关键词: 重金属吸附； Pb^2+； Cd^2+； 冻融

Abstract:

We used Pb²⁺ and Cd²⁺ as target pollutants to  study the effect of freezethawing cycles on the adsorption of heavy metals by soil, decuced the effect mechanisms, and analyzed the effect of  temperature on heavy metal adsorption on freezethaw soils. The results show that the freezethawing cycles reduced the Pb²⁺ and Cd²⁺ adsorption  on soil, and changed the slope of Pb²⁺ and Cd²⁺ adsorption isotherms. Freezthawing cycles changed the adsorption mechanism of soil from specific adsorption to nonspecific adsorption, and it promotes soil to desorbe and release Pb²⁺ and Cd²⁺ to the environment. Freezethaw did not change the therm odynamic property of Pb²⁺, Cd²⁺ adsorption on soil, with the rise of temperature, Pb²⁺ adsorptions on freezethaw soil and untreated soil were increased, which belong to endothermic reaction; but the adsorption of Cd²⁺ reduced with temperature rise, which belongs to the exothermic reaction. Under the same pH conditions,  the adsorption quantities of Pb²⁺ and  Cd²⁺ on freezethaw soil were lower than those on untreated soil.

Key words: heavy metal adsorption； Pb^2+； Cd^2+； freezethaw