A New Approach for the Leaching of Palladium from Spent Pd/C Catalyst in HCl–H2O2 System

• Published in: Protection of metals and physical chemistry of surfaces Vol. 57; no. 2; pp. 297 - 305
• Main Authors: Fotouhi-Far, Farshad, Bashiri, Hadis, Hamadanian, Masood, Keshavarz, Mohammad Hossein
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-03-2021; Springer Nature B.V
• Subjects: Activated carbon; Catalysts; Characterization and Evaluation of Materials; Chemical industry; Chemistry and Materials Science; Corrosion and Coatings; Diffraction patterns; Hydrogen peroxide; Image transmission; Independent variables; Industrial Chemistry/Chemical Engineering; Inorganic Chemistry; Leaching; Materials Science; Metallic Materials; Oxidation; Palladium; Physicochemical Processes at the Interfaces; Recovery; Response surface methodology; Surface properties; Tribology; response surface methodology; leaching; correlation; spent Pd/C catalyst; palladium recovery
• ISSN: 2070-2051; 2070-206X
• DOI: 10.1134/S2070205121010093

Recovery of the spent precious metal catalysts by suitable methods is very important for chemical industries. This work introduces a new method to provide the optimal conditions of the leaching of palladium from spent Pd/C catalyst in HCl–H
2
O
2
system. Response surface methodology (RSM) and the Box–Behnken method with four independent variables including HCl concentration (wt %), H
2
O
2
concentration (wt %), leaching temperature (°C) and leaching time (min) are used for building a new correlation. The transmission electron microscopy (TEM) images, wide-angle X-ray diffraction (XRD) patterns and adsorption/desorption isotherms of N
2
are used to study the changes of catalyst surface during the leaching process. According to the outputs of the new model, the predicted value for the maximum palladium recovery is equal to 80.6%, which is comparable with the experimental value (82.5%) in the same condition. The feasibility of complete palladium recovery from spent Pd/C catalyst by leaching method is also evaluated. The results show that leaching in extremely oxidizing conditions cannot lead to the complete palladium recovery from Pd/C catalyst because a considerable portion of the palladium remains on the carbon support surface. Moreover, the leaching process significantly can affect the surface properties of the activated carbon supports.