Preparation Of Cu-Fe/LDH@BiOI_1.5 And Study On The Performance Of Photocatalytic Degradation

In recent years,the contamination of antibiotics in water is very serious,which greatly affects our ecological environment and human health.Therefore,we urgently need to adopt appropriate methods to degrade antibiotics.Photocatalytic technology,as green,high-efficiency,and secondary pollution-free degradation method,is widely used by scientists.On the basis of this technology,Cu-Fe/LDH materials are selected to participate in the degradation of antibiotics,but the band gap value of Cu-Fe/LDH materials is relatively wide.And the recombination rate of photogenerated electrons is relatively high,so it needs to be modified on the basis of Cu-Fe/LDH.By doping the semiconductor material BiOI_1.5,this can not only adjust the band structure of the composite material,promote the absorption capacity of visible light,but also prolong the life of the carriers for achieve the purpose of efficiently degrading antibiotics.Therefore,the subject prepared the Cu-Fe/LDH@BiOI_1.5 composite photocatalyst by adopting the hydrothermal method,and degraded the tetracycline in the water to further determine the photocatalytic degradation ability of the composite material.Through a series of characterization methods,the mechanism of Cu-Fe/LDH@BiOI_1.5 photocatalytic performance improvement was analyzed.At the same time,to explore the practical applicability of composite materials,the article selected oxytetracycline（OTC,Oxytetracycline）,doxycycline（DOX,Doxycycline）,sulfamethoxazole（STZ,Sulfathiazole）and Sulfathiazole（SMX,Sulfamethoxazole）,which are antibiotics with high detection rate in water.With the help of HPLC-MS/MS separation and analysis method,the degradation rates of four antibiotics were explored,and the degradation mechanism of the antibiotics was inferred by monitoring the structure of the intermediate product by the mass spectrometry system.The main contents are as follows:Firstly,the article prepared a series of materials Cu-Fe/LDH,BiOI,BiOI_1.5 and Cu-Fe/LDH@BiOI_1.5.The Cu-Fe/LDH@BiOI_1.5 composite photocatalyst under the optimal conditions was prepared.The optimal conditions were finally established:the doping ratio of Cu-Fe/LDH and BiOI_1.5 was 1:10,the reaction time was 9 h,the reaction temperature was 140℃,and the p H value of the reaction solution was 7.Secondly,the degradation rate of tetracycline for the composite photocatalyst under the optimal conditions was 81%,which was much higher than that of the raw materials.Then,the article carried out a series of characterizations on the composite materials and analyzed the mechanism of enhanced catalytic activity.Through XRD,XPS,SEM and TEM characterization,the morphology and structure of BiOI_1.5,Cu-Fe/LDH and Cu-Fe/LDH@BiOI_1.5 were analyzed.The characterization of PL,ESR,UV-vis DRS,etc.explained that Cu-Fe/LDH@BiOI_1.5 has better charge transfer and separation efficiency.Then,the free radical capture experiment was carried out and the main active substances were·O₂^-and·OH,and the mechanism of the enhanced photocatalytic activity of the composite Cu-Fe/LDH@BiOI_1.5 was inferred.Thirdly,by optimizing the chromatographic and mass spectrometry conditions,a HPLC-MS/MS separation analysis and detection method was established.With this method,four antibiotics can be separated by a Sharpsil-H C₁₈ column（2.1×100 mm,3μm）.And further to judge the accuracy of the method.The results show that within the concentration range of0.01-10.0μg·m L^-1,the four antibiotics have a good linear correlation,and the linear correlation coefficient R~2 is above 0.9974.In addition,a mixed standard sample with a concentration of 1.0μg·m L^-1 was used for spike,and three mixed standard samples with a concentration of 0.1μg·m L^-1,0.5μg·m L^-1 and 5μg·m L^-1 were used as the standard sample.With the standard addition solution,the recovery rate of standard addition reached more than 90.24%.Moreover,the precision values of the four drugs are ranging from 2.00%to 3.80%,which fully shows that the error is extremely small.Based on the above results,it can be found that the method has high accuracy and can be used for the quantitative analysis of trace antibiotics in water.Finally,according to the quantitative analysis of the HPLC-MS/MS separation and analysis method,the degradation performance of the composite photocatalyst Cu-Fe/LDH@BiOI_1.5 on the four antibiotics was explored.The results showed that the degradation rates of BiOI,BiOI_1.5 and Cu-Fe/LDH@BiOI_1.5 to OTC were 41.46%,68.33%and 86.32%,respectively,and the degradation rates to DOX were 47.13%,69.28%and 87.25%,respectively.The degradation rates to SMX were 45.46%,58.31%and 89.42%,and the degradation rates to STZ were 47.18%,73.15%and 88.23%,respectively.It is confirmed that the composite photocatalyst Cu-Fe/LDH@BiOI_1.5 has the best photocatalytic performance.Finally,according to the monitoring of the antibiotic intermediate products by the mass spectrometry system,the corresponding structure was simulated,and then the degradation mechanism of the four antibiotics was inferred.