Innovated application of melamine for high-purity V2O5 preparation

In the context of the accelerated development of all-vanadium liquid flow batteries and vanadium-based alloys, there is a growing requirement for high-purity V₂O₅. In this study, vanadium shale leachate was used as raw material and V₂O₅ products with purity >99.9 % were prepared greenly and efficiently through vanadium precipitation by melamine adsorption, and the adsorption conditions and mechanisms were investigated. XPS, FTIR, DFT, and MD results show that the –NH₂ and N atoms on the melamine bind to VO₂⁺ through coordination, resulting in high adsorption performance. The Langmuir isothermal adsorption model predicted the maximum adsorption capacity of melamine for vanadium to be 892.86 mg/g. Furthermore, the adsorption thermodynamics indicated that the adsorption reaction was heat-absorbing and spontaneous. The pseudo-second-order kinetic model provided a superior description of the adsorption kinetic data at 363 K, and the adsorption process was found to be mainly controlled by the chemical reaction control kinetic model. The reaction conditions were optimized by response surface methodology, and under the optimized conditions, the vanadium precipitation rate was >99 %, the purity of the prepared V₂O₅ was >99.9 %, and the vanadium precipitation process did not produce ammonia–nitrogen wastewater. The method provides an efficient, economical, and environmentally friendly way for the preparation of high-purity V₂O₅.