温压条件下不同含水高岭石对NH_(4)^(+)吸附的分子模拟

Molecular simulation of NH_(4)^(+) adsorption by kaolinite with different water content under temperature and pressure

为研究高岭石对NH_(4)^(+)吸附的微观情况,通过Material Studio软件对高岭石单胞进行收敛性测试后构建了4×2×1不同水化程度高岭石模型,采用量子力学和经典力学方法对模型晶胞进行了理论计算和吸附实验研究.结果显示,在交换关联泛函GGA-PW91,K点4×3×2,截断能600eV条件下,得到了高岭石稳定结构模型(误差<2%);高岭石对NH_(4)^(+)的吸附受温度影响明显,随温度升高,吸附量逐渐减少,与吸附实验结果一致;动力学结果显示吸附类型主要为物理吸附,吸附作用力为范德华力和库仑力.

In order to study the microscopic situation of NH_(4)^(+) adsorption by kaolinite,kaolinite models with different hydration degrees of 4×2×1 were constructed after the convergence test of kaolinite monocytes by Material Studio software.The theoretical calculation and adsorption experiment of the model cell were carried out by using the methods of quantum mechanics and classical mechanics.The results showed that the stable structure model of kaolinite is obtained(error<2%)under the conditions of exchange correlation functional GGA-PW91,K point 4×3×2 and truncation energy 600eV.The adsorption of NH_(4)^(+) by kaolinite was obviously affected by temperature.With the increase of temperature,the adsorption capacity decreases gradually,which was consistent with the experimental results.The kinetic results showed that the adsorption type was mainly physical adsorption,and the adsorption forces were Van der Waals force and Coulomb force.The research results were helpful to supplement the research on the kaolinite properties and have a guiding role in the control of ammonia nitrogen pollution in soil of rare earth mines.