2-羟乙基三甲基氯化铵抑制蒙脱石水化膨胀的密度泛函计算

DFT study on the inhibition of hydration expansion of montmorillonite by 2-hydroxyethyl trimethyl ammonium chloride

为探究2-羟乙基三甲基氯化铵(LHDJ)抑制蒙脱石水化膨胀的机理,基于密度泛函理论的方法研究了干态和湿态环境中LHDJ在蒙脱石表面的吸附机理。结果表明,干态环境下,LHDJ在蒙脱石001表面和层间都能稳定吸附,但LHDJ在Na-001表面吸附主要是静电作用,在None-001表面和层间的吸附是氢键和静电引力的共同作用,钠离子的存在并不利于LHDJ吸附在蒙脱石001表面。湿态环境下,LHDJ与水分子协同吸附,水分子将LHDJ和蒙脱石表面桥联起来并增强它们之间的静电作用和氢键作用。LHDJ抑制蒙脱石水化膨胀的机理主要是:LHDJ在水溶液中产生大量正电离子,中和蒙脱石表面的负电性,减弱颗粒间的静电斥力;同时,LHDJ可以牢固地吸附在蒙脱石外表面,随吸附量的增加,阻碍水分子在表面的吸附,但并不改变蒙脱石的亲水性;此外,LHDJ易进入层间交换出钠离子,依靠静电作用、氢键作用和水分子的桥联作用与上下两表面吸附牢固,拉紧层间距,水分子不易进入层间增大层间距。

To investigate the mechanism of 2-hydroxyethyltrimethylammonium chloride（LHDJ）inhibiting hydration swelling of montmorillonite（MMT）,the adsorption of LHDJ on dry and hydrated MMT surfaces was studied based on Density Functional Theory（DFT）.It is found that LHDJ can be adsorbed stably on the MMT 001 surface and internal surfaces under dry conditions.The adsorption of LHDJ on the Na-001 surface is mainly electrostatic,while the adsorption on None-001 surface and internal surfaces is the interaction of hydrogen bond and electrostatic attraction.The presence of Na ions is not conducive to the adsorption of LHDJ on the MMT 001 surface.In the presence of H_2 O,the LHDJ and H_2 O exhibit a cooperative adsorption,H_2 O bridges the surfaces of MMT and LHDJ and enhances their electrostatic interactions and hydrogen bonding.The mechanism of LHDJ inhibiting hydration expansion of MMT：LHDJ produces a large amount of positive ions in aqueous solution,neutralizing the negative charge of the MMT surface andweakening the electrostatic repulsion between the particles.At the same time,LHDJ adsorbs firmly on the surface of MMT,hinders the adsorption of H_2 O and weakens the hydration membrane repulsion,meanwhile it does not change the hydrophilicity of MMT due to its short chain length.Furthermore,LHDJ is easy to enter the interlayer exchange of Na ions,and adsorbs firmly with internal surfaces through electrostatic interaction,hydrogen bonding and H_2 O bridging.The distance between the layers is shortened,and water molecules cannot easily enter the interlayer to increase the interlayer spacing.