![]() ![]() In an environment of gold-bearing rocks, the dissolved gold content is 40 times higher than in comparable non-gold-bearing areas (Benedetti and Boulègue, 1991). Some iron and sulfur oxidizers (e.g., Acidothiobacillus ferrooxidans, Acidithiobacillus thiooxidans) contribute to the disintegration of important gold ores (Nordstrom and Southam, 1997). Furthermore, the current high price of gold has led to intensive research into the precipitation of gold. The impact of the use of microbial activity for the solution and precipitation of gold was undervalued for a long period, thus affording the opportunity for economic and environmentally friendly gold bio-processing. Not sure how the neighbors will react if I buy a face mask, might report to city so not sure if I can keep doing this without some sort of neutralization fume hood, sorry for the long talk just happy I got my first gold refining project.Precipitation/Bioaccumulation of gold is the precipitation of fine-grained gold colloids by microbial activities. I will post pics on my next batch with melt, just had the most horrible headache from inhaling the fumes. The only problem is a) it smells so bad that even setting the solution outside to settle you can smell the rotten egg since the wind carries it.ī)BH3 is some nasty stuff, I got some on my pinky toe and ripped a small portion of skin so I followed msds and dipped feet in water for 20 minutes. No one mentioned to me that gold is resistant to h2s and na2s.basically I was working with silver so much I thought it was the same stuff but it resisted!!!!!!I love its inertness, it's sort of mythical when you think of it, I was getting ready to throw away some of this borohydride but it's truly amazing. The sodium borohydride reduced it to elemental form and I ended up with huge clunks. This is essentially a puzzle where the elimination of H2S and Na2S simply cannot be done chemically, the closest solution I currently have to this would be to add NaOH to the lixivant thereby creating Na2S and then reducing the gold thiosulfate to Au2s then adding NaBH4, since NaBH4 is extremely stable in basic solutions I can then add some acid to drop the gold particles but then this would create h2s and then I will need to accept that some gold sulfide is still in solution. The SEM-EDS and XPS analyses indicate that the precipitate coating on gold surfaces is mainly S 2 in CoS and S 8. ![]() So if I successfully reduce the gold thiosulfate to Gold(0) and a side reaction were to occur with Na2S and water we would produce H2S thereby creating Au2S again on the surface of the Gold(0) sediment. I recently bought 1kg NaBH4 and thought of using this instead of the na2s but I have no idea what the products will be but my hunch is that Na2S will be created. 3.I would not mess with NaBH4 (the wheel was invented already) I. 2.What converts thiosulphate to sulfur is acid, not alkali. We could then roast the colloids thereby getting some polysulfide derivative of gold sulfide but this would really cause smelly problems in the neighborhood. open access Abstract Numerous non-cyanide leaching lixiviants have been developed, among which thiosulfate is considered the most promising alternative to cyanide due to its non-toxicity, low price, high leaching rate and excellent characteristics in dealing with carbonaceous and copper-bearing gold ores. 1.Gold thiosulphate should react with NaOH to precipitate gold oxide. If we were to use excess thiosulfate and perhaps we get some gold thiosulfate we know that the gold thiosulfate will in fact reduce to Au2S but it will also produce elemental sulfur. Once we figure out the leaching ratios we have to contend with reducing with na2s possibly with a higher ph. Whenever you use thiosulfate as a leaching mechanism we have to use excess na2s2o3 since the s2o3 compound is used up at an accelerated rate in relation to ph.higher ph equates to the redevelopment of s2o3 but the near elimination of the electrodes. The process comprises reduction precipitation of the gold from solution by the addition of stabilized alkali metal borohydride, preferably sodium or potassium borohydride, at ambient temperature and pressure. There is a lengthy thread on gold thiosulfate with iron being the main reducer but it offers more criticisms than solutions. A process is disclosed for the direct recovery of gold from thiourea, thiocyanate or thiosulfate solutions or acidified thiourea leach liquor. I am starting to question the whole process of gold thiosulfate refining.
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