Energy Feature of Air Bubble Detachment from a Low-Rank Coal Surface in the Presence of a Dodecane–Oleic Acid Collector Mixture

Abstract

It has been generally proved that mixed collectors can enhance the flotation of low-rank coal (LRC). However, the inhibition effect of mixed collectors on the detachment between particles and bubbles is still unclear. In this paper, the energy feature of air bubble detachment from the LRC surface in the presence of dodecane (D), oleic acid (OA), and the mixture of dodecane and oleic acid (OA–D) was studied. The effect of collectors on the LRC surface property was analyzed using contact angle measurement, X-ray photoelectron spectroscopy, and wetting heat measurement. The force and displacement during the detachment process were measured synchronously using microforce balance. The results showed that the collector treatment increased the C–C/C–H content and decreased the content of oxygen-containing groups on the LRC surface. The synergistic effect between OA and D enabled the mixed collector to exhibit higher contact angle and wetting heat. Bubble detachment from the LRC surface can be divided into two stages: bubble stretching and bubble sliding, which corresponded to activation energy and detachment work, respectively. The activation energy and detachment work decreased in the same order of OA–D > OA > D, indicating that the mixed collector OA–D increased the energy of bubble detachment from the LRC surface and enhanced the adhesion strength. The theoretical detachment work was calculated, and the calculated results were in agreement with the measured results. This research provides a new perspective on the mechanism of LRC flotation being improved by mixed collectors.

Construction of a Green-Comprehensive Evaluation System for Flotation Collectors

“…First, the flotation collector poses a hidden danger to the environment during production, transportation, and use [12,13]; second, the hazards caused by the environmental impact and health impact during water circulation in the coal processing plant are not treated, so operators [14][15][16]. The flotation collector has the characteristics of a strong hazard, many types, and large dosage, so the establishment of a flotation collector evaluation system can do a good job of controlling the flotation collector from the source and also can promote the healthy and green development of a coal processing plant [4,[17][18][19].…”