A novel renewable collector from waste fried oil and its application in coal combustion residuals decarbonization

A novel renewable collector was prepared by transesterification of waste fried oil (WFO), which was used to remove the unburned carbon in the coal combustion residuals (CCRs). The specific preparation process included purification, filtration, alkali catalysis, and oxidation (ozonization). Coal gasification ash (CGA) and coal fly ash (CFA) are the two main CCRs, and their properties were analyzed by XRD, SEM, FTIR and XPS. The results showed that most of CGA and CFA particles had rough surface and strongly hydrophilic surfaces owing to the existence of abundant oxygen-containing functional groups (35.93% and 66.95%, respectively). Waste fried oil collector (WFOC) was rich in oxygen-containing groups, which could be adsorbed onto carbonaceous matter surfaces to achieve hydrophobization. Ozonization could increase the content of oxygen-containing functional groups (C--O, -C-O-C-, etc) in O3-WFOC. As the oxidation time increased, CGA and CFA had the same increasing trend of the flotation rate (fastly-slowly-fastly-slowly), and the better ozonization time was 2 h. This work demonstrated that WFOC/O3-WFOC could reduce the dependence on traditional collectors, cut down the flotation cost and solve the environmental problems caused by large amounts of CCRs and WFO by "waste control through waste".