Abstract：The sulfur content in sulfide forms was an important index for bauxite beneficiation. It was usually obtained by subtracting the content of sulfate from total sulfur. Therefore, the determination method of sulfate in high sulfur bauxite had attracted attention. The high sulfur bauxite sample was decomposed by hydrochloric acid (1+1). Then aluminum and iron were separated by ammonia precipitation, while calcium was separated by ammonium carbonate precipitation. After filtration, barium chromate suspension was added into the acid solution to react with sulfate to form barium sulfate precipitate and chromate ion. The pH of solution was adjusted to 9-10 with ammonia water. The excessive barium chromate and formed barium sulfate were removed by filtration. The chromate ions generated in replacement by sulfate existed in the filtrate, and it was determined by barium chromate spectrophotometry. Then the content of sulfate could be indirectly calculated according to the absorbance of chromate. Consequently, the determination of sulfate in high-sulfur bauxite was realized. The coloring conditions were optimized. The results showed that the mass concentration of sulfate in range of 1-200μg/mL had good linear relationship with its corresponding absorbance. The linear correlation coefficient was 0.9999, and the detection limit was 0.36μg/mL. The proposed method was applied for determination of sulfate in actual sample of high-sulfur bauxite. The relative standard deviations (RSD, n=6) of determination results were between 1.6% and 1.8%. The recoveries were between 95% and 105%. The sulfate content in high-sulfur bauxite was determined and compared by the proposed method and gravimetric method, respectively. The determination results were basically consistent.
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