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A large amount of nitrogen-containing gas escaped from the silver separation operation must be absorbed by the liquefied flue gas receiver and scrubber before it can be emptied.
Introduction to the core method of chemical purification gold and silver purification
The aqua regia gold method is suitable for the purification of crude gold with a silver content less than 8%. Generally use concentrated aqua regia, 1 part of industrial nitric acid plus 3~4 parts of industrial hydrochloric acid. Prepare aqua regia in a fire-resistant glass or heat-resistant porcelain jar, first add hydrochloric acid, then slowly add nitric acid while stirring. The reaction was strong, many bubbles were released and some nitrogen oxide gas was generated, and the color of the solution gradually changed to orange.
Introduction to the core method of chemical purification gold and silver purification
During operation, the crude gold is first quenched into granules or cast (rolled) into thin slices, placed in a dissolving dish, and 3 to 4 parts of concentrated aqua regia are added to each part of crude gold in stages. With agitation under autothermal and post-heating, the gold goes into solution and the silver remains in the slag. The dissolving dish must be placed in a large plate or a large container to avoid loss caused by the breaking of the dissolving dish. After dissolving, filter, and reduce gold with ferrous iron (or sulfur dioxide or oxalic acid), the gold powder is carefully washed, and then treated with nitric acid to remove impurities, washed, dried, and cast into ingots to produce gold ingots with a gold content of more than 99.9% . The gold separation operation is repeated 2 to 3 times, and the silver chloride produced is recovered by reduction with iron filings or zinc powder.
Introduction to the core method of chemical purification gold and silver purification
The raffinate after recovery of gold contains a small amount of gold, which can be mixed with excess ferrous iron, left to stand for 12 hours, and crude gold can be recovered by filtration. The mother liquor contains residual gold and platinum group metals. Add zinc nuggets or zinc powder to replace until the solution is clarified, filter, wash the filter residue, and dry to produce platinum group chemical concentrates, which are sent to separate platinum group metals.
