Gertsen Maria, Perelomov Leonid, Kharkova Anna, Burachevskaya Marina, Hemalatha S, Atroshchenko Yury
Laboratory of Soil Chemistry and Ecology, Faculty of Natural Sciences, Tula State Lev Tolstoy Pedagogical University (Tolstoy University), Lenin Avenue, 125, 300026 Tula, Russia.
Laboratory of Biogeochemistry, Faculty of Natural Sciences, Tula State Lev Tolstoy Pedagogical University (Tolstoy University), Lenin Avenue, 125, 300026 Tula, Russia.
Toxics. 2024 Sep 30;12(10):713. doi: 10.3390/toxics12100713.
For many decades, natural and modified clay minerals have been used as adsorbents to clean up aquatic and soil ecosystems contaminated with organic and inorganic pollutants. In this study, organoclays based on bentonite and various amphoteric and nonionic surfactants were synthesized and tested as effective sorbents for lead ions. The maximum values of R were obtained when describing the sorption processes using the Langmuir model, which ranged from 0.97 to 0.99. The adsorption of lead ions by these organoclays was investigated using different sorption models including the Langmuir, Freundlich, and BET. It was found that, according to the values of limiting adsorption to the Langmuir equation, the synthesized organoclays formed an increasing series: organoclay with cocamide diethanolamine < bentonite < organoclay with lauramine oxide < organoclay with sodium cocoiminodipropionate < organoclay with disodium cocoamphodiacetate < organoclay with alkyl polyglucoside. The Gibbs energy for all of the analyzed samples was calculated and found to be negative, indicating the spontaneity of the cation adsorption process in the forward direction. The maximum value of the adsorption capacity of lead cations on organoclay-based bentonite with alkyl polyglucoside was 1.49 ± 0.05 mmol/g according to the Langmuir model, and 0.523 ± 0.003 mmol/g as determined by the BET model. In the process of modifying bentonite, there was an increase in negative values of the zeta potential for organoclays compared to the initial mineral, which clearly enhanced their electrostatic interactions with the positively charged lead ions. It was hypothesized, based on the physicochemical principles, that exchange adsorption is the main mechanism for lead absorption. Based on chemical approaches, organoclays based on amphoteric surfactants absorb lead mainly through the mechanisms of electrostatic attraction, ion exchange, and complexation as well as the formation of insoluble precipitates. Organoclays based on nonionic surfactants, on the other hand, absorb lead through mechanisms of complexation (including chelation) and the formation of insoluble chemical precipitates. The comparison of isotherms from different models allows us to find the most accurate match between the model and the experimental data, and to better understand the nature of the processes involved.
几十年来，天然和改性粘土矿物一直被用作吸附剂，用于清理受有机和无机污染物污染的水生和土壤生态系统。在本研究中，合成了基于膨润土以及各种两性和非离子表面活性剂的有机粘土，并将其作为铅离子的有效吸附剂进行了测试。使用朗缪尔模型描述吸附过程时，R的最大值在0.97至0.99之间。使用包括朗缪尔、弗伦德利希和BET在内的不同吸附模型研究了这些有机粘土对铅离子的吸附。结果发现，根据朗缪尔方程的极限吸附值，合成的有机粘土形成了一个递增序列：椰油酰胺二乙醇胺有机粘土<膨润土<月桂胺氧化物有机粘土<椰油亚氨基二丙酸钠有机粘土<椰油两性二乙酸二钠有机粘土<烷基多苷有机粘土。计算了所有分析样品的吉布斯自由能，发现其为负值，表明阳离子吸附过程在正向是自发的。根据朗缪尔模型，基于膨润土的烷基多苷有机粘土对铅阳离子的最大吸附容量为1.49±0.05 mmol/g，根据BET模型测定为0.523±0.003 mmol/g。在膨润土改性过程中，与初始矿物相比，有机粘土的ζ电位负值增加，这明显增强了它们与带正电的铅离子的静电相互作用。基于物理化学原理推测，交换吸附是铅吸附的主要机制。基于化学方法，基于两性表面活性剂的有机粘土主要通过静电吸引、离子交换和络合以及形成不溶性沉淀的机制吸附铅。另一方面，基于非离子表面活性剂的有机粘土通过络合（包括螯合）和形成不溶性化学沉淀的机制吸附铅。不同模型等温线的比较使我们能够找到模型与实验数据之间最准确的匹配，并更好地理解所涉及过程的本质。
