**2. Membrane distillation process**

### **2.1 Principle**

Membrane distillation is a thermal membrane process in which a hydrophobic membrane separates a cold and hot stream of water [32, 33]. The hydrophobic propriety of the membrane stops the passage of liquid water through the pores while allowing the passage of water vapor. The temperature shift between the two membrane surfaces produces a vapor pressure gradient that allows water vapor to cross through the membrane, and finally, the water vapor is condensed on the colder surface.

*Preparation and Evaluation of Hydrophobic Grafted Ceramic Membrane: For Application… DOI: http://dx.doi.org/10.5772/intechopen.104899*

**Figure 1.** *Schematic presentation of AGMD in counter current flow configuration.*

Finally, we obtained a distillate of very high purity. Membrane distillation may be used in various modes differing, for example, in a protocol of permeates collection [34].
