Mechanistic insights into the role of ether-bearing collectors in enhancing low-rank coal flotation: Experimental and molecular simulation

Abstract

Low-rank coal (LRC) exhibits poor floatability due to its porous structure and oxygen-rich surfaces, requiring high doses of ecologically harmful traditional collectors. Understanding coal-reagent interactions is crucial for utilizing green alternatives with targeted interfacial regulation. In this study, an efficient reagent (ADO) composed of ether-based surfactant fatty alcohol polyoxyethylene ether (AEO-9) and diesel oil (DO) is introduced to improve the flotation performance of LRC. Flotation experiments show that ADO significantly outperforms DO, achieving a maximum recovery rate of 95.16 %, representing an increase of more than 30 % compared to DO. Microscopic observations confirm that AEO-9 reduced the collector droplet size from 10.6 μm to 3.35 μm in solution and enhanced its emulsification performance. ADO-modified coal exhibited superior wettability with an increased contact angle and accelerated spreading compared to DO. FTIR and XPS analyses revealed a significant reduction in hydrophilic groups after ADO modification compared to DO, accompanied by an increase in hydrophobic groups. Moreover, charge distribution analysis shows that AEO-9 enhances ADO adsorption on coal surfaces through hydrogen bonding interactions. The adsorption energy of ADO is substantially lower than that of DO. Molecular dynamics results show that the diffusion coefficient of water molecules in the ADO system is 1.930 × 10⁻⁹ m²/s, compared to 2.170 × 10⁻⁹ m²/s in the DO, confirming ADO’s superior ability to enhance the hydrophobicity of low-rank coal surfaces. This study significantly improves the flotation efficiency of LRC by proposing a novel collector with biodegradability and elucidates the mechanism of enhancing flotation performance from a microscopic perspective.