Application Of Functionalized Zirconium-based MOF Materials In Treatment Of Dye Wastewater

MOFs is an organic-inorganic hybrid solid composed of metal ions/clusters and organic linkers with regular pore channels or pore structures.Due to its rich structural diversity and tailoring,MOFs are considered to be a promising and unique porous material.Among them,the Ui O-67 structure in UIO series zirconium-based MOFs has become one of the most popular Zr-based frameworks for wastewater treatment due to its excellent biocompatibility,hydrothermal stability and thermal stability,no secondary pollution after structural decomposition and excellent chemical stability.In this paper,Ui O-67 was used as precursor,and a series of porous materials were synthesized by modification.The properties of UIO-67 in dye adsorption and oxidation catalytic reactions in dye wastewater were studied.The main research contents are as follows:1.The synthesis of Ce-doped Ui O-67 nanocrystals was via one-step hydrothermal method and their potential use for waste water treatment to remove organic dyes.The adsorption study of the material shows that the Ce-doped Ui O-67 nanoparticles preferentially adsorb the cationic dyes such as rhodamine B and malachite green rather than the anionic dyes such as methyl orange.Adsorption capacities are 754.4,589.2 and 191.6 mg g-1 for rhodamine B,malachite green and methyl orange respectively.Based on its zeta potential and adsorption isotherm,it is understood that Ce doping increases its electrostatic interactions,and as a consequence,improves the adsorption capacity for cationic dyes.In addition,it is found that a pseudo-second-order kinetics and the Langmuir isothermal model were suitable for describing the adsorption behavior of cationic dyes onto the Ce-doped Ui O-67.2.A post-synthetic approach using nitrogen-containing substances modify Ui O-67 was proposed to enhance its adsorption for Congo red.Results showed that N was successfully incorporated into Ui O-67 frameworks to prepare of NX-Ui O-67,through coordination interaction with Zr-O clusters.Compared to parent Ui O-67,the obtained NX-Ui O-67 exhibited a significant increase in adsorption of Congo red,and the adsorption capacities for Congo red were in the following order: NU-Ui O-67(2360 mg g-1)> NT-Ui O-67(1986.3 mg g-1)> NA-Ui O-67(1493 mg g-1).Moreover,the pseudo-second-order kinetics and the Langmuir isothermal model exhibited a better fit to describe the adsorption behavior of Congo red onto the NX-Ui O-67.3.Ce-Ui O-67 was synthesized by adding cerium instead of a part of zirconium into the UIO-67 skeleton by one-step hydrothermal synthesis method,and then the synthesized material was calcined at high temperature.The synthesized materials were used as catalyst in the Fenton-like oxidation of methylene blue model reaction with H2O2 as oxidant.The experimental results of the catalyst show that the Ce-Ui O-67-400 catalyst calcined at 400℃ has a larger pore size,which is conducive to H2O2 decomposition and ·OH catalysis of methylene blue.Under the optimal conditions,methylene blue removal rate reached 94.1% within 30 min.