Polysulfide Generation Using MnO2 Catalyzed Oxidation of White Liquor

The effect of mixing intensity and oxygen partial pressure on the generation efficiency of polysulfide using the catalytic oxidation of sodium sulfide by manganese dioxide was studied in a high-intensity batch-operated reactor. Synthetic white liquor was used in the study. Reaction parameters included the impeller speed (power dissipation), oxygen partial pressure and catalyst type. Increased power dissipation increased the rate, yield and selectivity of polysulfide generation up to an oxygen partial pressure of 230 kPa. Increased oxygen pressure increased the rate of polysulfide formation (to the 0.69 ± 0.12 power) but decreased yield and selectivity. The rate of thiosulfate generation (inferred using a mass balance) exhibited an induction period that was longest at low oxygen partial pressures.