氯盐体系隔膜电积锡晶须产生及抑制基础研究

Large amounts of copper and tin enriched polymetallic powders were produced during E-waste resources recycling. Presently, most of them were sold to copper smelting plants as smelting raw materials to be charged with concentrates to recover copper and other valuable metals. Wherein the tin not only failed to be recovered effectively, but also caused seriously interferece to the copper recovery. The applicants preliminarily investigated a membrane electrodeposition technics, which was proved can separate and recover tin from copper-tin polymetallic powders cleanly and effectively, but the emergence of a large number of tin "whisker" during tin electrodeposition hindered the membrane electrodeposition smoothly. This proposal intends to combine electrochemical test and modern characterization means to investigate the crystal nucleation, growth law during tin membrane electrowinning, and to clarify the generation mechanism of tin whisker during tin electrodeposition. In addition, this proposal also plan to study the effect of solution properties, process parameters and external field coupling on anion, cation concentration distribution and variation characteristics around the surface and the side of electrode plate during tin membrane electrowinning, and summarizes its mass transfer laws, to obtain its influence law on current efficiency and as resultant tin morphology, and to establish the mapping relationship between membrane electrodeposition conditions and whisker morphology as well as to reveal the whisker inhibitory mechanism. Finally, this proposal also plan to carry out the optimization experiments to obtain key measures of tin whisker inhibition under the "long cycle, large plate " conditions, and obtain a technology prototype of tin membrane electrowinning of chloride system. Results of this proposed research will provide a theoretical basis for effective separate tin from copper and tin enriched polymetallic powders of E-waste.

电子废弃物资源再生过程常产出大量含铜锡多金属粉，目前主要将其作为炼铜原料搭配入铜冶炼炉使用，其中的锡不仅未能得到有效回收，而且对铜的回收造成严重干扰。采用氯盐体系隔膜电积技术可实现铜锡多金属粉清洁、高效预脱锡，但电积过程出现大量锡“晶须”现象，阻碍了隔膜电积的有效进行。本项目拟采用电化学测试与现代分析表征手段相结合的方法开展氯盐体系锡隔膜电积过程晶体成核、生长规律研究，阐明锡晶须产生机理；研究不同溶液性质、工艺参数和外场耦合条件下阴极板表面与侧面处阴、阳离子的浓度分布、变化特征，总结其传质特征，获得其对阴、阳极电流效率和电锡板形貌的影响规律，建立隔膜电积条件与电锡形貌的内在映射关系，揭示锡晶须抑制机制；在此基础上开展氯盐体系锡隔膜电积过程优化及调控试验，获得“长周期、大极板”条件下隔膜电积锡晶须抑制的关键措施，形成氯盐体系锡隔膜电积技术原型，为电子废弃物铜锡多金属粉高效脱锡提供理论依据。

电子废弃物资源再生过程常产出大量含铜锡多金属粉，目前主要将其作为炼铜原料搭配入铜冶炼炉使用，其中的锡不仅未能得到有效回收，而且对铜的回收造成严重干扰。采用氯盐体系隔膜电积技术可实现铜锡多金属粉清洁、高效预脱锡，但电积过程出现大量锡“晶须”现象，阻碍了隔膜电积的有效进行。本项目采用电化学测试与现代分析表征手段相结合的方法开展了氯盐体系锡隔膜电积过程晶体成核、生长规律研究，阐明了锡晶须产生机理；研究了不同溶液性质、工艺参数和外场耦合条件下阴极板表面与侧面处阴、阳离子的浓度分布、变化特征，查明了离子传质特征，揭示了其对阴、阳极电流效率和电锡板形貌的影响规律，建立了隔膜电积条件与电锡形貌的内在映射关系，阐明了锡晶须抑制机制；在此基础上开展氯盐体系锡隔膜电积过程优化及调控试验，获得了“长周期、大极板”条件下隔膜电积锡晶须抑制的关键措施，形成了氯盐体系锡隔膜电积技术原型，为该方法的规模化应用提供了理论参考，也为该技术的产业化实施提供了理论依据。研究表明，锡隔膜电沉积过程受扩散控制，遵循三维成核和晶粒长大机制，耦合超声外场后，溶液中Sn（II）扩散得到促进，控制步骤由扩散控制转变为扩散和电化学混合控制，锡沉积遵循三维半球型成核和晶粒长大机制。超声振动作用能分散阴极成核过程形成的较大晶核，抑制“晶须”的形成。锡隔膜电积时槽内离子浓度分布受到入口流速、电流密度、电积时间、槽内离子互相作用的影响而发生变化。增加进液速度及降低HCl浓度有利于提高电解液平均密度及阴极表面Sn2+的最低浓度。电积时极板边缘发生离子环流，顶部环流速度高于边缘处离子环流速度，且流体密度梯度影响离子对流方式。极板周围电流密度分布呈非均匀分布，在电极边缘发生电流偏转。电流密度的增加，能降低阴极表面Sn2+最低浓度及流体的平均密度，同时也将增加阴极表面流体的平均流速，也使得阴极产物厚度不均匀。