Beneficiation and influencing factors of coal-series kaolin for the reduction of COD

Coal-series kaolin is the product of seam deposition in coal-accumulating basin. With the high content of reducing substances such as pyrite and fossil, the COD (chemical oxygen demand) can range from 5000 to 30,000 μg/g in coal-series kaolin, which is a serious disadvantage for the clarification of glass industry. Through reverse flotation, the COD has effectively enriched in flotation froth products, while the COD in flotation concentrate is 3533 μg/g, and can be reduced to 290 μg/g at 450 °C, which is only < 2% of the raw ore. The oxidizing roasting of flotation concentrate has great significance for the decreasing of COD in the coal-series kaolin. Pyrite would also have great influence on the reduction of COD, with a high degree of oxidation, COD decreases more significantly, and the content of pyrite shows linear correlation with COD, which would provide an approximate method to evaluate the COD in coal-series kaolin.