Preparation And Properties Of Photocatalytic Ethylene Scavenger Based On Preservation Of Fruits And Vegetables

Ethylene is beneficial to the growth and ripening of fruits and vegetables.Moreover,it can improve the flavor and taste of fruits and vegetables,but it will also accelerate the process of decay and deterioration,resulted in the economic losses.Therefore,reasonable control of the ethylene concentration in the packaging is significant that can extend the shelf life of fruits and vegetables effectively.In the preservation of fruits and vegetables,1-MCP or KMnO₄ is often used to remove excess ethylene in the packaging.Although those ethylene scavengers are easy to use,their performances are unstable,the reactions are irreversible,and some of them are toxicity in some way.The application of TiO₂/ACF composite photocatalytic material to the removal of ethylene in fruit and vegetable packaging can not only utilize the adsorption-photocatalytic synergistic effect to degrade ethylene efficiently,but by the virtue of the reaction characteristics of TiO₂who will react only under specific illumination conditions,it can control the removal of ethylene by light touch,reasonably regulate the ethylene concentration in the packaging and meet the ethylene concentration requirement for the preservation of fruits and vegetables in different conditions.In this paper,TiO₂ was prepared by Sol-gel method using butyl titanate as the reactor.Combined the mechanical stirring and ultrasonic cavitation technology,the prepared TiO₂powder was dispersed into aqueous solution with sodium hexametaphosphate as dispersant to prepare uniformly dispersed TiO₂ suspension.TiO₂/ACF composite photocatalytic ethylene scavengers was prepared by immersion-lifting-drying method with activated carbon fiber?ACF?as the carrier.The effect of the environmental factors and conditions to the photocatalytic degradation of ethylene by TiO₂/ACF was studie.The main research contents and results as follows:?1?Preparation of nano-TiO₂.The nano-TiO₂ was prepared by Sol-gel method in anhydrous ethanol with butyl titanate?TNB?as the precursor,and glacial acetic acid was used to slow the reaction rate.The effects of calcination temperature,deionized water and pH on the photocatalytic performance of TiO₂ were investigated by single factor experiment.The orthogonal test was used to optimize the calcination temperature,amount of deionized water,absolute ethanol and glacial acetic acid.The results showed that when the calcination temperature was 550?,the pH value was 2.5,and the volume ratio of TNB:deionized water:absolute ethanol:glacial acetic acid was 10:2.5:39:0.5,the photocatalytic performance of TiO₂was the best.?2?Preparation of TiO₂/ACF composite material.Using TiO₂ powder as raw material,deionized water as solvent,adding dispersant,utilizing mechanical stirring and ultrasonic treatment to disperse the suspension.Then making ACF as carrier,the TiO₂ was load onto ACF by immersion-lifting-drying process,referring to the powder sintering method and the fabric's padding-drying-baking process.Studied the effect of the different type and amount of dispersant,quantity ratio of TiO₂,stirring time,ultrasonic treatment time and immersion times on the photocatalytic performance of TiO₂/ACF composite material.The results show that the dispersant has an important effect on the preparation of TiO₂/ACF composite material.Combined all the preparation factors,the optimal condition was obtained.The photocatalytic performance of the prepared TiO₂/ACF is the best,as the ethylene degradation rate reach to71.62%.?3?Study on the effect of envirnmental conditions and using factors to the photocatalytic degradation of ethylene.The TiO₂/ACF composite material was applied to the photocatalytic degradation of ethylene.The effects of UV wavelength,light intensity,temperature,relative humidity,oxygen concentration and ethylene concentration on the photodegradation of ethylene by the TiO₂/ACF composite material were investigated.The results show that the shorter the wavelength of ultraviolet light,the shorter the distance of light source,the stronger the light intensity,the higher the temperature,the relative humidity,the oxygen concentration and the initial concentration of ethylene,the greater the degradation rate of ethylene.