Recovery of Silver from the Nitrate Leaching Solution of the Spent Ag/α-Al2O3 Catalyst by Solvent Extraction

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.