Kinetics of Alumina Removal from a Calcined Kaolin with Nitric, Sulphuric and Hydrochloric Acids

Abstract

A B S TRA C T : An investigation of the acid-leaching of a calcined kaolin was made to compare the reaction kinetics of hydrochloric, nitric, and sulphuric acids. The acid concentrations used were 5.9 and 8-6 normal. Reaction temperatures used were 95 ~ 80 ~ and 60 ~ C. Particular attention was given to finding a reaction equation which would mathe- matically represent the kinetic data. A nucleation rate equation of the general form, 1 In = kt ~, was found to represent these data. Values of m varied from 1.10 to 1--x 1 "55 depending on the experimental conditions. Under the conditions employed the rate of alumina leaching is fastest with hydro- chloric acid, slower with sulphuric acid, and slowest with nitric acid. The rate controlling steps are proposed from the experimental evidence.