Novel Fenton Oxidation Process For The Degradation Of 4-nitrophenol Characterized By The Electrochemical Reduction Of Fe³⁺

The phenolic wastewater is characterized by high toxicity and difficult treatment.It is necessary to carry out safety treatment and disposal in order to avoid environmental risks.Fenton oxidation technology belonged to advanced oxidation technology can achieve good results in treating phenolic wastewater.Fenton oxidation has the advantages of rapid reaction speed,obvious effect of degrading organic pollutants and simple equipment.However,the follow-up treatment after Fenton oxidation has the disadvantage of producing large amounts of iron-containing sludge.This research will build an electro-iron-reduction Fenton oxidation system,to achieve the purpose of reducing the amount of iron-containing sludge in the Fenton reaction.The research includes three parts:?i?to explore the ideal cathode materials for investigating their ability of converting Fe³⁺to Fe²⁺,and obtain optimized reaction conditions,?ii?based on the study of reduction of Fe³⁺,an electro-iron-reduction Fenton oxidation system was developed to degrade 4-nitrophenol solution,and the effects of various factors on the degradation of pollutants were investigated.?iii?to explore the effect of electro-iron-reduction Fenton oxidation system on the degradation of 4-nitrophenol solution toxicity.The main conclusions are presented as follows.?1?Ti/SnO₂-Sb₂O₅-IrO₂ material used as anode,as the mixed electrolyte solution of Fe₂?SO₄?₃ and Na₂SO₄?0.1mol/L?as the research object,the effect of different cathode materials on the conversion of Fe³⁺was investigated.Under optimized voltage conditions,the ability of graphite cathode on conversion of Fe³⁺is stronger than Ti cathode.?2?Carbon nanotubes?CNT?used modifing graphite?GE?to prepare GE-CNT cathode.Through cyclic voltammetry scans,the GE-CNT electrode shows a clear reduction peak at cathode potential of 0.3-0.4V.This potential range is the best Fe³⁺reduction potential.Under the optimized potential,after 60min and 180min,the conversion rate of Fe³⁺by graphite cathode is 60.2%and 88.5%respectively.The conversion rate of Fe³⁺by GE-CNT cathode is 63.4%and 91.5%respectively.?3?Fe³⁺was used as a catalyst to degrade 4-nitrophenol to investigate the effect of electrochemical reduction.With the same initial 4-nitrophenol concentration,the speed of degradation of 4-nitrophenol by electro-iron-reduction Fenton oxidation was significantly faster than that of ordinary Fenton oxidation in the initial reaction stage.Showing that rapid conversion of Fe³⁺at the cathode provides more Fe²⁺for Fenton reaction procress.?4?At low dosage of Fe²⁺(40:1 molar ratio of H₂O₂ to Fe²⁺),The electro-iron-reducing Fenton oxidation method not only obtains a faster degradation speed,but also the degradation effect is also similar or slightly better than that of the ordinary Fenton oxidation.?5?The cumulative aerobic rate curve of activated sludge was used to explore the change of toxicity before and after treatment of 4-nitrophenol solution,it is shown that the toxicity of the phenol solution after electro-iron-reduction Fenton oxidation was greatly declined.The results of this research show the electro-iron-reduction Fenton oxidation system can achieve the same or even better degradation effect than the ordinary Fenton oxidation by reducing the initial iron salt dosage.Therefore,it is possible to reduce the amount of sludge produced by the Fenton oxidation process.This study has a good application prospect.