摘要
在20℃充氮条件下,模拟无氧的中性水环境,研究了高岭石和蒙脱石两种粘土矿物对微量(≤200μg·L-1)三价砷的吸附动力学和等温吸附特征。结果表明,高岭石对As(Ⅲ)的吸附量大于蒙脱石,反应24h后达到平衡,吸附动力学模型可用Freundlich方程描述,热力学行为遵循Langmuir和Freundlich吸附等温线,As(Ⅲ)在粘土矿物上的吸附机理可能是亚砷酸与粘土矿物的>AlOH羟基位发生表面络合反应的化学专性吸附,高岭石的吸附速率、吸附能和最大吸附量均大于蒙脱石。
The main objectives of studies were to investigate the characteristics of thermodynamics and kinetics of trace arsenite（ ≤ 200 μg·L^-1） adsorbed on two typical clay minerals（ kaolinite and montmorillonite ）respectively in a condition of 20 ℃ and pH=7, modeling anaerobic environment of groundwater with nitrogen-filled continually to avoid oxidation of trivalenee arsenic. The adsorbed arsenite analysis was conducted using atomic fluorescence spectrometry（ AFS ）. The results of experiment showed adsorption capacities of kaolinite toward arsenite were higher than montmorillonite, which suggested the exposed hydroxyl groups at particle edges of both clay minerals have a major role in the adsorption of arsenic, the sorption equilibrium reached after reacting 24 hours and Freundlich kinetics equations had a better simulation （R^2〉0.98） than Elovich kinetics equation that indicated the reactions were typical nonlinear surface adsorption with limited adsorption sites. The isothermal experiment showed both Langmuir and Freundlich isothermal equations can describe the thermodynamic behaviors of adsorption very well（R^2〉0.99 ）, which indicated adsorption of arsenite on clay minerals is mainly chemical specialized adsorption in single molecule layer as complexation reactions of arsenite combined with〉AlOH bands of clay minerals, provided with slow adsorption rate and invariable adsorbability independent of cover degree, and all of the rate, energy, capacities of adsorption and adsorbability of arsenite on kaolinite were greater than that on montmorillonite.
出处
《农业环境科学学报》
CAS
CSCD
北大核心
2008年第6期2246-2250,共5页
Journal of Agro-Environment Science
基金
国家自然科学基金(40472122)
中国地质调查局项目(水[2008]03-03-14)
关键词
三价砷
反应动力学
吸附
高岭石
蒙脱石
trivalenee arsenic
reaction kinetics
adsorption
kaolinite
montmorillonite
