Mass Transfer

The movement of molecules of a substance to and across an interface from one phase to another. For example, the amount (mass) of ozone that transfers from air, across the air-water interface and into water; or the amount of organic material that transfers from water to a solid adsorption surface.

The rate and amount of mass transfer can be increased by:

1. enlarging the interface boundary by increasing the area of the interface or by rapid renewal or clearance of the interface; 2. increasing the concentration difference (which is the driving force) across the interface boundary, and/or; 3. increasing the length of time (contact time) the interface boundary exists.