Fouling reduction and flux enhancement of visible light driven nitrogen doped titanium dioxide-polyvinyl difluoride photocatalytic membrane: modelling and optimization of multiple variables

Abstract

In this study, the performance of nitrogen-doped titanium dioxide polyvinylidene difluoride photocatalytic membrane (N-TiO2-PVDF) in water treatment was assessed. The effect of solution pH (4–10) and salt (NaCl) concentration (7–40 g/l) on the permeate flux was investigated for disinfection of water containing E. coli. Modelling and optimization were done using response surface methodology (RSM) based on central composite design (CCD). Flux was modelled with a quadratic polynomial. The Analysis of Variance had a high predicted R2 of 0.83, with less than 0.2 difference with adjusted R2 indicating adequate response variation with a coefficient of variance (CV%) of 3.27%. The coefficient of variance (CV%) in the model did not exceed 10% indicating adequate variation and reliability in the response. The model had an optimum flux value of 5.3 ml/7cmD/min at pH 7 and 7 g/l NaCl concentration. The N-TiO2-PVDF membranes were hydrophilic resulting in an 80% higher mean flux than the PVDF membrane. This was attributed to antifouling properties resulting from the photocatalytic activity of N-TiO2 nanoparticles. The solar-based N-TiO2-PVDF membrane effectively disinfected water containing E. coli, with no bacterial regrowth, enhanced flux and reduced fouling.