Rhodium, recovery of wastes

Precious metals reclamation Precious metals reclamation is the recycling and recovery of precious metals (i.e., gold, silver, platinum, palladium, iridium, osmium, rhodium, and ruthenium) from hazardous waste. Because U.S. EPA found that these materials will be handled protectively as valuable commodities with significant economic value, generators, transporters, and storers of such recyclable materials are subject to reduced requirements. 

The recovery of heavy metals from solid waste poses more challenges. The Eastman Chemical Company process for the manufacture of acetic anhydride by the carbonylation of methyl acetate involves a proprietary process for the continuous recovery of rhodium and lithium from the process tar (see Section 4.6). 

Hydrated rhodium(III) chloride, chloroamminerhodium(III) salts, and a note on the recovery of rhodium wastes, synthesis 57... 

HYDRATED RHODroM(m) CHLORIDE, CHLOROAMMINERHODIUM(in) SALTS, AND A NOTE ON THE RECOVERY OF RHODIUM WASTES... 

Solid Waste - The platinum/rhodium catalyst requires treatment after a certain campaign length depending on the combustion pressure and, due to its high cost, is returned to the manufacturer for credit. Deposits of catalysts can be recovered from various parts of the plant these are also returned to the catalysts manufacturer for recovery of platinum and rhodium. Spent water treatment resins may be returned to the resin producer or burned in high-temperature kilns. 

The nature of the wastes being treated by Hovione is shown in Figure 2.10. They arise from semi-synthetic tetracycline production of around 60 tonnes per annum. A separate plant, operated under GMP conditions, was constructed for the specific purpose of waste minimisation through treatment and recycling. The major items handled are solvent (acetone, methanol), a precious metal catalyst (rhodium) and an organic (triphenyl phosphine). All aspects of the recovery processes are carefully interfaced such that the whole operation is balanced. Solvent distillation is carried out continuously, whereas other unit operations are carried out batch-wise. 

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