Preparation Of TiO₂/Bi₂WO₆ Photocatalyst And Study On Its Degradation Of Patulin In Apple Juice

Agricultural products were susceptible to fungal infection and retained mycotoxins during planting,storing and processing,which seriously threaten food safety and human health.Therefore,it was urgent to carry out research on effective removal technology of related mycotoxins.Due to its unique characteristics and high efficiency of non-thermal processing technology,photocatalysis technology had gradually become one of the research hotspots of mycotoxin detoxification technology.In this study,PAT,a common harmful pollutant in fruit and vegetable products,is taken as an example to investigate the effect of Bi₂WO₆and TiO₂on the degradation efficiency of PAT,afterwords,the composite catalyst is characterized.Afterwards,it was applied to apple juice to study the effects of catalyst concentration,UV power,reaction temperature and initial toxin concentration on the photocatalytic degradation of PAT and fit the degradation data onto a first-order kinetic equation.Finally,the quality difference and safety of apple juice before and after photocatalytic treatment were investigated.Specific research content and conclusions are as follows:1.Preparation and characterization of TiO₂/Bi₂WO₆composite catalyst.Using a one-pot hydrothermal method to prepare the composite catalyst,we determined the optimal preparation process of the catalyst.Combined with the results of SEM,XRD,XPS,BET,FT-IR,UV-Vis,and PL,to analyze the microscopic reasons for the improvement of photocatalytic performance after the combination of the two:a hetero-junction structure was formed into the two catalysts,which improved the aggregation phenomenon of the catalysts,with slight changes in their surface chemical states;Compared to TiO₂,the absorption spectrum of TiO₂/Bi₂WO₆underwent a red shift;Compared to Bi₂WO₆,TiO₂/Bi₂WO₆had a larger specific surface area;The PL spectrum indicated that the carrier recombination rate of TiO₂/Bi₂WO₆was lower than that of the two monomer photocatalysts.Cyclic experiments had shown that after four recycling cycles,the degradation rate of the composite catalyst for PAT could still attain 91.5%,it had excellent recyclability and stability.2.Process optimization of TiO₂/Bi₂WO₆degradation of PAT in apple juice.The results showed that the optimal degradation process of PAT was:catalyst concentration 1.0 g/kg,UV power 4 w,reaction temperature 25℃.According to the orthogonal test results,the influence of UV power,reaction temperature,and catalyst concentration on the degradation effect of PAT gradually decreased.3.Kinetic study of photocatalytic degradation of PAT in apple juice.The reaction rate constants and half-lives obtained from fitting the first-order kinetic equations suggest that,catalyst concentration and initial toxin concentration first increased the reaction rate and then decreased it,however,the reaction temperature and the UV lamp power were directly proportional to the degradation rate.Finally,the total reaction rate equation was obtained comprehensively considering the fitting results of the data:K=6.0014×10-4C10.1730P1.8422T’0.2246C20.2891.4.Effect of photocatalytic degradation of PAT on apple juice quality.To investigate the effects of photocatalytic treatment on sensory indicators,physical and chemical indicators,and nutritional indicators of apple juice under optimal process conditions.Result represented:photocatalytic treatment had little effect on the mouthfeel of apple juice（p≥0.05）,however,30 min photocatalytic treatment can significantly affect the smell of apple juice（p<0.05）;photocatalytic treatment could improve the color index of apple juice（p<0.05）,the browning index and turbidity of apple juice both decreased significantly,the physicochemical indexes（p≥0.05）,but the titratable acid content and solid acid ratio changed significantly（p<0.05）;for the nutritional quality of apple juice,photocatalytic treatment did not significantly affect the total phenolic content,total sugar content,and DPPH radical scavenging capacity（p≥0.05）,but the total flavonoids content of apple juice was decreased by 8.71%（p<0.05）.5.Safety evaluation of photocatalyst and apple juice after photocatalytic treatment.TiO₂/Bi₂WO₆,Bi₂WO₆and photo-catalyzed apple juice were used to infect Hep G2 cells,and their cytotoxicity to Hep G2 cells was investigated in vitro.The results were shown as follows:with the increase of pholocatalyst concentrations,the growth rate and survival rate of Hep G2cells decreased gradually,increased the cell membrane damage,and the intracellular Ca²⁺concentration also abnormally increased,but for experimental group with catalyst concentration lower than 10μg/kg,the effect of these two catalysts on cells was relatively small,indicating that both catalysts had good biocompatibility;For positive apple juice,the photocatalytic treatment after 60 min had less effect on the proliferation rate of the cell,the integrity of the cell membrane,and the increase of the intracellular Ca²⁺concentration,the photocatalytic treatment significantly reduced the toxicity of apple juice.