Upcycling cellulose acetate from discarded cigarette butts: Conversion of contaminated microfibers into loose-nanofiltration membranes for selective separation

This work reports the recovery and subsequent conversion of cellulose acetate (CA)polymer from waste cigarette filters into semi-permeable membranes. The recycling process comprised of step-wise solvent washing to remove the organics and other adhering impurities from the smoked filter, followed by dissolution, filtration and reprecipitation. The recovered polymer was thoroughly characterized and compared with the commercial and unsmoked cigarette filter derived CA to determine the purity and changes in polymer's physicochemical properties after subjection to smoke and heat. Membranes were fabricated using all three types of CA by immersion precipitation technique, systematically characterized (ATR-FTIR, SEM, contact angle, zeta potential)and tested for dye/salt separation. Optimized membranes showed high rejection for various dyes with <15 percent rejection for monovalent and divalent salts. Furthermore, long term testing (150 h)using real industry effluent revealed steady performance with excellent flux recovery and persistent organics rejection.