Effect of Ultrasonic Pretreatment on Oxidized Coal Flotation

Xu, Min; Xing, Yaowen; Gui, Xiahui; Cao, Yijun; Wang, Dongyue; Wang, Longwu

doi:10.1021/acs.energyfuels.7b02115

Cited by 60 publications

(34 citation statements)

References 33 publications

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“…To this end, many studies have focused on the methods to enhance the flotation performance of oxidized coal, such as grinding, 7 thermal pretreatment, 8 and microwave 9 and ultrasonic particle surface pretreatment. 10 These methods could improve the floatability by removing surface oxygen groups. However, surface pretreatment can eliminate limitedly the oxygenated functional groups on the coal surface.…”

Section: Introductionmentioning

confidence: 99%

Effect of Nanobubbles on the Flotation Performance of Oxidized Coal

et al. 2020

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In this study, the effects of air bubbles and nanobubbles on flotation performance and kinetics of oxidized coal were investigated. The surface properties of the coal sample before and after oxidation were characterized by a scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The nanobubbles on highly oriented pyrolytic graphite (HOPG) were observed by an atomic force microscope (AFM). The interaction between coal and conventional bubbles in the absence and presence of nanobubbles was explained by induction time. Flotation results showed that oxidized coal flotation in the presence of nanobubbles resulted in 10% higher combustible matter recovery than conventional air bubble flotation. Moreover, it was found that the flotation of oxidized coal in the absence and presence of nanobubbles can be best described using the first-order model with the rectangular model. AFM images analysis showed that a large number of nanobubbles were produced and attached to the oxidized coal surface. The induction times of the oxidized coal in the absence and presence of nanobubbles were 1000 and 39 ms, respectively, indicating that the existence of nanobubbles effectively promotes the interaction between oxidized coal and macroair bubbles. In addition, the agglomeration between oxidized coal particles also occurred spontaneously in the presence of nanobubbles, which was helpful in improving the combustible matter recovery and flotation rate of oxidized coal.

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Section: Introductionmentioning

confidence: 99%

Effect of Nanobubbles on the Flotation Performance of Oxidized Coal

et al. 2020

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“…It is reported that the cavitation effect produced by ultrasonic has a significant effect on coal particle size (Mao et al, 2018; Ozkan, 2012; Xu et al, 2017; Zheng et al, 2018). Coal particle sizes were measured using S3500 laser particle size analyzer manufactured by MICROTRAC before and after ultrasonic pretreatment, and the results are exhibited in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…When the ultrasonic times were 10 and 12 min, the content of each particle size range was almost the same. This was due to the fact that the coarse particles were easily broken into small particles under the cavitation effect generated by ultrasonic (Xu et al, 2017). Thus, the content of 0.250–0.125 mm particles decreased significantly.…”

Section: Resultsmentioning

confidence: 99%

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Improvement of Low‐Rank Coal Flotation Based on the Enhancement of Wettability Difference between Organic Matter and Gangue

Sun

Zhang

Xie

et al. 2021

J Surfact & Detergents

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The main reason for low separation efficiency in low rank coal (LRC) flotation was the small wettability difference between organic matter and gangue. To improve LRC flotation response, a new method based on the expansion of wettability difference was proposed in this investigation. This method is that changing the adsorption liquid environment (adding Ca2+) to enhance the selective adsorption of surfactants on the surface of organic matter and increase its hydrophobicity, meanwhile applying ultrasonic desorption to remove the surfactants adsorbed on the gangue. The experiments were conducted on organic matter, gangue, and raw coal and combined with surfactant adsorption/desorption capacity, FTIR, and wetting heat determination to explore the underlying mechanism. The best flotation performance of raw coal was obtained when desorption time was 30 s. Surfactant adsorption results indicated that Ca2+ could promote the adsorption of surfactant on organic matter, but has insignificant effect on gangue. Under ultrasonic condition, surfactant capacity adsorbed on gangue decreased in the presence of Ca2+, but the addition of Ca2+ could inhibit surfactant desorption. However, in the raw coal, the surfactants could be removed from gangue surface under ultrasonic and Ca2+ because of the low proportion of gangue in raw coal and weaker adsorption strength of Ca2+ on gangue, as indicated by the ash reduction. Wetting heat results suggested that wettability difference between organic matter and gangue was expanded after ultrasonic treatment. This study may have some guiding significance for improving LRC flotation.

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“…The results showed that ultrasound waves can enhance de-sulfurization performance and reduce the amounts of iron and sulfur in coal during high-sulfur coal flotation. Xu et al [24] found that the flotation kinetics and yield of the clean coal increased with ultrasonic pretreatment time. Chen et al [25] indicated that nano-bubbles on molybdenite particle surfaces were the main cause for the high floatability.…”

Section: Introductionmentioning

confidence: 99%