酸性矿山废水环境中富Cd/Pb施氏矿物电沉积调控机制研究

It’s difficult to remove the heavy metals by precipitate process in acidic aqueous solution, but schwertmannite mineral can do this during its formation in acid mine drainage. This may be a new way for heavy metals control and is of great significance for acid mine drainage treatment. So in this project, we choose Cd and Pb as the typical metals to simulate the formation of Cd/Pb-doped schwertmannite in the electrochemical deposition system which is easy to control the reaction conditions. We will use integrated methodologies including electrochemical techniques, chemical composition analysis and mineralogical approaches to (i) seek and optimize the impact factors governing the electrodeposition of schwertmannite, (ii)investigate the photoactivity effect of preformed deposit schwertmannite nuclei on the deposition rate and output of schwertmnanite, and (iii) observe the effects of Cd/Pb on the electrodeposition of schwertmannite, elucidate their immobilization mechanism during the Cd/Pb-doped schwertmannite deposit. We hope the outcome data in the proposed project will help to guide the growing of Cd/Pb-doped schwertmannite especially in the high concentration of acid mine drainage.

重金属离子在酸性条件下活性高，难以沉淀去除，而富重金属施氏矿物的形成为酸性矿山废水（Acid mine drainage, AMD)中重金属的固定提供了新的思路。本项目利用电化学沉积体系，研究施氏矿物析出的影响因素，探索施氏矿微晶的光电效应对施氏矿物的进一步成矿的作用，获得施氏矿电化学沉积的规律；基于富Cd/Pb施氏矿物共沉淀生长过程的电化学特性、热动力学特征、矿物的表观形貌及结构特征以及Cd/Pb在施氏矿物中的存在形态及结合方式，探明Cd、Pb在施氏矿物共沉淀生长过程中的作用机制及固定机理；由此阐明富Cd/Pb施氏矿物电沉积成矿的调控机制，为AMD污染的控制与治理提供理论依据。

构建了施氏矿物电化学沉积方法促进施氏矿物成矿，并研究了电化学体系中施氏矿物的形成过程与成矿机理；利用化学组分分析和矿物学表征手段探讨了施氏矿物电化学沉积过程中主要影响因素有：电流密度、电解模式、DO供应以及电解温度等；结合经典施氏矿物人工合成方法，对比、分析电化学成矿施氏矿物样品的特点：电化学沉积法可在较短时间内获得矿物产量较高、比表面积大、粒径500nm ~ 900nm的 具有针须发育的海胆球状施氏矿物；在H+-Pb2+-Fe2+-SO42-体系中，探究了Pb2+对施氏矿物沉积的影响以及共沉淀的作用机制： PbSO4优先形核结晶，这些微晶促进了施氏矿物异相形核生长；在H+-Cd2+-Fe2+-SO42-体系中，探究了Cd2+对施氏矿物沉积的影响以及共沉淀的作用机制：在酸性条件下（pH～3），Cd2+主要以游离态形式存在，共沉淀部分的Cd则是通过交换施氏矿表面羟基中的H+形成Fe-O-Cd；在H+-Cr6+-Fe2+-SO42-体系中，探究了Cr6+对施氏矿物沉积的影响以及共沉淀的作用机制：铬酸根主要通过取代施氏矿物矿内层双齿双核吸附的SO42-点位，形成富Cr施氏矿物；对高岭土酸洗废水通过电解诱导铁矿物沉淀预处理，研究了废水中悬浮物、电解时间、电解电压以及废水pH对电解过程中溶解态离子的影响。电解预处理对TFe和Fe2+的去除效果较好，SO42-次之，Al3+影响不大。