A Comparison of Cloud Point Extraction and Ion Exchange in Recovery of Pt, Pd, and Rh from Spent Autocatalytic Converters Chloride Leach Solutions

Although solvent extraction (SX) and precipitation (PPT) are utilized in the recovery of PGMs from ore concentrate leach solutions, these processes are not very efficient for the direct recovery of PGMs from spent autocatalytic converters (SACs) leachates due to the lower metal solution concentration. In this study, Cloud Point Extraction (CPE), a laboratory liquid-liquid extraction method that utilizes a surfactant and a complexing agent to extract metal ions is investigated as an alternative technique for the recovery of PGMs from SACs leach solutions. While CPE has shown capability of PGMs recovery at trace levels, CPE studies from PGM SACs leach solutions and elution of the PGMs from the CPE surfactant rich phase (SRP) are scarce. In this work, the CPE of PGMs from a synthetic SACs leach solution was investigated, using Triton X-100 as the surfactant, 2-mercaptobenzothiazole (2-MBT) as the complexing agent and SnCl2.2H2O as the activator. This was compared to PGMs recovery using ion exchange (IX). The leach solution concentration was based on literature with a composition (ppm) of: Pt (IV)-72, Pd (II)-350, Rh (III)-72, Al (III)-11000, Mg (II)-1500, and Fe (III)-700. Under optimal conditions, CPE extractions obtained were 99% Pt, 99% Pd and 94% Rh while IX extractions were 99% Pt, 98% Pd and 36% Rh. From the results, CPE’s ability to recover metals from trace level concentrations suggest the possibility of integrating it with other metal recovery techniques to reduce feed solution recycles and cut down on industrial costs.