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采用间歇法(batch method)模拟研究醋酸-醋酸铵缓冲体系中柠檬酸、草酸和苹果酸三种低分子量有机酸对高岭石的溶解特征。结果表明:柠檬酸、草酸和苹果酸三种有机酸均能显著促进高岭石的溶解,溶解能力都是随其浓度和酸度的升高而增强;当有机酸浓度为1mmol/L,pH3.5时,草酸>柠檬酸>苹果酸;pH5.5和pH4.5时,柠檬酸>草酸>苹果酸;而当有机酸浓度≥5mmol/L时,草酸>柠檬酸>苹果酸,且对高岭石的溶解能力都大于无机酸。当柠檬酸、草酸和苹果酸浓度为1mmol/L时,反应级数(nHL)分别为0.09、0.27和0.18,速率常数(kHL)分别为4.03×10-13、2.62×10-12和4.73×10-13;当其浓度为5mmol/L时,其反应级数(nHL)分别为0.16、0.37和0.16,速率常数(kHL)分别为1.38×10-12、2.32×10-11和4.97×10-13;其浓度为10mmol/L时,反应级数(nHL)分别为0.18、0.34和0.16,速率常数(kHL)分别为2.17×10-12、2.60×10-11和6.05×10-13。对于柠檬酸和草酸而言,在促进高岭石溶解的作用上,相对于质子,配体的贡献是主要的;而对于苹果酸而言,配体的贡献是次要的。配体促进溶解速率(RL)可以用配体浓度的指数形式来表示。对柠檬酸、草酸和苹果酸而言,pH5.5时,分别为RL=10-13.01[配体]0.23、RL=10-13.28[配体]0.70和RL=10-13.72[配体]0.38;pH4.5时,分别为RL=10-13.00[配体]0.51、RL=10-13.03[配体]1.05和RL=10-14.07[配体]0.77;pH3.5时,分别为RL=10-12.99[配体]0.64、RL=10-12.72[配体]0.89和RL=10-14.61[配体]1.69。
The batch method was used to simulate the dissolution of kaolinite from citric acid, oxalic acid and malic acid in acetic acid-ammonium acetate buffer system. The results showed that all the three organic acids, citric acid, oxalic acid and malic acid, could significantly promote the dissolution of kaolinite. The dissolubility of kaolinite was enhanced with the increase of its concentration and acidity. When the concentration of organic acid was 1 mmol / L, pH3. 5, oxalic acid> citric acid> malic acid; at pH5.5 and pH4.5, citric acid> oxalic acid> malic acid; and when the concentration of organic acid was> 5mmol / L, Lvshu dissolved more than inorganic acids. When the concentrations of citric acid, oxalic acid and malic acid were 1 mmol / L, the reaction order numbers (nHL) were 0.09, 0.27 and 0.18, respectively, and the rate constants (kHL) were 4.03 × 10-13, 22.62 × 10-12 and 4.73 × 10-13. When the concentration was 5 mmol / L, the reaction order (nHL) were 0.16, 0.37 and 0.16, respectively, and the rate constants (kHL) were 1.38 × 10-12, 2.32 × 10-11 and 4.97 × 10 -13, respectively. When the concentration was 10 mmol / L, the reaction order numbers (nHL) were 0.18, 0.34 and 0.16, respectively. The rate constants (kHL) were 2.17 × 10-12, 2.60 × 10-11 and 6.05 × 10-13, respectively. For citric acid and oxalic acid, the contribution of the ligand is predominant relative to the proton in promoting kaolinite dissolution, whereas the contribution of the ligand is minor for the malic acid. Ligand-facilitated lysis rate (RL) can be expressed as an exponential form of ligand concentration. For citric acid, oxalic acid and malic acid, RL = 10-13.01 [ligand] 0.23, RL = 10-13.28 [ligand] 0.70 and RL = 10-13.72 [ligand] at pH 5.5, respectively ; at pH 4.5 they were RL = 10-13.00 [ligand] 0.51, RL = 10-13.03 [ligand] 1.05 and RL = 10-14.07 [ligand] 0.77; at pH 3.5 they were RL = 10-12.99 [Ligand] 0.64, RL = 10-12.72 [Ligand] 0.89 and RL = 10-14.61 [Ligand] 1.69.