Identification of material and physical features of membrane distillation membranes for high performance desalination

In this paper, the performances of various membranes were assessed in Direct Contact Membrane Distillation (DCMD) under different feed velocities and inlet temperatures. The membranes studied included a polyvinylidenefluoride (PVDF) microfiltration membrane with a non-woven support layer, a polytetrafluoroethylene (PTFE) microfiltration membrane with a non-woven support layer, and three MD membranes made from PTFE of different pore size and all with a structured scrim support layer. The results showed that distillation using PTFE membranes produced much higher flux than that of the PVDF microfiltration membrane at the same operational conditions, and the support layer affected not only the flux, but also the energy efficiency (0.51–0.24). The results also show that increasing the velocity of the feed and its inlet temperature increased the flux, but the rate of flux increase diminishes at high velocities. The mass transfer coefficient improved for thinner support and active layer membranes, leading to fluxes as high as 46 L m−2 h−1 at 80 °C. The heat transfer characteristics were found to be superior for the open scrim backed membranes compared to the non-woven support membranes, resulting in significantly greater thermal efficiency for the scrim backed membranes.