混合电解质引发“蒙脱石-胡敏酸”凝聚的动力学研究  

Kinetic Study of Montmorillonite-humus Condensation Induced by Mixed Electrolyte

作　　者：何艾洲 喻琳乔 李航[1] HE Aizhou;YU Linqiao;LI Hang(College of Resources and Environment,Southwest University,Chongqing 400715,China)

机构地区：[1]西南大学资源环境学院,重庆400715

出　　处：《土壤学报》2025年第2期422-435,共14页Acta Pedologica Sinica

基　　金：国家自然科学基金项目(42077014)资助。

摘　　要：自然土壤通常是多种胶体和多种电解质同时并存的,然而已有的土壤胶体凝聚研究大多在单一电解质和单一胶体条件下进行。利用动态光散射(DLS)技术,系统研究了混合电解质条件下“蒙脱石(Mont)-胡敏酸(HA)”混合胶体的凝聚动力学过程。结果表明:(1)在混合电解质条件下,无论是单一胶体还是混合胶体,实验仅观察到一个临界凝聚浓度(CCC),这表明混合电解质中两种阳离子共同作用于胶体的凝聚。(2)虽然混合电解质体系中两种阳离子共同作用于胶体凝聚,但从胶体凝聚速率、CCC或凝聚活化能可以发现,竞争吸附能力强的那种离子在凝聚中起决定性作用。例如,在99%Mont+1%HA混合胶体体系中,Na+K混合体系的CCC(97.41 mmol·L^(-1))非常接近K+单独存在的CCC(94.91 mmol·L^(-1)),表明Na+在此混合胶体凝聚中的作用几乎可以忽略,即在Na+K混合体系中K+对胶体凝聚起决定性作用。(3)增加HA的含量显著提高了混合胶体的稳定性,导致需要更高的电解质浓度才能引发胶体凝聚。该效应可归因于HA的加入增加了有机/无机复合胶体颗粒的表面电荷密度,进而增强了颗粒之间的静电排斥力。本研究的科学发现对于进一步揭示土壤有机-无机复合体的形成机制具有指导意义。【Objective】Natural soil typically consists of a variety of colloids and multiple electrolytes coexisting simultaneously.However,existing studies on soil colloid coagulation have mostly been conducted under conditions involving a single electrolyte and a single colloid.In this study,the coagulation dynamics of a mixed colloid system comprising montmorillonite and humic acid under mixed electrolyte conditions were systematically investigated attempting to explain the coagulation effect and mechanism of mixed electrolyte on the mineral-organic mixture.【Method】Using dynamic laser scattering(DLS)technique,the coagulation kinetics of montmorillonite colloids and montmorillonite-humic acid mixed colloids under the influence of mixed electrolytes were studied by considering key parameters such as the average coagulation rate,critical coagulation concentration in the Na++K+mixed system,K+plays a decisive role in colloid coagulation.(2)Increasing the content of humic acid significantly enhanced the stability of the mixed colloid,resulting in the requirement of a higher electrolyte concentration to induce colloid coagulation.This effect can be attributed to the fact that the addition of humic acid increased the surface charge density of the organic/inorganic composite colloidal particles,thereby strengthening the electrostatic repulsion between particles.【Conclusion】The scientific findings of this study not only provide guiding significance for further unraveling the formation mechanism of soil organic-inorganic complexes,but also shed light on the cooperative role of cations in colloidal coagulation under mixed electrolyte conditions.The results underscore the decisive role of the cation with stronger competitive adsorption ability in colloid coagulation.Furthermore,the study reveals that increasing the content of humic acid significantly enhanced the stability of the mixed colloid,necessitating a higher electrolyte concentration to induce colloid coagulation.These insights contribute to the understanding of th

关 键 词：混合电解质 有机-无机混合胶体 动态光散射 离子竞争吸附 

分 类 号：S153.3[农业科学—土壤学]