Highly efficient and sustainable cationic polyvinyl chloride nanofibrous membranes for removal of E. coli and Cr (VI): Filtration and adsorption

Abstract

Both plastic (e.g., polyvinyl chloride (PVC)) solid waste and bacteria/heavy metal ions-containing wastewater pose a severe threat to the environment, which must be addressed simultaneously by developing highly efficient and sustainable strategies. Novel cationic PVC nanofibrous membranes with high filtration and adsorption capability were fabricated by electrospinning and surface grafting, and then employed for the removal of bacteria (e.g., E. coli) and hexavalent chromium (Cr (VI)) ions for wastewater treatment. A cationic pendant, methylimidazolium, was covalently anchored on the surface of PVC nanofibers and verified using FTIR-ATR, NMR, and SEM measurements. As a result, the optimized cationic PVC nanofibrous membrane (PVC-MIM) exhibited remarkable filtration efficiency for E. coli (LRV ≥ 6.1) from contaminated water, and a maximum adsorption capacity of 285.7 mg/g against Cr (VI). Kinetics, isotherms, and thermodynamics of the nanofibrous PVC-MIM membrane in the adsorption process were extensively investigated. The separation mechanism was proposed based on size exclusion, charged interactions, and hydrogen bonding/coordination between the membrane and the targets. Used sewer pipes and electric cables were employed as raw materials to fabricate modified nanofibrous membranes (0.9 g) to then manufacture of a spiral-wound PVC-MIM nanofibrous membrane cartridge. The resulting system exhibited a retention rate as high as 100 % when 24 L of simulated tanning wastewater containing concentrated suspended solids, oil, ammonia–nitrogen, chloride, and other pollutants were tested for a dynamic adsorption process. Furthermore, the nanofibrous membrane cartridge could be recycled ten times while the regeneration ratio remained as high as 91.0 %.