# Tin (Sn, SnO) removal from a very low pgm sweep material



## Platz (Jul 10, 2022)

Hello fellow refiners,
I have stumbled across a sweep type material which contains around 20% Sn and traces of Ir, Rh and Ru (0.02%). With slightly more Pt and Pd (0.2%). The issue is I cannot find a refiner who will credit the Ir Rh and Ru since it is under the payable limit and the Sn results in hefty charges, making the job non viable at present. Does anyone have details of a process which is capable of solubizing tin well but not the pgm. I have tried all the leach media I know; classic mineral acids, aqua regia, acid peroxide, casutic, caustic peroxide but the Sn will just not solubilze to a signifcant leach efficency. Any help on this would be greatly appreciated.


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## Lino1406 (Jul 10, 2022)

Try Zn powder together with HCl, it should reduce SnO2 to solubilized form


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## Platz (Dec 21, 2022)

Lino1406 said:


> Try Zn powder together with HCl, it should reduce SnO2 to solubilized form


Thanks, I did try this and it did improve things. Biggest trouble I had was the pgm and tin had actaully alloyed so that once most of the tin dissoved the pgms dissolved and needed additional zinc to precipitate back out.


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## orvi (Dec 22, 2022)

With that low PGM content it would be painful to get it out in decent recovery. How did you prove or establish the content of PGMs ? This low concentration should be determined with good machines. Where the material came from ? Because it has very unique composition.


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## Platz (Dec 22, 2022)

orvi said:


> With that low PGM content it would be painful to get it out in decent recovery. How did you prove or establish the content of PGMs ? This low concentration should be determined with good machines. Where the material came from ? Because it has very unique composition.


The Pgm content by nickel sulphide fire assay with ICP determination. The material is a combination of sludges from an effluent process at a metal stripping plant and usually contains platinum, iridium and ruthenium but mostly tin.


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## Platz (Dec 22, 2022)

_Once burnt to mill and sample, the tin oxidises but also alloys with the pgm making chemical removal of the tin near impossible_


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## orvi (Dec 23, 2022)

Platz said:


> _Once burnt to mill and sample, the tin oxidises but also alloys with the pgm making chemical removal of the tin near impossible_


I am no expert by far on any industrial scale applications and actual huge processes, but only thing that comes to my mind is to convert tin oxides to tin, or remove the tin oxdes chemically to enrich the material in PGMs.

Pure theory time 

1. You can pyrometallurgically reduce all components down to metals by smelting, obtaining tin metal as major constituent, with minute PGMs. This, in theory could be electrorefined - but as we all know, tin is very stubborn metal to deposit electrochemically, and it will require specific setup with scrapers to cope with growth of long tin crystals. Benefit would be quite nice enrichment of PGMs to the anode slimes, as tin has very low potential, so it could be run the way practically none of the PGMs make it into the solution (which will be strongly reducing due to tin (II) compounds). Once proper electrolyzer would be established and tested, running the thing would only cost the electricity used, with some minor costs like making new electrolyte, casting anodes (easy peasy work with tin melting point  ) etc 

2. Wash away or smelt away the tin oxides with strongly basic liquid/flux. This will be in my opinion much harder to execute than electrolysis, but also easier on the equipment neccessities.


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