Oxidative Bayer Digestion of Sedimentary Bauxite Aiming at the Extraction of Alumina from Chlorite

Abstract

Chlorite is a typical aluminum-bearing mineral found in sedimentary bauxite deposits. To achieve the efficient extraction of alumina from chlorite, this study proposes an oxidative Bayer digestion and compares the reaction behavior of chlorite under the conventional Bayer digestion conditions. During the conventional high-temperature Bayer digestion process, chlorite hardly reacts with sodium aluminate solution, resulting in a low digestion rate of alumina. Through comparative experiments with the addition of sodium nitrate as an oxidant, it was found that ferrous ions in the chlorite were easily oxidized to trivalent iron, leading to the phase transformation of chlorite, and enhancing the digestion of alumina. The relative digestion rate increased from 88.39% under conventional digestion to 95.48% under oxidative Bayer digestion. In this process, nitrate ions are transformed into nitrite ions and ammonia gas. These research findings provide important theoretical insights for the large-scale extraction and utilization of sedimentary bauxite deposits with a high chlorite content.