Membrane Distillation and Osmotic Membrane Distillation in Downstream Processing

Membrane distillation is a relatively new process alternative to conventional separation methods like distillation and reverse osmosis concerning cost and energy saving technology. Membrane distillation is beneficial over other separation techniques in terms of theoretical rejection of ions, macromolecules, colloids, cells and other nonvolatile compounds and also lowers operating temperature and pressure making it more advantageous for thermally sensitive solutions. The cost of the process is reduced considerably compared to conventional distillation because of reduced vapor space. In contrast, there are some limitations of MD. The major limitation being the definition of the phenomenon: the process requires an aqueous solution, and it should be dilute so that wetting of hydrophobic membranes is avoided. This limits membrane distillation to applications such as desalination (currently dominated by reverse osmosis), removal of trace volatile organic compounds from waste water, and concentration of ionic, Colloidal, or other relatively Non-volatile aqueous solutions. Membranes have always been an integral part of downstream processing. The present review summarizes the state of the art of Membrane distillation and osmotic membrane distillation process in downstream processing with importance to the work done after the year 2008.The review also covers the necessary techniques needed for characterization membranes used in MD.