Performance Of Flow-Through Electro-Fenton Reactor On Basis Of Monolithic-Carbon Cathode In Degradation Of Organic Pollutants

Electro-Fenton technology can produce·OH with strong oxidation by reaction of Fe²⁺and H₂O₂ produced by cathodic oxygen reduction to degrade organic pollutants in water.In electro-Fenton reaction,the determinant of reation efficiency is the rate of H₂O₂ production.Porous carbon is currently the most selective material for H₂O₂ production.However,porous carbon is usually in the form of powder or particles,and carbon are generally pressed into an electrode after being mixed with binder,and the binder between carbon particles causes a high electrical resistivity.In addition,the pore structure of powder and particles is disordered,and even pores and pores are not connected,and the solution is difficult to diffuse into the internal pores,so only the outer surface contributes to the reaction.In order to solve the above problems,the monolithic carbon electrode is prepared by high temperature carbonization,chemical activation and alkaline thermal etching using wood blocks with natural long straight channels as raw materials,and the resistivity is low due to the carbon skeleton connection,and the long straight channel and the porosity ensure that most of the inner surface can contact the solution.On basis of this multi-channel monolithic carbon material,the following work was carried out:A monolithic porous carbon material（MPC）was obtained by carbonizing wood.In order to improve its ability to produce H₂O₂,MPC was modified by two treatment methods to regulate the surface pore structure and surface oxygen-containing groups.One was chemically activated by KOH as a chemical activator to produce pores,MPC was immersed in 3 mol/L KOH solution for 9 h,then dried,and heating treated at 800^oC for 1 h to obtain activated monolithic porous carbon（AMPC）.Another treatment was the surface oxidation for MPC,MPC was placed in 5 mol/L KOH solution and hydrothermally oxidized at 180^oC for 12 h to obtain oxidized monolithic porous carbon（OMPC）.Scanning electron microscopy,thermogravimetric analysis,specific surface area and pore structure analysis,fourier transform microscopic infrared spectroscopy,X-ray photoelectron spectroscopy were performed.The results show that MPC has rich long channel and highly hydrophilic,and the specific surface area of AMPC is higher than that of MPC,and the specific surface area of OMPC is lower than that of MPC.MPC,AMPC and OMPC are richer in oxygen-containing functional groups,and the two modification methods can increase oxygen content of carbon surface.When pH was 1 and applied voltage was-0.5 V（vs.SCE）,the concentration of H₂O₂produced by plate-type MPC and AMPC were 538μmol/L and 1.26 mmol/L,respectively,which the latter was 1.3 times higher than the former.The concentration of cylindrical MPC,AMPC and OMPC were 128μmol/L,206μmol/L and 422μmol/L at applied current of 10 mA,and OMPC exhibits better ability to produce H₂O₂.Both specific surface area and surface oxygen content play a role in the production of H₂O₂,and the surface oxygen content plays a more important role,and the activity of producing H₂O₂ is directly proportional to its surface oxygen content.The continuous flow reactor was used for the degradation pollutants.A Pt mesh was used as anode,H₂O₂ produced by OMPC as cathode reacts with the added Fe²⁺to form·OH for degrading organic pollutants.50 mmol/L Na₂SO₄ was electrolyte,and applied current was 10mA,and the main influence factor of the electro-Fenton reaction was optimized.The results showed that the optimum dosage of Fe²⁺was 0.3 mmol/L and the hydraulic retention time was100 s,and the removal rate of phenol,sulfamethoxazole and bisphenol A at an initial concentration of 10 mg/L was 74%-82%.Under the same conditions,the removal rate of homogeneous Fenton reaction was 90%.Moreover,the electro-Fenton reaction is stable and can last for at least 10 h.In summary,monolithic porous carbon has the ability to produce H₂O₂,and both activation and surface oxidation can improve the oxygen reduction ability of the carbon material.The continuous flow electro-Fenton reactor can make full use of the produced H₂O₂ to efficiently degrade pollutants by means of mass transfer.