无氨硫代硫酸盐贵液锌银界面反应机制研究

The non-ammonia thiosulfate leaching technology has been developed for silver extraction from silver sulfide mineral resources, which is efficient and environmentally benign. Zinc cementation was evaluated as a method for the recovery of silver from non-ammonia thiosulfate leach solutions. It was found that it is possible to achieve appreciable cementation rates of silver onto a zinc substrate. However, some basic scientific problems about phase interfacial reaction are still not fully solved.. Zinc is a reactive metal, not only zinc oxide and silver thiosulfate complex ions reduction reaction occurs on solid-liquid interface, but also the electron migrates between zinc surface and meta-stable sulfur oxygen ions and copper thiosulfate complex ions. Therefore, in this project, the following investigations will be carried out by combine of thermodynamic calculations, quantum chemical calculations, electrochemical test and kinetics research: ①the mechanism of redox reactions of zinc and sulfur oxygen ions, and the effect on the cementation of the redox product; ②the competition mechanism of silver thiosulfate complex ions and copper thiosulfate complex ions with zinc on the phase interface. The project will theoretically explain the solid-liquid phase interface reaction of zinc cementation of silver from non-ammonia thiosulfate pregnant solution. It will provide theoretical supports for rational development and efficient recovery the silver resources, and research foundation for industrial applications of thiosulfate technology.

无氨硫代硫酸盐法是一种高效、绿色的硫化银矿浸出技术，锌粉置换可有效回收浸出贵液中的银，成本低廉、反应快速，是无氨硫代硫酸盐法回收硫化银矿的关键技术之一，但关于置换过程中相界面反应的一些基础科学问题研究还不够。. 锌性质活泼，固液界面不仅发生锌与硫代硫酸银络离子的氧化还原反应，还存在锌与亚稳态硫氧离子及硫代硫酸铜络离子间的电子迁移，项目采用热力学计算、量化计算、电化学测试和动力学研究相结合的方法，重点研究：①锌与硫氧离子间作用机制及界面产物对后续置换的影响；②硫代硫酸络铜离子和络银离子在锌界面的竞争机制。本项目将从理论上阐释锌粉从无氨硫代硫酸盐贵液置换银过程中的固液相界面反应，为我国银资源的合理开发和高效回收提供理论支撑，为硫代硫酸盐法的广泛应用奠定研究基础。

无氨硫代硫酸盐浸银贵液中主要金属为银和铜，以硫代硫酸盐络离子形态存在。锌能自发地从硫代硫酸盐溶液中置换银和铜，且锌粉与硫代硫酸银、硫代硫酸铜络离子的反应十分迅速，置换产物为银和铜单质。当贵液中含有大量的硫代硫酸铜时，被锌置换出的单质铜可作为置换剂协同锌与贵液中的硫代硫酸银离子发生置换反应，从而提高银的沉积速率。该过程会导致锌粉对铜的置换率有所下降。浸出贵液中的铜离子虽然消耗一定量的锌粉，但能在不增加锌粉用量的前提下提高银的回收率，有利于资源的高效回收。.锌置换铜首先形成铜锌合金，与硫代硫酸铜作用最终转变为单质铜。锌置换银未发现锌银合金的中间产物，银直接以单质的形态沉积出来。单质铜、银为球形颗粒有序致密地排列在锌表面，沉积物布满锌的表面后可从锌的表面脱落，裸露出新的表面继续发生置换反应。置换过程中硫代硫酸银和硫代硫酸铜离子的分解会产生少量银和铜的氧化物及硫化物。硫代硫酸根、硫酸根、亚硫酸根和连四硫酸根离子的存在会引起锌的微量溶解，导致锌粉表面附着微量的氧化锌、硫化锌，但并不会对置换产生明显的影响。