Hongru Qu,Yimin Zhang,Hong Liu,Nannan Xue,Yiping Wang
In traditional methods for preparing vanadium electrolytes, challenges include lengthy processes, high costs, and difficulties in deeply separating vanadium and impurities. This study introduces an innovative approach utilizing an H 2 O 2 -NaClO efficient selective oxidative stripping system within the D2EHPA extraction process. This method was optimized at a pH of 12, with a phase ratio (O/A) of 6:1, a reaction temperature of 45 °C, and a reaction time of 8 min. The concentration of H 2 O 2 was set at 1.5 %, with a volume ratio between H 2 O 2 and NaClO of 95 % to 5 %. Under these conditions, the vanadium stripping rate in a single stage reached 95.13 %. The low concentration (1.5 %) of H 2 O 2 increased the single-stage stripping rate of vanadium by nearly 50 %, reducing H 2 O 2 usage by at least 25 %, while NaClO enhanced the stability of H 2 O 2 . The prepared electrolyte contained impurity ion concentrations of less than 10 ppm, meeting Chinese national first-class standard of Electrolyte for vanadium flow battery. The electrolyte demonstrated excellent electrochemical and charge–discharge performance, with Coulombic efficiency, voltage efficiency, and energy efficiency reaching 85.45 %, 89.58 %, and 76.55 %, respectively, achieving 95 % of the standard electrolyte’s performance. This method significantly shortens the process and reduces costs by 25.29 % compared to the traditional V 2 O 5 dissolution method. This study offers a novel approach to producing high-purity electrolytes through a shorter, cost-effective process.
Qiwen Zhang,Yong Fan,Yimin Zhang,Peng Liu,Hong Liu,Zihanyu Zhang,Xiuqiong Fu
Molten salt electrolysis is a promising method for producing metallic vanadium, overcoming the limitations of conventional processes, such as high purity requirements for raw materials and high impurity content. This study introduces an innovative approach utilizing soluble vanadium–aluminum alloy anodes in KCl–LiCl molten salt, where vanadium is dissolved as V2+ and V3+. Optimal conditions were identified as 0.3 A cm−2 current density, 500 °C temperature, and 6 h duration. High purity metallic vanadium was prepared under these conditions, and the electrolysis efficiency reached 89.53%. Electrochemical analysis revealed three reduction processes: Al(III) → Al, V(III) → V(II) and V(II) → V. In molten salts, vanadium ions existed in coordination forms as VCl2, VCl3, VCl42−, and VCl63−, while aluminum ions were present as AlCl4−. The process was confirmed as diffusion-controlled, with calculated V(III) diffusion coefficients. Nucleation mechanism analysis demonstrated dual vanadium deposition pathways: instantaneous and progressive nucleation. Fluoride ions were found to enhance reaction kinetics through chloride substitution in aluminum complexes, increasing free chloride availability for vanadium coordination and improving ion mobility. The developed method offers significant advantages in energy efficiency and product quality compared to traditional metallurgical approaches, providing insights for optimization of molten salt electrolysis systems in refractory metal production.
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