Abstract
Hydrolysis reaction of aluminium sulphate solutions of various concentrations and hydrolysis reaction of ferric sulphate solutions of various concentrations with the addition of aluminium sulphate have been investigated in an autoclave at 185゜C and 200゜C. The results indicate that Al3+ ion concentration increases with an increase in the sulphuric acid concentration in the solutiions when the hydrolysis reaction of the aluminium sulphate solutions proceeds to completion. Al3+ ion concentration is higher at 185゜C than 200゜C at the same sulphuric acid concentration in the solutions. A plot of logarithmic value of Al3+ ion concentration against logarithmic value of the sulphuric acid concentration shows a linear relationship which can be expressed by an empirical formula. The H2O corners of the equilibrium diagrams of Al2O3 - SO3-H2O system at 185゜C and 200゜C are established from the experimental data. Fe2O3 precipitates at lower sulphuric acid concentration region and Fe (OH) SO4 precipitates at higher sulphuric acid concentration region when the hydrolysis reaction of the ferric sulphate solutions proceeds to completion. However, the sulphuric acid concentration at which Fe2O3 begins to precipitate with the addition of aluminium sulphate is lower than without aluminium sulphate. Fe3+ ion concentration increases with an increse of the sulphuric acid concentration, and with an increase of the amount of aluminium sulphate at the same sulphuric acid concentration. Moreover, Fe3+ ion concentration is higher at 185゜C than 200゜C. A plot of logarithmic value of Fe3+ ion concentration against logarithmic value of the sulphuric acid concentration in the region where Fe2O3 precipitates, or in the region where Fe (OH) SO4 precipitates can be expressed by an empirical formula. The H2O corners of the equilibrium diagrams of Fe2O3-SO3-H2O system in the presence of aluminium sulphate at 185゜C and 200゜C are established from the experimental data.
