Application of Carboxylic Acid in Low-Rank Coal Flotation

In this investigation, the possibility of carboxylic acid used as collector to float low-rank coal was explored and alkane was also used to be compared. The effect of different lengths of carbon chain of carboxylic acid and alkane on flotation performance was studied. XPS and contact angle measurements were adopted to determine the properties of low-rank coal and make explanations for flotation results. The XPS results showed that there were many hydrophilic functional groups, such as C-O, C=O, and O=C-O, on the surface of low-rank coal. Accordingly, the contact angle of raw coal is low, which indicates that the low-rank coal is difficult to float. The flotation results showed that the flotation of low-rank coal in the presence of carboxylic acid contributed to better flotation performance than that obtained by alkane, which indicated that carboxylic acid can be more effective collector than alkane to float low-rank coal. The combustible matter recovery increases first and then decreases with the increase of carbon atoms in molecular structure of carboxylic acid. And this indicates that a proper length of carbon chain has great importance for improving flotation performance of carboxylic acid used as collector.