羟基铁聚合阳离子插层蒙脱石对盐酸四环素的吸附特性研究

成功制备了羟基铁聚合阳离子插层蒙脱石(Fe-Mt),采用XRD、FT-IR、TEM和BET比表面积测定等方法对其结构进行表征,并以盐酸四环素(TC)作为目标污染物,系统开展了Fe-Mt对TC的吸附性能研究,最后考察了溶液pH值、阴离子种类及其浓度对TC吸附的影响。研究结果表明,采用Langmuir和Freundlich两种等温吸附模型均可很好描述pH=3.0时Fe-Mt对TC的吸附,但前者(R20.98)相对优于后者(R20.98)。酸性条件有利于TC的吸附,同时Fe-Mt对TC的吸附随着背景电解质浓度的升高而增强,这种现象正好与蒙脱石的情况相反。在优化反应条件下(吸附剂投加量为1.0 g/L),阴离子类型显著影响Fe-Mt对TC的吸附,对TC的理论最大吸附量的增大顺序为:SO2-4NO3-Cl-,分别对应500.0、339.0和316.5 mg/g。在酸性条件下Fe-Mt对TC的吸附机理表现为多种吸附模式并存,其中以表面配位和阴离子静电作用为主。

A study of the adsorption characteristics of the hydroxyl-iron polycation intercalated montmorillonite for tetracycline hydrochloride

Hydroxyl-iron polycations-intercalated montmorillonite(Fe-Mt) was successfully synthesized and characterized using the methods of XRD, FTIR, TEM, and N₂_adsorption/desorption analysis. The adsorption of the target contaminant tetracycline hydrochloride(TC) on Fe-Mt from aqueous solutions was examined in batch experiments. Effects of the pH values of solution and types and concentrations of anions were systematically investigated. The adsorption isotherms of Fe-Mt at pH=3.0 can be fitted well with both the Langmuir and Freundlich models, with the former(R²>0.98) better than the latter(R₂<0.98), which indicated that the monolayer adsorption was the dominant model for the TC adsorption. In contrast to the starting montmorillonite(Mt), the adsorption capacities of Fe-Mt were increased with the increasing concentration of anions under the acidic solution condition that was favorable for the TC adsorption. Under a certain optimum condition, the types of anions can dramatically influence the TC adsorption on Fe-Mt, and exert the effect on the adsorption capacity in order of SO₄^2->>NO₃^->Cl^-, corresponding to the theoretical maximums of 500.0, 339.0 and 316.5 mg/g, respectively. At the acidic pH, the TC adsorption on Fe-Mt displays the coexisting of multi-models and the surface complexation, with the anion electrostatic attraction being the dominant model.