一种复合土壤调理剂的制备及其镉污染农田修复效果

Preparation of a composite soil conditioner and its effect on remediation of Cd-contaminated farmland

为弥补粉煤灰、硅藻土、蒙脱石及生石灰作为农田土壤镉污染修复材料在应用过程中存在的不足,以粉煤灰、硅藻土、蒙脱石和生石灰为原料,制备成复合土壤调理剂(MT),并对其进行比表面积、扫描电镜、ICP-MS和X射线荧光光谱表征及镉吸附试验,以探究其制备温度、吸附性能和吸附机理;以MT为钝化剂,开展镉污染田间修复试验,探究其修复效果及机理。结果表明,MT最佳制备温度为250℃,其比表面积为21.92 m^(2)/g,较反应前增大近1倍,其对镉的饱和吸附量高达270.27 mg/g,MT吸附性能提升主要依靠反应后增加的比表面积和生成的絮状水化物质。当MT按0.35%施加时,糙米中镉含量较空白降低了76.6%,低于GB 2762—2017的镉限值(0.2 mg/kg),MT主要通过吸附作用来降低土壤镉有效态含量,进而实现减少水稻对土壤镉的吸收累积,其效果优于单独使用粉煤灰、硅藻土及蒙脱石,安全性高于生石灰。同时有助于降低现行镉污染农田修复成本,可为我国农田土壤镉污染治理与修复提供一定的技术参考。

In order to make up for the deficiencies of fly ash,diatomite,montmorillonite and quicklime as remediation materials in Cd-contaminated farmland,fly ash,diatomite,montmorillonite and quicklime were used as raw materials to prepare a composite soil conditioner(MT),and its BET,SEM,ICP-MS,X ray fluorescence spectrum characterization and Cd adsorption experiments were carried out to explore its preparation temperature,adsorption performance and adsorption mechanism.By using MT as the passivation agent,Cd-contaminated farmland restoration experiment was carried out to explore its remediation effect and mechanism.The result showed that the optimal preparation temperature was 250℃,the BET of it can reach to 21.92 m^(2)/g,which was nearly one times larger than that before reaction,the saturated adsorption capacity for Cd was as high as 270.27 mg/g.The improved adsorption performance of MT mainly depended on the increase of BET and the formation of flocculent hydrated substances after reaction.When MT was applied at 0.35%,the content of Cd in brown rice was decreased by 76.6%,which was lower than the maximum allowable amount(0.2 mg/kg)of Cd in GB 2762—2017.MT reduced the available Cd in soils mainly through adsorption,thus reducing the absorption and accumulation of Cd in rice.Its effect was better than that of fly ash,diatomite and montmorillonite used alone,and the safety was higher than quicklime.It could help to reduce the cost of remediation Cdcontaminated farmland,and the research could provide some technical references for Cd pollution control of farmland in China.