Evaluating the efficiency of modified hydrophobic PVDF membrane for the removal of PFOA substances from water by direct contact membrane distillation

Abstract

This study addresses the global issue of the contamination of water resources by per- and poly-fluoroalkyl substances (PFAS). PFAS are notoriously difficult to remove due to their resilient alkyl-fluorinated chains. We examined the potential of hydrophobic PVDF membranes in direct contact membrane distillation (DCMD) to eliminate perfluorooctanoic acid (PFOA) from Water. For desalination, both commercial and custom-made PVDF membranes exhibited a permeate flux of approximately 13 LMH, with salt rejections of 98.39 % and 99.95 %, respectively. In the case of PFOA removal, the fabricated PVDF membrane outperformed its commercial counterpart. It boasted an initial permeate flux of 16 LMH and a PFAS rejection of 95.8 %, compared to the commercial membrane's 13 LMH and 67.31 %. Furthermore, the custom membrane exhibited superior resistance to fouling, experiencing less flux decline. Employing response surface methodology (RSM), we identified the optimal combination of feed concentration (30 ppm), (60 °C), and flow rate (1.5 LPM) to yield a flux of 9 LMH and a PFOA rejection of 95.41 %. Feed temperature emerged as the most influential factor in DCMD performance. This study offers a novel approach to concentrating and removing emerging contaminants from wastewater and highlights the efficacy of tailored membrane technology in addressing pressing environmental challenges.