Incorporation of negatively charged silver nanoparticles in outer-selective hollow fiber forward osmosis (OSHF-FO) membrane for wastewater dewatering

Thin film nanocomposite (TFN) outer selective hollow fiber forward osmosis (OSHF FO) membranes incorporated with negatively charged silver nanoparticles (NPs) were fabricated for wastewater dewatering. The performances of five silver loading concentrations, namely 0% (pristine), 0.0002%, 0.0005%, 0.0010%, and 0.0015%, were compared. Among the four non-zero loading concentrations, 0.0010% showed the best performance. The pristine membrane had a better flux performance than the silver-loaded membranes; however, the silver-loaded membranes lasted longer (over 30 days) and had a higher flux recovery after salt cleaning. The pristine membrane also concentrated the feed solution 4 h faster than the silver-loaded membranes (68 h); however, the performance was not stable, and the water flux continuously decreased. In contrast, the performance of the silver-load membranes was more stable and plateaued between 2 LMH and 3 LMH. Due to the negatively charged silver NPs, the TFN OSHF FO membranes showed a stronger fouling resistance and stable performance, and thus a longer life expectancy. Therefore, the use of TFN OSHF FO membranes with embedded silver NPs can be an alternative strategy for wastewater treatment and dewatering.