温度７０から１１０℃における硫酸第二鉄溶液の加水分解によるゲーサイト沈殿

Abstract

A hydrolysis reaction was carried out by adding a certain amount of zinc oxide into the sulphuric acid acidified ferric sulphate solutions with various concentrations at 70 °C, 80 °C, 90 °C, 100 °C and 110 °C respectively for more than 168 hours. The composition of solutions and the precipitation of goethite, which were balanced with solutions at an equilibrium state when the hydrolysis reaction proceeded to completion, were examined. It was found that the precipitation of goethite occurred from the region where ferric ion concentration increased slightly with an increase of the sulphuric acid concentration to the region where ferric ion concentration increased suddenly. In the region where goethite was precipitated, the sulphuric acid concentration in the solution increased with raising temperature, e. g. the precipitation of goethite occurred in the solution with the sulphuric acid concentration up to 8.4 g/l at 70 °C, 11.8 g/l at 80 °C, 15.5 g/l at 90 °C, 16.5 g/l at 100 °C, and 21.0 g/l at 110 °C respectively. The ferric ion concentration increased with an increase of the sulphuric acid concentration at the same temperature, and decreased with raising temperature at the same sulphuric acid concentration. A plot of logarithmic value of sulphuric acid concentration against logarithmic value of ferric ion concentration showed a linear relationship which can be expressed by empirical formulas at the individual temperature.