丁基黄药对选矿区土壤吸附铅镉的影响

选矿废水排放和尾矿库溢流等会将大量残留的选矿药剂带入选矿区周边土壤和水环境.采用批处理实验，研究了不同pH、初始丁基黄药（PBX）、Pb²⁺和Cd²⁺浓度下，PBX对某铅锌选矿区土壤吸附Pb²⁺和Cd²⁺的影响；并通过BCR连续提取，研究了不同浓度PBX处理后土壤中铅镉形态变化.结果表明，PBX明显抑制了土壤对Pb²⁺和Cd²⁺的吸附.PBX浓度为40mg·L^-1时，土壤对Pb²⁺和Cd²⁺的吸附量分别由未经PBX处理时的3540 mg·kg^-1和387mg·kg^-1降至3085 mg·kg^-1和100mg·kg^-1.无论是否添加PBX，土壤对Pb²⁺和Cd²⁺的吸附动力学过程可用准二级动力学模型拟合，表明Pb²⁺和Cd²⁺在土壤上的吸附是以化学吸附为主.PBX与Pb²⁺、Cd²⁺形成疏水性难溶络合物以及在土壤表面存在竞争吸附是降低土壤Pb²⁺和Cd²⁺吸附量的主要原因，表明PBX能增加Pb²⁺和Cd²⁺在土壤中的迁移性.PBX对土壤Pb²⁺和Cd²⁺吸附的抑制作用随初始Pb²⁺和Cd²⁺浓度的增大而减弱，随初始PBX浓度及溶液pH值的增大而加强，Freundlich方程能较好描述其等温吸附特征.低含量PBX （100mg·kg^-1）下土壤中可交换态和可还原态镉含量有所增加，可导致土壤中镉的活化；但PBX可降低土壤中可交换态和可还原态铅含量，且随PBX含量升高，铅活性降低效果越显著，这与Pb （C₄H₉OCS₂）₂的络合能力比Cd （C₄H₉OCS₂）₂强有关.研究结果表明应加强选矿废水中残留药剂对土壤中铅镉等重金属潜在生态风险的防控.

Effect of Butyl Xanthate on Pb2+ and Cd2+ Adsorption by Soil Around a Dressing Plant

Flotation agents can enter the soil and water environment around mining areas through beneficiation wastewater discharge and overflow from tailings ponds. The adsorption of Pb²⁺ and Cd²⁺ on soil around a lead-zinc dressing plant was investigated in the presence of potassium butyl xanthate (PBX). Batch experiments were conducted with different initial pH, PBX, Pb²⁺, and Cd²⁺solution concentrations. The fractions of lead and cadmium were altered after treatment with different concentrations of PBX. The results showed that adsorption of Pb²⁺and Cd²⁺ on soil was seriously inhibited by PBX. When PBX concentration was 40 mg·L^-1, the adsorption capacity of Pb²⁺ and Cd²⁺ decreased from 3540 mg·kg^-1 and 387 mg·kg^-1 to 3085 mg·kg^-1 and 100 mg·kg^-1, respectively. The Pb²⁺ and Cd²⁺ adsorption kinetic process was best fitted by the quasi-second-order kinetic model, which indicated that the adsorption process of Pb²⁺ and Cd²⁺ on soil was mainly chemical adsorption. The formation of a hydrophobic and insoluble complex and competitive adsorption between PBX, Pb²⁺, and Cd²⁺ on the soil surface was the main reason for reducing the adsorption capacity. The results showed that PBX could increase the mobility of Pb²⁺ and Cd²⁺ on soil. The degree of impact improved with increasing initial concentration of PBX and pH but decreased with increasing initial concentration of Pb²⁺ and Cd²⁺, and the adsorption isotherms conformed to the Freundlich isotherm. Under low PBX content (100 mg·kg^-1), exchangeable and reducible cadmium contents in the soil increased, which could lead to the activation of cadmium in soil. However, the addition of PBX to the treated soil could reduce the content of exchangeable and reducible lead. As the concentration of PBX increased, the reduction effect also increased, which was related to the stronger complex stability of Pb(C₄H₉OCS₂)₂ than that of Cd(C₄H₉OCS₂)₂. The results showed that residual flotation reagents in beneficiation wastewater may increase the potential ecological risk of heavy metals such as Pb and Cd in soil, and the prevention and control of the potential ecological risk should be strengthened.