醋酸/醋酸铵缓冲体系中苹果酸对高岭石的溶解特征

Dissolution of Kaolinite Induced by Malic Acid in HAc/NH_4Ac Buffer Solution

采用间歇法(batch method)模拟研究醋酸/醋酸铵缓冲体系中苹果酸对高岭石的溶解特征。结果表明,反应液中Al、Si浓度随苹果酸浓度提高、反应液pH降低及反应时间的推移而增加;有缓冲溶剂的苹果酸作用下,高岭石表现出Al的优先释放。且低浓度苹果酸(≤5mmol.L-1)时,随着酸度的升高,配体促进溶解速率(RL)减小;高浓度苹果酸(10mmol.L-1)时,随着酸度的升高,配体促进溶解速率(RL)增加,但增幅随pH的降低而减弱。随着酸度的升高,配体对高岭石溶解的相对作用减弱,但相对于质子对高岭石的溶解作用,本试验浓度及酸度范围内,其对高岭石溶解的贡献较小。

Experiment was conducted to investigate the dissolution character of kaolinite induced by malic acids with batch method in HAc/NH4Ac buffer solution. The results showed that the concen- tration of A1 and Si from kaolinite increased with concentration of malic acids and acidity of reactive solution and process of reactive time. The preferential Al-release of kaolinite was observed initially in HAc/NH4 Ae buffer solution of malic acids. Ligand-promoted kaolinite dissolution rates（R1.） reduced with the acidity enhancement when the concentration of malic acids was no more than 5 mmol ~ L-l; the rates（RL） were enhanced with the acidity enhancement when the concentration of malic acids wasn＇t less than 10 mmol ~ L 1 ,but the amplitude evidently weakened. The contribution amplitude of Ligand-promoted kaolinite dissolution evidently reduced with the acidity enhancement, but as far as the contribution of proton-promoted kaolinite dissolution was concerned, in the range of concentration and acidity of malic acids in the experimentation,the contribution of Ligand-promoted kaolinite dissolution was less