张 锐,于 锋,邢耀文,等. 浮选颗粒条栅结构表面润湿行为特性研究[J]. 选煤技术,2024,52(4):13−21. DOI: 10.16447/j.cnki.cpt.2024.04.002
    引用本文: 张 锐,于 锋,邢耀文,等. 浮选颗粒条栅结构表面润湿行为特性研究[J]. 选煤技术,2024,52(4):13−21. DOI: 10.16447/j.cnki.cpt.2024.04.002
    ZHANG Rui, YU Feng, XING Yaowen, et al. Study of grid-structured flotation particle surface wetting behavior characteristics[J]. Coal Preparation Technology,2024,52(4):13−21. DOI: 10.16447/j.cnki.cpt.2024.04.002
    Citation: ZHANG Rui, YU Feng, XING Yaowen, et al. Study of grid-structured flotation particle surface wetting behavior characteristics[J]. Coal Preparation Technology,2024,52(4):13−21. DOI: 10.16447/j.cnki.cpt.2024.04.002

    浮选颗粒条栅结构表面润湿行为特性研究

    Study of grid-structured flotation particle surface wetting behavior characteristics

    • 摘要: 矿物颗粒间表面润湿性差异是浮选成功的关键,受表面化学性质与物理形貌结构的双重影响。为进一步明确表面物理形貌结构对液滴在矿物颗粒表面上润湿行为的影响,采用光刻显影技术制备了5种具有不同粗糙度系数和表面面积分数的条栅结构聚二甲基硅氧烷(PDMS)表面,并利用自制的动/静态接触角测量系统及润湿三相接触线行为测试系统对液滴在PDMS表面上的润湿行为进行了测试。动/静态接触角测试结果表明:当表面粗糙度系数相同时,固体表面面积分数增加,条栅结构表面不同润湿方向上的接触角均呈减小趋势,而当表面面积分数相同时,条栅结构表面不同润湿方向上的接触角则与固体表面粗糙度系数呈正相关;此外,各样品表面垂直于条栅结构方向的动/静态接触角均大于平行方向(即θ > θ),且不同润湿方向上接触角的差异随样品表面润湿性的增强而减小。动态接触角测试结果还表明:表面接触角滞后(Δθ = θaθr)与表面面积分数呈正相关,而与表面粗糙度系数呈负相关,且前进与后退接触角的预测值与试验值基本吻合,说明动态接触角能够真实地反映固体表面润湿性;此外,在液滴滚动时,其运动行为总是周期性地发生后端接触线先从固体表面分离,而后液滴重新与固体表面发生黏附形成新的前端接触线的过程,这种运动特性在不同条栅结构表面上完全相同。润湿三相接触线行为测试结果表明:液滴在条栅结构表面优先沿着条栅结构方向润湿或去润湿,而跨越条栅结构润湿时,受表面微结构的“钉扎”作用,润湿半径远小于平行润湿方向,且三相接触线在不同条栅结构表面的移动均呈现“解钉—钉扎—再解钉—再钉扎”的一种断续周期性过程。研究结果深化了矿物颗粒表面物理形貌结构对其润湿行为特性的影响,可为后续通过表面形貌调控颗粒表面润湿性起到一定的理论支撑作用。

       

      Abstract: Difference of mineral particles in surface wettability is the key to success of flotation process, and the wetting characteristics are influenced by both surface chemical properties and physical morphological structure. In order to further clarify the influence of surface physical morphology on wetting behavior, five groove-structured surfaces with different roughness coefficients and percentages of surface area are prepared with polydimethysiloxane sheet (PDMS) as material and through photo-engraving process. Then the wetting behavior of droplets on PDMS surface is explored using self-made dynamic/static contact angle measuring system and the three-phase contact line movement testing system. As indicated by both dynamic and static contact angle measurements, when the surface roughness remains unchanged, the contact angles in different wetting directions on groove-structure surface all tend to decrease with the increase of surface area, and when the percentages of surface area are identical, the contact angles in different wetting directions are positively correlated with roughness of solid surface; the dynamic and static contact angles of droplets in the direction perpendicular to the grooves on the surfaces of different specimens are all greater than those in the parallel direction (i.e.θ > θ), and the difference in values of contact angles in different wetting directions tends to decrease with the increased wettability of solid surface. Results of test on dynamic contact angles also indicate that the hysteresis of contact angels (Δθ = θaθr) is positively correlated with percentage of surface area and negatively correlated with surface roughness, and the predicted values of both forward and receding contact angles are basically in agreement with the actually measured values, indicating that the dynamic contact angels of droplets can truly reflect the change in surface wettability; and the droplet when rolling is observed to always undergo a cyclic motion on different structured solid surfaces, namely, its rear-end contact line first separate from the solid surface and then adhere onto the latter to form a front-end contact line. As shown by results of test on three-phase contact line, the droplets are more inclined to move first along the grooves and in this case a better wetting and dewatering effect can be expected than in the case when the droplets travel across the grooves as the wetting radius of each droplet is much reduced under the pinning effect of the microstructure of solid surface; the three-phase contact line moves on the groove-structured surface intermittently in a cyclical process of depinned−pinned−deppinned−pinned. The work made in the paper sheds more light on the effect of physical morphological structure of surface mineral particles on characteristics of wetting behavior, which provides a certain theoretical support for the follow-up research work in this field.

       

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