A flotation collector for the separation of unburned carbon from fly ash

A very good separation of unburned carbon from fly ash was achieved with a laboratory flotation machine by employing a mixture of 4-dodecylphenol (DDP) and hexadecane (HXD) as a collector. No other reagent was required. Good results were obtained by recleaning either the concentrate or the tailings in two-stage flotation tests. Therefore, it was possible to reduce the carbon content of a selected fly ash from an initial level of 25% to a final level of 6.0% or less. At the same time it was possible to recover 87-95% of the carbon in the concentrate and 70-80% of the fly ash in the tailings by recleaning the concentrate. The lowest fly ash carbon content (2-3%) was realized by recleaning the tailings, but this also reduced fly ash recovery.