Mineralogy Characteristics of Sedimentary Bauxite in Western Guangxi

China is the world’s largest aluminum producer and consumer. With the development of China’s aluminum industry, bauxite resources are consumed continuously and highly dependent on imports. In 2019, China’s imports exceeded 100 million tons of bauxite, with an increase of 21.9%, and in 2020, imports reached a record high of 110 million tons, and dependency on importing bauxite is increasing from 5% in 2001 to 50%. Therefore, high-sulfur bauxite becomes an important new resource. A large number of high-grade high sulfur sedimentary bauxite has been found in China. However, due to the high sulfur content (S>0.7%) in high sulfur sedimentary bauxite, which seriously affects the subsequent aluminum extraction process, it has not been used in industry. If it can be developed and utilized in industry, it is of great significance to the development of the aluminum industry.

In order to clarify the ore properties and the possible industrialization technical indicators of sedimentary bauxite in Western Guangxi.

X-ray fluorescence spectroscopy, polarizing microscope, X-ray diffraction and scanning electron microscopy were applied to investigate composition and properties of the sedimentary bauxite ore, which provided important reference data for the development of this type of bauxite.

(1) The content of Al₂O₃ in the ore is 64.21% and the content of S is 5.13%. According to the classification of the bauxite industrial index quality, the ore belongs to high sulfur deposit type bauxite. (2) The aluminum minerals in the ore are mainly diaspore and chlorite, with fine crystal size, oolitic aggregate form and smooth surface for diaspora. The main iron minerals are pyrite, hematite and limonite. The pyrite exists in the form of euhedral, semi-euhedral and allotriomorphic crystals, and the size of crystal particles is different. Some of the coarse-grained and medium-grained pyrites have a particle size of more than hundreds of microns. Compared with the accumulated bauxite in the same source layer, the biggest difference of sedimentary bauxite in Western Guangxi is that it contains an amount of pyrite. (3) Diaspore and pyrite are the main useful minerals of bauxite, there are differences in the distribution between the two minerals in the ore. The difference is conducive to the use of crushing and grinding methods to dissociate mineral monomers, and then select appropriate mineral processing methods to separate pyrite.

It is possible to dissociate the main minerals in the high sulfur sedimentary bauxite by crushing and grinding. Based on previous experiments on high-sulfur bauxite, the high-sulfur problem of the sedimentary bauxite can be effectively separated from pyrite by mineral processing. Monomer separation can be achieved by crushing and grinding, with removal of the pyrite by flotation by a mineral processing reagent system. Thus, the aluminum-containing minerals after floating sulfur meet the requirements of alumina extraction and feeding in the next step.