Equilibrium Diagram in the System, Fe2O3-SO3-H2O, at Elevated Temperatures. Hydrometallurgical studies on hydrolysis of the ferric sulphate solutions at elevated temperatures(2nd Report).

Hydrolysis of acidic ferric sulphate solutions of various concentrations has been investigated in an autoclave at temperatures of 150°, 170°, and 220°.The results obtained were as follows:1. When hydrolysis of ferric sulphate solutions was at equilibrium, the concentration of ferric ion increased with an increase in the sulphuric acid concentration in solutions, while at the same sulphuric acid concentration, the concentration of ferric ion decreased considerably with an increase in temperature.2. In hydrolysis of ferric sulphate solutions, ferric oxide, Fe203, was precipitated at lower concentrations of sulphuric acid, and ferric basic sulphate, Fe (OH) SO4, was precipitated at higher concentrations of sulphuric acid.3. At a temperature of 150°, hydrolysis and precipitation of ferric oxide occurred up to the sulphuric acid concentration of 53.4g/l, and above 53.4g/l, ferric basic sulphate was precipitated. Empirical formulas of the ferric ion concentration and the sulphuric acid concentration in solutions were as follows. up to the sulphuric acid concentration of 53.4g/l, log [Fe3+ (g/l)]=3.24log [H2SO4 (g/l)]-4.44 above 53.4g/l, log [Fe3+ (g/l)]=0.45 log [H2SO4 (g/l)] +0.454. At a temperature of 170°C, hydrolysis and precipitation of ferric oxide occurred up to the sulphuric acid concentration of 54.8g/l, and above 54.8g/l, ferric basic sulphate was precipitated. Empirical formulas of the ferric ion concentration and the sulphuric acid concentration in solutions were as follows. up to the sulphuric acid concentration of 54.8g/l, log[Fe3+ (g/l)]=4.07log[H2SO4(g/l)]-6.32 above 54.8g/l, log [Fe3+ (g/l)] =1.24log [H2SO4 (g/l)]-1.425. At a temperature of 220°C, hydrolysis and precipitations of ferric oxide and ferric basic sulphate occurred in wider concentration of sulphuric acid between 58.2g/l and 67.1g/l. Therefore the sulphuric acid concentration which allowed single precipitation of ferric oxide or ferric basic sulphate was not determined exactly. The sulphuric acid concentration, 67.5g/l, was determined from the point of intersection of the curved line of stable region of ferric oxide and that of ferric basic sulphate. up to the sulphuric acid concentration of 67.5g/l, log [Fe3+ (g/l)]=3.31 log [H2SO4 (g/l)]-5.91 above 67.5g/l, log [Fe3+ (g/l)]=1.43 log [H2SO4 (g/l)]-2.336.Equilibrium diagrams in the system, Fe2O3-SO3-H2O, at the temperatures of 150, 170, and 220°C were established from the experimental data.