Study On Regeneration Of Saturated Activated Carbon By Photocatalysis Coupled Three-dimensional Electrochemical Reactor

The large specific surface area and abundant pore structure of activated carbons（ACs）make it have good adsorption performance,excellent deodorization,decolorization and removal of organic pollutants.ACs have a excellent adsorption capacity for a wide variety of pollutants,however,with the accumulation of adsorbed substances,Activated carbons will reach adsorption saturation and lose their adsorption capacity for pollutants eventually,therefor,saturated ACS should be treated.The regeneration of ACs can effectively remove the pollutants adsorbed by saturated activated carbon and realize the recycling of activated carbon.Hence,The exploitation of new activated carbon regeneration technology meets the development concept of green environmental protection.The main process of the ACs regeneration is the desorption and degradation of pollutants,and the ideal state is that the adsorption capacity of ACs can be restored as well as the desorbed contaminants are degraded.In this work,according to the characteristics of electrochemical regeneration and Photocatalytic regeneration,a Photocatalytic coupled three-dimensional electrode reactor（3D-PER）was constructed.The photocatalytic regeneration technology was combined with the electrochemical regeneration technology,which is expected to achieve the regeneration of ACs and effective degradation of the desorbed contaminants.In this study,the performance of different regeneration methods of electrochemical,photocatalytic and photoelectric coupling regeneration were compared in terms of the regeneration efficiency of Phenol-saturated activated carbon,in addition,the optimal range of different influencing factors were discussed systematically on the basis of 3D-PER.The changes of the structural and chemical properties of ACs before and after regenerated were compared.According to the residual substance concentration in the regeneration process,the regeneration mechanism of saturated activated carbon by 3D-PER was demonstrated preliminarily.The experimental results are as follows:（1）The optimum conditions for the saturated ACs to be regenerated by electrochemical means are as follows:regeneration time 24 h,voltage intensity 8 V,type and concentration of electrolyte 2%Na Cl,initial p H=11,and cycle flow rate 47m L/min.Under these conditions,the regeneration efficiency of activated carbon can reach 73.38%,and the regeneration efficiency of activated carbon is just 37.43%after4 cycles.（2）The optimal conditions of photocatalytic regeneration of saturated activated carbon are as follows:regeneration time 24 h,Na₂SO₄ was used as regeneration solution with a concentration of 2%,initial p H=9,circulation rate 47 m L/min.The regeneration efficiency of activated carbon could reach 72.89%,and the regeneration efficiency of activated carbon was 49.35%after 4 times of recycling.（3）The optimum conditions for the saturated ACs to be regenerated by photoelectric oxidation coupling with electrochemical reaction are as follows:regeneration time 8h,Na Cl was used as regeneration solution with a concentration of1%,initial p H=7,cycle flow rate 47 m L/min.the regeneration efficiency of activated carbon could reach 76.54%,besides,the regeneration efficiency was still above 70%after 4 cycles.（4）Photoelectric coupling regeneration not only own higher regeneration efficiency but also lower phenol content and total organic carbon（TOC）concentration in the regenerated solution compared with electrochemical regeneration or photocatalytic regeneration.Moreover,the regeneration time of ACs could be sharply reduced from 24 h to 8 h,electrolyte concentration is decreased from 2%to 1%.The regeneration efficiency is obviously superior to the other two methods after multiple cycles.（5）The surface morphology and pore structure of ACs before and after regenerated by three different kinds of regeneration methods were characterized by SEM,XRD and BET.The results showed that both the surface area of ACs,which is regenerated by electrochemistry or photocatalysis,less than 90 m²/g.Even the hardness of activated carbon decreased as well as pore structures collapsed severely.Thus,conclusions could be drawn from the results that activated carbon which by photoelectric coupling regeneration perform the best adsorption capacity,moreover,the specific surface area and internal pore structure of ACs could maintain satisfactory stability after multiple regeneration cycles.