Glass Stove Tops
Challenge
Recycle and save glass electric stove tops while recouping as much of the coated precious metals.
Deposition
Gold, Platinum and Palladium
Substrate
Glass
Results
A novel process was developed utilizing our patented new solutions and all steps were done in the same etching/processing tank, which limited the loss of precious metals, avoided the use of a high temperature furnace, obtained a minimum 99.9% purity and produced a scalable process for a variety of uses in-house rather than using a outside vendor.
One of our clients, an European market leader in cleaning, with a focus on cleaning precision parts, became interested in purchasing a license for our recycling technology, to expand their business and add to their services, the ability to clean precision and high value parts and components that had precious metal depositions.
The client was skilled in cleaning precision parts with non-precious depositions.
They had customers orders with gold, platinum and palladium deposited onto glass surface that were typically cleaned by weaker current aqua regia (see our FAQs for more details) by the client.
Once the deposition was dissolved by the weaker aqua regia, the client would send the solution to one of the major refineries.
The glass surface was scrapped after the cleaning.
The client gave us a task to develop a technology that would allow them to separate QANTITATIVELY (see our FAQs for detailed info) the three metals, purify them to high purity, and transfer them into a metallic form that could be sold (smelt them), with a final challenge to do all of this In-House.
We first considered the current available technologies:
• As explained in other case studies and our FAQs, the cyanides could not be used, because (i) they would not dissolve the gold trapped underneath platinum and palladium, (ii) the client would have to apply for certificates to use highly toxic cyanides, and (iii) the cyanides would need to be heated to have at least some effect on possible dissolution of platinum (the client was not equipped to heat larger volumes of solutions up, ).
• The current state-of-the-art aqua regia does not dissolve glass, but would not separate all three metals QUANTITATIVELY (see our FAQs for detailed info) and the final purification would bring loss of the precious metals. Why would it, you may ask? Well, during the dissolution of gold, platinum and palladium, there are three inorganic compounds created in situ (in the solution). It takes quite a few technological steps necessary to separate them QUANTITATIVELY, not to mention the loss of precious metals associated with each step that negatively affects the yield.
• Blasting by different blasting media would not make sense, because the current state-of-art aqua regia does not over etch the glass, so it does not need to be protected.
• The weaker aqua regia, potassium iodide/iodine, thiourea/sulfuric acid/iron(III) sulfate and some other processes were ruled out too, because the use of weaker aqua regia made no sense and the other possibilities or potential solutions would not serve reliably in larger scale.
We knew, that ideally we were looking for a technology that would:
• dissolve all three of the deposited precious metals;
• make the chemical compounds of the three metals simple to separate from each other, preferably during the dissolution;
• avoid using a furnace for smelting the palladium (a much more expensive furnace necessary than the one for processing gold due to the higher melting point of palladium);
• be inexpensive;
• be robust and simple enough to scale-up, in remote locations if necessary and processed by a staff with little or no technical experience.
Our patented solution became our technology of choice because we knew that:
• the gold creates an organic complex in the solution during dissolution of the metal;
• the platinum creates organic complex in the solution during dissolution of the metal;
• palladium creates inorganic salt during dissolution.
As a result, we found that:
(1) It is quite straightforward to convert the complex of gold, dissolved in the etching solution, into metallic gold by our patented new technology directly in the processing tank.
(2) It is quite straightforward to remove organic salt of platinum, dissolved in the etching solution, from the processing tank by our new patented technology. The consequent technological step provides platinum sponge.
(3) So this leaves nothing but the palladium’s inorganic salt in the same processing tank.
As described above, all of our new technological steps are processed in the same etching/processing tank, so the possible loss of precious metals exhibited by other competitive and currently used solutions, are brought to an absolute minimum.
Our novel process can then treat the palladium salt, first, so it can avoid the use of a furnace for smelting palladium, and secondly obtain a minimum 99.9% purity.
The final yield of all three metals turned out the same as the expected theoretical yield obtained from Atomic Absorption Spectroscopy (AAS) analysis of the etching mix.