离子交换树脂对D-甘油酸的吸附热力学和动力学

D-甘油酸是一种重要的甘油衍生物，具有解酒护肝的功能。关于D-甘油酸生产方法的研究已有不少，但对其分离方法及分离机理的研究却鲜见报道。通过静态吸附实验，研究了D-甘油酸在201×7阴离子交换树脂上的等温热力学和动力学特性。结果表明，D-甘油酸在201×7阴离子交换树脂上的最大平衡吸附容量随pH的增加而降低，其吸附等温线符合Freundlich模型。在293~308 K下，吸附焓变为14.77 kJ·mol^-1，表明该吸附过程为吸热过程。升高温度有利于提高吸附速率，但对最大平衡吸附容量影响不大。同时，采用动边界模型描述D-甘油酸在该树脂上的交换行为，分别考察了料液浓度、树脂粒径和温度对交换过程的影响。交换过程的吸附速率随D-甘油酸浓度和温度的增加而增大，但随树脂粒径的增大而减小。研究表明该离子交换过程的速率控制步骤为颗粒扩散过程，交换过程的反应速率常数k₀为1.22×10^-3，反应级数a为0.631，表观活化能E_a为14.90 kJ·mol^-1，并得到了动力学总方程。

Thermodynamics and kinetics of D-glyceric acid adsorption on ion exchange resin

D-glyceric acid, one of the promising glycerol derivatives, has various biological functions such as accelerating ethanol and acetaldehyde oxidation. Plenty studies on the synthesis but few studies on downstream processes to recover D-glyceric acid were available. A static equilibrium adsorption was performed to study isothermal thermodynamics and kinetics of D-glyceric acid adsorption onto 201×7 strong basic anion exchange resin. The results showed that the adsorption process followed the Freundlich isothermal model at different pH and temperature conditions, which the maximum adsorption capacity decreased with increasing initial pH. The change of adsorption enthalpy was 14.77 kJ·mol^-1 at 293-308 K, suggesting an endo-thermic adsorption process. Raising temperature improved adsorption rate with limited influence on equilibrium adsorption capacity. The Dynamic Boundary Model was used to investigate adsorption kinetics with a focus on effects of D-glyceric acid concentration, resin particle diameter and adsorption temperature. The results suggested the particle diffusion was rate-limiting step of the adsorption process. The adsorption rate increased with the increase of D-glyceric acid concentration and temperature, but decreased with the increase of resin particle diameter. The general kinetics equation was obtained with the rate constant of exchange (k₀), reaction order (a) and the apparent activation energy of reaction (E_a) as following k₀=1.22×10^-3, a=0.631, E_a=14.90 kJ·mol^-1.