Robust dual-layer nanofibrous membrane with PTFE skin for acid/alkali recovery via membrane distillation

Membrane separation is a promising technology for the treatment of acid/alkali wastewater. However, their poor stability when exposed to corrosive media at elevated temperatures was still a challenge that hindered their wide application. Herein, a robust dual-layer bicomponent membrane consisting of an electrospinning polytetrafluoroethylene (PTFE) skin and a poly(vinylidene fluoride) (PVDF) fiber substrate was facilely fabricated by sequential electrospinning and hot-pressing for acid/alkali recovery via membrane distillation (MD). Benefitting from the low surface energy and chemically inert characteristics of PTFE, the as-prepared membranes showed superhydrophobic characteristics (151.23 ± 2.23°), and strong acid/alkali resistance at elevated temperatures. MD experiments showed that the optimized membranes exhibited a permeate flux of 24.23 ± 0.36 kg m^-2·h^-1 while maintaining superior flux stability and re-usability. In addition, high retention performance and up to 60 % water recovery were achieved, regardless of whether acid/alkali solutions were used as the feed. These findings indicated that this dual-layer membrane might act as a promising candidate for concentrating acid/alkali solution while generating fresh water via MD.