金属有机框架化合物NH2-MIL-101(Cr)对铅(Ⅱ)的吸附性能研究

通过溶剂热法,制备出金属有机框架化合物NH₂-MIL-101(Cr)。使用X射线衍射仪(XRD)、场发射扫描电子显微镜(SEM)和全自动比表面积及微孔物理吸附和化学吸附分析仪对NH₂-MIL-101(Cr)的晶相结构、微观形貌和比表面积进行表征。结果表明,制备的NH₂-MIL-101(Cr)为正八面体形貌,比表面积高达1 656 m²/g。使用NH₂-MIL-101(Cr)对水体中Pb(Ⅱ)进行吸附,结果表明:在30 mg/L含Pb(Ⅱ)溶液中,加入0.03 g NH₂-MIL-101(Cr)吸附剂,振荡吸附100 min,达到吸附平衡,平衡吸附量为49.84 mg/g。NH₂-MIL-101(Cr)对Pb(Ⅱ)的吸附过程满足拟二级动力学和Langmuir吸附等温模型,说明NH₂-MIL-101(Cr)表面活性吸附位点分布均匀,对Pb(Ⅱ)的吸附属于均相单分子层化学吸附,实验饱和吸附量为71.25 mg/g。NH₂-MIL-101(Cr)吸附材料利用EDTA再生使用6次后,吸附量仅下降20.97%,说明NH₂-MIL-101(Cr)具有较好的再生循环使用性。取某电池车间经处理过的Pb(Ⅱ)质量浓度为30 mg/L的废水,加入0.03 g NH₂-MIL-101(Cr)吸附剂,控制pH值为6,振荡吸附100 min后,测定溶液中剩余的Pb(Ⅱ)质量浓度为0.1 mg/L(低于国家最高排放标准0.5 mg/L),说明NH₂-MIL-101(Cr)是一种良好的Pb(Ⅱ)去除剂。

Study on adsorptive property of Pb(Ⅱ) by metal-organic frameworks NH2-MIL-101(Cr)

The metal-organic frameworks, NH₂-MIL-101(Cr), were synthesized by solvothermal method. The crystal phase structure, microstructure morphology and specific surface area of NH₂-MIL-101(Cr) were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), and fully automatic specific surface area and micropore physical and chemical adsorption analyzer. The results showed that NH₂-MIL-101(Cr) had an ortho-octahedral morphology with the specific surface area up to 1 656 m²/g. NH₂-MIL-101(Cr) was used for adsorption of Pb(Ⅱ) from an aqueous solution. The results showed that the adsorption equilibrium could be reached within 100 min under the following conditions: the mass concertation of Pb(Ⅱ) was 30 mg/L; the dosage of NH₂-MIL-101(Cr) was 0.03 g; the solution was shaken for adsorption. The equilibrium absorption capacity was 49.84 mg/g. The adsorption process of Pb(Ⅱ) by NH₂-MIL-101(Cr) conformed to the pseudo-second order kinetics and Langmuir isothermal adsorption model, which indicated that the active sites on surface of NH₂-MIL-101(Cr) were uniformly distributed. The adsorption of Pb(Ⅱ) belonged to homogeneous monolayer chemical process. The saturation adsorption capacity in experiments was 71.25 mg/g. The adsorption capacity of NH₂-MIL-101(Cr) only decreased by 20.97% after regeneration for 6 cycles using EDTA, indicating that NH₂-MIL-101(Cr) had excellent performance of regeneration. The wastewater containing 30 mg/L Pb(Ⅱ) was sampled from one battery plant. After adding 0.03 g of NH₂-MIL-101(Cr), the pH was adjusted to 6. The measured mass concentration of Pb(Ⅱ) was only 0.1 mg/L (which was lower than 0.5 mg/L in national maximum emission standard) after oscillation adsorption for 100 min, indicating that NH₂-MIL-101(Cr) was a good removal agent for Pb(Ⅱ).