Kinetic study on leaching of iron in Partially Laterised Khondalite rocks for ceramic industrial applications

Abstract

Partially Laterised Khondalite (PLK) rocks are the waste materials generated during mining of bauxite. These PLK rocks even though contain >40% of Al2O3 are not suitable for metallurgical industries due to the presence of reactive silica. The rock is not directly suitable for value addition as it contains major discoloring element (iron oxide) as impurity which renders it unsuitable for use as a filler material. Physical methods such as magnetic separation, flotation, scrubbing etc. are not fully successful for removal of iron from PLK rocks. Acid leaching techniques are the only alternative method to minimize iron content in the PLK rocks. Present investigation is to get superfine particles from PLK rocks by stage crushing followed by classification using hydrocyclone. These superfine particles are subjected to hydrochloric acid leaching to remove the iron content and the final product is suitable for industries. First order reaction kinetics is found to be fit for the experimental results. The apparent activation energy for F1 model is 48.8 kJ/mol and for R3 model is 71.1 kJ/mol, which is much less compared to leaching of iron from bauxite. The brightness of the product is 80% which is desirable for filler industries. Ceramic properties of the product are compared with the Indian Standard and are found suitable for ceramic industries. (C) 2012 Elsevier B.V. All rights reserved.