Klučáková Martina
Faculty of Chemistry, Brno University of Technology, Purkyňova 464/118, 612 00 Brno, Czech Republic.
ACS Omega. 2020 Nov 30;5(49):31518-31524. doi: 10.1021/acsomega.0c03311. eCollection 2020 Dec 15.
In this work, the dissociation of humic acids is investigated from the point of view of their mean activity coefficients. They are determined on the basis of two different concepts: sparingly soluble substance and multistep mechanism. It was found that the mean activity coefficients are generally higher, if the traditional concept is applied to the data, excepting the HA-A sample. Both the used concepts provide the mean activity coefficients dependent on the ionic strength, the amount of dissolved humic acids, and the types of electrolyte added in the studied suspensions. Their values based on the concept of a multistep mechanism and determined for humic acids in NaCl and NaI form a continuous curve and the individual character of their ions did not assert. It means that activity coefficients were affected only by the ionic strength and valence factor of the electrolytes irrespective of their chemical composition. The mean activity coefficients obtained for humic acids in HCl are lower in comparison with NaCl and NaI due to the common ion H. Comparing the results obtained for individual humic acids, we can state that the results obtained for the HA-E sample are very different from those of other samples. It seems that its solubility is very high, but the majority of the dissolved particles remained in the molecular form and only a small amount of ions is formed.
在这项工作中，从腐殖酸的平均活度系数角度研究了其离解情况。基于两种不同概念对其进行测定：微溶物质和多步机制。结果发现，如果将传统概念应用于数据，除HA - A样品外，平均活度系数通常更高。所使用的这两种概念均能得出依赖于离子强度、溶解腐殖酸的量以及在所研究悬浮液中添加的电解质类型的平均活度系数。基于多步机制概念并针对NaCl和NaI中的腐殖酸所确定的它们的值形成一条连续曲线，且未显示出其离子的个体特性。这意味着活度系数仅受电解质的离子强度和价态因素影响，而与其化学组成无关。由于存在共同离子H，腐殖酸在HCl中获得的平均活度系数相较于NaCl和NaI更低。比较针对各个腐殖酸获得的结果，我们可以说，针对HA - E样品获得的结果与其他样品的结果差异很大。似乎其溶解度非常高，但大多数溶解颗粒仍以分子形式存在，仅形成少量离子。
