Recovery of platinum from secondary materials: electrochemical reactor for platinum deposition from aqueous iodide solutions

Abstract

A circulating bed particulate reactor was designed, developed, and demonstrated to facilitate recovery of dilute dissolved platinum species from concentrated aqueous iodide solutions, an essential component for the overall process proposed for the recovery of Pt from secondary materials using benign conditions. A detailed design for the reactor was undertaken using the Fluent TM computational fluid dynamics software to predict electrolyte and particulate flows, and Maple TM for simulating the electrochemical performance. Insight was gained into the design features required for successful operation and demonstrated in the reactor design, including effects of electrolyte flow rate, additional inlet nozzle locations, bed depth in the direction of current flow, draft tube width, and its proximity to the inlet nozzle. Good agreement was found between the reactor model predictions and the results of the experimental matrix conducted to define the reactor performance. The electrodeposit produced by the reactor was found to be adherent even under transport controlled operation, supporting the assertion that mechanical interactions in a circulating particulate bed can improve deposit morphologies in transport and mixed controlled deposition regimes. The model predictions and the experimental results both showed that the reactor could be operated with charge yields of ca. 45 %, corresponding to specific electrical energy consumptions of ca. 1.0 kWh kg -1 Pt and hence negligible operating cost compared with the value of the product. Graphical abstractKeywords Iodide Á Platinum Á Circulating particulate bed electrode Á Tri-iodide Á Secondary materialsDiffusion coefficient for species i in solution (m