| In recent years,with the continuous development of the dye industry,how to treat more and more dye wastewater has become an urgent problem to be solved.Metal Organic Frameworks（MOFs）have been widely used in the field of dye wastewater treatment due to their unique advantages.However,with the structure of dyes has become more and more complex in recent years,MOFs are also facing huge challenges in the treatment of dye wastewater.Therefore,more and more researchers have improved the applicability of MOFs to treat dye wastewater through modified methods.MIL-101（Fe）has been widely used in the field of dye wastewater treatment due to its large specific surface area.It is often used as an adsorbent to treat dye wastewater through adsorption.However,its adsorption mechanism mostly relies on electrostatic action,which limits its ability to absorb dyes with the same charge.Therefore,it is very necessary to select a suitable surface modifier to modify the surface of MIL-101（Fe）,overcome the defects of MIL-101（Fe）itself,and expand its scope of application in the field of dye wastewater treatment.In this paper,the metal organic framework material MIL-101（Fe）is prepared by solvothermal method,and 3-aminopropyltriethoxysilane（APTES）is selected as the surface modifier to modify the surface of MIL-101（Fe）,denoted as NH2@MIL-101（Fe）.Then the optimal conditions for modification of APTES are determined by adsorption experiments.The experimental results show that the optimal conditions for modification are:the dosage of APTES is 6m L,the volume ratio of H2O and APTES is 0,the reaction time is 2 h,and the reaction temperature is 45℃.And under the best conditions,the adsorption rate of methylene blue by NH2@MIL-101（Fe）increased from 3.5%to 99.6%,and the adsorption rate is significantly improved.The SEM characterization results show that the morphological characteristics of NH2@MIL-101（Fe）modified by APTES does not change,and there is no structural collapse.The characterization results of fourier transform infrared spectroscopy show that the characteristic absorption peaks of MIL-101（Fe）still exist in NH2@MIL-101（Fe）,and the characteristic absorption peaks of APTES appears at the wave numbers of 3410 and 3479cm-1.It shows that APTES has been successfully grafted onto the surface of MIL-101（Fe）.X-ray diffraction characterization results show that after surface modification of MIL-101（Fe）using APTES as a surface active modifier,the characteristic peak of MIL-101（Fe）still exists in NH2@MIL-101（Fe）.The spectrum does not change,indicating that APTES is only grafted onto the surface of MIL-101（Fe）,and does not destroy the crystal structure of MIL-101（Fe）.Zeta potential characterization results show that the Zeta potential value of NH2@MIL-101（Fe）increases.This may be because the amino groups grafted to the surface of MIL-101（Fe）are protonated and exist in a positively charged form.In the aqueous solution,it is proved that APTES has been successfully grafted to the surface of MIL-101（Fe）.In the study of adsorption performance,the adsorption isotherm of methylene blue by NH2@MIL-101（Fe）conforms to the Langmuir adsorption isotherm;the results of adsorption kinetics show that the adsorption of methylene blue by NH2@MIL-101（Fe）conforms to the quasi-first order kinetic model,and the correlation coefficient is greater than 0.9;the results of adsorption thermodynamics show that the adsorption of methylene blue by NH2@MIL-101（Fe）is an endothermic,spontaneous and entropy-increasing process,and the adsorption process is chemical adsorption.The results of the adsorption characteristics study show that the increase in hydrophobicity is the main reason for the increase in the adsorption rate of NH2@MIL-101（Fe）to methylene blue.After 5 adsorption cycles and regeneration experiments,NH2@MIL-101（Fe）still maintains a high level of methylene blue.The removal rate of NH2@MIL-101（Fe）is still relatively stable after being soaked in water for 24 hours,and the structure is not damaged. |
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