Fly ash nanoparticles as a CO2 foam stabilizer

•Fly ash nanoparticles were generated by mechanical size reduction.•Carbonaceous material in fly ash promoted the formation of O/W emulsion.•Surface modification of fly ash nanoparticles was necessary to make a stable CO2-foam.•Addition of DTAB in fly ash nanoparticles of low carbon content resulted in stable CO2-foam formation.•Turpentine oil was suitable for fly ash nanoparticles of high carbon content to make CO2-foam.

In this study, the use of coal fly ash nanoparticles as a stabilizer to generate stable CO2 foams was explored. Considering the heterogeneous nature of fly ash, the samples were pretreated or separated into several different types of varying carbon content. The carbonaceous material present in the fly ash samples played an important role in generating stable oil/water (O/W) emulsions. As the carbon content in the fly ash sample increased, more emulsion was generated; also, the droplet size decreased and uniformity improved. A similar trend was observed in the CO2 emulsion tests. The fly ash samples containing carbonaceous material produced more emulsion phases with denser structures. It was difficult to generate stable CO2 foams without additives. However, fly ash nanoparticles combined with additives such as surfactants or collectors, specifically dodecyltrimethylammonium bromide and turpentine oil, produced stable and dense CO2 foams.

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