氨基功能化微硅粉的制备及其对镉污染土壤的钝化效果研究

Preparation of amino functionalized microsilica powder and its passivation effect on cadmium contaminated soil

以工业废弃物微硅粉为基体材料,通过硅烷偶联反应将氨基固载到微硅粉表面,制备一种高效重金属吸附材料——氨基功能化微硅粉(SFK),并将其应用于镉污染土壤的钝化治理。吸附试验结果显示,SFK对重金属Cd(Ⅱ)的吸附符合Langmuir吸附等温线模型,最大吸附量为43.83 mg/g。扫描电子显微镜-能谱、傅里叶变换红外光谱及X射线光电子能谱表征结果分析可知,吸附主要通过氨基与Cd(Ⅱ)发生配位反应而固定在SFK表面。土壤培养试验和小白菜盆栽试验结果显示:当SFK施用质量分数为3%时,土壤有效态Cd质量比显著降低,未种植小白菜土壤和种植小白菜土壤中Cd质量比的降幅分别为47.10%和78.17%;小白菜生物量显著增加,小白菜地上和地下部分Cd质量比分别降低了81.63%和63.56%。本文主要体现了“以废治废”的思路,制备的SFK材料可应用于镉污染农田土壤的治理。

The heavy metal passivator(SFK)is prepared by the modification of industrial waste silica fume through heat treatment,acid activation,and graft modification with a silane coupling agent.The surface microstructure and chemical composition of the materials are investigated by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),and X-ray photoelectron spectroscopy(XPS).The results show that amino functional groups were successfully grafted on the surface of SFK materials,and the SFK forms a complex to immobilize Cd mainly through the coordination bond between a large number of amino functional groups and Cd(Ⅱ).The static adsorption experiments show that the adsorption of Cd(Ⅱ)follows the Langmuir adsorption isotherm model,and the maximum adsorption capacity is 43.83 mg/g,indicating that the adsorption mainly occurs in the monolayer adsorption.A pot experiment of pakchoi is used to study the passivation effect of SFK passivator on cadmium contaminated soil.Different passivation treatments can significantly reduce the mass ratio of DTPA-Cd extracted in soil,and the maximum reduction rates of unplanted pakchoi soil and planted pakchoi soil are 47.10%and 78.17%,respectively.After applying SFK to cadmium contaminated soil,pakchoi grew well,and the mass ratio of Cd in the aboveground part of the harvested pakchoi was greatly reduced.On the one hand,the soil pH value increased with the increase of the dosage of SFK,resulting in a decrease in the effective Cd mass ratio that can be absorbed by plants in the Cd-contaminated soil.On the other hand,Cd with strong activity can be effectively immobilized on the surface of SFK,thus reducing the mass ratio of heavy metal Cd in the soil DTPA-extracted state.Therefore,SFK can reduce the bioavailability of Cd in the soil through surface coordination adsorption and precipitation,thereby reducing the toxicity of pakchoi.This research mainly embodies the idea of“using waste to treat waste”,and the prepared silica fume modified material is expected to be used in the remediation of cadmium contaminated farmland soil.