粉煤灰对污染土壤中铜镉的稳定化

Immobilization of Cu and Cd in Contaminated Soil by Coal Fly Ash

采用批衡量吸附和室内培养实验,考察了粉煤灰对Cu和Cd的吸附等温线及0.2%、0.5%、1%和2%用量的粉煤灰对土壤pH、有效态Cu和Cd、以及5种化学形态Cu和Cd分布的影响。结果表明:粉煤灰对Cu和Cd的吸附等温线均可以用Langmuir和Freundlich方程进行拟合,其对Cu的最大吸附量(9.90 mg/g)高于对Cd的最大吸附量(9.43 mg/g)。随着粉煤灰用量的增加,土壤pH显著增加,有效态Cu和Cd显著降低。同时,粉煤灰处理显著降低了离子交换态Cu和Cd含量,增加了铁锰氧化物结合态Cu和Cd含量,降低了Cu和Cd活性,使活性态Cu和Cd逐渐向潜在活性态和非活性态转化。其中培养60天后,2%处理的粉煤灰处理较对照pH提高了0.44个单位,离子交换态Cu和Cd分别降低了35.7%和35.9%。因此,粉煤灰能够有效吸附Cu和Cd,显著降低土壤有效态和离子交换态Cu和Cd的含量,在重金属稳定化修复应用中具有较好的应用前景。

Adsorption isotherms of Cu and Cd by coal fly ash were studied through a batch equilibrium experiment and an incubation experiment. Soil pH, available and five chemical speciation of Cu and Cd were also investigated to study the immobilization of Cu and Cd by coal fly ash with application rates of 0.2%, 0.5%, 1% and 2%. The results showed that both the Langmuir and Freundlich equations can be used to describe the sorption of Cu and Cd by the coal fly ash, and maximum sorption amounts of Cu（9.90 mg/g） was higher than that of Cd（9.43 mg/g）. Soil pH was significantly increased and available Cu and Cd were decreased with the increasing of application rates of coal fly ash. Meanwhile, the application of coal fly ash significantly decreased the concentrations of exchangeable Cu and Cd and increased the concentrations of Cu and Cd bound to Fe-Mn oxides, which decreased the mobility factors of Cu and Cd, and promoted to the transformation of Cu and Cd from active to inactive fractions. In the soils treated by 2% coal fly ash, soil pH increased 0.44 unit and the concentrations of exchangeable Cu and Cd decreased 35.7% and 35.9% than those in the control after 60 days incubation, respectively. This study indicated that coal fly ash can effectively adsorb Cu and Cd, and reduce available and exchangeable Cu and Cd, which can be applied to immobilize heavy metals in contaminated soils.