Developing helical carbon functionalized chitosan-based loose nanofiltration membranes for selective separation and wastewater treatment

This study reports an effective method for preparing oxygenated helical carbon impregnated chitosan-based loose nanofiltration membrane, cross-linked with sodium dodecyl sulfate (SDS) for selective solute permeation and various industrial wastewater treatment. The structural and functional properties of as prepared thin-film composite (TFC) membranes were thoroughly characterized using ATR-IR, FE-SEM, contact angle, and zeta potential measurements. Performance testing using various feed streams under different testing conditions revealed that the optimized membrane showed >90.0% rejection for dyes (both cationic and anionic) and humic acid, and <8.0% rejection for MgSO4 with 40.0-60.0 L.m(-2).h(-1) flux at 3 bar operating pressure. The study was extended using four different real industrial wastewaters as feed solutions. In all cases, the rejection values for salts resembled with that of simulated wastewater with significant removal of organic pollutants (reduced COD, BOD and TOC). Thereafter, long term (>100 h) studies were conducted using simulated wastewater spiked with multiple foulants as feed constituents and the results showed >90.0% rejection for organic matters and foulants with a long-term stable flux profile. The membranes were stable even after repeated operating cycles without any significant reduction in flux or rejection, demonstrating their potential to be used as an effective pre-treatment media for various industrial wastewaters.

Automated summary

This study introduces a novel nanofiltration membrane preparation method for industrial wastewater treatment, with characterized membrane structure and performance demonstrating high rejection rates, stable flux, and repeated use potential.