考虑非均衡吸附的多孔介质中循环注入污染物运移规律

Transport laws of contaminant in porous media considering non-equilibrium adsorption under cyclic injection

由经典的吸附解吸作用下污染物运移控制方程出发,将Freundlich线性等温吸附模型中溶质浓度上升、下降过程视为吸附、解吸过程,从而建立了非均衡吸附问题理论模型;并给出了累计质量分数及相对浓度的相关表达。利用Comsol Multiphysics数值分析方法讨论了三角函数、高斯脉冲函数循环注入下污染物运移规律,结果表明:吸附、解吸平衡常数的差值对污染物吸附量有较大影响,其值越大吸附量则越大;随着弥散度的增大,穿透曲线峰值有先增大后减小趋势,且穿透过程越久。此外,对于连续注入,注入时间存在一个临界值,小于该值时溶质浓度峰值随注入时间的增大而增大,而大于该值时溶质浓度峰值恒等于注入浓度平均值;且注入时间越大峰值出现时刻越晚;而相对浓度随注入时间的增大而减小。

According to the classical equations for contaminant transport considering the effect of adsorption and desorption, a theoretical model for non-equilibrium adsorption is obtained by regarding the Freundlich linear isotherm as an adsorption and desorption process. Then, the relevant expressions for the cumulative mass fraction and the relative concentration are given correspondingly. The transport laws of contaminant are analyzed by Comsol Multiphysics for the cyclic injection of the trigonometric function and Gauss pulse function. The results show that there is an obvious impact on the adsorption capacity of contaminant due to the difference between the constant of adsorption and desorption. The adsorption amount increases with the increase of the difference. On the other hand, with the increase of the dispersivity, the peak of breakthrough curve has a decreasing trend at first and then increases. Also, the penetration process increases with the increase of the dispersivity. In addition, there is a critical value of injection time, below which the breakthrough peak increases with the increase of the injection time. Beyond this threshold, it maintains a steady state and is equal to the injection concentration of pollutant.