Influence of low dose gamma-ray irradiation on the performance and degradation of PVDF ultrafiltration membrane

Poly vinylidene fluoride (PVDF) UF membranes in water were exposed to gamma rays irradiation from 0 to 100 kGy using a cobalt source. The absorbed dose provoked the rupture of C-F bonds, giving 0.02-0.38 mg of free F- ion per gram membrane. Increasing the absorbed dose led to a more hydrophilic membrane surface, more fissures in the membrane, and a lower of water permeability. The pure water flux of a membrane irradiated at 100 kGy was reduced by 44% compared to the pristine membrane. During filtration of low level radioactive wastewater that contained surfactants, the flux decreased at a slower rate for the irradiated membrane than for the pristine membrane. The retention of most ions remained stable. SEM images of the fouled membranes show a decrease in salt crystal contents on the fouling layer with increasing absorbed dose. Lower levels of salt deposits may contribute to a decrease in Ag(I) retention. Overall, upon exposure to low levels of irradiation, the membrane pure water flux was reduced, and membrane fouling was alleviated. These factors should be considered in membrane system design.