Innovative Gamma-irradiated membrane for enhanced performance in membrane distillation treatment of real textile-dy

Abstract

For the first time, a novel method to enhance the water flux and wetting resistance of polyvinylidene fluoride (PVDF)-based membrane distillation (MD) membranes by subjecting the polymer solution to gamma irradiation prior to phase inversion (i.e. denoted as deep gamma-irradiated PVDF-MD membrane) was implemented in this study. Compared to conventionally prepared PVDF-MD membrane (i.e. phase-inversion without gammairradiation), the deep gamma-irradiated PVDF-MD membrane exhibited larger but more evenly distributed pore sizes and higher porosity (i.e. 84 ± 1.9 % vs 76 ± 1.2 %), resulting in a 1.8-fold increase in water flux. The enhanced membrane pore structure and water flux of the deep gamma-irradiated PVDF-MD membrane were attributed to the facilitated cross-linking between polymers induced by high-energy gamma-irradiation. More­ over, the fourier transform infrared spectroscopy data indicate that the deep gamma-irradiated PVDF-MD membrane exhibited a higher β/α phase ratio compared to the non-irradiated membrane. When tested with a real textile wastewater, the deep gamma-irradiated PVDF-MD membrane achieved water flux of 38.7 L/m2.h and colour removal of >99.5 % at feed and distillate temperatures of 70 ◦C and 20 ◦C, respectively. Moreover, this enhanced PVDF-MD membrane helped concentrate dye in the wastewater by a factor of 2.5, from an initial colour concentration of 1536 PtCo to 3882 PtCo, after 12 h of operation without any evidence of membrane pore wetting. The results reported here draw important practical implications for realisation of MD to boost circularity in textile dyeing facilities.