An Overview of Membrane Distillation

Membrane distillation (MD) is an arising desalination technology due to several of its outstanding advantages over the conventional reverse osmosis (RO) and thermal desalination technologies. It is thermally driven and utilizes the hydrophobic membranes to separate the volatile solutes from the nonvolatile solution. In MD process, the vapor from the aqueous solution transports through the hydrophobic membrane and condensates at the other side of the membrane as the high-quality product. The membranes applied in MD process should have high liquid entry pressure (LEP), low thermal conductivity, optimum membrane thickness, optimum mean pore size and narrow pore size distribution, as well as high porosity and low tortuosity to ensure the excellent MD performance. Besides desalination, MD can also be applied in the removal of heavy metals and the recovery of valuable materials. This chapter describes the fundamental principles, membranes, and applications of MD. Besides that, the hydrophobization of membranes which includes the use of low surface energy membrane materials, functionalization with low surface energy materials as well as the applications of nanotechnology has also been discussed.