Contactors and Membrane Distillation

Contactors have a number of advantages compared to simple liquid/gas absorb-er/strippers or liquid/liquid extractors. Perhaps the most important advantage is high surface area per volume. The contact area of membrane contactors compared to traditional contactor columns is shown in Table 13.2. Membrane contactors provide 10-fold higher contactor areas than equivalent-sized towers. This makes membrane 

Liquid-gas contactor to remove Gas-liquid contactor to separate 

Liquid-liquid contactor with two immiscible liquids to remove dissolved VOCs from water (23) 

Liquid-liquid contactor with two miscible liquids (membrane distillation) to remove pure water from a salt solution (31-33) 

The main disadvantages of contactors are related to the nature of the membrane interface. The membrane acts as an additional barrier to transport between the two phases that can slow the rate of separation. Over time, the membranes can foul, reducing the permeation rate further, or develop leaks, allowing direct mixing of the two phases. Finally, the polymeric membranes are necessarily thin (to maximize their permeation rate) and consequently cannot withstand large pressure differences across the membrane or exposure to harsh solvents and chemicals. In many industrial settings, this lack of robustness prohibits the use of membrane contactors. 

---