Salt aqua regia as a green solvent for recovering precious metals

Spent catalysts are valuable secondary resources of precious metals. Traditional methods of recovering precious metals typically use highly corrosive aqua regia, which is extremely dangerous and leads to severe environmental pollution. Here, we report an alternative route to recover precious metals from spent catalysts us-ing purely inorganic salt solutions consisting of Al(NO3)(3)center dot 9H(2)O and NaCl, which we name salt aqua regia.The precious metals palla-dium and gold can be completely dissolved in it. In simulated and real recovery processes, high-purity palladium and gold products are obtained through leaching and one-step electrodeposition. The solvent keeps almost the same dissolution properties and elec-trochemical stability even after three cycles. As salt aqua regia is safe and non-volatile and has good solubility for precious metals and electrochemical stability, it has excellent prospects for applica-tion in precious metals recovery.

Automated summary

An alternative method for recovering precious metals from spent catalysts using salt aqua regia is reported. The salt aqua regia solution, made of purely inorganic salts, can completely dissolve palladium and gold. It exhibits good solubility and electrochemical stability, making it a promising candidate for precious metals recovery.