改性环糊精金属有机骨架材料对亚甲基蓝吸附性能研究

Adsorption performances of carboxylated cyclodextrin-based Metal-Organic Framework for MB

采用环保合成工艺化学修饰一种羧基化不溶性金属有机骨架材料(γ-CD-MOF-COOH),用于去除低浓度亚甲基蓝染料(MB),对γ-CD-MOF-COOH进行表征,并系统研究其对MB吸附性能。结果表明,γ-CD-MOF-COOH对MB具有良好的去除能力,拟二阶动力学模型可以很好地阐明MB的吸附过程。Sips模型的模拟效果较好,γ-CD-MOF-COOH对MB的最大吸附质量比为335.74 mg/g。热力学分析表明,去除MB的过程是自发的吸热反应。γ-CD-MOF-COOH在经过5次循环再生试验吸附率仍达首次的98%以上,表现出良好的MB去除能力。不同吸附机制之间的协同作用是γ-CD-MOF-COOH对MB去除率较高的原因。

Environment-friendly cyclodextrin-based metal-organic framework material(γ-CD-MOF)is obtained withγ-CD as the organic ligand and KOH as a metal ion by vapor diffusion method.However,γ-CD-MOF has poor stability and dissolves rapidly in an aqueous solution,which limits the application ofγ-CD-MOF in practical water treatment and remediation.In this work,a citric acid-crosslinked water-insoluble cyclodextrin-based metal-organic framework material(γ-CD-MOF-COOH)is prepared by an environmentally friendly synthetic process for the removal of low concentrations of methylene blue(MB).And theγ-CD-MOF-COOH composites are systematically characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR),and powder X-ray diffractometer(XRD).The influences of adsorption conditions,adsorption kinetics,isotherms,and thermodynamics toward MB remediation are studied.The results show that temperature and pH have little effect on MB adsorption,the MB removal rate ofγ-CD-MOF-COOH is higher than 96.23%within the range of conditions studied.The adsorption process of MB is well clarified by the pseudo-second-order kinetic model in the kinetic experiment,indicating that the adsorption of MB byγ-CD-MOF-COOH belongs to the chemisorption behavior.The Sips model has the best simulation effect,and the maximum fitted adsorption capacity ofγ-CD-MOF-COOH for MB is 335.74 mg/g.Thermodynamic analysis shows that the process of removing MB is a spontaneous and endothermic reaction.Moreover,the MB removal rate ofγ-CD-MOF-COOH is still higher than 98.62%after 5 cycles,showing excellent MB adsorption capacity.The synergistic effect between the host-guest inclusion effect,hydrogen bonding,and electrostatic attraction is the reason for the higher removal rate of MB byγ-CD-MOF-COOH.The above results indicate thatγ-CD-MOF-COOH has good stability,cost-effectiveness,and great potential for low-concentration methylene blue dye(MB)removal from wastewater.It also provides a new idea for the use of cyclodextrin-based metal-organic framework material to treat organic dyes in wastewater.