从锌浸出渣中回收银的技术研究进展

Technical Research Progress of Silver Recovery from Zinc Leaching Residue

综述了从锌浸出渣中回收银的工艺与研究现状,简述了各方法的原理以及银的最新回收技术。浸出渣中银的赋存状态、银含量高低、物料处理的难易程度不同,锌浸出渣中银回收的方法也不同,主要包括:浮选法、浸出法、火法、选冶联合法及溶剂冶金与微生物浸出等新兴技术。浮选法因低成本、工艺简单的优势广泛应用于选矿行业;浸出法是先利用氰化物、氯盐、硫代硫酸盐等药剂,将锌浸出渣中的金、银等贵金属溶解,再通过离子交换、锌粉置换或活性炭吸附等方法回收;由于浸出渣中银大多被铁钒包裹,难以直接浮选或直接浸出回收浸出渣中的银,需转变银的赋存状态,对浸出渣进行预处理,主要有酸性焙烧、还原焙烧、酸性浸出、碱性转化等方法。火法的原理是利用浸出渣中金属的沸点差异进行有价金属的分离,火法成本高,污染严重,不利于环保,难以适应经济可持续发展趋势。溶剂冶金是指利用有机溶剂、离子液体、共晶溶剂(DESs)、无机溶剂等非水溶剂从锌渣中提取有价金属的过程;微生物浸出是利用微生物及其代谢产物溶浸矿石中有价金属的绿色环保技术;溶剂冶金与微生物浸出虽有着巨大的经济与社会效益,但此类技术仍不太成熟,应加大其研究力度。单一的冶金或选矿方法虽然各有优势,但存在成本高、作业环境差,不利于环保、金属回收率不理想等问题,指出在现有的技术条件下,改进设备和优化工艺更为实际,例如,提高设备热利用效率、抗腐蚀能力、自动化程度等;对银赋存状态十分复杂的浸出渣,优化选冶联合法的工艺是一种行之可效的方法。此外,加大溶剂冶金与微生物浸出方面的研究,训化适宜于浸出渣有价金属回收的专属菌种,与化学浸出和浮选组成联合流程,以期能高效、低成本、绿色环保地达到较好的回收效果。

The current state of the technology and research in the recovery of silver from zinc leaching residue is re⁃viewed,the principles of each method and describing state-of-art Ag recycling technologies.Depending on the state of silver in the leaching residue,the silver content and the difficulty of material processing,the methods of silver recovery in zinc leach residue mainly include:flotation,leaching,pyrometallurgical,combined method of beneficiation and solvometallurgy and bioleaching,etc.Flotation method is widely used in mineral processing industry because of the advantages of low cost and simple process;leaching method is to first use cyanidation,chloride salt,thiosulfate and other agents to dissolve the precious metals such as gold and silver in the zinc leaching residue,and then recover them by ion exchange,zinc powder re⁃placement or activated carbon adsorption;as most of the silver in the leaching slag is wrapped by Jarosite,it is difficult to flotation directly or leach directly to recover the silver in the leaching slag,so the fugitive state of silver needs to be changed and the leaching slag is pretreated,mainly by acid roasting,reduction roasting,acid leaching,alkaline conversion,etc.The principle of pyrometallurgical is to use the difference in the boiling point of metals in the leaching slag for the separation of valuable metals,the high cost of the fire method,pollution is not conducive to environmental protection,it is difficult to adapt to the development trend of economic sustainability;solvometallurgy is the process of extracting valuable metals from zinc slag using non-aqueous solvents such as organic solvents,ionic liquids,deep-eutectic solvents(DESs)and inorganic solvents;bioleaching is a green and environmentally friendly technology that uses microorganisms and their metabolites to leach valuable metals from ores,solvometallurgy and bioleaching have huge economic and social benefits,but such technolo⁃gies are still not very mature and more research should be done on them.a single metallurgical or beneficiation method,al⁃though each has its own advantages,has high costs,poor operating environment,not conducive to environmental protection,and unsatisfactory metal recovery rates,and It is pointed out that under the existing technical conditions,it is more practical to improve the equipment and optimize the process,to improve the efficiency of heat utilization,corrosion resistance,auto⁃mation,etc.;for the leaching slag with a very complex state of silver deposit,optimizing the process of the combined method of beneficiation and metallurgy is a well-tried and effective method,In addition,increase the research on solvometallurgy and bioleaching,train the exclusive strains suitable for leaching slag valuable metal recovery,and chemical leaching and flo⁃tation to form a joint process,in order to achieve a better recovery effect with high efficiency,low cost and green.