Preparation of high purity platinum nitrate using spent Pt-Rh catalyst from the production of nitric acid

• Published in: Journal of Central South University 2023, Vol.30 (1), p.85-94
• Main Authors: Liu, Kai-ming, Qiu, Yun-ren, Li, Yan
• Format: Article
• Language: English
• Subjects: Acids; Ammonium chloride; Catalysts; Engineering; Leaching; Metallic Materials; Nitrates; Nitric acid; Platinum; Potassium; Potassium chloride; Potassium hydroxides; Purity; Reaction kinetics; Rhodium; Temperature effects
• ISSN: 2095-2899; 2227-5223
• DOI: 10.1007/s11771-022-5214-3

Preparation of high purity platinum nitrate using spent Pt-Rh catalyst from the production of nitric acid was studied, including separation of rhodium from aqua regia leaching solution, precipitation with ammonium chloride to obtain ammonium chloroplatinate precipitate, calcination of precipitate to obtain sponge platinum, dissolving with aqua regia and removing nitric acid to obtain chloroplatinic acid, precipitation with potassium chloride and reduction with potassium oxalate to obtain potassium chloroplatinite, hydrolysis with potassium hydroxide, removal of potassium and chloride, and neutralization with nitric acid. Effects of temperature, concentration, time and pH on the purity and yield of intermediate and final products were investigated and the suitable operating conditions were obtained. The yield of platinum nitrate is 94%, the mass fraction of Pt 2+ in platinum nitrate is greater than 15%, and the mass fractions of Cl − and K + are far less than 0.005%. The reaction kinetics and thermodynamics of potassium chloroplatinate to potassium chloroplatinite was studied, and the reaction order is 1.39 for PtCl 6 2− and 1.55 for C 2 O 4 2− , and the activation energy is 35.13 kJ/mol.