Adsorption of Ionic Pollutants
The surface of an individual clay particle or organic colloid is negatively (-) charged.
As a consequence their surfaces attract and adsorb positively charged ions (cations). When
water is added to soil, cations can move into solution, attracted to the clay particle or organic
colloid surface .Cation exchange is therefore defined as the interchange between a cation on
the surface of any negatively charged particle (i.e. clay mineral or organic colloid) and the
soil solution.