Experimental Study On The Synergistic Degradation Of Low Concentration Typical VOCs By Activated Carbon Supported TiO2 Adsorption And Catalytic Oxidation

Volatile organic compounds（VOCs）have become one of the main atmospheric pollutants in China.VOCs pollution in some industries is characterized by large total emissions,wide sources,and low concentrations,posing a threat to human health and hindering sustainable economic development.Efficient and stable treatment methods are urgently needed.In response to the problems of short adsorption saturation cycles and poor load shock resistance in traditional adsorption media,this paper proposes the concept of "coupling activated carbon adsorption nano TiO₂ photocatalytic oxidation degradation and regeneration" based on the characteristics of activated carbon adsorption,TiO₂ photocatalytic oxidation,and activated carbon photocatalytic regeneration,as well as the characteristics of low concentration VOCs.This aims to achieve efficient synergistic degradation of low concentration VOCs through adsorption catalytic oxidation in the activated carbon nano TiO₂ cross-linked structure.The highly effective adsorption catalytic materials were synthesized by sol-gel method;Attempt to dope and modify the prepared adsorption catalytic materials by utilizing the transparent properties of glass microspheres;Xylene was selected as a typical VOC s waste gas for adsorption photocatalytic degradation experiments and the degradation mechanism was preliminarily analyzed;Experiments were conducted on the photocatalytic in-situ regeneration of adsorption catalytic materials and the degradation effect of regenerated adsorption photocatalytic materials.The main research content and results of this paper are as follows:1.The activated carbon and 5 A zeolite were selected as carriers,and the activated carbon TiO₂ and zeolite TiO₂ were prepared by the sol gel method.The glass beads were used to dope the two adsorption catalytic materials respectively.Through XRD,TG-DSC,SEM,BET and other characterization tests on the prepared adsorption catalytic materials,it was found that the best preparation condition was when the calcination temperature was 400℃ and the load was 20%,TiO₂ in the adsorption catalytic materials prepared under this condition mainly exists in anatase crystal form.2.The adsorption and degradation effects of activated carbon TiO₂ material and zeolite TiO₂ material on typical VOCs xylene were tested through static and dynamic experiments,respectively.The degradation and purification performance of activated carbon TiO₂ material for xylene was better than that of zeolite TiO₂ material;In the preliminary experiment of adsorption photocatalytic degradation,compared with the sum of individual adsorption and individual photocatalytic degradation efficiency,the degradation efficiency of xylene increased from 65.4%to 88.2%under conditions,demonstrating a good synergistic effect between adsorption reaction and catalytic oxidation reaction when using adsorption catalytic materials.3.Active carbon TiO₂ adsorption catalytic material was selected for dynamic experiments to study the factors affecting the adsorption photocatalytic effect.The influencing factors include catalyst dosage,light intensity,initial concentration of xylene,contact time,and number of repeated uses.The results showed that under the optimal experimental conditions of using 6g of activated carbon TiO₂ material with a load of 20%,an initial concentration of 100 mg/m3 of xylene,a light intensity of 18 W,and a contact time of 7 seconds,the reduction efficiency of xylene was 92.3%;As the number of repeated uses of activated carbon TiO₂ materials increases,the degradation efficiency of xylene decreases.After three repeated uses,the degradation efficiency of xylene decreases from 86.3%to 50.6%;It was found that hole（h+）,hydroxyl radical（·OH）and superoxide radical（·O₂-）were the main active substances involved in the degradation of xylene in the process of adsorption photocatalytic degradation of xylene.4.Conduct in-situ photocatalytic regeneration of saturated adsorption catalytic materials,and conduct xylene degradation experiments on the regenerated adsorption catalytic materials.The regeneration rates of the adsorption catalytic materials after five regenerations are 88.9%,87%,84.2%;79.8%,and 75.6%,respectively.This indicates that the regenerated adsorption catalytic materials still maintain good adsorption photocatalytic performance,making it possible to use working gaps for photocatalytic regeneration of adsorption catalytic oxidation materials.Using activated carbon TiO₂ adsorption catalytic materials regenerated under different conditions;xylene degradation experiments were conducted to investigate the effects of regeneration time,gas flow rate,particle size,light intensity,and repeated regeneration times on the material regeneration effect.The results showed that after 4 hours of regeneration,the activated carbon TiO₂ adsorption catalytic materials were basically completely regenerated,with a regeneration rate of 86.2%;The optimal photocatalytic regeneration effect is achieved with a gas flow rate of 6L/min,activated carbon particle size of 50-60 mesh,and light intensity of 18W.The regeneration rate of the adsorption catalytic material is 88.9%.