Thermodynamic simulation was conducted to design a new process of stepwise precipitating NH4VO3 and NaHCO3 from regulating the CO2 carbonation of Na3VO4 solution.Firstly,a new(V)Ⅴspeciation model for the aqueous solution containing vanadate and carbonate is established by using the Bromley-Zemaitis activity coefficient model.Subsequently,thermodynamic equilibrium calculations are conducted to clarify the behavior of vanadium,carbon,sodium,and impurity species in atmospheric or high-pressure carbonation.To ensure the purity and recovery of vanadium products,Na3VO4 solution is initially carbonated to the pH of 9.3-9.4,followed by precipitating NH4VO3 by adding(NH4)2CO3.After vanadium precipitation,the solution is deeply carbonated to the final pH of 7.3-7.5 to precipitate NaHCO3,and the remaining solution is recycled to dissolve Na3VO4 crystals.Finally,verification experiments demonstrate that 99.1％of vanadium and 91.4％of sodium in the solution are recovered in the form of NH4VO3 and NaHCO3,respectively.
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