Removing antibiotics from watercourses by surface immobilization of TiO2 nanoparticles on poly(vinylidene fluoride) membranes by recrystallization under pressure

• Original method for immobilization of TiO 2 nanoparticles on PVDF membranes. • Recrystallization of the polymer by compression fixes the nanoparticles to the surface. • Scalable processing for membrane production and recycling. • Effective degradation of ciprofloxacin and other antibiotics The increasing presence of antibiotics in wastewater, a serious risk to public health and the environment, can lead to the generation of antibiotic-resistant bacteria and disturb the ecological balance. Among the possible solutions are photocatalytic mechanisms, which are not based on the absorption/adsorption of the contaminant and so avoid the need for further elimination or destruction; the contaminants are instead directly inactivated by breaking down their molecular structure in a simple and economical process. Although titanium dioxide (TiO 2 ) has been widely explored for this purpose, the particles need to be chemically attached to the support, which means they can be inactivated, which raises the cost and complexity of the procedure. Our approach is based on immobilizing TiO 2 in a non-solvent induced phase separation poly(vinylidene fluoride) (PVDF) membrane by means of mechanical compression. Both the non-solvent induced phase separation and mechanical compression techniques are widely used in industrial settings due to their simple, inexpensive and sequential implementation, while PVDF-based supports use their high degree of stability to resist the photocatalytic action of TiO 2 free radicals. PVDF/TiO 2 membranes degraded 77% of tetracycline, 56% of ciprofloxacin and 24% of metronidazole from respective solutions after 4 hours of UV exposure and maintained their photocatalytic activity unaltered for up to 4 consecutive cycles. The degradation kinetics were linear in the 0.5 to 2.5 mg/L range, while the membranes had a large surface area with 89% of exposed TiO 2 , 80% UV transparency between 360 - 380 nm, and 62% of PVDF polar structures to prevent fouling.