黄土性土壤吸附Cr（VI）的动力学与热力学研究

摘要

Three different kinds of loess from the Ningxia province were investigated for their Cr( VI) re-moval ability from aqueous solutions. The species of chromium, adsorption thermodynamic and kinetics characterics were also discussed. Under the interference of Cl-( NaCl ) , SO4 2-( Na2 SO4 ) and HCO3 -( NaHCO3 ) ,study the change ability of removal of Cr( VI) from aqueous solutions. The conclusion of the adsorption kinetic and thermodynamics analysis:smaller apparent adsorption of Cr ( VI ) exist in the soil when 50 min later;the adsorption isotherm of Cr( VI) in loess soil can be depicted with Freundlich equa-tion and Langmuir equation. Freundlich isotherm and Langmuir both could be better describe the Cr( VI) adsorption behavior of the soil. From the Freundlich isotherm fitting constants obtained can be seen,1 is more than 1 indicating not a preferential adsorption adsorption. If it meets the adsorption of Langmuir e-quation,it means that Cr( VI) adsorption on the soil surface is a single molecular layer. Adsorption and desorption have a quantity of certain reversibility. The Loess soil does not has a function for the enrich-ment of Cr( VI) . It is the reason the loess contain different minerals and it’ s pH determines the physical and chemical properties that the absorption capacity of Cr( VI) is limited.%采用静态吸附实验方法研究对比了来自宁夏地区三种黄土性土壤对Cr ( VI )的吸附及其动力学和热力学特性,实验测定吸附动力学和吸附热力学曲线,获得吸附动力学与热力学模型,并考察了Cl-( NaCl)、SO42-( Na2 SO4)、HCO3-(NaHCO3)等共存离子对黄土性土壤吸附Cr(VI)的影响。动力学研究结果表明,在黄土吸附Cr(VI)实验中,吸附50 min后,吸附基本达到饱和；热力学研究结果显示,Cr(VI)在黄土性土壤中吸附等温线可用Freundlich和Langmuir方程描述,Freundlich吸附等温式拟合得到的常数1均大于1,证明不是优惠吸附；吸附符合Langmuir方程,说明在黄壤表面,Cr( VI)的吸附为单分子层吸附；吸附-解吸具有一定的可逆性,黄土性土壤对Cr( VI)的吸附能力不强,吸附量较低,这是因为黄土所含不同的矿物质和其酸碱度等理化性质决定了其对Cr( VI)的吸收能力有限。