Environmentally-friendly emulsion-like collector prepared from waste oil: Application in floatation recovery of unburned carbon in coal fly ash

The decarbonization of waste coal fly ash (CFA) and the reuse of waste oil are concerned in this study. The waste oil in kitchen waste was purified and emulsified into emulsion-like collector to reduce the dependence of CFA flotation on non-renewable collector. The feasibility of preparing microemulsion from waste oil by using OP-10 as surfactant, n-pentanol or n-hexanol as co-surfactants was studied. The pseudo ternary phase diagram was used to analyze the emulsification performance. Emulsification results show that waste oil can be prepared into microemulsion under harsh conditions. The concept of an emulsion-like, which does not require water, was proposed because the flotation process was carried out in an aqueous environment. Three emulsion-like (M waste oil:SAR = M2:8, M5:5, M8:2) were used to verify the effect of the ratio of surfactant on the decarburization efficiency. The flotation results show that the carbon removal rate can reach 94.64% under the conditions of appropriate reagent ratio and dosage. In addition, the flotation kinetic analysis was verified, nonlinear fitting results show that the classical first-order model can more accurately explain the flotation kinetic characteristics of CFA flotation by emulsion-like collector. XPS analysis results show that the content of carbon-based hydrophobic groups in CFA is only 59.9%, which indicates that the assistance of collector is necessary to improve the flotation efficiency. The present study realizes the goal of “treating waste with waste” and provides an innovative idea to realize the reuse of CFA and waste oil.