It’s common knowledge that safety gloves and glasses as well as a mask must be worn during rhodium plating and that the area must be well ventilated. However sometimes the consideration given to working with this substance ends when rhodium plating solutions are exhausted and it comes time for disposal. Not only is it potentially harmful to the environment to release untreated solution into the water table, you could be flushing valuable metals down the drain!
Spent solution can be processed using items that are easily available and which can be stored in the plating area for future use. This simple procedure neutralises the diluted sulphuric and/or phosphoric acids and recovers any remaining metals ready for refining.
Equipment needed:
- 2 plastic containers large enough to hold the solution
- 1 plastic colander big enough to fit across the top of the plastic container
- 1 pack of large coffee filters (they should cover all of the colander holes so try restaurant supply companies if your supermarket only has small filters)
- 1 wooden or plastic spoon with a long handle
- 1 pair of household-type rubber gloves
- 1 pair of plastic safety glasses
- 1 Large box of baking soda (sodium bicarbonate)
Process:
- Step 1: Put on your rubber gloves and safety glasses before you begin handling the solution.
- Step 2: Carefully pour the spent rhodium plating solution up to the halfway mark of one of the plastic containers, leaving the top half empty to accommodate the bubbling action in this process. Place the long-handled spoon into the solution.
- Step 3: Open the box of baking soda and very slowly add a small amount at a time to control the bubbling action that will be produced by the introduction of sodium bicarbonate into the rhodium solution. This bubbling will off-gas carbon dioxide, which is relatively harmless. Keep stirring the solution gently and regularly with the long-handled spoon. When bubbling no longer occurs with the addition of more baking soda, the solution has a neutral pH balance.
- Step 4: Add some more baking soda (approximately ½ to 1 cup depending on how much of solution you’re processing) to make the solution alkaline. Stir very well and then allow the solution to settle for an hour or so.
- Step 5: Line the plastic colander with 3 layers of wet coffee filters and place in the top of the second bucket.
- Step 6: Carefully pour the mixture of sodium bicarbonate and rhodium solution through the filter-lined colander into the second container. Any residue left in the first container should be rinsed out with water and also run through the filter. The solution coming through the filter should be clear.
- Step 7: When all of the solution has dripped through the filters, the liquid in the second container is safe to pour down the drain. The filter can be allowed to air dry and then and the solids or carbonate sludge in the filter can be put into your sweeps refining container
Please note that CPM do not recover the Rhodium from spent solution, but we can recover any Gold, Silver, Platinum and Palladium.
For more info on other ways to maximise your refining returns, check out CPM’s helpful tips or contact your region’s Sales Executive
