For rough gold with a gold content of less than 95%, initial treatment involves powdering. After powdering, the powdered gold is subjected to acid leaching using nitric acid to remove impurities such as silver and copper. The filtered solution is then processed for silver recovery. The insoluble gold powder undergoes aqua regia dissolution; insoluble residues from this process are subsequently sent for silver recovery. A secondary refining process is applied, where once reduced, 99.99% pure gold is cast into granules or ingots. The refined gold returns to the aqua regia process for further dissolution. After drying, the refined gold is formed into granules and then cast into standard gold ingots.

For raw materials with a gold content of 95% or higher, they can be directly smelted in a medium-frequency furnace, cast into ingots, and then subjected to high-efficiency electrorefining using a gold refining electrolysis system. The refined gold is then cleaned, dried, and finally cast into finished gold ingots.

(1) Dissolve in aqua regia:The residues are placed in a reaction container, and hydrochloric acid (HCl) and nitric acid (HNO3) are added in a 3:1 ratio by mass. The mixture is heated to a temperature between 60°C and 80°C using steam, allowing gold and platinum to dissolve in the solution. After the reaction is complete, the solution is filtered and washed, with the filtrate being sent for platinum extraction.

(2) Based on the differences in the reaction processes of platinum and gold, a separation is performed:Ammonium chloride (NH4Cl) is added to the filtered solution to precipitate platinum, while gold does not form a precipitate at this stage. The solution is then filtered again, and the resulting ammonioplatinum chloride is calcined to produce crude platinum, which contains gold in a high-temperature solution that is then sent for gold reduction.

(1) Mercury and Palladium Add nitric acid to the alloy and stir, heat the solution to approximately 50°C, allowing mercury and palladium to dissolve. Filter the solution to obtain filtrate and residue. The residue contains gold and platinum, which are then fed into the precious metal refining process.

(2) Silver Deposition Add hydrochloric acid to the solution in the reaction container to form silver chloride precipitate. Filter the solution to obtain silver chloride powder and palladium-containing solution. Process the silver chloride for precious metal recovery, while the palladium-containing solution is processed for palladium recovery.

(3) Replacement Add silver chloride to the reaction container and dissolve it in water. Add iron powder for replacement. Filter the solution. The residue is coarse silver powder.

(4) Palladium Oxidation Transfer the palladium-containing solution into a reactor, add 10% sodium chlorate solution for oxidation. After 1-2 hours of oxidation, add ammonium chloride to precipitate palladium. Filter after the reaction is complete and transfer the filtrate to the replacement unit.

Palladium Refining Process: 

1) Palladium Refining 

① Complex Dissolution Transfer ammonium palladium chloride into the refining process. Add an appropriate amount of water for solvation. Add ammonia for complexation, heating the solution to 80°C during this step. Filter after dissolution.

② Acidification and Precipitation Transfer the complex solution to a reactor, slowly add hydrochloric acid for acidification. Filter after reaction completion, transferring the filtrate to the replacement unit.

③ Reduction by Ammonia After two complexations and acidifications, perform a third complexation. Add prepared ammonium water solution (80%) in the ratio of 1 kg palladium to 1 Lammonium water. Slowly add the yellow powder solution, heat to boiling, stir thoroughly until the solution is completely reduced. Filter and wash the residue. The filtrate is sent to the replacement unit, while the residue becomes palladium sponge.