超临界CO_(2)萃取铅锌尾矿重金属工艺研究

Study on the process of supercritical CO_(2)extraction of heavy metals from lead and zinc tailings

铅锌尾矿中含有多种有毒有害重金属,进行尾矿无害化处理,对实现矿业资源利用与生态环境保护具有重要意义.以二乙基二硫代氨基甲酸钠为络合剂,利用超临界CO_(2)萃取技术探究了络合剂添加量、萃取温度、萃取压力和萃取时间对铅锌尾矿中重金属萃取率的影响,并通过正交试验得到重金属的最佳萃取条件及影响因素大小,根据萃取反应前后铅锌尾矿的XRD、SEM结果等分析该过程对尾矿样品性质的影响.结果表明:选取络合剂添加量为7%(w/w),萃取温度为45℃,萃取压力为25 MPa,萃取时间为100 min,超临界CO_(2)萃取技术对尾矿中重金属具有较好的萃取率;不同因素对Pb萃取率的影响大小为萃取温度>萃取时间>萃取压力,且在60 min、45℃、25 MPa条件下,萃取率最佳可达69.42%.Zn和Cu的最佳萃取条件分别为100 min、50℃、30 MPa和80 min、45℃、30 MPa;萃取过程对尾矿的微观形态和矿物组成影响不大,这也为超临界CO_(2)萃取技术用于尾矿资源化提供了保障.

Lead-zinc tailings contain a variety of toxic and harmful heavy metals,and the harmless treatment of tailings is of great significance to the realization of mining resource utilization and ecological environment protection.In this study,sodium diethyldithiocarbamate was selected as the complexing agent,and the supercritical CO_(2)complex extraction technology was used to study the effects of various parameters,including the amount of complexing agent,extraction temperature,extraction pressure and extraction time on the extraction rate of heavy metals in lead-zinc tailings,and the optimal extraction conditions of heavy metals and the effects level of these factors are obtained through orthogonal experiments.According to the XRD patterns and SEM results of the lead-zinc tailings before and after the extraction reaction,the influence of this process on the properties of tailings samples were analyzed.The results showed that the optimum extraction of heavy metals from tailings could be obtained when complexing agent dosage was 7%(w/w),extracting temperature was 45℃,pressure was 25 MPa and time was 100 min.Different parameters impact the the Pb extraction rate followed by Temperature>Time>Pressure,and the maximum extracting rate reached 69.42%under the conditons of 60 min,45℃,and 25 MPa.The optimal extraction conditions for Zn and Cu were 100 min,50℃,30 MPa and 80 min,45℃,30 MPa,respectively.The whole extraction process had little effect on the microscopic morphology and elemental composition of the tailings,which provides a strong technical support for the safe use of supercritical CO_(2)extraction in tailings resource utilization.