Construction Of Three-dimensional Electrolysis System With Modified Activated Carbon For The Treatment Of Cu-EDTA Containing Wastewater

The three-dimensional electrochemical oxidation method is a new advanced oxidation technology developed by adding particle electrodes in the traditional two-dimensional electrolysis system.The existence of particle electrodes in the three-dimensional electrolysis system has attracted widespread attention for several potential advantages,such as improving the low current efficiency and poor mass transfer effect of the traditional two-dimensional electrolysis system.To overcome the limitation of the pure carbonaceous materials,potassium ferrate（K₂FeO₄）was used as an iron-containing catalyst,which is loaded on the surface of activated carbon materials by means of ball mill grinding.It can endow carbon materials with a special graphitized structure and excellent electron transport capabilities after high-temperature calcination.In this paper,the K₂FeO₄/AC particle electrode was constructed to investigated the effect of Cu-EDTA treatment,and the reaction mechanism was also revealed.Through the selection of activated carbon types,acid treatment and K₂FeO₄loading methods,the best preparation method of K₂FeO₄/AC particle electrode was determined.The experimental results showed that the best preparation process of load K₂FeO₄ on the nutshell activated carbon which has been modified by hydrochloric acid by means of ball milling.The prepared K₂FeO₄/AC particle electrode had a higher removal rate of Cu（II）and COD than the original nutshell carbon particle electrode which was 12.3%and 14.0%.Compared with the original nutshell activated carbon particle electrode,the graphitization degree of the K₂FeO₄/AC particle electrode was significantly improved,and a large number of graphene nanosheets were produced on the surface.The operating conditions of the three-dimensional electrolysis system for treating Cu-EDTA containing wastewater were optimized.The experimental results showed that the optimal operating conditions for the three-dimensional electrode system to treat the Cu-EDTA concentration of 50 mg L^-1 were:current intensity of 30m A cm^-2,solution p H of 5,and Na₂SO₄ electrolyte concentration of 0.05 mmol L^-1.After 180 min treatment,the removal rate of Cu（II）and COD can reach 96.8%and92.5%,respectively.The K₂FeO₄/AC particle electrode had good stability,and the treatment effect was only reduced by 10%after 5 consecutive operations.The removal rate of Cu（II）and COD of K₂FeO₄/AC particle electrode could be recovered to 95.3%and 93.7%of the first use after hydrochloric acid regeneration treatment.The reaction process of the three-dimensional electrode system with K₂FeO₄/AC particle electrode in the treatment of Cu-EDTA containing wastewater,and the effect of the particle electrode were analyzed.The results showed that,the Cu（II）and COD removal of the three-dinemsional electrolysis system was better when compare with the two-dimensional electrode system or a solo adsorption system,and showed a significant synergistic effect on the removal of Cu（II）.Under the action of electric current,the K₂FeO₄/AC particle electrode had both indirect oxidation and direct oxidation,in which promote the production of hydroxyl radicals.The existence of K₂FeO₄/AC particle electrode also helped to accelerate the electron transfer rate and strengthen the direct oxidation ability.