(165b) Direct contact membrane distillation (DCMD) membrane distillation techniques for desalination
Direct contact membrane distillation (DCMD) is one of the simplest and most widely used membrane distillation techniques for desalination. It is a thermally driven separation process and is sought to achieve high water vapor flux while being thermally efficient. Typically, a hydrophobic porous membrane is used and water vapor from the salt solution is allowed to pass through the pores and condense on the other side of the membrane. Investigation on other structures of membranes is carried out. Membranes include those in the form of an integral composite, in which the structures of PVDF membranes are changed, and a stacked composite, in which different membranes are stacked on top of each other (e.g. a hydrophobic ePTFE membrane over a hydrophilic PVDF membrane, and a hydrophobic PVDF membrane over another hydrophobic PVDF membrane). These membranes were found to yield a higher water vapor flux than the conventional single hydrophobic membrane. Membranes are also characterized using a variety of characterization techniques: Contact angle, liquid entry pressure (LEP), bubble-point pressure, scanning electron microscopy (SEM), and atomic force microscopy (AFM).