Unsupported electrospun membrane for water desalination using direct contact membrane distillation

Abstract

Abstract In this project, an unsupported electrospun poly(vinylidene fluoride)‐co‐hexafluoropropylene (PVDF‐HFP) membrane was used for water desalination using direct contact membrane distillation (DCMD). The membrane was electrospun using a laboratory‐scale machine with multiple nozzles that was developed in‐house. Critical process parameters, including the applied voltage and polymer concentration, were optimized to obtain bead‐free electrospun membranes with fiber diameters less than 300 nm. To improve the membrane thermal stability and performance, the selected electrospun membrane was heat‐pressed at 160°C. The untreated and heat‐pressed membranes were tested in a DCMD setup at different feed temperatures (60, 70, and 80°C) and feed flow rates (0.4, 0.6, and 0.8 L/min), while maintaining the permeate temperature and flow rate at 20°C and 0.2 L/min, respectively. The modified electrospun membrane exhibited a very high permeate flux (>37.5 kg/m 2 /h) and a salt rejection rate of 99.99% at a feed temperature of 70°C. The performance of the heat‐pressed unsupported PVDF‐HFP electrospun membrane was nearly identical to a commercially available polytetrafluoroethylene (PTFE) supported membrane. These promising results demonstrate that relatively low‐cost electrospun membranes can be easily produced and successfully used in DCMD to minimize the capital cost and increase the energy efficiency of the process.