Preparation Of Enzymatic-Photo Integrated Nanocatalyst And Its Application In Degradation Of Organophosphorus Pesticides

As a representative of complex pollutants,organophosphorus pesticides are widely distributed in the environment and seriously harmful to the environment and human health.The traditional degradation method is difficult to completely degrade the complex pollutants and its reaction condition is usually harsh.As a typical representative of green sustainable catalysis,enzymatic catalysis and photocatalysis have received more and more attention recently.However,the shortcomings of biological enzymes and common photocatalysts are limitted application for their high cost,difficult recycle and the poor degradation of complex pollutants.In this subject,we are aimed to design an enzymatic-photo integrated nanocatalyst which combined a stable and biocompatible photocatalytic carrier and organic phosphorus hydrolase(OPH).The enzymatic-photo integrated nanocatalyst degrade the organic phosphorus under mild conditions.The main research contents are as follows:Flower-like BiOBr microspheres were prepared by a hydrothermal method,we use bismuth nitrate pentahydrate and hexadecyltrimethylimidazole bromide(C16MIMBr)as precursors.The prepared flower-like BiOBr microspheres are uniformly dispersed,with a particle size of about 2 to 3?m,which is self-assembled by the 2D sheet of BiOBr.The specific surface area is 29.01 m²/g and the average pore size is 8.29 nm.The organic phosphorus hydrolase(OPH)and flower-like BiOBr microspheres were immobilized by physical adsorption.The immobilization conditions were:immobilized in a Tris-HCl buffer solution(p H=8)at 170 rpm for 60 min at room temperature,and the amount of immobilized protein was 44.96 mg/gsupport,and the specific enzymatic activity was 230.1 U/g.The obtained OPH@BiOBr enzymatic-photo integrated nano-catalyst was used to cascade degrade organophosphorus pesticides.Under the visible light,methyl parathion was completely degraded in 1.5 h,and the intermediate product(p-NP)was degraded to 81%within 3 h.The obtained OPH@BiOBr enzymatic-photo integrated nanocatalyst possessed a good reusability.Hollow TiO₂(H-TiO₂)was prepared by using the wrinkled SiO₂ nanoflower as a template,the TiO₂ spherical shell layer was uniformly coated on the SiO₂ nanoflower core,then the template was selective etched.The gold nanoparticles(3 to 5 nm)were loaded on the H-TiO₂ surface.Au-H-TiO₂ is uniformly dispersed which is hollow shell microsphere with a particle size of about 360 nm,its specific surface area is 226.19 m²/g and average pore size is 11.70 nm.Through the preparation of hollow structures and metal doping,the effective use of visible light by TiO₂ is achieved,and large surface defects are conducive to the excitation and transfer of photogenerated electron-hole pairs.And the internal hollow structure of the carrier is conducive to multiple absorption of light.The large surface area and suitable pore size are conducive for the immobilization of OPH enzyme molecules and provide a large number of adsorption sites for enzyme molecules.Adsorption methods are used to combine them with OPH enzyme molecules OPH@Au-H-TiO₂ enzymatic-photo integrated nanocatalyst was prepared by immobilization.After shaking at 170 rpm for 90 min at room temperature,the maximum amount of immobilized protein was 160.15 mg/g_support,and the specific enzymatic activity was 528.49 U/g.Cascade degradation of methyl parathion under visible light,the degradation rate can reach 100%in 30 minutes.After 2.5 h,82.64%of the p-NP was degraded.After reuse 4 times,the degradation activity of OPH@Au-H-TiO₂enzymatic-photo integrated nanocatalyst for methyl parathion was kept at 75%.