Hydrophobic Zn-doped Fe2O3/PVDF-Co-HFP composite membranes for enhanced water recovery using direct contact membrane distillation

Novel Polyvinylinidefluoride co-hexafluoropropylene composite membranes for direct contact membrane distillation (DCMD) were prepared in a 2-step process by (i) incorporating fluoroalkylsilane (FAS) functionalised hydrophobic Zn-doped Fe2O3 nanoparticles (0-0.45 wt%), and (ii) functionalisation with FAS. The optimum membrane (M-2e) membrane with 0.3 wt% nanoparticles displayed the highest water contact angle of 135 +/- 0.3 degrees, with a 75 % porosity and permeate vapour flux of 10 L/m(2)h when tested with synthetic seawater (35,000 ppm NaCl) as feed solution for up to 24 h which agrees with the predicted values using the Dusty-Gas model. The M-2e could recover pure water from synthetic pharmaceutical wastewater with a constant flux of 16 L/m(2)h for up to 6 cycles of operation (10 h each) and produced permeate with <15 <mu>S/cm and organic content 0.670 +/- 0.002 ppm. The membrane proved to be robust in recovering water (conductivity < 20 <mu>S/cm) for up to 60 h from both (i) synthetic municipal wastewater and (ii) secondary treated effluent from the sewage treatment plant of the National Institute of Technology Calicut hostels The membrane developed in this study holds the potential to recover water continuously from secondary treated effluent using DCMD.