Efficiency Evaluation And Mechanism Study Of Iron Modified Materials For Catalytic Ozonation Of Antibiotics

Antibiotics are widely used in clinical treatment due to their excellent antibacterial properties.However,due to insufficient absorption and metabolism of antibiotics in animals,a large amount of antibiotics cannot be fully utilized and excreted from the body.In addition,the biological treatment process of wastewater cannot fully degrade antibiotics in the water,so some antibiotics eventually enter the environmental medium.The residual antibiotics in the environment will induce the production of antibiotic resistant genes and bacteria,posing a serious threat to human health and ecosystems.Ozonation is considered as a practical and efficient antibiotic treatment technology because of its good oxidation effect and low secondary pollution.The development of efficient catalytic materials is the key to improve the efficiency of ozonation.Research has found that doping Fe with other materials can significantly improve its catalytic ozonation performance.Therefore,this article modifies CeO2,CoFe2O4,and MCM-41 through Fe doping,and prepares three catalytic materials:Fe-CeO2,Fe2O3-CoFe2O4,and Fe-Ce-MCM-41.The catalytic performance of the materials is explored through experiments on ozonation of antibiotics,and the physicochemical properties of the materials are analyzed using relevant characterization methods.The reaction mechanism is explored through experimental and theoretical analysis.The main research content of this work is as follows:(1)Fe doped CeO2 catalytic materials were prepared by hydrothermal method and applied to the catalytic ozonation of amoxicillin(AMX).Under the optimal conditions(the initial solution pH of 7.0,FC-0.3 dosage of 0.5 g/L,O3 dosage of 4 mg/min),the AMX and TOC removal by the optimal material(FC-0.3,Fe/Ce atomic ratio of 0.3)reached 98.1%at 24 min and 55.2%at 36 min,respectively.Improved the AMX mineralization efficiency by 3.7 times.The mechanism of FC-0.3 promoting catalytic ozonation was revealed through experiments and theoretical calculations:1)Highly abundant surface-active sites(i.e.,-OH)enabled the adsorption of H2O and O3,which was favorable to the generation of reactive oxygen species(ROS)and improved the reaction probability for ROS and contaminants.2)The synergistic effect between Ce4+/Ce3+and Fe3+/Fe2+redox couples accelerated the electron transfer and formation of ROS.More than 42%of ·OH was generated in the presence of FC-0.3,and the·OH,·O2-and 1O2 were the main ROS that contributed to AMX degradation.The surface OH groups played a key role in the catalytic ozonation.The oxygen vacancies(OVs)played an important role in electron transfer,Ce and Fe were the active sites of electrons transfer following the sequence of(Ce3++Fe2+)→(Ce4++Fe3+)→(Ce3++ Fe2+)redox reaction.The degradation pathway investigation and toxicity evaluation revealed that some more toxic intermediates were generated during the ozonation process,and sufficient mineralization are required to meet safe discharge.(2)Bicrystalline mixed oxide of Fe2O3-CoFe2O4 were prepared by coprecipitation method and applied to the catalytic ozonation of ciprofloxacin hydrochloride(CIP).The experimental results showed that the optimal Fe/Co atomic ratio was 5(CoFe5Ox).Under the optimal experimental conditions(initial solution pH of 7.0,CoFe5Ox dosage of 0.4 g/L,O3 dosage of 4 mg/min),the degradation and mineralization efficiency of CIP in the CoFe5Ox/O3 system reached 98.2%at 24 min and 48.7%at 60 min,respectively.The degradation kinetic constant and the mineralization efficiency were 4.8 times and 2.8 times that of sole O3 system respectively.The mechanism of CoFe5Ox promoted catalytic ozonation was revealed through experiments and theoretical calculations:·OH,·O2-and 1O2 are the main ROS,and the contribution of·OH is greater than that of ·O2-and 1O2.Surface OH groups played a key role in the catalytic ozonation of CoFe5Ox/O3 systems.Co and Fe were active sites for electron transfer,and the synergistic effect between Co and Fe improved electron transfer and ROS formation.Co3+/CO2+and Fe3+/Fe2+cycles enhanced the catalytic ozonation performance of CoFe5Ox materials.(3)Fe and Ce doped MCM-41(Fe-Ce-MCM-41)were prepared by hydrothermal method and applied to the catalytic ozonation of tetracycline(TC).The experimental results showed that the optimal Si/Fe/Ce atomic ratio was 60/0.7/0.3.Under the optimal experimental conditions(initial solution pH of 4.5,Fe-Ce-MCM-41 dosage of 0.4 g/L,O3 dosage of 6 mg/min),the degradation and mineralization efficiency of TC in the Fe-CeMCM-41/O3 system reached 98.0%at 18 min and 66.1%60 min,respectively.The mineralization efficiency were 6.3 times that of sole O3 system.Experimental results and materials analysis revealed the mechanism of Fe-Ce-MCM-41 promoting catalytic ozonation:·OH and ·O2-were the main ROS produced during catalytic ozonation,and surface OH groups existed in the catalytic ozonation process.The coexistence of Fe and Ce significantly increases the acidity of metal modified MCM-41.The increase in the number of Lewis acid sites was conducive to the decomposition of ozone.The exposed Fe and Ce on the catalyst surface are active sites for electron transfer.The excellent adsorption of MCM-41 combined with the redox coupling of Fe3+/Fe2+and Ce4+/Ce3+promoted the catalytic performance of Fe-Ce-MCM-41.The three Fe modified materials prepared in this experiment effectively promoted the catalytic ozonation of antibiotics in water,and their respective catalytic mechanisms were systematically explored.The research results can provide theoretical reference and technical ideas for the synthesis of new high-efficiency ozonation catalysts.