为探究丙三醇在硅藻土材料上的吸附机理以及聚乙二醇对其脱附的缓释作用,本文采用Materials Studio 7.0软件,模拟计算硅藻土与丙三醇接触时体系间的能量和粒子交换,以及2个体系内部的分子平移、转动、伸缩、置换等随机热运动,获取丙三醇分子在硅藻土中的吸附密度分布、吸附等温线及吸附位点等数据,进而分析硅藻土的结构及其表面化学基团与吸附性能之间的构效关系。在此基础上,进一步采用量子化学和分子动力学相结合的方法,从热力学和动力学2个角度研究丙三醇与聚乙二醇 (三聚体E3) 在硅藻土上的竞争吸附行为,以及在623 K条件下的动力学传质扩散机制,从而探究聚乙二醇对丙三醇脱附的缓释作用,并通过实验验证模拟结果。模拟结果表明:丙三醇的饱和吸附量与硅藻土晶间孔孔径呈非线性正相关,且发生孔内填充吸附所需压力各异;脱附过程中,层间分子可能会产生额外的相互作用,从而改变分子的扩散速率。同时,引入适量聚乙二醇后,丙三醇与聚乙二醇之间形成较强的氢键作用,增强了丙三醇的吸附强度,实现了脱附过程的缓释。623 K下的脱附动力学实验表明,丙三醇在硅藻土中的脱附行为符合一级动力学模型。加入聚乙二醇后,丙三醇的总脱附时间增加约14 min,脱附速率常数由0.043 min-1降至0.022 min-1,证明聚乙二醇不仅能增强丙三醇在硅藻土上的吸附,还可实现其缓释脱附。
Abstract
In this study, Materials Studio 7.0 software was employed to investigate the adsorption mechanism of glycerol on diatomaceous earth and to evaluate the sustained release effect of polyethylene glycol (PEG) on glycerol desorption. The simulation analyzed energy and particle exchanges between diatomaceous earth and glycerol upon contact, incorporating molecular behaviors such as translation, rotation, stretching, and substitution. Key data, including adsorption density distributions, isotherms, and adsorption sites of glycerol within diatomaceous earth, were obtained. These results were used to analyze the structure-activity relationship between the surface chemical groups of diatomaceous earth and its adsorption performance. Building upon this, a combined approach utilizing quantum chemistry and molecular dynamics simulations was applied to explore the competitive adsorption behavior and kinetic mass transfer diffusion mechanisms of glycerol and polyethylene glycol (specifically the trimer E3) on diatomaceous earth under 623 K. Thermodynamic and kinetic analyses revealed the role of PEG in modulating the desorption process of glycerol. The simulation results indicated that glycerol's saturated adsorption capacity is positively correlated with the pore size of diatomaceous earth, and the pressure required for pore-filling adsorption varies accordingly. During desorption, interactions between interlayer molecules were found to influence molecular diffusion rates. Notably, the introduction of an appropriate amount of polyethylene glycol resulted in strong hydrogen bonding with glycerol, which enhanced glycerol's adsorption strength and slowed its desorption rate. Desorption kinetics experiments under 623 K supported these findings: the addition of polyethylene glycol increased the total desorption time of glycerol by 14 minutes and reduced the desorption rate from 0.043 min-1 to 0.022 min-1. These results demonstrate that PEG effectively enhances the adsorption of glycerol on diatomaceous earth and enables sustained release behavior.
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