| Antibiotics are a kind of pharmaceuticals that are used frequently in people's daily life.As a result of the heavy use of antibiotics,they are continuously transported to environmental media.At present,antibiotics are frequently detected in water samples of various river basins.At the same time,a large number of antibiotics in the environment can induce the emergence of resistant bacteria or resistance genes,which poses a potential threat to human health and ecological environment.Therefore,the research on the treatment of antibiotic-contaminated water has been highly concerned.Recent studies have shown that photocatalysis can degrade antibiotic organic pollutants effectively.However,the limitations of traditional inorganic semiconductor materials,such as low specific surface area,low photocatalytic activity,modified difficulties,etc.,limit further improvement of their photocatalytic performance.While emerging MOFs materials are expected to become a kind of ideal photocatalytic materials for the treatment of antibiotic wastewater because of the large specific surface area,high porosity and good tunability.Hence,this study started from the preparation of MOFs based photocatalysts with good stability,took the degradation removal of representative antibiotic pollutants in water as the application goal,first explored the water stability of MIL-68?In?-NH2 and the adsorption performance of MIL-68?In?-NH2/graphene oxide composite,then optimized the preparation methods of MIL-68?In?-NH2/graphene oxide and CdS/ZIF-8 derived porous carbon composites,and finally obtained MOFs based photocatalysts with high adsorption,high catalytic activity and good structure stability.Meanwhile,based on the systematic characterization of composite photocatalyst,the correlation between the structure and photocatalytic properties was revealed and the corresponding reaction mechanisms were also illustrated.The main research contents and conclusions are as follows:?1?The presence of water molecules was not conducive to the synthesis of MIL-68?In?-NH2.Secondly,MIL-68?In?-NH2 would undergo partial hydrolysis in acidic environment,but its acid sensitivity was lower than that of MIL-68?In?.In the acidic environment with pH 3 and 5,the specific surface area of MIL-68?In?-NH2 remained basically unchanged,while that of MIL-68?In?decreased significantly.Under strong acid environment?pH=1 and 2?,no matter it was MIL-68?In?or MIL-68?In?-NH2,both the crystallinity and specific surface areas were significantly decreased.In addition,the hydrothermal stability of both MIL-68?In?and MIL-68?In?-NH2 was poor.Under the condition of 80?hot water and12 h,the loss of specific surface area of MIL-68?In?-NH2 sample was nearly 90%,and the crystal structure of MIL-68?In?was completely destroyed.Finally,under the condition of room temperature immersion,the study showed that MIL-68?In?-NH2 had better water resistance than MIL-68?In?.According to the research,the relatively high alkalinity of MIL-68?In?-NH2 itself and the steric hindrance of ligand may be the main reasons for its good structure stability in water environment.?2?The In-MOF@GO composite was prepared by one-pot solvothermal method by combining MIL-68?In?-NH2 and graphene oxide?GO?.Studies have shown that the introduction of GO would not change the crystal structure of MIL-68?In?-NH2,but it will limit the crystal growth of MIL-68?In?-NH2,with the significantly decreasing crystal size of MIL-68?In?-NH2 in the prepared composites.In addition,studies have shown that the introduction of appropriate amount of GO could improve the porosity of materials.In the adsorption application of rhodamine B?RhB?,the adsorption process of RhB by In-MOF@GO composite conformed to the pseudo-second-order kinetic model and Langmuir isotherm model.According to the Langmuir model,the maximum adsorption capacity of In-MOF@GO for RhB was 267 mg g-1.At the same time,the study showed that the initial pH had a significant effect on the adsorption process,and at pH 6,In-MOF@GO-2 showed the best adsorption performance for RhB.In the research on the recycling utilization with ethanol as desorption agent,the adsorption performance of In-MOF@GO composite decreased slightly,but it still showed good recycling performance and structural stability.The adsorption process may mainly involve?-?interactions,electrostatic attraction and pore adsorption.This is the first attempt to combine MIL-68?In?-NH2 with GO and explore the preparation method and adsorption performance of their complex,which provides an important reference basis for the optimized preparation of MIL-68?In?-NH2/GO composite photocatalyst in the following studies.?3?Based on the previous exploration,the study prepared the graphene oxide sheet and MIL-68?In?-NH2 composite photocatalytic materials with better structure by using the simple control method of mixing metal salt and graphene oxide?GrO?sufficiently.The results showed that MIL-68?In?-NH2 crystals were grown on the graphene oxide sheet with high efficient load in the prepared MIL-68?In?-NH2/GrO composite.Moreover,the introduction of GrO promoted the increase of material porosity and a small amount of mesoporous structure was formed.At the same time,the introduction of GrO adjusted the energy band structure of the catalyst,significantly enhanced the material's absorptivity in the visible region,and thus improved the utilization rate of light energy.The results of performance tests showed that the photocatalytic degradation removal efficiency for amoxicillin by MIL-68?In?-NH2/GrO was93%after 120 min of visible light irradiation,which was much higher than the photocatalytic activity of MIL-68?In?-NH2?60%?under the same conditions.In addition,the solution pH had an important influence on the photocatalytic efficiency for amoxicillin degradation by MIL-68?In?-NH2/GrO in visible light,and the best removal performance was obtained when pH was 5.The efficient load of MOFs crystal on the graphene oxide sheet layer was achieved by using the above method.Meanwhile,the close interface contact between the graphene sheet layer and MIL-68?In?-NH2 was favorable for the transmission and separation of photogenerated electrons,which was of great significance for the improvement of the photocatalytic activity of MIL-68?In?-NH2.?4?Combining the advantages of MOFs derived porous carbon materials and inorganic semiconductors,a new kind of CdS/ZIF-8 derived porous carbon composite photocatalyst was successfully constructed.On the one hand,porous carbon material?MPC?derived from ZIF-8with a high specific surface area was used to disperse CdS particles.Meanwhile,silane coupling agent was introduced to regulate the growth of CdS in order to improve its load rate and dispersion.On the other hand,CdS nanoparticles and ZIF-8 derived porous nitrogen doped carbon materials had close interfacial contact,which was favorable for the rapid transfer of photo-generated electrons between the two components and thus effectively improved the separation efficiency of photo-generated carriers.At the same time,it is shown that a series of CdS/MPC composites prepared with different CdS loads all had high specific surface areas,and the carbon material derived from ZIF-8 was proved to be nitrogen-doped porous carbon,which has better electrical properties and would be conducive to smooth electron transfer.After CdS and ZIF-8 derived nitrogen doped porous carbon were combined,the absorptivity of the sample in the visible region was greatly enhanced.The performance test results of a series of compounds with different CdS loads showed that the visible light photocatalytic activity of the CdS/MPC composites for cephalexin was superior to the pure CdS,and the activity was optimal when the theoretical CdS load was 20wt%.At the same time,CdS/MPC composite showed good performance stability and photostability.In addition,the possible mechanism for the further improvement of photocatalytic activity of CdS was proposed,and through the free radical capture experiments,the reactive species of?OH and?O2-played an important role in the photocatalytic reaction. |
PDF Full Text Request