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脂肪酸不飽和度對低階煤浮選強化的影響機制

Influence mechanism of fatty acid unsaturation on the intensification of low-rank coal flotation

  • 摘要: 為研究脂肪酸不飽和度對低階煤浮選的影響,選擇碳原子個數相同但雙鍵個數依次增加的油酸、亞油酸和亞麻酸作為浮選捕收劑對低階煤進行浮選,并與非極性捕收劑柴油進行對比,通過顆粒–氣泡間粘附力測試和藥劑吸附的分子動力學模擬,揭示了不飽和脂肪酸強化低階煤浮選的作用機制。結果表明,不飽和脂肪酸的浮選性能優于柴油,低階煤浮選產率隨脂肪酸不飽和度增加而增加。采用掃描電鏡(SEM)、傅里葉變換紅外光譜(FTIR)和X射線光電子能譜(XPS)對低階煤表面形貌和官能團進行分析。SEM結果表明,低階煤表面疏松,含有大量孔隙與裂隙,不利于藥劑在煤表面的鋪展。FTIR和XPS結果表明低階煤表面含有大量含氧官能團,表面疏水性較差,導致浮選回收率較低。對不同捕收劑條件下氣泡與煤表面粘附力進行測定,發現氣泡與煤表面間最大粘附力隨捕收劑不飽和程度增加而增加,這說明顆粒可浮性增加。進一步對不飽和脂肪酸吸附的分子動力學模擬進行分析,可知不飽和脂肪酸通過其極性基團與煤表面極性基團間形成氫鍵,從而在煤表面鋪展。雙鍵個數增加使得不飽和脂肪酸極性增加,在煤表面的鋪展程度逐漸增加,導致顆粒可浮性增加,這是低階煤浮選回收率隨脂肪酸不飽和程度增加而增加的主要原因。

     

    Abstract: To study the effect of fatty acid unsaturation on low-rank coal flotation, oleic acid, linoleic acid, and linolenic acid with the same number of carbon atoms but an increasing number of double bonds were selected as flotation collectors and compared with conventional nonpolar collector diesel oil. Adhesion force measurements between particles and bubbles and molecular dynamics simulation of reagent adsorption were used to reveal the mechanism of unsaturated fatty acids enhancing low-rank coal flotation. The flotation results show that unsaturated fatty acid collectors surpass nonpolar diesel oil in flotation performance, and the flotation yield of low-rank coal increases with fatty acid unsaturation. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to analyze the surface morphology and surface functional groups of low-rank coal. SEM results show that the surface of low-rank coal is loose and contains many pores and cracks, which is not conducive to the spreading of chemicals on coal surfaces and the mineralization of bubbles and particles. The results of FTIR and XPS show that the surface of low-rank coal contains several oxygen-containing functional groups and has poor hydrophobicity, resulting in low flotation recovery. The adhesion force between bubbles and coal surfaces was measured in different collector solutions. The maximum adhesion between bubbles and coal surfaces increased with collector unsaturation in diesel oil, oleic acid, linoleic acid, and linolenic acid systems, indicating an increase in the floatability of coal particles with collector unsaturation. Furthermore, the molecular dynamics simulation of unsaturated fatty acid adsorption showed that unsaturated fatty acids spread on coal surfaces through hydrogen bonding between the polar groups of these molecules and surfaces. With an increasing number of double bonds, unsaturated fatty acids become more polar, and the spread of unsaturated fatty acids on coal surfaces gradually becomes more extensive, which leads to increasing particle floatability. This is the main reason for the increase in flotation recovery of low-rank coal with unsaturated fatty acids.

     

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