煤基半焦对重金属土壤中铬和镉的原位钝化及作用机制分析OACSTPCD

The rapid growth of industrialization and urbanization has caused serious heavy metal pollution in soil,among which chromium and cadmium are highly toxic and detrimental to the environment.In this study,semi-coke was prepared through pyrolysis by utilizing the abun-dant resources of Shihezi coal and Urumqi coal.The semi-coke was then used as immobilization material for chromium and cadmium-contaminated soil,with the goal of remediating and impro-ving the heavy metal-polluted soil.The characteristic temperatures of pyrolysis of two kinds of coal samples were obtained by thermogravimetric analysis,and the pore structures of the semi-cokes were characterized by N2 isothermal adsorption.The effects of action time and additive amount of semi-coke passivator on the available content of heavy metals in single and compound contaminated soil were studied by heavy metal extraction test.The results show that the surface characteristics of Urumqi coal-based semi-coke are more suitable for heavy metal immobilization,and the pore size is mainly concentrated in the range of 1.8 nm-4.0 nm;the number of acidic functional groups and basic functional groups per unit area is higher,which are 0.0026 mmol/m2 and 0.0164 mmol/m2,respectively.The available content of Cr and Cd decreases by 78%and 21%,respectively,when the additive amount is 5%with particle size of 300 μm-500 μm and the interaction time of 90 d.Compared with single contaminated soil,the immobilization effect of Cr and Cd in composite contaminated soil decreases slightly due to competition.In addition,after adding semi-coke to the soil,due to the buffering effect of semi-coke,the p H value remains stab-ly within the weak alkaline range,while the organic matter content and cation exchange capacity increase;the physical and chemical properties of the soil are improved,and the soil fertility is enhanced.