Targeted recovery of precious metals from catalyst waste using ionic media and ion exchange

贵金属（PM）是一种稀有的天然金属化学元素，具有很高的经济价值。该组由金、银和铂族金属（PGM）、钯、铂、铱、锇、铑和钌组成。在上个世纪，由于需求的快速增长，PM的生产、使用和价格都有了相当大的增长。从矿石中生产纯金属的金属生产过程主要通过露天采矿进行，产生大量不需要的气体释放到环境中;高能耗和水，由于存在危险化学品而无法重复使用。此外，社会对金属开采方式的日益关注，导致越来越多的活动家要求国家和公司不再从通过不环保，不道德和破坏社会的做法生产金属的国家获得贵金属。探索使用环境和经济上更可持续的方法从矿石中回收PM并从废物中回收PM，将大大改善目前特别是金属铱，锇，铑和钌的供需差异。由于贵金属在电子和汽车工业中的使用越来越多，更环保和可持续的做法将是一种非常好的方法。目前用于PM回收的方法通常经济成本高，并且需要消耗大量的能源和/或危险化学品。非常需要开发符合日益严格的环境法规的、在环境和经济上更可持续的回收方法。对PM日益增长的需求和它们的稀有性使得它们从废物中回收高度排序;目前的方法目前确实具有高回收率，但受到高成本和高能源使用的影响。目前，基于活性炭（AC）和离子交换（IX）的工艺具有高的回收率，但受到缓慢的动力学和AC和IX使用氰化物的阻碍。此外，使用深铕溶剂（DES）只是最近才用于PM回收，特别是金和银。目前还没有关于DES如何恢复铂族金属的文献。这同样适用于金属-金属氧化物催化剂（MoMO），因为PM微溶于浓酸。此外，在催化剂中与金属如钴一起使用的PGM，目前在酸性介质中极难将PGM与过渡金属分离。目前关于DES在金属回收中的应用的研究不足，以能够开发环境绿色浸出工艺。此外，能够使用IX和DES组合，其中IX对低级金属具有亲和力，DES潜在地具有将PM与过渡金属分离的亲和力。这种单元操作的组合有可能创造一种经济和环境上可持续的回收方法。

Precious metals (PMs) are rare, naturally occurring metallic chemical elements of high economic value. This group consists of gold, silver and platinum group metals (PGM), palladium, platinum, iridium, osmium, rhodium and ruthenium. The production, use and price of PMs has grown considerably in the last century due to rapid growth in demand. The process of metal production from their ores to produce pure metal predominantly takes place through open-pit mining creating a lot of unwanted gases to be released into the environment; high energy consumption and water which cannot be reused due to the presence of hazardous chemicals. Additionally, the growing social concern for the way that metals are mined has created a growing number of activists that are demanding countries and companies no longer obtain their precious metals from countries where metals are produced via eco-unfriendly, immoral and socially damaging practices. An exploration into using more environmentally and economically sustainable methods of recovering PMs from ores and recycling them from waste would significantly improve the supply and demand discrepancy that is currently being seen especially with the metal's iridium, osmium, rhodium and ruthenium. More environmentally benign and sustainable practices will be a greatly sort after methodology due to the increased use of precious metals in the electronics and automobile industries.Current methods that are being used for PM recovery are usually economically costly, and require the consumption of large amounts of energy and/or hazardous chemicals. Development of more environmentally and economically sustainable recovery methods that will conform to increasingly stringent environmental regulations is highly needed. The growing demand for PMs and the rarity of them makes their recovering from waste highly sort after; current methods do currently have high recovery rates, but are impacted by high cost and high energy usage. Currently activated carbon (AC) and ion exchange (IX) based processes have high rates of recovery but are hampered by slow kinetics and the usage of cyanide for both AC and IX. Additionally, the cost of resins has caused a high cost of the process and high toxicity of the waste is a major drawback of those methods.Furthermore, the use of Deep Eutectic Solvents (DES) has only recently been used for PM recovery specifically gold and silver. There is no literature on how DES would work with recovery of PGMs. The same applies to metal on metal oxide catalysts (MoMOs), as the PMs are sparingly soluble in concentrated acids. Moreover, the PGMs that are used with metals such as cobalt in catalysts, separating the PGMs from transition metals is currently extremely hard to do in acidic media. There is currently insufficient research regarding the application of DES in metal recovery to be able to develop an environmentally green leaching process. Additionally, being able to use IX and DES combined, with IX having an affinity towards low-grade metals and DES potentially having affinity to separate PMs from transition metals. This combination of unit operation has the potential to create both an economically and environmentally sustainable recovery methodology.