 2 SO 4 (>70%) due to the unsatisfactory distribution of the positively charged domains.…”