The Photocatalytic Degradation Performance Of Nano-TiO₂ Photocatalytic Pervious Concrete

With the development of the automobile industry,the number of motor vehicles has increased sharply,and a large amount of automobile exhaust has been discharged into the air,causing serious urban air pollution.Currently,emissions reduction and physical adsorption are often used to reduce urban air pollution levels,but the air pollution problem is still serious.Nano-TiO₂ dioxide is a good semiconductor photocatalyst,with the advantages of low toxicity,chemical stability and strong light absorption,which can form a REDOX potential on the surface of nano-TiO₂ by absorbing photon energy to oxidize and reduce automobile exhaust into harmless substances such as water,carbon and salt.Pervious concrete has good environmental benefits and can alleviate problems such as heat island effect and surface runoff.Photocatalytic pervious concrete can effectively degrade automobile exhaust,and the photocatalytic products attached to the surface of the photocatalytic permeable concrete can be washed away by rain along the permeable concrete.The photocatalytic performance of photocatalytic pervious concrete is related to the distribution of nano-TiO₂ on the surface of photocatalytic pervious concrete.However,TiO₂is a nanometer particle,which is difficult to observe through ordinary microscopes.Field emission electron scanning microscopes,with the advantages of wide magnification range and high resolution,are often used to analyze the microscopic morphology and composition of samples.The magnification of the field emission electron scanning microscope can reach80,000 times,and the distribution of nano-TiO₂ particles on the surface of pervious concrete can be clearly observed.In addition,the reaction of photocatalytic degradation of automobile exhaust gas is incomplete,and harmful substances such as nitrous acid will be produced during the reaction.The zebrafish acute toxicity test is a method to determine the lethal toxicity of zebrafish caused by water-soluble substances.The biological toxicity of photocatalytic redox products can be evaluated through the zebrafish acute toxicity test.Based on the Science Technology Development Program of Jilin province project"Research and application of ecological green pervious pavement materials in cold region".In accordance with the requirements of photocatalytic applications,the contact area of nano-TiO₂and ultraviolet light,the microstructure of nano-TiO₂ distribution on the surface of pervious concrete,and the biological toxicity of photocatalytic degradation products were investigated.The aim is to develop an environmentally friendly photocatalytic permeable concrete that can effectively improve the urban environment.The specific work is as follows:（1）Determined the basic components of the photocatalytic pervious concrete degradation automobile exhaust performance test system.Selected a reasonable test light source,initial ventilation concentration and photocatalytic degradation test time through the experiment.Described the test operation to evaluate the photocatalytic degradation performance of the photocatalytic pervious concrete and put forward the evaluation index characterizing the photocatalytic automobile exhaust degradation.（2）The photocatalytic pervious concrete was prepared by spraying TiO₂ coating on the surface of pervious concrete.The basic conditions of the photocatalytic reaction and the light intensity for the experiment were clarified.The effect of the particle size of nano-TiO₂,the nano-TiO₂ dosage,the TiO₂ coating amount and dispersant dosage on the photocatalytic performance were studied.In addition,the solvent of the TiO₂ coating is changed to obtain better adhesion of the TiO₂ coating and improve the photocatalytic durability of the photocatalytic pervious concrete.（3）The field emission environmental scanning electron microscope was used to obtain the microscopic distribution structure of nano-TiO₂ particles on the surface of the photocatalytic pervious concrete,and the microscopic pictures obtained through the electron microscope were processed by Image-Pro Plus,and the ratio of the area of nano-TiO₂ to the area of the base material was calculated.The area ratio is used to characterize the contact area between nano-TiO₂ and ultraviolet light.Comparing the micro parameters with the macro performance,the micro parameters explain the change trend of the photocatalytic performance of the photocatalytic pervious concrete.（4）In this paper,the acute toxicity of photocatalytic pervious concrete and its photocatalytic products were investigated through alkali dissolution test and zebrafish acute toxicity test.p H value and p H value stabilization time were used as the evaluation index of alkali dissolution test to characterize the effect of photocatalytic pervious concrete and its photocatalytic products on the environmental acid-base balance.Zebrafish lethality and healthy rate were used as the evaluation index of zebrafish acute toxicity test,which characterizes the toxic effects of photocatalytic pervious concrete and its photocatalytic products on organisms and the environment.