Study on Carbon Removal from Coal Gangue to Purify Kaolin by Flotation with Different Collectors

In order to explore the effects of carbon chain length of nonpolar saturated hydrocarbons and the type of polar groups on coal gangue flotation, five saturated hydrocarbons with different carbon chain lengths and seven hydrocarbons and hydrocarbon derivatives with different groups were selected for flotation. The results show that the flotation effect is better when the number of carbon atoms in the carbon chain exceeds 13. Oxygen-containing functional groups possess greater electronegativity and polarity compared to hydrocarbon groups, resulting in better flotation performance. Collectors containing oxygen-based groups achieves the highest recovery rate of combustible body and the ash content of kaolin, which are 71.67 and 88.34%, respectively. The carbon molecules in coal gangue contain a higher proportion of carbon oxygen structure, and more hydrogen bonds can be formed between them and the oxygen-containing functional groups in the collectors, which makes the stronger binding effect between them. The results of infrared and XPS testing of coal gangue show that the carbon–oxygen structures on the surface of coal gangue is more than 60%. The solid nuclear magnetic test results of coal gangue show that the proportion of carbon–oxygen structures in the whole material is close to 20%.