不同土壤对Cr吸附的动力学特征

Kinetic characteristics of hexavalent chromium apparent adsorption on different soils

该文采用振荡平衡法比较了来自中国15个省区16种土壤对Cr(VI)的吸附及其动力学特性,并探讨了土壤pH值、阳离子交换量、黏粒含量和有机质对Cr(VI)吸附及其动力学参数的影响。结果表明:具有较低土壤pH值和较高物理黏粒含量的土壤对Cr(VI)具有较大的表观吸附量,而土壤阳离子交换量和有机质因素对土壤Cr(VI)的表观吸附量影响较小。酸性土壤对Cr(VI)吸附能力较强,可以采用一级动力学方程和抛物线方程描述Cr(VI)在酸性土壤中的动力学行为,且土壤的表观吸附速率和平衡时的吸附量与土壤的pH值呈显著(p<0.05)负相关关系,而与物理黏粒含量呈显著(p<0.01)正相关关系;而碱性土壤对Cr(VI)吸附能力较小,很难用动力学方程描述其吸附动力学特性。可见,土壤pH值不仅影响土壤对Cr(VI)的表观吸附量,并且对Cr(VI)表观吸附动力学特征产生了较大影响。

16 different kinds of soils which collected from 15 provinces in China were chosen to study the Cr （Ⅵ）＇s kinetic characteristics of apparent adsorption and its influencing factors using vibration batch equilibrium techniques. The results show that bigger apparent adsorption of Cr （Ⅵ） exist in the soils with lower pH value and higher clay content, but soil cation exchange capacity and organic matter content has little effects on apparent adsorption of Cr （Ⅵ）. The acid-soils have bigger adsorptive capacity for Cr （Ⅵ） and their Cr （Ⅵ） adsorption kinetic characteristics can be well described by the first-order equation and intra particle diffusion model, the equilibrium adsorptive capacity and the adsorption speed of acid-soils have the negative correlation （p〈0.05） with soil pH value, while have the positive significant correlation （p〈0.01） with the content of clay. On the contrast, the alkali-soils have the small adsorptive capacity of Cr （Ⅵ）, and it is difficult to imitate its kinetic characteristics by any kinetic models. It can be concluded that soil pH value is the main factor that affects not only chromic acid apparent adsorption in soils, but also the kinetic characteristics of those soils.