Reducing the pathogenicity of wastewater with killer vapor-induced phase separation membranes

Abstract

While smart antibacterial surfaces with bacteria-killing/bacteria-releasing properties have been reported, no strategy existed up to date to prepare phase-inversion membranes having these capabilities in one single step, without any surface-modification. We addressed this challenge by synthesizing two copolymers made of butyl methacrylate (BMA) units and of 2-(dimethylamino)ethyl methacrylate (DMAEMA), poly(BMA-r-DMAEMA), or (trimethylamino)ethyl methacrylate chloride (TMAEMA), poly(BMA-r-TMAEMA), both miscible with poly(vinylidene fluoride) (PVDF), and prepared membranes by the vapor-induced phase separation process. Results showed that all membranes were able to kill almost 100% of bacteria that came into contact with the surface. A washing procedure with a saline solution of sodium hexametaphosphate permitted to regenerate the membrane modified with poly(BMA-r-TMAEMA). Strong hydration of the interface between positively-charged brushes and dead bacteria after docking with hexametaphosphate anions, combined to the excess of negative charges, results in bacteria release following conformational changes of poly(BMA-r-TMAEMA) polyelectrolyte brushes. However, the membrane modified with poly(BMA-r-DMAEMA) could not be regenerated, likely because poly(BMA-r-DMAEMA) does not behave as a polyelectrolyte. Results also reveal that poly(BMA-r-TMAEMA)-modified PVDF membranes were able to kill various species of bacteria, and that multiple cycles could be successively run. The prepared MF membranes are able to kill the majority of microorganisms once they contact the membrane during filtration. Domains of applications are numerous from wastewater-treatment to healthcare applications, wherever bacteria are wanted dead after separation.