Season 3 Challenges

Ferous Oxide

The refining of pure gold from lower Karatage gold (gold is alloyed with copper, silver & zinc for improved strength) involves various operations such as preparation, melting, refining and granulation, which requires typically 4 h for completion. The process time followed for the entire gold recovery operation is considerably high and therefore needs the intervention of process specialists to reduce the lead time. In the context of refining, the traditional aqua regia (mixture of Hydrochloric and nitric acids in the proportion of 3:1 volume ratio, respectively) method is used to refine pure gold (24Karat = 99.99% purity) from 22Karat (91.7% purity) and 18Karat (75% purity) obtained through exchange of gold by the customers and factory scrap. However, the corrosive nature, occupational and environmental hazards pertaining to storage, handling and disposal of aqua regia make the refining process more critical from the perspectives of people safety and scale-up. Therefore, suitable solutions are invited to develop an eco-friendly route to extract gold, as an alternate for aqua regia based treatment process. 

  • Options tried to solve before:

Pyrometallurgical process was tried earlier to selectively oxidize the impurity elements such as copper, zinc etc. and recover pure gold from low Karatage gold.

  • Future state:

1) Faster & safer process to achieve required gold composition in required volume from various inputs.
2) Environment friendly process - acidless (deployable at various locations so that alloy is made close to place of use-decentralized).
3) An alternate process to separate out unnecessary impurity elements.

  • The solution must meet following requirements:

There should not be any gold loss during the refining process.

  • Success criteria:

1. Developing a new process to reduce the process time and achieving the purity with minimum use of chemicals and achieve 9999 gold purity.
2. Removal of undesirable impurities except gold, copper and silver.



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