One of the most rarely considered area of recyclable material is the residual dust particles left after the manufacturing process. The dust accumulates on the floor and is gathered up in the normal cleaning process. There is a wide assortment of materials that are swept up each with its own intrinsic value. When gold is used in production, the residual shavings or dust is highly valuable. Typically, gold polishing dust is the residual from jewelry manufacturing. The dust swept up must go through a process to prepare the material for recycling.
- A magnet is used to pick out iron and steel particles.
- Using a process known as gentle annealing, combustible materials such as wood, paper, pitch, wax, grease, etc. are burned away.
- Hydrochloric acid is used to dissolve any non-precious metal impurities such as lead or tin.
- The solution is poured off and the metal is washed.
- Scraps are melted together relying on the ability of acids to attack base metals and in the process isolate gold. It is critical that the scrap contain no more than 25% gold.
- The scrap is stirred with a quartz or carbon rod and poured into water so as to create small spherical pieces called shot. This is the last step before purification step.
- The purification process involves dissolution in Nitric acid and then in Aqua Regia.
- Further steps in the purification process prepares the gold for reuse.
If you use gold polishing dust or gold itself in your production or manufacturing process, please give us a call today (214)493-8363. The dust your sweeping up and throwing away may contain precious metals that can be recycled.