Study on Energy Characteristics and Hysteresis Effect of Cadmium in Soils

[Objective] The research aimed to study the effects of adsorption and desorption on the bioavailability of heavy metals in soil. [Method]Batch techniques were used to study the energy characteristics of adsorption and hysteresis effect of desorption of cadmium in 12 typical agricultural soils from China. [Result]Adsorption process of cadmium in soils was spontaneous process. With the increasing temperature, it could promote the adsorption of cadmium in soils. The value of Gibbs free energy( ΔG°) could be used to predict the desorption ability of cadmium in soils. The main mechanism of the cadmium adsorption in soils was the chemical bond force. There was hysteresis effect in the process of cadmium desorption,and with the increase of cadmium concentration in the equilibrium the hysteresis effect was enhanced. When pH and calcium carbonate content were higher,the hysteresis index was greater because of the cadmium forming the inner complexes and cadmium carbonate precipitation in the soils. [Conclusion]The study could provide some reference and gist for prevention of heavy metal polluted soils and for remediation of contaminated soils.