On the utilization of waste fried oil as flotation collector to remove carbon from coal fly ash.

In this paper, the waste fried oil was used to remove the unburned carbon in coal fly ash during flotation process, and found that the waste fried oil could be a novel collector for the removal of carbon from coal fly ash. The results implied that the wetting rate of the fly ash after treated by waste fried oil was decreased, meanwhile the contact angle was increased. A significant decrease in wetting heat was observed, which indicated a weaker interaction between deionized water and fly ash after treatment with waste fried oil. Flotation tests showed that the content of unburned carbon could be reduced effectively through froth flotation when took waste fried oil as collector. FTIR analysis testified that waste fried oil had abundant oxygen-containing groups that could be adsorbed in a carbonaceous matter to achieve hydrophobization. X-ray photoelectron spectroscopy, scanning electron microscope, and energy dispersive analyses showed that the main compositions of flotation concentrate products were unburned carbon, whereas the tailing products consist of aluminum and silicon, which confirmed the superior separation performance when the waste fried oil was used as a collector in coal fly ash flotation. This investigation provides an approach to remove the unburned carbon in coal fly ash based on the principle of "waste control through waste", which can solve the environmental problems brought by large amounts of both coal fly ash and waste fried oils.