镁铝水滑石对水中Sb(V)的吸附性能研究

Study on the Adsorption Properties of Sb(V) by Mg/Al Layered Double Hydroxides

采用共沉淀法合成了阳离子摩尔比为2∶1(2Mg/Al LDHs)和4∶1(4Mg/Al LDHs)的镁铝水滑石,利用X射线衍射仪、比表面积及孔径分布仪和zeta电位分析仪表征了两种水滑石的基本性质,并且研究了不同p H值、不同时间、不同初始浓度以及共存离子种类等因素对镁铝水滑石吸附Sb(V)的影响。结果表明,由于CO_3^(2-)在层间的排列方式不同导致镁铝水滑石晶面间距存在明显差异;并且两种水滑石具有较高的总孔容积、比表面积和等电点。镁铝水滑石对Sb(V)的吸附动力学和吸附等温式分别可以由假二级动力学模型和Langmuir吸附等温式描述。模型拟合结果显示,2Mg/Al LDHs的吸附速率和吸附量分别高达0.19 g/(mg·h)和50.52 mg/g。镁铝水滑石对Sb(V)的去除机制主要包括表面物理吸附、阴离子交换和静电吸引等。

Magnesium-aluminium layered double hydroxides with cationic molar ratio of 2:1 (2Mg/Al LDHs) and 4:1 (4Mg/Al LDHs) was synthesized by coprecipitation method. The basic properties of the two layered double hydroxides were characterized by X-ray diffraction, speci fic surface area and pore size distribution and zeta potential analyzer. The adsorption of Sb(V) on magnesium-aluminium layered double hydroxides at different pH, different time, different initial concentration and types of coexisting ions was studied. The results show that the spacing between crystal planes of Mg/Al layered double hydroxides is obviously different due to the different arrangement of CO 3^2- between layers, and the two layered double hydroxides have higher total pore volume, speci fic surface area and isoelectric point. The adsorption kinetics and isotherm of Mg/Al layered double hydroxides on Sb(V) can be described by pseudo-second-order kinetic model and Langmuir adsorption isotherm, respectively. The model fitting results showed that the adsorption rate and amount of 2Mg/Al LDHs were as high as 0.19 g/(mg h) and 50.52 mg/g, respectively. The removal mechanism of Sb (V) by Mg/Al layered double hydroxides mainly includes surface physical adsorption, anion exchange and electrostatic attraction.