Optimization Of Microwave Regeneration Process And Study On Regeneration Mechanism Of Waste Activated Carbon

As an excellent adsorbent,activated carbon is widely used in air purification,sewage treatment,pharmaceutical and chemical industries.In recent years,with the development of society and the improvement of the quality of life,the use of activated carbon has also increased,resulting in serious waste activated carbon pollution.China has clearly stipulated that waste activated carbon is a solid waste,which must be properly disposed of.However,the current treatment measures for waste activated carbon are not perfect,and there is still a long way to go before the recycling of waste activated carbon.Activated carbon regeneration is a clean,economical and efficient technical means,and it has an inestimable positive effect on the promotion of activated carbon application and environmental protection.In this paper,the activated carbon loaded with formaldehyde was taken as the research object,and the microwave-water vapor regeneration treatment was carried out to investigate the effects of regeneration temperature,regeneration time and water vapor flow rate on the product's Iodine adsorption value and the product's yield,to optimize the regeneration conditions and explore the regeneration mechanism.Subsequently,the waste activated carbon and the regenerated activated carbon were characterized and tested,and the adsorption performance of the regenerated activated carbon on formaldehyde was tested.First of all,the Design-Expert software was used to design the response surface methodology experiment.The optimized regeneration conditions were 20 minutes regeneration time,850 degrees Celsius regeneration temperature,and 5 grams of water vapor flow per minute.Among them,the regeneration temperature had the greatest influence,and the influence of the water vapor flow rate was the smallest.Under the optimized conditions,the iodine adsorption value of the regenerated activated carbon was 1026 mg,and the yield was 70.4 percent.Under optimized conditions,the yield of activated carbon multiple regeneration experiments were above 60 percent.The adsorption performance of the first three times regenerated activated carbons was relatively stable and slightly improved.The adsorption performance of the activated carbon began to decrease,and the degree of decline gradually decreased after several regenerated.The analysis showed that the essence of microwave-water vapor regeneration was to raise the waste activated carbon to a high temperature by microwave irradiation,so that the water vapor contacted the material and reacted under high temperature conditions,so that the waste activated carbon was regenerated.Then,Boehm titration showed that the number of various functional groups on the surface of the regenerated activated carbon increased,which was beneficial to improve the adsorption capacity.The specific surface area and pore structure analysis showed that the specific surface area of the regenerated activated carbon increased by 30 percent compared with the waste activated carbon,the pore volume increased by 48 percent,the pore size was mainly microporous and small-sized mesopores,and the number of large pores was relatively small.Scanning electron microscopy showed that there was ablation on the surface of the regenerated activated carbon,the carbon skeleton was clear,the microporous structure was abundant,and the pore opening condition was improved.Finally,the adsorption isotherm fitting analysis of the regenerated activated carbon showed that the adsorption process accorded with the Langmuir equation,which indicated that the adsorption of formaldehyde by the activated carbon belonged to monolayer adsorption.The n value of the Freundlich equation fitting result was greater than two,indicating that the chemical bond force played a major role in the adsorption process.The kinetic model fitting of formaldehyde adsorbed by regenerated activated carbon showed that the fitting curve of the quasi-second-order kinetic model could more accurately describe the experimental data points.The fitted equilibrium adsorption capacity of 4.97 mg/g was consistent with the experimentally determined formaldehyde saturated adsorption amount of 4.92 mg/g,which indicated that the adsorption of formaldehyde by activated carbon was a combination of physical adsorption and chemical adsorption.At the same time,it has also proved that the regenerated activated carbon could be used for indoor air purification,and the regeneration process was feasible.