失活酵母菌吸附猕猴桃汁中氯吡脲的动力学及热力学研究

Kinetics and Thermodynamics of Forchlorfenuron Biosorption from Kiwifruit Juice by Inactivated Yeast Biomass

摘要:

通过批量吸附试验，以失活酵母菌为吸附剂，研究其对猕猴桃汁中氯吡脲的吸附动力学及热力学。主要采用准一级动力学方程、准二级动力学方程、粒子内部扩散方程及Elovich方程对吸附反应动力学数据进行拟合；利用Langmiur等温吸附模型、Freundlich等温吸附模型、Temkin等温吸附模型及Dubinin-Radushkevich等温吸附模型对吸附反应热力学特征进行研究。结果表明：吸附动力学行为最符合准二级动力学方程，意味着化学吸附是其速率控制步骤。氯吡脲的浓度在0.5~10 μg/mL范围内，其吸附平衡数据与Freundlich等温吸附模型拟合性最好，说明失活酵母菌对氯吡脲的吸附不是理想的单分子层吸附。热力学参数△G <0，△H<0，△S <0，表明在293~310 K范围内，失活酵母菌对氯吡脲的吸附是一个自发进行的、放热、熵减小的过程，低温有利于失活酵母菌对氯吡脲的吸附。

Abstract:

Inactivated yeast biomass was used as the adsorbent for batch biosorption experiments to study the kinetics and thermodynamics of biosorption of forchlorfenuron from kiwifruit juice. First, the pseudo-first-order kinetics model, pseudo-second-order kinetics model, intra-particle diffusion equation, and Elovich equation were used to fit the biosorption kinetics process. Then, Langmuir isotherm model, Freundlich isotherm model, Temkin isotherm model, and Dubinin–Radushkevich isotherm model were employed to analyze the biosorption thermodynamic characteristics. The results showed that biosorption kinetics was best described by the pseudo-second-order model, indicating that chemical biosorption was the rate-limiting step. The equilibrium data fitted well with the Freundlich model when the forchlorfenuron concentration ranged from 0.5 to 10 μg/mL, which revealed that the biosorption of forchlorfenuron by inactivated yeast biomass was not an ideal monomolecular layer adsorption. The thermodynamic parameters △G, △H, and △S were negative within the temperature range of 293 to 310 K, showing that the biosorption is spontaneous, exothermic, and accompanied by a decrease in entropy. Additionally, the biosorption of forchlorfenuron by inactivated yeast biomass was more favorable at lower temperatures.