聚羧酸盐侧链长度对水煤浆分散性能的影响及其作用机理

合成了一系列具有不同侧链长度的梳型聚羧酸盐(PC),研究了PC侧链长度对水煤浆的分散和流变性能的影响,使用X射线光电子能谱(XPS)分析了PC在煤水界面的吸附,并结合水煤浆Zeta电位及PC对煤颗粒的润湿性探讨了PC的分散作用机理,为设计制得高效的聚羧酸盐水煤浆分散剂提供依据。结果表明:长主链、短侧链和高阴离子基团含量的PC500(侧链聚合度n=11)具有优良的分散性,所制水煤浆属假塑性流体。PC在煤表面呈单分子层吸附,其中PC500的吸附密度和吸附厚度均最大,分别为0.638 mg·m-2和4.20 nm,其对煤粒润湿性也较好,所制水煤浆Zeta电位绝对值最高。侧链长度适中的PC500通过平衡吸附层厚度与Zeta电位发挥空间位阻和静电斥力作用分散水煤浆,其可有效地降低水煤浆Gibbs能,使煤粒间"团聚"减弱,浆体分散性提高。

Action mechanism and effect of side chain length of polycarboxylate dispersant on dispersion of coal-water slurries

Comb-like polycarboxylate dispersants (PC) with different side chain lengths ranging from 8-23 nm were synthesized using esterifiedmacromer of methoxypolyethyleneglycol (MPEG)-acrylic acid (AA), AA and styrene sulfonic sodium (SSS). The molecular structure of PC was analyzed by testing its anionic group content and relative molecular. Experiments were performed to study the influence of the length of PC side chain on dispersion and rheological properties of coal water slurry (CWS). The adsorption behaviors of PC on coal/water interface were analyzed by X-Ray photoelectron spectroscopy (XPS), which was combined with the Zeta potential and the wettability of PC on coal to investigate the action mechanism of PC dispersions in order to provide the basis for designing more efficient polycarboxylate dispersants. The results showed that the dispersibility of PC500 (n=11) was the best due to its structure of long main chain, short side chains and high anionic group content. The CWS using comb-like PC was represented as pseudoplastic fluid, which was best matched with Herschel-Bulkley model. The monolayer adsorption of PC500 on the coal surface possessed the highest adsorption density (0.638 mg·m^-2) as well as the maximum thickness (4.20 nm) with better wettability and the highest Zeta potential on coal. PC500 wearing the proper length of the side chain played the steric hindrance and electrostatic repulsion to disperse CWS by balancing adsorption thickness and Zeta potential. PC500 with the right length of the side chain can reduce Gibbs of CWS to weaken “reunion” among the coal particles while improving dispersibility of CWS.