Abstract
Spent vanadium catalysts of sulfuric acid production (main elemental composition in wt%: 7.5 V, 9.1 K, 10.2 S, 23.2 Si and 1.4 Fe) can be used as a secondary source of vanadium. Extraction of vanadium was studied using two-step leaching (acidic and reductive) of spent vanadium catalysts with further oxidizing of leaching solutions. The factors leaching and hydrolysis temperature, concentration of leaching (H2SO4, Na2SO3) and oxidizing ((NH4)2S2O8) reagents, solid/liquid ratio, mixing parameters, and time of leaching and thermohydrolysis were systematically investigated. The solubility of V2O5 was investigated as a function of temperature, pH of sulfuric acid solutions, and concentration of Na2SO3. The kinetics of V2O5 solubility and reduction were also studied. The vanadium leaching yield after a two-step recovery was 98 wt% after acidic (H2SO4, pH 1.2–1.3) leaching with ultrasonic treatment for 5 min at ambient temperature, followed by reductive leaching in 0.01 Mol/L Na2SO3 solution for 15 min at ambient temperature. The highest vanadium extraction yield from leaching solutions was 98 wt% obtained through oxidizing of leaching solutions by 30 wt%. (NH4)2S2O8 with a molar ratio n(V2O5)/n((NH4)2S2O8) of 5/1 for a reaction time of 5 min at 80–90 °C. the extracted vanadium product was V2O5 with a purity of 85–87 wt%. The technological scheme has been developed to recycle all obtained products and sub-products
Highlights
Vanadium is a valuable metal widely dispersed in the Earth’s crust
Vanadium is widely used within the chemical and petrochemical industry, where it is employed for the production of a variety of vanadium compounds, used for instance to prepare catalysts (Khorfan et al 2001)
Morphology and elemental composition of the sample surface were investigated by Scanning Electron Microscopic (SEM) analysis using a Scanning Electron Microscope JSM 5610 LV equipped with the Energydispersive X-ray spectroscopy system EDX JED 2201 JEOL (Japan)
Summary
Vanadium is a valuable metal widely dispersed in the Earth’s crust (the 22nd most abundant element). SVC is one of the most preferable secondary raw materials for vanadium extraction, as it contains 5–10 wt% of vanadium along with other valuable components, such as Cu, Ni, Mo, and Co, in the form of oxides or sulfates (Akcil et al 2015; Erust et al 2016). Khorfan et al (2001) described a three-step process of SVC utiliza tion involving acidic leaching, oxidation and precipitation to recover vanadium pentoxide but the efficiency of this method was rather low – 70 wt%. This work focused on selective metal extraction, and aimed to understand different extraction/utilization parameters of leaching and oxidation to recover vanadium in an efficient way and with high purity of obtained V2O5
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