Study On Degradarion Of Phenolic Wastewater By Electrochemical Coupled Advanced Oxidation Process

The treatment of refractory organic pollutants through advanced oxidation processes（AOPs）to avoid their potential environmental risks has received widespread attention.As an efficient and clean oxidant,hydrogen peroxide（H₂O₂）has been widely used in AOPs.In H₂O₂ based AOPs,strong oxidizing hydroxyl radicals（·OH）generated by media play an important role in the treatment of organic pollutants.In situ electrochemical oxygen reduction reaction to synthesize H₂O₂ is a green and convenient production method,and avoids the dangers of H₂O₂ storage and transportation,so it is very ideal.Compared to traditional aeration methods,gas diffusion electrodes（GDEs）are currently ideal electrode devices for electrochemical reactions involving gases.For electrochemical coupled degradation technology,its matching is an important issue.In order to construct an integrated technology of catalyst material,electrode,and degradation electrochemistry,a carbon-cloth based gas diffusion electrode was prepared using modified Ketjin black as a 2e^-ORR catalyst and polyvinylidene fluoride（PVDF）as a binder for the electrosynthesis of H₂O₂.Furthermore,phenol was used as the target for the degradation of organic compounds,and electrochemical coupling Fenton technology and Peroxone technology were constructed for acidic and alkaline environments to explore the degradation process.First of all,common carbon black was screened and selected to have excellent ORR catalytic performance and 2e^-selectivity.Through a simple and rapid acidification and oxidation process,the oxidation degree of Ketjin black was adjusted by adjusting time and temperature.Electrochemical tests were conducted on a series of samples.The results showed that the acidified Ketjin black（AFK）exhibited excellent ORR catalytic performance and 2e^-selectivity.The optimal sample E_onset increased by 110 m V,and the H₂O₂ yield was above95%,The delocalization strength and range of electrons on the surface of carbon materials with different oxygen containing functional groups were calculated by DFT,and it was found that the three configurations of epoxide was the optimal active center configurations for ORR two electrons.Secondly,gas diffusion electrodes（named AFK-GDE and K-GDE,respectively）were assembled using Ketjin black and acidified oxidized Ketjin black as catalysts and PVDF as adhesives.The electrosynthetic H₂O₂ test was conducted on it.At 1,5,10,20,and 30 m A cm^-2,the H₂O₂ production of AFK-GDE as the cathode increased by 27.03%,22.03%,14.13%,10.34%,and 7.52%at 10 minutes,and at 1 m A cm^-2,AFK-GDE had a lower cell voltage.The effect of different anodes on the production of H₂O₂ was further explored.The oxygen evolution potential of BDD electrode is much higher than that of Ti/Ru O₂-Ir O₂electrode,so using BDD as anode has higher hydrogen peroxide production.Following a life test,AFK-GDE was able to operate stably for 192 hours,with tank pressure fluctuating around 3.9 V,H₂O₂ production maintained at around400 mg dm^-3,and current efficiency stabilized at around 80%.AFK-GDE has good long-term stability and high current efficiency within 192 hours.The AFK-GDE after operation was characterized and remained basically unchanged,further demonstrating the stability of the electrode.AFK-GDE was further amplified to prepare a 10 cm×10 cm sized electrode and tested for electrosynthesis of H₂O₂.Finally,using AFK-GDE as a cathode to generate H₂O₂ in situ,electrochemical coupled induced Fenton technology and Peroxone technology were constructed for acidic and alkaline wastewater,and degradation experiments were conducted with phenol as the target degradation product.For phenol solution with an initial COD of 420 mg dm^-3（p H=3）,induced electro-Fenton technology can achieve complete degradation in 60 minutes,which is1.56 and 1.88 times faster than traditional electro-Fenton and packed electro-Fenton under the same conditions,respectively.For a phenol solution with an initial COD of 450 mg dm^-3（p H=11）,the electro-Peroxone technology can achieve complete degradation within 60 min.The kinetic rates of the electrochemical coupled induced Fenton technique and the Peroxone technique under the optimal degradation conditions investigated were 8.49×10^-4and 9.24×10^-4 s^-1,respectively.The electric energy consumption of the two technologies was further calculated as 12.07 and 2.28 W h g_COD^-1,respectively.Finally,a degradation experiment was conducted for actual petrochemical wastewater,with an initial COD of up to 11857 mg dm^-3.The wastewater was degraded using an electrochemically coupled deodorization technology suitable for the p H of the wastewater,and the degradation was complete within 12 h.