Synergistic Leaching of Vanadium from Spent Catalysts Using H_۲SO_۴–H_۲C_۲O_۴: Experimental Validation and Kinetic Model

A comprehensive study of vanadium(V) recovery from spent vanadium catalysts (SVCs) of the SVD (K-D) brand was conducted using the sulfuric acid–oxalic acid binary system. Achieving ۹۶.۵ ± ۱.۲% recovery was experimentally confirmed under optimal parameters: ۲۰% (v/v) H₂SO₄ + ۰.۳ M H۲C۲O۴, ۹۰ °C, L/S = ۱:۲۰, t = ۱۸۰ min. Kinetic analysis of individual modes based on the Shrinking core model (SCM) showed that sulfuric acid leaching is limited by diffusion through the product layer (Ea = ۲۸.۴ ± ۲.۱ kJ/mol), while oxalate leaching is limited by a mixed control (Ea = ۲۲.۷ ± ۱.۸ kJ/mol). Chemical control with Ea = ۵۵.۰ ± ۳.۲ kJ/mol (R۲ > ۰.۹۹) was observed during the initial stage of the binary-system leaching process: a fast initial period (۰→۸۴% in ۳۰ min, k = ۰.۴۵ mg L⁻¹ min⁻¹) and a slow final period (۸۴→۹۶.۵% in ۱۵۰ min). High process selectivity was established (V/Fe = ۴۵:۱). The solid residue was represented by amorphous SiO۲ (residual V۲O۵ < ۱.۵%), suitable for reuse. V۲O۵ with a purity of ۹۸.۸% (grade Vn-۱) was obtained. The proposed synergy model demonstrated high predictive accuracy and was validated by experimental data, confirming its applicability for describing the synergistic effects in the studied system, with strong potential for efficient and more sustainable vanadium recovery from spent catalysts.

کلیدواژه ها:

spent vanadium catalysts ، synergistic leaching ، Shrinking core model ، Kinetics ، oxalic acid ، Vanadium recovery