Performance of new generation membrane distillation membranes

Membrane distillation has been a known desalination process for many years, but its commercial implementation has been hampered by low water fluxes and the need for low cost heat sources. With greater emphasis being placed on energy efficiency, membrane distillation coupled with waste heat or solar heat sources to drive the process is being reconsidered. In particular, the use of membrane distillation to treat brine concentrates is receiving renewed attention, as it results in increased water recovery and lower brine discharges, and high salt concentrations do not increase the driving force requirements for membrane distillation. In this paper, four different membranes, one made of polyvinylidenefluoride (PVDF) and three made of polytetrafluoroethylene (PTFE) of different pore sizes, were assessed the performance in membrane distillation under different hot feed flow rates and inlet temperatures. The results show that the PTFE membranes had a much higher flux than that of PVDF at the same operational conditions, and PTFE membranes of large pore size produced higher flux than that of the small pore size. The results also showed that increasing the flow rate of the hot feed and its inlet temperature increased the flux, but the rates of increase decreased with increasing flow rate and inlet feed temperature.