Preparation of Na4V2O7 Powder by Solid-State Reaction
As one of the critical intermediate compounds of the sodium roasting converter slag, sodium pyrovanadate (Na4V2O7) powder was synthesized by solid-state reaction using NaCO3 and V2O5 as raw materials in this study. The preparation was first evaluated by thermodynamic software FactSage® with the minimum Gibbs free energy principle. Effect of temperature (T) and partial pressure of carbon dioxide P(CO2) was analyzed, and the results indicated that the reaction proceeds extensively with increasing temperature and reducing P(CO2). TG-DSC was applied to further characterize the preparation process, and it can be found that the reaction proceeds extensively near 540 °C corresponding to carbon dioxide gas escaping. Non-isothermal kinetics with a single scan rate was applied to the solid-state reaction, the average apparent activation energy was obtained using Freeman–Carroll method, equal to 102 ± 6 kJ/mol by mathematic fitting. In addition, XRD further verified the phase composition of Na4V2O7, and a large number of voids were detected from SEM images caused by the gas release.
KeywordsNa4V2O7 Thermodynamic analysis TG-DSC Apparent activation energy
This work was supported by the National Key R&D Program of China (2018YFC1900500), China Postdoctoral Science Foundation (2018M640898), and Graduate Scientific Research and Innovation Foundation of Chongqing, China (Grant No. CYS19001).
- 2.Xiang JY, Huang QY, Lv XW, Bai CG (2017) Multistage utilization process for the gradient-recovery of V, Fe, and Ti from vanadium-bearing converter slag, J Hazard Mater 3361Google Scholar
- 3.Xiang JY et al. (2019) A multi-step process for the cleaner utilization of vanadium-bearing converter slag. Paper presented at the 148st TMS Annual Meeting, San Antonio, Texas, 10–14 Mar 2019Google Scholar
- 4.Kolta GA, Hewaidy IF (1972) Phase diagrams of binary systems vanadium oxide-sodium carbonate and vanadium oxide-sodium sulfate 25(7):327–330Google Scholar
- 5.Slobodin BV, Fotiev AA (1965) Phase diagram of the Na2O-V2O5 system. Russ J Appl Chem 38(4):801–806Google Scholar
- 6.Wilson JR, Kerby RC (1973) Solid-liquid phase equilibria for the ternary systems V2O5-Na2O-Fe2O3, V2O5-Na2O-Cr2O3, and V2O5-Na2O-MgO, Can J Chem 51:1032–1040Google Scholar
- 7.Pei GS et al (2019) A literature review of heat capacity measurements method. Paper presented at the 148st TMS Annual Meeting, San Antonio, Texas, 10–14 Mar 2019Google Scholar
- 10.Bjoernberg A (1979) Multicomponent polyanions. 24. The crystal structure of Na4V2O7·(H2O)18. Acta Chem Scand Ser A 33:539Google Scholar
- 11.Florenskij K, Pkomarov B, Vvolkov V, Pnikolaeva O, Vkudryashova A, Fbashkirova A, Schajkina E A SU736751A1 pyro:vanadium-is used as colour indicator for high-temp. gas redox mediumGoogle Scholar
- 15.Reich L, Levi W (1968) Macromolacular review. Wiley-Interscience, New York, p 173Google Scholar