Adsorption Mechanisms Of Tetracycline On Modified Zirconium Metal Organic Framework In Wastewater

Antibiotics are a new class of trace pollutants,which are widely used in the treatment of humans and animals,and have attracted increasing attention due to their frequent detection in environmental water in recent years.Adsorption method is one of the effective methods to remove antibiotics from water.The adsorbent is the core of the adsorption method.It is of great engineering practice significance and economic value to develop an efficient,economical and sustainable use of the adsorbent.Metal-organic frameworks（MOFs）have attracted more and more attention due to their unique pore structure,uniform pore size distribution,high specific surface area,chemical inertness and easily modified inner surface of pores.At the same time,compared with traditional adsorbents,MOFs are easy to specifically modify the properties of pollutants.Therefore,metal-organic frameworks adsorbents have become one of the significant studies in recent years.However,the reported shortcomings of MOFs such as complex synthesis steps,limited adsorption capacity,poor hydrothermal stability and low reuse efficiency limit their wide application.The development of efficient adsorbents to solve the above shortcomings will be the main direction of future adsorption technology development.In this study,a metal-organic framework adsorbent with high adsorption capacity and good hydrothermal stability was successfully prepared by solvothermal method,introducing functional groups and metal ions.The adsorption mechanism of tetracycline antibiotics was discussed through its adsorption study,which has certain guiding significance for engineering application.The main contents and conclusions of this paper are as follows:The adsorption material MN-Ui O was successfully prepared by a simple solvothermal method with Zr²⁺as the metal center,p-diamino terephthalic acid as the functional organic ligand and Mn metal ions as the introduction.The adsorption material CMN-Ui O was successfully prepared by using Zr²⁺as metal center,p-diamino terephthalic acid as functional organic ligand and introducing Ce and Mn bimetallic ions.The adsorption properties of the two materials for TC were studied.The materials were characterized by zeta potential analyzer,thermogravimetric analysis,scanning electron microscopy（SEM）,X-ray diffraction（XRD）and Fourier transform infrared spectroscopy（FT-IR）.Many characterizations show that they are octahedral structure,and have very large specific surface area and uniform particle size.At the same time,MN-Ui O and CMN-Ui O have good chemical stability and thermal stability.Through the adsorption experiment,the effects of various influencing factors（temperature,solution p H and ionic strength）on the adsorption of antibiotics by magnetic mesoporous materials were studied,and the desorption-regeneration experiment was carried out.The experimental results show that the adsorption effect of the material on TC is CMN-Ui O>MN-Ui O>Ui O-66,which is due to the different ligands of the material and the introduction of metal ions.It shows that the introduction of amino and metal ions will change the adsorption performance of the adsorbent.Langmuir model and pseudo-second-order kinetic model are suitable for adsorption isotherms and kinetics of MN-Ui O and CMN-Ui O,respectively.From the results of thermodynamic experiments,it can be seen the chemical reaction process occurred when MN-Ui O and CMN-Ui O adsorbed TC was a spontaneous endothermic process.The results showed that the adsorption capacity of MN-Ui O was the best at p H=7-8 and CMN-Ui O was the best at p H=8-9.In addition,MN-Ui O and CMN-Ui O can be effectively regenerated and reused more than five times.These results show that MN-Ui O and CMN-Ui O are promising adsorbents for removing TC in water.The possible adsorption mechanism was proposed.The-NH2 and Zr-O bonds in MN-Ui O and CMN-Ui O play an important role in TC adsorption in water.At the same time,considering the molecular structure of antibiotics,MN-Ui O and CMN-Ui O,the p H value of antibiotic solution,it can be concluded that the adsorption of TC antibiotics is a complex process.The main adsorption mechanism is electrostatic interaction.The interaction ofπ-πbond and hydrophobic interaction promote the adsorption of MN-Ui O and CMN-Ui O on TC.In addition,the adsorption efficiency of Ce and Mn bimetallic modified materials is better than that of Mn single metal modified materials,which indicates that the synergistic effect between Ce and Mn binary components may be related to the strong chemical bond force between transition metals and TC molecules,which improves the adsorption efficiency of materials.