不同性质铁铝土对砷酸根吸附特性的比较研究

采用批平衡法研究了8种不同性质铁铝土对砷酸根的吸附特性,分别运用Langmuir单表面方程和Langmuir双表面方程对等温吸附数据进行拟合,以较优拟合方程求出土壤对砷的最大吸附量,并采用简单线性相关分析法探讨土壤性质对砷吸附能力的影响。结果显示,铁铝土对砷吸附强烈,吸附等温线均为非线性。双表面方程对吸附等温线的拟合效果优于单表面方程。采用双表面方程预测的吸附量和实测值的决定系数(0.935～0.978)大于采用单表面方程预测获得的决定系数(0.989～0.998)。土壤的砷吸附能力可采用高能表面和低能表面两种吸附位点进行解释。采集于云南昆明的砂页岩母质发育的红壤具有最强的砷吸附能力,根据Langmuir双表面方程计算的最大吸附量为3 498 mg kg-1。土壤的砷吸附能力受到土壤中游离氧化铁、全铝、全铁、黏粒和全磷含量的显著影响,最大吸附量与这几种土壤组成与性质因子呈显著正相关关系。

Comparative study on adsorption of arsenate on Ferrallitic soils different in property

Laboratory batch experiments were carried out to study adsorption of arsenate on eight ferrallitic soils different in property. The Langmuir one-surface equation and the Langmuir two-surface equation was used to fit the data of arsenate adsorption, separately. Adsorption capacities of the soils were derived by the better fitting equation. Effects of soil properties on arsenate adsorption were explored through simple linear regression analysis. Results show that ferrallitic soils were high in arsenic adsorption capacity, all displaying non-linear adsorption isotherms, which were better fitted by the Langmuir two-surface equation than by the one-surface equation. The correlation coefficients between the adsorption capacities predicted by the two-surface equation and measured values (0.989 to 0.998), were higher than the determination coefficients obtained through prediction by the one-surface equation (0.936 to 0.978). The high adsorption capacity of the soils could be explained with the existence of high-energy and low-energy surface adsorption sites in the soils. Among all the soils tested, the red soil developed from sand shales in Kunming, Yunnan Province showed the highest arsenic adsorption capacity, which was 3 498 mg kg-1, according to the calculation with the Langmuir two-surface equation. Contents of citrate-dithionite extractable Fe, total Al, total Fe, clay and total P exhibited more significant positive influence on arsenic adsorption capacity of the ferrallitic soils than any other soil properties.