The article presents experimental data on the electrochemical oxidation of vanadium-bearing ore with the aim of increasing the efficiency of vanadium extraction during subsequent hydrometallurgical processing. Three different charge compositions were studied during the preliminary oxidative roasting stage, differing in the type of oxidizers used: calcined soda, sodium chloride, and their mixture in a mass ratio of 9:1. Electrochemical oxidation was carried out in a sulfuric acid medium using a membrane electrolysis cell equipped with an MK-40 type diaphragm. Experimental studies were conducted by varying key technological parameters: H₂SO₄ concentration (5–15%), solid-to-liquid phase ratio (1:2–1:5), temperature (25–85 °C), process duration (0.5–3 h), and current density (100–1000 A/m²). It was found that preliminary roasting promotes the conversion of vanadium into higher oxidation states, predominantly V⁵⁺, which significantly increases its solubility during subsequent electrochemical treatment. For the first time, the kinetic patterns of electrochemical vanadium leaching were identified, as well as the limiting mechanism of the process, associated with the formation of poorly soluble oxide films on the ore surface. Optimization of the electrochemical oxidation parameters allowed us to achieve vanadium extraction into solution up to 92%.

Developing efficient technologies for vanadium recovery from refractory raw materials requires an understanding of the thermodynamic and electrochemical behavior of vanadium during acid leaching. This study investigates hydrogen peroxide-assisted sulfuric acid leaching of roasted vanadium-bearing ores from the Greater Karatau region using standard Gibbs free-energy calculations, Pourbaix diagrams, and electrode-potential calculations in HSC Chemistry 8.1.5. The reactions of the model vanadates NaVO₃, Na₃VO₄, and Na₄V₂O₇ with H₂SO₄ exhibited negative ΔG⁰ values at 25 and 65 °C, indicating thermodynamically favorable acid dissolution. The more negative ΔG⁰ values in the presence of H₂O₂ largely reflect the thermodynamic contribution of its decomposition and do not directly quantify its effect on vanadium extraction. Pourbaix diagrams indicated VO₂⁺ as the thermodynamically stable dissolved V(V) species under strongly acidic oxidizing conditions. The higher equilibrium potential of the H₂O₂/H₂O couple relative to VO₂⁺/VO²⁺ indicates the thermodynamic feasibility of oxidizing residual V(IV) to V(V). Competing reactions of Na₂CO₃ with mineral–matrix components may consume the sodium reagent during roasting. The calculations were qualitatively consistent with previously obtained vanadium extraction of 78.70–80.15% from roasted Balasauskandyk and Kurumsak ores at 65 °C. An integrated five-stage physicochemical model is proposed, requiring direct experimental validation of individual stages.