典型黄壤和石灰土对Cd的吸附解吸特性

Adsorption and Desorption Characteristics of Cadmium in Yellow Soil and Limestone Soil

为评估Cd在不同土壤中的迁移能力及环境风险,分析了贵州省地带性黄壤和石灰土对重金属Cd的吸附解吸特性。结果表明：在试验浓度范围内,Cd在黄壤和石灰土中的吸附量均随着加入Cd浓度的增加而增加,吸附率逐渐下降。当初始溶液中Cd的浓度达310mg/L时,石灰土与黄壤中吸附的Cd含量达2 626mg/kg和1 507mg/kg,对Cd的吸附率分别为84.74%和48.64%。Freundlich和Henry方程均可以用来拟合Cd^2＋在2种土壤中的等温吸附过程,Langmuir和Temkin方程则不适合用来描述,Freundlich的拟合效果最好。在试验浓度范围内,Cd在黄壤和石灰土中的解吸量均随着加入Cd浓度的增加而增加,解吸率逐渐升高最终趋于稳定,黄壤对Cd的解吸率稳定在25%～30%,石灰土对Cd的解吸率稳定在6%～7%。Cd在酸性黄壤中的吸附能力较石灰土弱,解吸性能较石灰土强,环境风险较高。

Yellow soil and limestone soil were chosen to study the adsorption and desorption of cadmium in these soil in order to evaluate the ability of migration and environmental risks.The results showed that within the test range,Cd adsorption increased with increasing initial concentration,and limestone soil had a much higher Cd adsorption capacity than yellow soil.While the adsorption rate declined.When the Cd concentration in adsorption equilibrium was 310mg/L,the amount of adsorbed Cd was 2 626mg/kg in limestone soil,but 1 507 mg/kg in yellow soil.While the adsorption rate of Cd in limestone soil and yellow soil was 84.74%and 48.64%respectively.The adsorption isotherm of Cd in the two soils could significantly conform to Freundlich and Henry equations,while Langmuir and Temkin equation was not applicable to describe the isothermal adsorption process of Cd in yellow soil and limestone soil.Within the test range,Cd desorption increased with increasing initial concentration.The desorption rate increased gradually tending to be stable,yellow soil desorption rate of Cd eventually stabilized at25%～30%,limestone soil desorption rate of Cd in 6%～7%.Adsorption capacity of Cd in limestone soil was significantly higher than that in yellow soil,while desorption capacity reversed with higher environmental risk.