Surface chemistry of kaolinite and Na-montmorillonite in aqueous electrolyte solutions at 25 and 60 °C: Experimental and modeling study
Surface chemistry of kaolinite and Na-montmorillonite in aqueous electrolyte solutions at 25 and 60 °C: Experimental and modeling study
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DOI：
10.1016/j.gca.2006.07.017
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发表时间：
2006-09
影响因子：
5
通讯作者：
E. Tertre;S. Castet;G. Berger;M. Loubet;E. Giffaut
中科院分区：
文献类型：
--
作者：
E. Tertre;S. Castet;G. Berger;M. Loubet;E. Giffaut
在25 ° C和60°C下，通过使用酸/碱连续滴定和批实验的电位测量来研究高岭石和钠蒙脱石样品的水界面化学。使用批实验方法，观察到反映矿物溶解的pH值的连续漂移。因此，连续滴定法似乎是研究固体表面反应的最佳方法。对于每种粘土矿物，计算净质子表面过量/消耗作为pH和离子强度（0.025、0.1和0.5M）的函数。在25°C下，根据文献数据，蒙脱石的零净质子消耗对应的pH值似乎取决于离子强度，而高岭石的值是恒定的，接近5。在60°C下也得到了类似的结果，这表明粘土矿物的零净质子消耗点不依赖于温度，至少在60°C以下。另一方面，温度升高引起净质子表面过剩略有增加。最后，扩散双层形式主义（DDLM）是用来模拟实验数据。该模型涉及两个过程：质子化/去质子化的两种类型的边缘网站（铝醇和硅烷醇）和H+/Na+交换反应的基础表面上，而一小部分的负结构电荷仍然未得到补偿。这最后一个过程保持一个负的表面电位，无论溶液的pH值，这是在协议与电动数据。
The aqueous interfacial chemistry of kaolinite and Na-montmorillonite samples was investigated by potentiometric measurements using acid/base continuous titrations and batch experiments at 25 and 60°C. Using the batch experimental method, a continuous drift of pH was observed reflecting the mineral dissolution. Consequently, the continuous titration method appears to be the best way of studying solid surface reactions. For each clay mineral, the net proton surface excess/consumption was calculated as a function of pH and ionic strength (0.025, 0.1 and 0.5M). At 25°C, and according to the literature data, the pH corresponding to zero net proton consumption for montmorillonite appears to depend on ionic strength, whereas the value for kaolinite is constant and close to 5. Similar results are obtained at 60°C, which suggests that the point of zero net proton consumption for clay minerals does not depend on temperature, at least up to 60°C. On the other hand, the temperature rise induces a slight increase of the net proton surface excess. Finally, the diffuse double layer formalism (DDLM) is used to model the experimental data. The model involves two processes: the protonation/deprotonation of two types of edge sites (aluminol and silanol) and H+/Na+exchange reactions on basal surfaces, while a tiny proportion of the negative structural charge remains uncompensated. This last process maintains a negative surface potential whatever the pH of the solution, which is in agreement with electrokinetic data.