Preparation Of Ethylenediamine Modified MIL-101 And Its Adsorption Performance On Oxytetracycline

Since the heavy production and use of antibiotic drugs have resulted in serious environmental problems,currently,researches about removing the pollutants from wastewater efficiently become a hot topic.As one of the multifunction advanced materials,metal-organic frameworks(MOFs)have captured significant focus of researchers from domestic and overseas due to the favorable attributes of extremely high apparent surface areas,tailorable hole-size and facile modification on surface for targeting desired properties.In this work,the MIL-101 material with huge porosity was tentatively employed for adsorptive removal of oxytetracycline antibiotic,finding that the material exhibited a fast adsorption behavior for oxytetracycline,while the adsorption capacity did not show expected superiority.In order to unlock the adsorption potential further,ethylenediamine was applied to decorate the adsorbent via post-synthesis modification.Results showed that the decorated MIL-101 exhibited a remarkable enhancement for oxytetracycline adsorption compared with virgin MIL-101.In this paper,primarily,MIL-101 was prepared in high-pressure autoclave with reactants including nitric acid chromium and terephthalic acid in presence of HF and deionized water as a mineralizer and solvent,respectively.The material was subsequently functionalized by ethylenediamine(ED)with the refluxe-reaction method in presence of anhydrous methylbenzene as solvent,producing the modified MIL-101(ED-MIL-101).Technologies involving XRD?SEM?FT-IR?TGA and BET were used to characterize MIL-101 and ED-MIL-101.Characterized results for MIL-101 are consistent with literatures reported,showing MIL-101 sample in this work is well-synthesized.Compared with the unmodified MIL-101,after modified,ED-MIL-101 displays a decrease in specific surface area and pore volume,and a slightly poor crystallinity while the basic framework remain integrity.To test adsorptive performance for oxytetracycline on two materials,the adsorption kinetics experiment was conducted and result revealed that ED-MIL-101 exhibited a five-fold capacity of MIL-101 for oxytetracycline capture in the same condition.Besides,adsorption data for two adsorbents can be well-fitted by Pseudo second-order model.To explore the adsorption mechanism,isotherms and thermodynamics of oxytetracycline adsorption were investigated.Results showed that Langmuir model could fit adsorption behavior well and the adsorption process is a spontaneously exothermic reaction.Experiments of pH effect on adsorption have been conducted.It has been concluded that electrification of ED-MIL-101 surface changes from positive to negative.Moreover,the adsorbent demonstrates significant capacity for oxytetracycline at the pH range from 4 to 10 and electronic interaction is involved in the adsorption process.Finally,regeneration of oxytetracycline-loaded ED-MIL-101 was studied with HCl solution and ethanol wash method under ultrasound,and the adsorbent still exhibited high adsorption capacity toward OTC after three run regeneration.