Role of dodecane on coal particle-bubble interaction in aqueous phase

Abstract

Even if coal particles are hydrophobic, interaction between these particles and air bubbles can be enhanced by nonpolar oil in froth flotation. The role of a nonpolar liquid dodecane on coal particle-bubble interaction in aqueous phase was investigated and compared to that of a solid analogue, paraffin wax via a combined application of water contact angle and particle-bubble stability measurements, and molecular dynamics simulations. It was found both dodecane and paraffin wax can increase hydrophobicity of coal surface and attachment stability of coal particle-bubble aggregates when they covered the coal particles. Despite similar chemical structure and hydrophobicity, dodecane was more effective than paraffin wax. Molecular simulations confirmed that, comparing to the unmodified coal particle, both dodecane and paraffin wax models could increase the attachment strength of coal particle. However, different from immobile solid paraffin wax, we demonstrated that the liquid like properties of the dodecane layers present on the coal particle surfaces play an essential role in the particle-bubble interaction. When the coal particle covered by dodecane arrived at gas−water interface, the dodecane molecules will migrate and rearrange to form a new film at this interface. In addition to hydrophobic attraction of the gas bubble, the dodecane film will provide additional adhesion towards the coal particle due to oleophilicity of the coal particle, enhancing the stability of bubble-particle aggregate.