Silver is recovered from the leaching solution of the spent Ag/α-Al2O3 catalyst by solvent extraction. Most of the silver in the spent catalyst was dissolved by using HNO3 solution. The parameters such as concentration of lixiviant, reaction temperature, pulp density, and stirring speed, which might affect the dissolution of silver from the spent catalyst, were investigated. McCabe-Thiele plots predicted that complete extraction of Ag from the leaching solution could be obtained with LIX63 at an O/A ratio of 1 in 3 stages, while complete stripping of Ag from the loaded LIX63 could be obtained with thiourea at an A/O ratio of 1 in 2 stages. Countercurrent extraction and stripping simulation tests were carried out to confirm this prediction. More than 99.89% of Ag with purity of 99.91% was recovered from the leaching solution. Finally, a complete flow sheet of the process for separation and recovery of Ag from the spent catalyst was demonstrated.

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Platinum and base metals (Al, Fe, Si) are present in the chloride leaching solutions of spent reforming catalysts. In order to develop a process to recover platinum from such leaching solutions, batch and continuous ion exchange experiments were performed using a strong anionic resin (DiaionSA10AP). The adsorption equilibrium data of Pt are described by the Langmuir adsorption isotherm. Batch experiments indicate that it is possible to separate Pt and Fe from other metal ions in the present leaching solution. Fe was selectively removed from the loaded resin using diluted HCl, while Pt was eluted using thiourea after Fe removal. The results of column experiments verified the feasibility of the separation and recovery of platinum from leaching solutions using the present process. The elution efficiency exceeded 99% for both Pt and Fe. The recovery percentage of Pt from the leaching solution using this method was 99.3%.