The impact of gamma-irradiation on physical properties and membrane distillation performance of PTFE and PVDF hollow fiber membrane

The impact of gamma irradiation on physical properties and membrane distillation (MD) performance of polytetrafluoroethylene (PTFE) and poly vinylidene fluoride (PVDF) hollow fiber membranes were investigated. As the gamma irradiation dose increased to 150 kGy using a 60Co source, the mean pore diameter of PTFE and PVDF decreased by 26.7 % and 13.9 %, membrane surface roughness decreased by 59.3 % and 10.1 %, water contact angle reduced from 106.2° to 99.8° and 108° to 94.6°, and the tensile stress and strain at break were decreased by 81.9 % and 5.1 %, respectively. While the porosity of PTFE and PVDF membrane increased from 31.3 % to 39.0 % and from 58.3 % to 60.4 %. Liquid entry pressure (LEP) of PTFE and PVDF membranes were increased by 60.5 % and 4.5 %, respectively, due to the CF2 bond breakage, shortened molecular chain and swelling membrane structure revealed by the SEM, AFM, FTIR and XPS. Less than 10 % change of VMD permeate flux and decontamination factor (DF) of 134Cs were found between the pristine membrane and irradiated membranes of both PTFE and PVDF membrane. From the perspective of MD performance, the gamma irradiation has no significant effect on the PTFE and PVDF membranes. Nevertheless, the weakened mechanical properties of PTFE and PVDF membrane affected by gamma irradiation should be evaluated strictly in the treatment of radioactive wastewater.