You can sell tin very easily—especially on platforms like eBay—if it’s pure. In my days running a PCB assembly factory, we purchased hundreds of kilos of pure tin. A soldering machine could use up about 5 kilos in just an hour of operation.
When recovering tin from solder, don’t overlook the other metals that often accompany it—mainly bismuth and sometimes indium. These metals are worth pursuing if you plan on a constant recovery operation; be sure to check their current market prices.
For recovery, I recommend a two-stage refining process:
- Primary Refining (Electrolysis):
Start by electrorefining the raw material. This stage is designed to separate tin from traces of copper, steel, silver, palladium, and other unwanted metals. An electrolytic process in a molten salt medium can help deposit tin on the cathode while leaving many impurities in the electrolyte. Adjusting the electrolyte composition and controlling the deposition potential is crucial to minimize the co-deposition of elements with similar properties.
- Secondary Purification:
After the initial electrolysis, further refining is needed to achieve 99.9% pure tin, which is essential for marketability at a good price. Separating tin from bismuth and indium can be tricky due to their similar physical and chemical properties. Here are some methods to consider:
- Selective Precipitation or Oxidation: Fine-tune the chemistry to precipitate out bismuth and indium while keeping tin in solution.
- Distillation or Zone Refining: Use thermal methods that leverage differences in boiling points or solubility to separate the metals.
- Tailored Electrolytic Conditions: Modify the electrolyte (pH, temperature, additives) and adjust the deposition current to favor the deposition of tin over bismuth and indium.
Each process will require some experimentation to optimize for your specific mixture of metals. With careful control, you can ensure that the final tin product reaches a purity level of 999 (99.9%), maximizing its market value.
For further technical details and additional methods on separating tin from soft metals like bismuth and indium, consider the following resources:
Happy refining and good luck with your recovery efforts!
