多种经典动力学模型分析土壤吸附重金属行为机制

Analysis of Adsorption Behaviors Mechanism of Heavy Metals on Soil by Various Dynamic Models

以“环境化学实验”中3种土壤样品吸附铜离子动力学实验为例,在伪一级(PFO)和伪二级(PSO)动力学模型的基础上,采用多种传统吸附反应和经验模型,如混合(MO)模型、伊洛维奇(Elovich)模型和里奇(RSO)模型等来验证PFO和PSO模型的有效性。并进一步根据吸附过程中的不同阶段,分别运用相对应的模型,如Boyd外扩散方程、唯象内部传质(IMT)模型、Weber&Morris模型和Langmuir动力学模型等来揭示土壤吸附行为机制。而且,在上述模型拟合中,改变R~2作为判断模型合理的唯一依据,综合利用多种数学误差函数计算方法,如χ^(2)、SSE、MSE和HYBRID来确定最佳吸附动力学模型。结果表明:PFO动力学模型具有普遍性,最符合土壤样品吸附反应和经验模型。具体来说,IMT模型最符合1号和2号土壤吸附行为,内扩散阶段控制着它们的吸附进程,属于物理吸附;而Langmuir动力学模型符合3号土壤,其内部的表面活性官能团决定着吸附过程,属于化学吸附。

Based on the pseudo-first-order(PFO) model and pseudo second order(PSO) model,a variety of traditional adsorption reactions and empirical models,such as mixed-order(MO) model,Elovich model and Ritchie's second-order(RSO) model,were used to verify the effectiveness of PFO model and PSO model,by taking three soil samples adsorption kinetics experiment of Cu~(2+) in Environmental Chemistry Experiment as examples.Further,according to the different steps of the adsorption process,corresponding models,such as Boyd's external diffusion equation,phenomenological internal mass transfer(IMT) model,Weber and Morris(WM) model and Langmuir kinetics model,were adopted to reveal the mechanism of soil adsorption behavior.Moreover,in the above model fitting,we used to change the correlation coefficient(R~2) as the only basis to judge the rationality of the model,and comprehensively applied various mathematical error function calculation methods,such as Chi-square(χ^(2)),residual sum of squares error(SSE),mean sum of squares error(MSE) and hybrid fractional error function(HYBRID) to determine the optimal adsorption kinetic model.The results show that the PFO model is universal and most suitable for soil samples adsorption reaction and empirical model.Specifically,the IMT model is the most consist with the adsorption behavior of No.1 and No.2 soils,and the internal diffusion stage controlls the adsorption process,which belongs to physical adsorption;Langmuir kinetics model conforms to No.3 soil,and its surface-active functional groups determines the adsorption process,which belongs to chemical adsorption.Therefore,the fitting analysis of various adsorption kinetic models has deepened students' understanding of the adsorption behavior for heavy metals in soil.