Study On The Degradation Of Phenolic Wastewater By Electro-peroxone Technology Combined With Biological Method

A large amount of organic wastewater is generated in the process of petroleum refining and chemical industry production,in which the phenolic components are difficult to be removed by conventional biological methods.The composition of phenol containing organic wastewater is complex,toxic and harmful,which is extremely harmful to the ecological environment.In this thesis,a carbon gas diffusion electrode was used as the cathode to generate hydrogen peroxide in situ,and a boron-doped diamond electrode was used as the anode to construct electro-peroxone（EP）reaction system,which triggered the reaction of O₃and H₂O₂by external ozone to generate strong oxidizing hydroxyl radicals（·OH）.The treatment of phenol-containing wastewater was carried out by means of a electrochemical reaction device,which was designed to efficiently degrade organic pollutants and improve the biodegradability of wastewater.Firstly,the experimental results of the degradation of simulant wastewater by the EP system based on gas diffusion electrode with phenol as the target pollutant showed that the removal efficiency of phenol was95.29%～98.91%with phenol concentration of 100～300 mg/L within 60 min.With phenol concentration increase to 1000 mg/L,the amount of phenol removal reached 96.22%and the degradation rate of TOC reached 57.96%within 140 min.The phenol degradation process basically followed the pseudo first order reaction kinetics model,and the energy required to remove each gram of phenol was only 0.02 k Wh.The acute biological toxicity test showed that the biological inhibition rate of phenol solution decreased from100%to 50%.On this basis,single-factor experiments were conducted to investigate the influence of operating parameters such as current density,p H,ozone concentration,electrolyte and plate distance on the degradation effect.The comparison with the conventional ozone oxidation,hydrogen peroxide oxidation and electrochemical oxidation techniques showed that the EP system based on gas diffusion electrodes achieved a significantly improved ability to degrade phenol.The successful generation of hydroxyl radicals was directly verified by EPR tests,and the results of radical quenching tests showed that the contribution of the radical oxidation pathway to pollutant degradation was about 50%.The hydroxylation was obtained as the main pathway for phenol degradation based on the electrophilic addition law and intermediate product structure analysis,accompanied by the dehydrogenation reaction and possible oxidative carbonylation.The EP system was applied to the pretreatment process of the actual phenol-containing petrochemical wastewater that was difficult to biodegrade.Phenol was completely removed after 90 min of treatment at weak acid and weak base conditions,and the TOC mineralization rate reached 69.80%and COD degradation rate reached 67.54%within 180 min,with a significant reduction of dissolved refractory organic matter and improvement of biodegradable possibility.Finally the anaerobic biological method was used for the subsequent treatment,compared with the raw wastewater,The SCOD removal rate of the anaerobic digestion effluent was increased by 10.45%.