The interaction of frothers with hydrophobic and hydrophilic sites of coal particles in NaCl solution

Abstract

Frothers are added in coal and mineral flotation to assist the formation of small air bubbles and stable froth. However, we have found that frothers can also adsorb on hydrophobic and hydrophilic sites of coal particles in flotation. In the current study, the interaction of two widely used frothers with coal particles in NaCl solution was investigated. While focused beam reflectance monitor was applied to measure the aggregation of coal particles, surface tension was measured to understand the aggregation of frother molecules. It was found that the adsorption of frothers on coal particles in NaCl solution was influenced by the NaCl-modified properties of frother molecules and coal particles. The presence of NaCl enhanced the intermolecular interaction between frothers and water and also facilitated the aggregation of coal particles. On hydrophobic sites, the hydrophobic interaction (CH/ π) between frothers and coal particles could be easily replaced by the stronger π/π interaction between coal particles, while on hydrophilic sites, the hydrophilic interaction between frothers and coal particles could be enhanced through ion-dipole attraction. Whether the hydrophobic interaction or the hydrophilic interaction played a dominant role in frother adsorption depended on the ratio of hydrophobic to hydrophilic sites and the formation of hemimicelles of frother molecules.