Molecular insight into the mechanism of benzene ring in nonionic surfactants on low-rank coal floatability

Abstract

In this work, a combined molecular dynamics (MD) simulations and experiments were adopted to study the microscopic mechanism of the benzene ring in nonionic surfactants on low-rank coal (LRC) flotation. Two nonionic surfactants with identical headgroups, nonylphenol ethoxylate (NPEO) and dodecyl ethoxyl ethers (C12EO), were selected as the research objects. Two LRC surface models with varying metamorphism degrees were constructed. The rationality of the constructed surface models was firstly discussed from the chemical composition and structure. The morphology of the surfactants and the adsorption energy obtained by MD suggested that the arrangement of polar oxygen atoms in the surfactant depended on its interaction with the polar groups of LRC, and the presence of the benzene ring in the nonionic surfactant hardly changed its arrangement on the LRC surface. The benzene ring in the nonionic surfactant can enhance its adsorption on the higher rank coal surface via the π-bonds while it cannot promote its adsorption on the lower rank coal surface. The results obtained from the experiments are in accordance with the simulation results.