Study On The Structure Of BNQDs/MIL-100(Fe) Photocatalyst And Its Mechanism Of Visible Light Degradation For Antibiotics

Recently,the massive production and misuse of antibiotics has led to increasing concentrations of these pollutants in the environment,especially in water.These antibiotics can cause damage to biological as well as human health.However,conventional water treatment technologies do not achieve efficient removal of antibiotics.Therefore,the search for an efficient,low-cost,and environmentally friendly treatment technology has become a major focus of attention in this field.Photocatalysis is an extremely important way to convert solar energy into chemical energy,and has been commonly and widely used in the environmental purification.Among them,metal organic frameworks（MOFs）are favored by researchers due to their controlled chemical structure and well-defined porosity.Based on these merits,in this study,the Fe based metal organic frameworks（MIL-100（Fe））were modified with boron nitride quantum dots（BNQDs）and the prepared complexes were used for the photocatalytic degradation of tetracycline hydrochloride,and the whole photocatalytic degradation process was investigated in depth as follows.（1）Considering the different adaptability of different Fe-MOFs to quantum dots.Three most widely studied Fe-MOFs were synthesized in this study.MIL-100（Fe）,which has a larger specific surface area and more suitable pore size,was selected as the negative carrier for BNQDs based on the BET test.The BNQDs with good dispersion both on the surface and inside the pores of the prepared complexes are favorable for BNQDs to enhance the light absorption capacity and improve the photocatalytic performance.（2）BNQDs/MIL-100（Fe）（MNB-X）complexes were successfully prepared by a simple hydrothermal method.After this,the structure of MNB-X was explored using several characterization methods.The crystallographic chemistry,structural features and specific surface area of the prepared MNB-X catalysts were explored using XRD,SEM,TEM and BET techniques.Also,the interfacial properties and structural features of the prepared photocatalysts were further explored using FTIR,XPS and EPR.The negative shift of 0.15-0.4 eV in Fe 2p,C 1s and O 1s binding energies in MNB-1 compared to MIL-100（Fe）was attributed to the lower binding energy due to the increased electron density of the introduced BNQDs that accelerate the transfer of photogenerated electrons.In addition,DRS tests determined the valence band structure of MNB-X.Finally,the introduction of BNQDs can effectively separate the electrons and holes generated by photoexcitation as confirmed by PL,photocurrent,and other tests,which demonstrate the excellent photocatalytic performance of the prepared complexes.（3）The photocatalytic activity of the MNB photocatalysts was investigated by visible light degradation of tetracycline hydrochloride（TC-HCl）.The results showed that the photodegradation of TC-HCl by the best performing MNB was 84.2%with an apparent rate constant of 0.02383 min^-1,which was 5.3 times higher than the MIL-100（Fe）,indicating that the introduction of BNQDs significantly improved the photocatalytic performance of MNB.In addition,the influence on pH and catalyst concentration on its performance in the whole degradation system were also investigated.The formed intermediates during the degradation of TC-HCl were measured through LC-MS/MS,which showed that the photocatalytic removal of TC-HCl did not only occur by adsorption,but actually degraded the pollutant into small molecule intermediates,water,and carbon dioxide.In addition,TOC analysis showed a strong mineralization of TC-HCl during the MNB photocatalytic process,with a TOC removal rate of 32%.The mechanism of photocatalytic degradation of TC-HCl was further explored through radical capture experiments and ESR signal testing,and the results showed that·O₂^-and h⁺generated by the MNB catalyst were the main contributors to the TC-HCl degradation system,while·OH contributed less to the degradation.The cycling experiments also showed the reusability and stability of the photocatalyst for TC-HCl degradation.This study provides new insights for the construction of reasonable complexes of MIL-100（Fe）-loaded BNQDs to obtain excellent photocatalysts and a feasible method to the preparation of QDs/MOFs for the removal of antibiotic contaminants from wastewater.