Study On Photocatalytic Degradation Of Aflatoxin B1 In Peanut Oil By Nano-TiO₂ And Iodine Modified TiO₂

Abstract:Peanut oil is one of the main edible oil for Chinese residents,and the annual output is 2 million tons.Peanut is rich in fat and protein,which is popular with the people,and,with the improvement of people's living standards,the amount of peanut oil and quality requirement is also greatly improved.However,there will be some residue of aflatoxin in the production process of peanut oil,which is considererd as C lass I carcinogens,mainly attacking the liver,and destructing the body's immune system.Therefore,there exists some safety problems in the preparation process of peanut oil,and removing the aflatoxin from peanut oil to ensure food safe is currently very concerned about the issue.In practice,there are some shortcomings or deficiencies among some traditional methods of removing aflatoxin?PHysical,chemical,biological,etc.?,affecting the yield and quality of peanut oil.In recent years,nano-titanium dioxide?TiO₂?PHotocatalysis is a rapidly developed high-tech,and has effect of PHotocatalytic degradation of organic matter and disinfection,which provides a potential application prospects for removing aflatoxin from peanut oil.However,TiO₂ that has absorbed ultraviolet light energy undergoes electron transition,and an electron transfers from valence band to conduction band.The valence band leaves a positively charged hole,and the conduction band generates negatively charged electrons,both of which form electron-hole pairs with high catalytic activity.But,only when the electron hole pairs do not occur recombination,TiO₂ will show a strong redox activity.In the practical application,the electron hole pairs are prone to recombination,resulting in the short average life of the carrier and the limitedpHotocatalytic activity.The non-metallic doping of TiO₂ can reduce the recombination probability of p Hotogenerated electrons and holes,which can solve this problem effectively that is a hot issue of domestic and foreign scholars.In this study,the effects of preparation conditions and process conditions on the degradation of aflatoxin B1 in peanut oil were investigated.Iodine doping conditions?concentration of KIO₃,pH of KIO₃?on the degradation rate of aflatoxin B1 were investigated,the kinetic equation of TiO₂pHotocatalytic degradation of AFB1 was establishedand the pHotocatalytic degradation of AFB1 by TiO₂ was carried out by liquid chromatograp Hy-mass spectrometry?LC/MS?.The characterization of the prepared materials was made and combined with the kinetic equation to analyze reaction mechanism.It provided a viable,reusable method for removing aflatoxin B1?AFB1?from agricultural products.The main findings are as follows:?1?The effect of single factor on the efficiency???of photocatalytic degradation of AFB1 was studied by using TiO₂photocatalytic reaction device of independent research and development.The effect of single factor of the preparation conditions?calcination temperature,calcination time and load layer?of quartz glass tube supported TiO ₂ was studied.With the calcination temperature and the calcination time increasing,the degradation rate?of AFB1 increased first and then decreased,and the degradation rate???decreaseed with the increase of the number of loading layers.The degradation effect of TiO₂ on AFB1 reached 70.58%to the best when thepreparation conditions is 400?,3h and 1 layers,which was 14.44%higher than the lowest degradation rate??=56.44%?,indicating the degradation effect was optimal under this condition.The effects of operating conditions?light intensity,cycle speed and AFB1 initial concentration?on the photocatalytic degradation of AFB1 were studied.The results showed that the effect of light intensity and cycle speed on the photocatalytic efficiency was significant,whose degradation effect reached 70.58%at 26?mol/m²s and 800ml/min,while the AFB1 initial concentration had little effect on the efficiency?.?2?Fixing calcination conditions of TiO₂ at 400?,3h,1 layer,the relationship between the degradation rate?and the reaction time was studied to construct the kinetic equation.The results showed that the photocatalytic degradation of aflatoxin B1 was first-order kinetics.As the slope of the equation k can be seen,the greater the intensity of light,the better the degradation effect?When the light intensity was 26,24,22?mol/m²s,k was 0.01295,0.00919,0.00614?.The degradation effect at 800ml/min achieved the best;the degradation effect was not affected by initial concentration.This result was consistent with the results of the single factor experiment.?3?KIO₃ was used as iodine source to modify TiO₂?I-TiO₂?.The concentration of iodine was controlled by adjusting the concentration of KIO ₃ and the preparation of I-TiO₂was controlled by adjusting the pH of KIO₃.When the concentration of KIO₃ was0.1mol/L and the p H was 3,the photocatalytic effect was the best of 81.96%.?4?Fixingthe conditions of KIO₃ at 0.1mol/L,pH=3,the relationship between the degradation rate?and the reaction time was studied to construct the kinetic equation of the photocatalytic degradation of AFB1.The results showed that photocatalytic degradation process of AFB1 was a first-order kinetics,and the slope of the equation k was consistent with the single factor experiment:the greater the light intensity,the greater the degradation rate;the maximum degradation rate was at 800ml/min,and initial concentration had little effect on the degradation rate of AFB1 in photocatalytic reaction process.?5?The peroxide value?<6meq/kg?,acid value?about 0.7mgKOH/g?and sensory quality were not affected by the preparation conditions,operating conditions and iodine doping conditions,which were maintained in the national standard.A T-test analysis of POV and acid prices showed that the value of P was greater than 0.05,which indicated no significant difference.?6??LC/MS?was used to analyze the photocatalytic degradation of AFB1 by TiO₂and I-TiO₂.The secondary ion spectrum showed that the degradation products of the two photocatalysts both had a molecular weight of 330 and 314,and the molecular formula were C₁₇H₁₄O₇ and C₁₇H₁₄O₆,respectively.The two degradation products also appeared in pure AFB1?self-degradation products?,and they were added two H on the furan ring and a molecular H₂O,thus,decreasing the toxicity.An intermediate product also appeared in the degradation products of TiO₂ and I-TiO₂,whose molecular ion peak was 283,the formula C₁₆H₁₁O₅,the degree of unsaturation 11.5,and the molecular weight smaller than AFB1 by30,which was presumed to be-OCH₂ group on the benzene ring.The toxicity of intermediate product did not reduce,and the intermediate product would continue to be degraded as the reaction progressed.Secondly,the degradation products of I-TiO₂ was more than TiO₂,and the molecular weight is 274 and 284.The double bond of first product was opened at the end of furan ring,and the latter lost one CO from coumarin–COO.?7?The FSEM result showed that the distribution of TiO₂?400?,3h,1layer?on the quartz tube was uniform and there was no large agglomeration phenomenon,which indicated that the quartz glass tube supported TiO₂ provided maximum contact area?cylindrical glass tube?for AFB1,improving photocatalytic efficiency.?8?XRD results showed that the grain size increased gradually with the increase of calcination temperature,the diffraction peak became more and more sharp,the proportion of anatase gradually decreased,and the proportion of rutile gradually increased.At 400?,the grain size of TiO₂ was 24.958nm,and the mass fraction of a natase was 80.69%.The ratio of anatase and rutile at this temperature,the size of particle size and the surface area of crystal were suitable for the rapid photocatalytic reaction.?9?The fourpreparation materials?a:TiO₂ calcination temperature 200?,1hb:TiO₂calcination temperature 400?,3h c:iodine-modified TiO₂ concentration 0.05 mol/L,p H=3d:iodine-modified TiO₂ concentration 0.1 mol/L,pH=3?were characterized by XPS,and the result showed that the ratio of Ti⁴⁺and Ti³⁺was 7.72,and the content of hydroxyl oxygen was 52.89%.The content ofTi³⁺and hydroxyl oxygen increased in turn?a-d?.The higher the content of Ti³⁺and hydroxyl oxygen on the surface of TiO₂,the stronger the photocatalytic performance of TiO₂.?10?DRS characterization results:Compared with pure TiO₂,pH=3 and pH=7widened the absorption of TiO₂ in the visible region,and the band gap decreased.