Alternative sources of alumina

The sustained decline in the extraction volumes of high-grade bauxite in Kazakhstan necessitates the integration of low-grade alumina-bearing and alternative alumina-containing raw materials, including kaolinitic clays, into the production cycle. Gradual depletion of such high-quality ores forms an objective basis for the industrial utilization of alternative alumina sources such as nephelines, kaolinitic ores, and clayey rocks, whose global reserves are estimated to exceed 25 billion tonnes. However, the high operational costs, significant energy consumption, and adverse environmental impacts associated with conventional extraction and processing technologies underscore the urgent need for novel technological approaches aimed at improving both economic efficiency and environmental sustainability in alumina production.

This paper explores a novel and cost-effective method for processing kaolinitic clays and nepheline ores through chemical activation. A central element of the proposed technology is the preliminary chemical activation of the raw material at the initial stage of the process. This operation is key to enhancing the subsequent gravity separation by enabling the effective isolation of high-quality kaolinitic and quartz products, thereby substantially reducing the material flow entering the sintering stage. Furthermore, chemical activation positively influences downstream hydrometallurgical processing, improving overall alumina recovery. The optimal activation conditions are tailored to the mineralogical characteristics of the raw material, highlighting the importance of feedstock-specific process design.

The study presents experimental results on the treatment of kaolinitic clays from Kazakhstan and Egypt, as well as nepheline from Kazakhstan, using a combination of chemical activation (with sodium bicarbonate), wet beneficiation, sintering with limestone, and leaching. The chemical activation step induces phase transformations that significantly enhance alumina solubility. As a result, an alumina extraction rate of 79.36% was achieved, demonstrating the feasibility and industrial potential of the proposed approach.

Dr. Nazym Akhmadiyeva is a specialist in processing of technogenic raw materials, metallurgy of alumina, aluminum, rare and rare-earth metals. She holds a PhD in Metallurgy from Satbayev University, Almaty, Kazakhstan. She is currently the head of the Lab Alumina and Aluminum Laboratory at the Institute of Metallurgy and Ore Beneficiation.