Soils from two towns of Hefei City in Anhui Province were chosen to investigate the

adsorption properties of heavy metals Hg, Pb under the influence of phosphate acid. Batch

equilibration method was used in this experiment to study the isotherm adsorption and adsorption

thermodynamics characteristics of heavy metals in two typical soils. The results show that phosphate

has effects on the absorption of heavy metals. With increasing phosphate, the Hg, Pb absorption also

increases. The Hg,  Pb absorption Gibbs free energies of the two soils are both negative, indicating that

their related chemical processes can take place spontaneously, and that the chemical sorption coexists

with the physical sorption. The absorption of Hg, Pb by the two kinds of soils are governed by positive

adsorption entropy processes.