Common carriers for supported palladium catalysts include alumina, cordierite (2MgO·Al2O3·SiO2), silica gel, activated carbon and zeolite. When selecting a process to recover palladium, the distribution of palladium in the carrier and the characteristics of the carrier must be considered. For example, for catalysts with alumina as the carrier, palladium is concentrated on the surface of the catalyst, and there is no active component in the center. Selective dissolution or carrier dissolution is often used. So far, the main treatment methods are:
(1)Chlorine volatilization method, palladium is chlorinated with chlorine under heating conditions, and palladium is absorbed and extracted after palladium is volatilized as chloride;
(2) Carrier dissolution method, the carrier is dissolved with acid or alkali to obtain slag containing palladium, and the filter residue is roasted and dissolved to extract palladium;
(3) Selective dissolution method, palladium is dissolved in an inorganic solvent while the carrier is not dissolved, and palladium is extracted from the solution;
(4) Full dissolution method, control strong leaching conditions and oxidizing atmosphere, so that the palladium in the carrier and catalyst is dissolved into the solution at the same time, and then palladium is extracted from the solution.
(5) Fire smelting method, smelting the carrier at high temperature to form slag, palladium enters the collector and is concentrated at the bottom of the furnace for recovery. Or the material is mixed with non-ferrous metal concentrate and palladium is recovered from the anode mud obtained by electrolysis;
(6) Incineration method, incinerate the carrier, dissolve the ash with aqua regia and extract palladium.
(7)Supercritical water oxidation method (SCWO), using supercritical material as the medium, the carrier carbon and organic poisons are rapidly oxidized with pure oxygen under homogeneous conditions to become harmless waste gas emissions, and the granular palladium oxide is filtered and refined into metallic palladium.
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silver-concentrate extraction processsilver-concentrate extraction processMethods of Silver-concentrate Extraction:
Silver refining is often conducted in cyano and thiosulfate solutions, while the use of HCl and HNO3 for silver leaching is limited. In HCl solution, silver primarily exists as AgCl, forming precipitates under high chloride concentrations. Thus, precipitation methods are commonly used to recover silver rather than leaching methods.
In HNO3 solution, silver mainly exists as AgNO3 with a higher solubility. However, nitric acid acts as a strong oxidizer, which can degrade or age the leach solutions. For effective silver leaching, the leaching agents must possess good anti-oxidation properties. As a result, there are very few effective leaching agents for silver.
In cyano compounds, silver reacts similarly to gold, forming complexes like K3[Ag(CN)2]. These can be leached using appropriate cyanide-based leach solutions.
In thiosulfate-containing solutions, silver forms Ag(S₂O₃), which can be leached by specific reagents. -
electrolytic silver refining processelectrolytic silver refining processAn electrolytic silver refining process in which crude silver is anodically dissolved and refined silver is cathodically deposited and at the same time accompanying metals are selectively extracted from the spent electrolyte and separately cathodically deposited after having been transferred into an aqueous phase and the regenerated electrolyte stripped of accompanying metals is recycled to the refining process and in which further the spent electrolyte is anodically enriched in silver and accompanying metals are cathodically deposited from the aqueous phase in a joint electrolysis step.
The invention resides in that the joint electrolysis step is carried out in a diaphragm cell in which a diffusion zone is provided between one each cathode and one each anode and separated from the anode zone by an anionic separating membrane and from the cathode zone by a cationic separating membrane and that the diaphragm cell is charged via the diffusion zone with accompanying metal extract.
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process for refining copper anode slimeprocess for refining copper anode slimeProcess For Refining Copper Anode Slime.:
1、Sulfuric roasting: recovery of selenium from the fumes;
2、Sulfuric immersion of copper: separation of copper solution and silver, followed by recovery of copper from the silver residue;
3、Alkaline leaching: removal of boric acid from alkaline solutions;
4、Chloride separation of gold: initial gold solution is reduced (the rough gold is refined into fine gold); after reduction, the solution is replaced with palladium and platinum;
5、sodium sulfite separation of silver: sodium sulfite separates silver from sodium sulfite solution; followed by ethanol reduction of rough silver powder;
6、Refining of rough silver: electrorefining of silver
