Contact angle and induction time of air bubble on flat coal surface of different roughness
Contact angle and induction time of air bubble on flat coal surface of different roughness
复制标题
不同粗糙度扁煤表面气泡的接触角和诱导时间
DOI：
10.1016/j.fuel.2018.02.140
复制
发表时间：
2018-06-15
期刊：
影响因子：
7.4
通讯作者：
Xie, Guangyuan
中科院分区：
文献类型：
--
作者：
Chen, Yuran;Xia, Wencheng;Xie, Guangyuan
煤的润湿性是表征煤颗粒表面疏水性和可浮性的重要参数，从而决定了煤的浮选行为。煤的润湿性主要受表面官能团的支配。然而，表面形貌在煤的润湿性中的作用尚未引起足够的重视。本文通过测量气泡与平坦煤表面的接触角，研究了粗糙度对煤润湿性的影响。此外，还介绍了一种测量接触角的新方法。气泡的形状由圆和椭圆两部分拟合而成。将块状煤颗粒作为煤样，用不同网格的砂纸进行抛光，得到不同粗糙度的特定平坦煤表面。利用附着时间测量和Wenzel理论进一步解释了为什么表面粗糙度对煤表面气泡接触角有显著影响。通过研究发现，煤的润湿性随着表面粗糙度的增加而降低。水可能被困在粗煤表面的孔隙/裂缝中，从而阻止了煤表面与气泡的附着和三相接触线的扩展。因此，附着时间和接触角随粗糙度的增大而减小。
The wettability of coal is an important parameter for representing the surface hydrophobicity and floatability of coal particle, and hence determines coal flotation behavior. The wettability of coal is primarily governed by the surface functional groups. However, the role of surface topography in the wettability of coal has not attracted enough attentions. This paper was to investigate the effect of roughness on the wettability of coal by measuring the contact angle between air bubble and flat coal surface. Besides, a new method to measure the contact angle is introduced. The shape of the bubble is fitted by both the circle and the ellipse. The lump coal particles were used as coal sample and polished by sand papers of different meshes to gain the specific flat coal surfaces of different roughness. The attachment time measurements and Wenzel theory were used to further explain why the surface roughness has significant effects on the contact angle of air bubble on coal surface. Throughout this paper, it was found that the wettability of coal was decreased with the increase of surface roughness. The water may be entrapped in the pores/cracks of rough coal surface which prevents the attachment between coal surface and bubble as well as the spreading of three-phrase contact line. Therefore, both the attachment time and contact angle were decreased with the increase of roughness.