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.

中文翻译：

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基于有机物与煤Gang石之间润湿性差异的增强，改进了低阶煤浮选工艺

低阶煤（LRC）浮选分离效率低的主要原因是有机质与煤石之间的润湿性差较小。为了改善LRC浮选反应，提出了一种基于扩大润湿性差异的新方法。这种方法是改变吸附液的环境（添加Ca ²⁺）以增强表面活性剂在有机物表面上的选择性吸附并增加其疏水性，同时进行超声解吸以去除吸附在脉石上的表面活性剂。对有机物，煤ue石和原煤进行了实验，并结合表面活性剂的吸附/解吸能力，FTIR和湿热测定来探讨其潜在机理。解吸时间为30 s时，原煤浮选性能最佳。表面活性剂的吸附结果表明，Ca ²⁺可以促进表面活性剂对有机物的吸附，但对脉石的影响不明显。在超声条件下，Ca ²⁺存在时吸附在脉石上的表面活性剂容量降低，但Ca ^2+的添加可以抑制表面活性剂的解吸。然而，在原煤，表面活性剂可以从脉石表面下超声和Ca除去²⁺因为脉石的原煤和Ca的弱吸附强度低比例的²⁺上煤矸石，通过灰分减少来表示。湿热结果表明，超声处理后有机物与煤石之间的润湿性差异扩大了。这项研究对于改善LRC浮选可能具有一定的指导意义。