title: Interaction Mechanisms between Air Bubble and Molybdenite Surface: Impact of Solution Salinity and Polymer Adsorption.
abstract: The surface characteristics of molybdenite (MoS2) such as wettability and surface interactions have attracted much research interest in a wide range of engineering applications, such as froth flotation. In this work, a bubble probe atomic force microscope (AFM) technique was employed to directly measure the interaction forces between an air bubble and molybdenite mineral surface before/after polymer (i.e., guar gum) adsorption treatment. The AFM imaging showed that the polymer coverage on the surface of molybdenite could achieve ∼5.6, ∼44.5, and ∼100% after conditioning in 1, 5, and 10 ppm polymer solution, respectively, which coincided with the polymer coverage results based on contact angle measurements. The electrolyte concentration and surface treatment by polymer adsorption were found to significantly affect bubble-mineral interaction and attachment. The experimental force results on bubble-molybdenite (without polymer treatment) agreed well with the calculations using a theoretical model based on the Reynolds lubrication theory and augmented Young-Laplace equation including the effect of disjoining pressure. The overall surface repulsion was enhanced when the NaCl concentration decreased from 100 to 1 mM, which inhibited the bubble-molybdenite attachment. After conditioning the molybdenite surface in 1 ppm polymer solution, it was more difficult for air bubbles to attach to the molybdenite surface due to the weakened hydrophobic interaction with a shorter decay length. Increasing the polymer concentration to 5 ppm effectively inhibited bubble attachment on mineral surface, which was mainly due to the much reduced hydrophobic interaction as well as the additional steric repulsion between the extended polymer chains and bubble surface. The results provide quantitative information on the interaction mechanism between air bubbles and molybdenite mineral surfaces on the nanoscale, with useful implications for the development of effective polymer depressants and fundamental understanding of bubble-solid interactions in mineral flotation. The methodologies used in this work can be readily extended to studying similar interfacial interactions in many other engineering applications such as froth flotation deinking and bitumen extraction in oil sands industry.
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 1H9, Canada.
authors.forename: Lei
authors.initials: L
authors.lastname: Xie
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 1H9, Canada.
authors.forename: Jingyi
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 1H9, Canada.
authors.forename: Duowei
authors.initials: D
authors.lastname: Yuan
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 1H9, Canada.
authors.forename: Chen
authors.initials: C
authors.lastname: Shi
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 1H9, Canada.
authors.forename: Xin
authors.initials: X
authors.lastname: Cui
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 1H9, Canada.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 1H9, Canada.
authors.forename: Qi
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 1H9, Canada.
authors.forename: Qingxia
authors.identifier: 0000-0002-4587-2086
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 1H9, Canada.
authors.forename: Hongbo
authors.identifier: 0000-0002-1432-5979
authors.initials: H
authors.lastname: Zeng