Determination of Sulfur in High-sulfur Bauxite by Alkali Fusion-Inductively Coupled Plasma-Optical Emission Spectrometry

When Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) is used to analyze the sulfur content of high-sulfur (S≤8%) bauxite, commonly used acid dissolving and alkali fusion methods cannot oxidize sulfur completely, leading to a false (lower) result of sulfur due to multiple valences of sulfur (-2, +4, +6). In this study, high-sulfur bauxite samples were fused with sodium hydroxide and leached out by hot water and hydrochloric acid, and the calibration curve was plotted through a matrix matching method to compensate for the spectral interferences of aluminum and sodium on sulfur. S182.034 nm (184 nm) was selected as the analytical line, and sulfur was analyzed by ICP-OES. Results show that sulfur in high-sulfur bauxite samples is completely oxidized with 3 g sodium peroxide at 700℃ for 10 min. The linear correlation coefficient of the calibration curve was 0.9999, the detection limit was 0.025 μg/mL, and the relative standard deviation (RSD, n=6) was less than 5%. Compared with the results of carbon sulfur analysis, there are no significant differences between the two methods. This method has the advantage of completely decomposing the samples without any loss, which will lay the foundations for the simultaneous determination of sulfur and other elements in high-sulfur bauxite by ICP-OES.