Keywords: mercury (II), ion exchange, tropical soils, specific adsorption, kaolinitic soil, Central Nigeria, clay, soil contamination, environmental pollution, exchange adsorption
Specific and exchange adsorption of mercury (II) on Ca-saturated kaolinitic soils in Central Nigeria
We studied the adsorption of Hg (II) in typical tropical soils in Central Nigeria. Results suggest that more Hg (II) is adsorbed specifically than by the reversible, cation exchange process, with the adsorption isotherms predominantly Langmuirian in form. Considering the acid, low organic matter content and kaolinitic clay nature of the soils, the specific adsorption is traceable to outer-sphere and inner-sphere complexes of Hg (II) involving silanol (≡SiOH) and aluminol (≡AlOH) sites on the clay mineral surfaces, and complexation with the organic matter. Thus, inputs of Hg (II) in these soils could lead to its accumulation to definite toxic levels.