Process development of kaolin pressure bleaching using carbohydrates in acid media

Abstract

The removal of iron from kaolin of industrial interest by acid leaching under pressure, using sucrose as reductive substance, has been studied. Several factors have been taken into consideration in the experimental runs planned, using an experimental design technique: acid concentration (H 2SO 4), sucrose concentration (C 12H 22O 11), temperature and time of treatment. The experimental tests were performed using industrial mineral concentration (30% w/v) in an autoclave device. The main effects and the significant interactions involved in the leaching process were found by ANOVA; a significant improvement in iron removal was obtained due to the presence of sucrose. Some considerations about the mechanism of the process have been made considering the behaviour of the carbohydrates in hot acid solutions. Furthermore, sequential leaching tests were carried out in order to examine the possibility of recycling leach solutions for the treatment of non-treated mineral. A methodological approach is shown in the study of leaching processes using factorial experiments instead of experiments changing “one factor at a time”. The experimental results demonstrate the possibility of using carbohydrates in the bleaching process of minerals of industrial interest.