Hydrolysis reaction of aluminium sulphate solutions and effect of addition of aluminium sulphate on hydrolysis reaction of ferric sulphate solutions at elevated temperatures

摘要

Hydrolysis reaction of aluminium sulphatesolutions of various concentrations and hydrolysis reaction offerric sulphate solutions of various concentrations with theaddition of aluminium sulphate have been investigated in anautoclave at 185beg C and 200beg C.The results indicate that A1~3+ ion concentration increases withan increase in the sulphuric acid concentration in the solutionswhen the hydrolysis reaction of the aluminium sulphate solutionsproceeds to completion. A1~3+ ion concentration is higher at 185~ than 200beg C at the same sulphuric acid concentration in thesolutions. A plot of logarithmic value of A1~3+ ion concentrationagainst logarithmic value of the sulphuric acid concentrationshows a linear relationship which can be expressed by an empiricalformula. The H_2O corners of the equilibrium diagrams ofAl_2O_3 – SO_3-H_2O system at 185beg C and 200beg C areestablished from the experimental data.Fe_2O_3 precipitates at lower sulphuric acid concentration regionand Fe (OH) SO_4 precipitates at higher sulphuric acidconcentration region when the hydrolysis reaction of the ferricsulphate solutions proceeds to completion. However, the sulphuricacid concentration at which Fe_2O_3 begins to precipitate withthe addition of aluminium sulphate is lower than withoutaluminium sulphate. Fe~3+ ion concentration increases with anincrease of the sulphuric acid concentration, and with an increaseof the amount of aluminium sulphate at the same sulphuric acidconcentration. Moreover, Fe~3+ ion concentration is higher at185beg C than 200beg C. A plot of logarithmic value of Fe~3+ion concentration against logarithmic value of the sulphuric acidconcentration in the region where Fe_2O_3 precipitates, or in theregion where Fe (OH) SO_4 precipitates can be expressed by anempirical formula. The H_2O corners of the equilibrium diagramsof Fe_2O_3-SO_3-H_2O system in the presence of aluminiumsulphate at 185beg C and 200beg C are established from the experimental data.