Insights into catalytic effect of Fe3+and MnO4-on SO2 absorption for phosphoric acid production by phosphate rock slurry

Wet flue gas desulfurization (WFGD), which has been successfully applied to industrial production, is a technology designed to eliminate SO2 in the phosphorus chemical process. The SO2 absorbed by the WFGD process can replace concentrated sulfuric acid in typical phosphoric acid production, thereby reducing the production cost of phosphoric acid. In this paper, Fe3+ and MnO4- were used to enhance the removal efficiency of SO2 from phosphate slurry and co-produce phosphoric acid. It is found that under the optimal absorption conditions (3 wt % Fe(NO3)3, KMnO4 1000 mg/L), the time of 100 % SO2 absorption rate of the slurry reaches 3.5 h, and the maximum concentration of phosphate ions in the slurry is 3177.04 mg/L. DFT calculation shows that in the process of MnO4-enhanced liquid phase absorption of SO2, the hydration reaction of SO2 to H2SO3 occurs first, followed by H2SO3 catalyzes oxidation to H2SO4. Remarkably, the Fe3+-MnO4- composite slurry can reduce the SO2 absorption barrier to 72.19 kJ/mol. This study provides a new method of phosphoric acid production by enhanced desulfurization of phosphate rock slurry, which greatly reduces the consumption of concentrated sulfuric acid in traditional phosphoric acid production through enhanced desulfurization of phosphate rock slurry. Simultaneously, this paper also holds potential value for exploring the mechanism of metal ions enhancing the SO2 absorption process.