Study On Photocatalytic Degradation Of Mycotoxin DON With Titanium-base Nanomaterials

Deoxynivalenol（DON）is a secondary metabolite produced by Fusarium graminearum and other fungi,which is widely found in wheat and other crops and their products,with strong toxicity and great harm to humans and livestock health.The existing DON reduction technology can not meet the actual demand.Titanium dioxide（TiO₂）photocatalytic degradation technology is efficient,green,low cost and mild reaction conditions,which is an ideal method for treating mycotoxins in food.Traditional TiO₂materials have a large forbidden band width,and photo-generated electrons and holes are easy to recombine,which weakens its catalytic activity and limits its practical application.In this study,the rare earth cerium（Ce）doping and semiconductor graphite carbon nitride（g-C₃N₄）compounding were used to modify TiO₂.X ray diffraction（XRD）,X ray photoelectron spectroscopy（XPS）,Transmission electron microscope（TEM）,Fourier transform infrared spectroscopy（FT-IR）,Ultraviolet-visible diffuse reflection（UV-Vis DRS）and other characterization methods were used to systematically analyze the synthesized materials.Under the irradiation of ultraviolet light,the photocatalytic degradation activity of DON of the two modified materials was evaluated,the degradation mechanism was studied,the photocatalytic degradation path of DON was deduced,and the cytotoxicity of DON degradation products was evaluated.The main research contents are as follows:（1）With tetrabutyl titanate and cerium nitrate hexahydrate as precursors,Ce-TiO₂nanomaterial with good catalytic degradation activity was successfully prepared by the sol-gel method under optimized synthesis conditions.Under ultraviolet light,DON and Rhodamine B（Rh B）were taken as target pollutants.By adjusting the initial concentration of DON solution,the dosage of catalyst and the acidity and alkalinity of the solution,the best photocatalytic degradation conditions of DON were selected,and the photocatalytic performance of 0.5Ce-TiO₂,1Ce-TiO₂,5Ce-TiO₂,10Ce-TiO₂,20Ce-TiO₂and 40Ce-TiO₂materials was evaluated.The experiment shows that 0.5Ce-TiO₂material has the best effect on degrading DON and Rh B,and the degradation rate in 240 min is above 90%.Active substance capture experiments show that holes（h⁺）and superoxide anion（·O₂^-）plays a major role.（2）With melamine and tetrabutyl titanate as precursors,the synthesis conditions were optimized,and the nano-g-C₃N₄/TiO₂heterojunction materials（0.25TCN,2TCN,3TCN and4TCN）with different proportions（0.25:1,2:1,3:1 and 4:1）were successfully prepared by the hydrothermal-calcination method.By optimizing the concentration of the reaction solution,the dosage of catalyst and the p H of the solution,the best experimental conditions of degradation were obtained.The evaluation of photocatalytic degradation performance of DON and Rh B showed that 0.25TCN composite had the best photocatalytic degradation activity,and the degradation rates of DON and Rh B reached 94%and 90%respectively after60 min of degradation,and were completely degraded at 240 min,which was higher than that of traditional TiO₂and g-C₃N₄materials.The capture experiment of active substances shows that·O₂^-and h⁺are the main active substances in the reaction,and both of them are oxidized with DON molecules to achieve the purpose of degradation.（3）Two stable intermediates produced in the photocatalytic degradation of DON by Ce-TiO₂materials were separated and analyzed by ultra-high performance liquid chromatography-quadrupole-timeofflighttandemmassspectrometer（UPLC-Q-TOF-MS/MS）,and the chemical formulas of the degradation products were estimated to be C₅H₈O₃and C₁₇H₁₈O₆,respectively.It comes from the analysis that the unstable six-membered ring intermediate formed by the C-O bond breakage at the 2nd position in DON molecular structure and the removal of the five-membered ring continues to undergo oxidation reaction,and the final degradation products are H₂O and CO₂.Human hepatoma cells（Hep G2）and porcine small intestinal epithelial cells（IPEC-J2）were selected as models,and the cytotoxicity of DON before and after degradation was evaluated by cell survival rate and ROS.The results showed that with the increase in photocatalytic degradation time,the cell survival rate increased obviously.Although the photo-catalyzed DON still has slight damage to cells,the damage degree is much lower than that of untreated DON,indicating that the toxicity of DON in the process of catalytic degradation gradually decreases.