碱金属离子及碱溶液对膨润土性能影响的研究进展

基于前人有关膨润土在碱性环境下的室内试验和数值模拟的研究结果 ,重点阐述了碱金属离子及碱溶液对膨润土矿物成分、微观结构、膨胀性和渗透性等方面的影响,讨论了温度、pH值与溶液浓度等对上述过程的影响。碱金属离子及碱性溶液不仅可交换膨润土中蒙脱石层间阳离子,而且可溶解膨润土中的蒙脱石,生成非膨胀性矿物,并随着温度和pH值升高,蒙脱石被溶解程度增加,从而导致了膨润土膨胀力减小,且随着温度、溶液浓度及pH值的增加,膨胀力削弱程度加强;同时,膨润土与碱金属离子及碱溶液接触时孔隙增多,进而渗透性增强,随着温度和溶液浓度增加,渗透性也明显增强。数值模拟可实现膨润土与碱性溶液长期接触时发生的矿物成分及渗透性变化的预测。高温、不同pH值的低碱性溶液及其耦合作用对膨润土的矿物化学成分、微观结构、膨胀力和渗透性的影响及机理研究应该是今后研究的重点。

Progress of research on the influence of alkaline cation and alkaline solution on bentonite properties

Based on the previous laboratory studies and numerical simulation on bentonite in alkaline environments,the effects of alkaline cation and alkaline solution on mineral composition,microstructure,swelling capacity and hydraulic properties of bentonite are emphasized in this paper,temperature,pH values and concentration are discussed as main affecting factors.When bentonite is exposed to alkaline cation or alkaline solution,microstructure of bentonite will be changed due to the dissolution of montmorillonite and the formation of secondary minerals,which results in the decrease of swelling pressure.The amount of the reduction of swelling pressure depends on the concentration of alkaline solution.Temperature,polyvalent cation,salinity and concentration are the main factors affecting hydraulic properties of bentonite under alkaline conditions.Therefore,future research should focus on the mechanism of coupling effects of weak alkaline solutions on the mineral composition,microstructure,swelling capacity and hydraulic properties of bentonite under different temperatures and different pH values.