Study On Electrochemical Regeneration Of Waste Activated Carbon And Its Safety Evaluation

Activated carbon is an excellent adsorbent,which is widely used in chemical industry,medical treatment,environmental protection and other fields,especially in water treatment.The use of activated carbon,such as solid waste,can cause waste of resources while polluting the environment.Although the traditional pyrolysis regeneration has high regeneration efficiency,the carbon matrix loss is serious and energy consumption is high.Therefore,searching for low temperature and high efficiency regeneration technology has become an urgent problem in the field of activated carbon regeneration.In this paper,electrochemical anodization is used to regenerate 2,4-dinitrotoluene-saturated activated carbon,which not only provides basic data for further research on electrochemical regeneration of activated carbon,but also opens up a new way for the regeneration process of activated carbon.Taking columnar activated carbon as the research object and 2,4-dinitrotoluene as the adsorbate,the electrochemical regeneration of activated carbon was carried out.The main contents of the research are as follows:adsorption properties of activated carbon,including adsorption isotherms and adsorption kinetics curve and calculation of adsorption performance parameters;electrochemical regeneration efficiency studies,including factors affecting regeneration efficiency:determination of electrolyte concentration,current density,regeneration time,pH,etc.;studies on the evolution of microstructure during electrochemical regeneration,including elemental analysis,micro-morphology and energy spectrum analysis,specific surface area and pore size analysis,X-ray diffraction analysis,infrared spectroscopy analysis,thermogravimetric analysis;The electrochemical properties of activated carbon were correlated by impedance spectroscopy.The main conclusions are as follows:(1)The quasi-secondary kinetic model can well fit the adsorption kinetics of2,4-dinitrotoluene on activated carbon;the adsorption isotherm of activated carbon accords with the Freundlich model;The calculation of thermodynamic parameters indicates that the adsorption reaction is a spontaneous and endothermic process;the process is dominated by physical adsorption,and is controlled by the external diffusion of particles and the process of intragranular diffusion.The external diffusion of particles is the main control step of the adsorption process.(2)Under the optimal conditions of considering the regeneration effect and reducing the energy consumption,under the optimal conditions of electrochemical regeneration of activated carbon:current density is 20mA/cm~2,pH is 5,electrolyte solution is 15g/L NaCl solution,regeneration time is 2h and the regeneration rate can reach 100%.(3)The microstructure analysis of activated carbon showed that after electrochemical regeneration of activated carbon,the number of pore shapes increased slightly,the average pore size increased slightly,and the specific surface area increased from the original484.132m~2/g to 572.289 m~2/g.The order degree and lamellar diameter of the microcrystalline layer become larger and the graphitization degree of activated carbon increases.The amount of carbonyl,carboxyl,ether or ester groups on the surface of activated carbon increased after regeneration.Thermogravimetric analysis showed that the adsorbent adsorbed on activated carbon was desorbed during electrolysis,and the activity was realized.Carbon regeneration.(4)After regeneration,the arc radius of the impedance spectrum of the regenerated activated carbon becomes larger and the contact resistance of the electrode increases.