![]() ![]() Alternatives to the current industrial practice of cyanidation 5, 6 and informal mercury alloying 7, 8 that are based upon selective extraction, precipitation, or adsorption of gold from leach solutions are being actively pursued 9, with the recycling of electronic waste (e-waste) the focus of much attention as it presents a significantly higher concentration of gold than its ores 10. The extraction of gold from its ores and its recycling from waste materials represent significant technological and environmental challenges 1, 2, 3, 4. This discovery could be exploited in metal refining and recycling processes due to its tuneable selectivity under different leaching conditions, the avoidance of organic solvents inherent to biphasic extraction, and the straightforward recycling of the precipitant. At 6 M HCl, complete collection of gold, iron, tin, and platinum occurs, demonstrating that adaptable selective metal precipitation is controlled by just one variable. ![]() The diamide is highly selective, with its addition to 29 metals in 2 M HCl resulting in 70% gold uptake and minimal removal of other metals. ![]() Gold is released from the precipitate on contact with water, enabling ligand recycling. ![]() The X-ray crystal structure of the precipitate displays an infinite chain of diamide cations interleaved with tetrachloridoaurate. Here we show that a simple tertiary diamide precipitates gold selectively from aqueous acidic solutions, including from aqua regia solutions of electronic waste. Precipitation processes are increasingly popular and are reliant on designing and understanding chemical recognition to achieve selectivity. In the case of black sand concentrates HCl can be used to at least reduce if not eliminate the "magnetic" fraction of the black sands - though this can be done with the black sands "as is" - it is best to first remove the magnetic fraction with a magnet to be treated with the HCl - & even then - the HCl will not dissolve away everything - it will just "reduce" it to a more workable concentrate due to the magnetite being complexes of other elements other then the elements of iron, nickel etc.The efficient separation of metals from ores and secondary sources such as electronic waste is necessary to realising circularity in metal supply. Part of the trick of working with acids is knowing what &/or how different acids react with different metals &/or there oxides - an example of what I am saying here is aluminum - nitric acid will NOT react with aluminum & therefore will not dissolve it - but aluminum will react (quite violently) with HCl (hydrochloric/muriatic) acid to dissolve it I am not sure what you mean by "concentrates" but if you are talking about "black" sand concentrates that are holding your "ultra" fine gold fractions - then yes - HCl (hydrochloric/muriatic acid) can be used to "assist" in further concentrating it (it won't dissolve away all the junk - but will certainly dissolve away some)Īcids - when used properly - can be a very useful tool in the recovery of very fine gold from concentrates - the trick is knowing when, where, & how to use them (this is a very deep subject - certainly more then I can cover here in a single post & it is certainly not always the best choice) ![]()
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