The Cathodic Behavior of Aluminum from Pt/Al2O3 Catalysts in Molten LiF-AlF3-CaF2 and Implications for Metal Recovery from Spent Catalysts

Abstract

Electrochemical behaviour of aluminium ions from the Pt/γ-Al2O3 spent catalyst in the eutectic [LiF (63.6 wt.%)–AlF3 (36.4 wt.%)]eutectic−5 wt.% CaF2 melt was studied by the means of cyclic voltammetry, chronopotentiometry and chronoamperometry methods. Tungsten rod (diameter 2 mm) was used as a working electrode. The XRD method was used to study the composition of melt collected near the working electrode and the spent catalyst. The aluminium reduction kinetics was studied concerning varying parameters like spent catalyst content in the melt and the temperature. The reduction of Al3+ ions on the tungsten electrode changed from diffusion-controlled to quasi-reversible process. The charge transfer coefficient and the diffusion coefficient were calculated from the data obtained from the above-mentioned methods. The estimated diffusion activation energy was 117.85 kJ.mole−1.