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Jan 01, 2016 · Gold precipitates are calcined and smelted to produce gold dore. For ores with high silver contents, the Merrill Crowe process where zinc dust is added to the clarified, de-aerated solution is often used to precipitate gold and silver
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Metal deposition method using Zn powder (Zinc precipitation) was first introduced by Sulman and Teed (1895). Basic usage of this method is the electron affinity of zinc metal is much higher than in metals gold and silver, then gold and silver metals will sink and …
Jan 01, 2016 · Cementation is an electrochemical, precipitation reaction involving oxidation and reduction processes, sometimes referred to as a redox reaction. The reaction describing zinc cementation of gold is given as follows: (31.1) 2 Au ( CN) 2 − + Zn o → 2 Au o + Zn ( CN) 4 2 −
Zinc precipitation on gold recovery. through zinc precipitation. After zinc-dust cementation, the processed gold is taken for smelting then moulded into blocks ready for sale. History of Zinc Precipitation The zinc cementation process was introduced in 1890’s and became an important part of the cyanidation process. C. W
In present article gold cementation features from cyanide solutions using dendritic zinc powders are studied. The powders were obtained by electroextraction from alkaline solutions. Powders with different physical properties were obtained by means of change in current density (from 0.5 to 2 A/m2) and NaOH concentration in solution (from 100 to 400 g/dm3) at the constant zinc concentration (10
Feb 25, 2010 · Another way of precipitating gold is with iron shavings or zinc dust. The iron or zinc does into solution and the gold coats the zinc or reports as a brown powder which is easy to melt into a globule of gold using an oxy-acetylene flame. There was a small gold mine in Zimbabwe where gold was collected by ordinary dish scrubbing iron wool
Q. I am an analytical chemist for a recycler. I am new to this area and have a question regarding a selective precipitation of gold from an anolyte solution of 10% by volume aqua regia. The solution also contains PGM. The gold is used to inquart the sample so the PGM materials are soluble. I would like to be able to recover, and reuse the gold without contamination from the other materials. Can anyone offer any insight to how to accomplish this gold selective recovery? Thanks so much in advance
A. Ferrous Sulfate is commonly used to precipitate gold without precipitating more than traces of the platinum group metals. However, this can only be done by first removing any free nitric acid still present in the aqua regia solution. This is usually done by first doing a triple evaporation process on the aqua regia solution. Details of all this can be obtained on the goldrefiningforum.com website
Q. Thanks Chris. But I thought that using ferrous sulfate will also precipitate out any Pd along with the Au. I was hoping for a straight up gold selective precipitating agent. Can you, or anybody else, please clarify? I may be mistaken on the Pd precipitation. Again many thanks to all for any assistance
A. You try oxalic acid. If you are trying to know the purity of gold sample, you prefer fire assay system. Pd will precipitate by ferrous not ferrous sulphate. Using ferrous, reduction takes place. OK, consider that FeSO4 contaminate your gold. I suggest that you wash the ppt by hot water to remove acid in it. check by pH paper. Then you add nitric acid to dissolve your ferrous and Pd in it. I hope you will understand the process
A. Ferrous sulfate won't drop either Pt or Pd along with the gold. About the only contaminate in the gold will be a little iron from the ferrous sulfate. If you have Pt or Pd, it is common to first use ferrous sulfate. Then re-dissolve in aqua regia and drop a second time with a sulfite such as sodium metabisulfite, sodium sulfite, or SO2. If you do this right, you should end up with at least 999.5 Fine gold. If you use urea to eliminate nitric, however, you could drag down some Pt or Pd when using any precipitant. Either use no excess nitric in the aqua regia or correctly evaporate the aqua regia to eliminate any excess nitric for best results. An excellent reference for the use of ferrous sulfate in the presence of Pt or Pd is C.M.Hoke's, "Refining Precious Metal Wastes" [affil. link to book on Amazon] It has been re-printed and is available from several places on the internet - IPMI, legend-reno.com, Ganoskin, etc. If they still sell it, I think Ganoskin has the best price. This 360 page book is the bible for refining jewelry scrap
Q. Hi, over the past few years, I have been recovering gold and silver from ores that contain these metals using aqua regia. I am familiar with CW Amen's book as well as CM Hoke. I now have ore concentrates that have gold, silver, and platinum group metals in it and can't find any detailed information on the correct and complete procedure for precipation of all metals when using Aqua Regia. Any help would be appreciated
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