SOME ASPECTS OF HYDROCHLORIC ACID-LEACHING OF KAOLINITE CLAY.

Abstract

A detailed investigation of the kinetics of dissolution of kaolinite clay in hydrochloric acid solution has been carried out. The rate of dissolution increases with calcination temperature, calcination time, and leach temperature. For example, almost 98% of the aluminum in the clay sample roasted at 540°C for 1 h can be dissolved in 20 min. The presence of fluoride ions in the leach solution significantly enhances aluminum dissolution. Changes in the pore structure of kaolinite clay due to calcination and hydrochloric acid leaching have been studied by a gas adsorption technique. The results obtained show that the surface area, macropore volume, and micropore volume of the leached residue increase with the extent of leaching up to a leach time of 1 h and thereafter decreases. Calcination at 500-750°C appears to destroy the structure of the clay but has no significant effect on the porous nature of the clay.