Recycling of palladium in waste palladium catalysts

As a precious metal with good corrosion resistance, high temperature resistance and stable electrical properties, palladium has been widely used in petrochemical, pharmaceutical, electronic, chemical catalyst and other fields. For example, palladium carbon catalysts are widely used in petrochemical and pharmaceutical industries for catalytic hydrogenation of unsaturated hydrocarbons or CO. Platinum palladium rhodium catalysts with cordierite as carrier are used in automobile exhaust catalysts, which is of great significance for protecting the environment. At present, my country’s palladium mineral resources are limited and far from meeting the development needs of various industries. Therefore, recycling and reusing palladium in waste palladium catalysts is of great significance for solving palladium resource shortages and environmental problems. 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 volatilizes 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 inorganic solvents 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 (SCWO), using supercritical substances 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.