A research team led by Prof. WAN Yinhua at the Institute of Process Engineering (IPE) of the Chinese Academy of Sciences has recently developed an innovative mix-charged nanofiltration (NF) membrane featuring horizontal charge distribution, designed specifically for wastewater treatment. This novel membrane exhibits remarkable salt permeation and organic matter retention capabilities as well as antifouling properties, making it particularly effective for treating high-salinity organic wastewater.
The findings were published in Environmental Science & Technology on Jan. 7.
Efficiently removing organic contaminants from high-salinity wastewater is essential for resource recovery and achieving zero discharge. While NF membranes are effective at separating organic compounds and monovalent salts, they often over-reject divalent salts. Modifying the charge characteristics of these membranes can improve salt permeation; however, the impact of charge spatial distribution on salt transport behavior has not been well understood.
To tackle this challenge, the researchers designed a mix-charged NF membrane with horizontal charge distribution using a unique combination of interfacial polymerization, polyester template etching, and solvent-induced polyamine intercalation.
This novel charge configuration results in high charge density and a near-electroneutral surface that facilitates the permeation of divalent salts. The size-dependent "plug-in" modification and covalent crosslinking further reduce pore size, enhancing the membrane's rejection of small organic molecules.
Furthermore, the membrane exhibits outstanding antifouling performance against both negatively and positively charged pollutants, thanks to its distinctive charge distribution and smooth surface.
"Our membrane achieves 58.6% salt permeation and 68.7% COD rejection when treating high-salinity organic wastewater—among the best results reported for NF membranes in the literature," said Prof. LUO Jianquan, corresponding author of the study.
This breakthrough offers promising new solutions for the treatment of high-salinity wastewater, paving the way for improved resource recovery and sustainability in wastewater management.
