Sun Jiaqi, Liu Xinmin, Li Hang, Ma Deyuan
Chongqing Key Laboratory of Interface Process and Soil Health, College of Resources and Environment, Southwest University, Chongqing 400715, China.
Materials (Basel). 2024 Dec 9;17(23):6012. doi: 10.3390/ma17236012.
In this study, the surface property parameters of non-swelling variable charge minerals, kaolinite and goethite, were determined using the ion-selective electrode method. The effects of experimental conditions, such as pH, ion concentration ratio, and liquid addition method, on the measurement results were clarified to provide a reference for accurately assessing the surface properties of variable charge materials. The research employed ion adsorption equilibrium experiments under varying pH levels, ion concentration ratios, and liquid addition methods. A combined surface property analysis was conducted using K and Ca as indicator ions to characterize surface parameters. The results were compared with the specific surface area obtained via the BET method to verify accuracy, thereby identifying optimal measurement conditions. The study led to the following five conclusions. (1) pH significantly affected the adsorption amount and ratio of indicator cations, thereby influencing the accuracy of surface property parameters. (2) The addition method and concentration ratio of electrolytes influenced the measurement accuracy by affecting the adsorption state and equilibrium time of the two indicator cations. (3) For kaolinite, the optimal initial pH ranged from 7.5 to 8.5 in the KOH + Ca(OH) system and from 8.0 to 8.5 in the KOH + CaCl system, while the equilibrium pH was 7.5 to 8.0 in both systems. The optimal ion concentration ratios were c:c = 2:1 and 9:1, respectively. (4) For goethite, the optimal initial and equilibrium pH values were 8.5 to 9.0 and 7.5 to 8.0, respectively, in both KOH + Ca(OH) and KOH + CaCl systems. The optimal ion concentration ratios were 4:1 and 20:1, respectively. (5) Through comparison, the optimal initial pH for measuring the two variable charge minerals was determined to be 8.5 ± 0.1, with the optimal equilibrium pH at 7.5 ± 0.1. However, the concentration ratios varied significantly, suggesting the need for systematic research by adjusting a series of ion concentration ratios based on the initial pH.
在本研究中，采用离子选择性电极法测定了非膨胀性可变电荷矿物高岭石和针铁矿的表面性质参数。阐明了pH值、离子浓度比和液体添加方式等实验条件对测量结果的影响，为准确评估可变电荷材料的表面性质提供参考。该研究采用了在不同pH值、离子浓度比和液体添加方式下的离子吸附平衡实验。以K和Ca作为指示离子进行了联合表面性质分析，以表征表面参数。将结果与通过BET法获得的比表面积进行比较以验证准确性，从而确定最佳测量条件。该研究得出了以下五个结论。（1）pH值显著影响指示阳离子的吸附量和比例，进而影响表面性质参数的准确性。（2）电解质的添加方式和浓度比通过影响两种指示阳离子的吸附状态和平衡时间来影响测量准确性。（3）对于高岭石，在KOH + Ca(OH)体系中，最佳初始pH值范围为7.5至8.5，在KOH + CaCl体系中为8.0至8.5，而在两个体系中平衡pH值均为7.5至8.0。最佳离子浓度比分别为c:c = 2:1和9:1。（4）对于针铁矿，在KOH + Ca(OH)和KOH + CaCl体系中，最佳初始和平衡pH值分别为8.5至9.0和7.5至8.0。最佳离子浓度比分别为4:1和20:1。（5）通过比较，确定测量两种可变电荷矿物的最佳初始pH值为8.5±0.1，最佳平衡pH值为7.5±0.1。然而，浓度比差异显著，表明需要根据初始pH值调整一系列离子浓度比进行系统研究。
