Sulfur Removal of High-Sulfur Bauxite
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Sulfur Removal of High-Sulfur Bauxite Zhanwei Liu 1,2
&
Hengwei Yan 1,2 & Wenhui Ma 1,2 & Ping Xiong 1,2
Received: 26 November 2019 / Accepted: 21 April 2020 # Society for Mining, Metallurgy & Exploration Inc. 2020
Abstract The sulfur in high-sulfur bauxite not only pollutes the environment but also harms alumina production. This study investigated the removal of sulfur from high-sulfur bauxite by adding Zn or ZnO during the Bayer process. The results showed that the different valence sulfur (S2−, S2O32−, SO32−, and SO42−) in sodium aluminate solution can be effectively removed by adding Zn during the digestion process. Adding ZnO removes the S2− in liquor, but the other sulfur compounds (S2O32−, SO32−, and SO42−) are not affected. The mechanism of sulfur removal has been elucidated, where the S2O32−, SO32−, and SO42− are first reduced to S2−, and after adding Zn, the S2− enters into red mud in the form of ZnS. The ZnO then reacts with S2− to generate the ZnS that enters into red mud. Thus, this is a new and effective method of sulfur removal by adding Zn during the digestion process. The results shed light on the removal of sulfur from high-sulfur bauxite during alumina production. Keywords High-sulfur bauxite . Bayer process . Sulfur removal . Zn . ZnO
1 Introduction The rapid development of the alumina industry has caused bauxite resources to be scarce. There are about 0.56 billion tons of diasporic high-sulfur bauxite in China [1], and the distribution of high-sulfur bauxite in China is shown in Fig. 1. Bauxite with a sulfur content higher than 0.7% is called high-sulfur bauxite. Such bauxite is mainly composed of alumina in middle-high proportion, silicon oxide in middle-low proportion, sulfur in high proportion (sulfur content is greater than 0.7%) and middle-high A/S (weight ratio of Al2O3 to SiO2) bauxite [2]. FeS2, as the main sulfur-containing mineral of high-sulfur bauxite, converts to H 2SO4 by acidification and oxidation, the high-sulfur bauxite surface pH is acidic, as shown in * Hengwei Yan [email protected] * Wenhui Ma [email protected] 1
State Key Laboratory of Complex Nonferrous Metal Resources Cleaning Utilization in Yunnan Province, Kunming University of Science and Technology, Kunming, Yunnan 650093, People’s Republic of China
2
National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology, Kunming, Yunnan 650093, People’s Republic of China
Fig. 2. H2SO4 on the surface can pollute the surrounding environment. Highly effective development and utilization of high-sulfur bauxite has an important practical significance to ensure a stable and secure supply of Chinese bauxite resources. Removal of sulfur is a crucial problem that needs to be addressed for the highly effective development and utilization of abundant high-sulfur bauxite resources. The most negative effects of the presence of sulfur during the Bayer process are as follows [2–4]: (1) Increase in the sulfur and iron content in aluminum hydroxide and alumina products. (2) Decrease in the di
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