Automatic-microbial Electro-fenton Systems: Fabrication And Their Performance For Degradation Of Acid Orange 7

The degradation of ecological water quality caused by various persistent organic pollutants?POPs?has become a serious issue of global society.As an important advanced oxidation technology,the Fenton technology is widely used to degrade POPs.Microbial electric Fenton technology?MEF?is a new type of decontamination technology formed by the coupling of Fenton technology and microbial fuel cell.Because of its unique advantages such as high efficiency and environment friendly,it has been widely studied by researchers in recent years.However,for microbial electro-Fenton systems,there are still some huge challenges,such as harsh pH environment,expensive system consumables.This study will take the following two measures to solve the above problems.On the one hand,a heterogeneous iron catalyst instead of Fe²⁺will be introduced as the iron source,in that case the pH range required for the Fenton reaction could be widened.On the other hand,the configuration of the MEF will be simplified to improve the pollutant degradation efficiency,reduce the cost and facilitate the application of the MEF for practical wastewater treatment.In this thesis,we studied the construction of an automatic electrofenton system driven by transpiration and its application in the removal of refractory pollutants.An iron/carbon?Fe@KSC?Fenton air cathode with microchannel structure was prepared from plants with microchannel structure,and two kinds of automatic electro-Fenton system?AMEFS?were constructed.Driven by a transpiration process like in plant,the performance of AMEFS for degradation of persistent organic pollutants in neutral environment was studied.This study mainly contains following two parts::In the first part of this paper,a Fe@KSC material with microchannel structure was prepared by taking the natural plant kenaf stem which has intrinsic microchannel structure as the precursor,carbonizing at high temperature and introduction of iron.XRD tests show that,in the Fe@KSC prepared at temperatures of 700?,800?and900?,the Fe element was existed in states of FeO,Fe/FeO,and Fe,respectively.Electrochemical performance test results showed that the Fe@KSC-800 has the best electrocatalytic activity toward oxygen reduction reaction in neutral solution.To study the electro-Fenton behavior of Fe@KSC and test it degradation performance towards AO7,Fe@KSC was placed vertically along the axis,partially immersed in water,and partially exposed to air.The results show that Fe@KSC could degrade AO7 by electro-Fenton reaction driven by a transpiration process like in plant,the Fe-KSC-800exhibited the best degradation efficiency of AO7 at a electrode potential of-0.3 V vs.Ag/AgCl,and the degradation efficiency reached 88%at 24 h.In the second part of the paper,two-electrodes AMEFS and single-electrode AMEFS are constructed with Fe@KSC-800 electrode as air cathode.Two-electrodes AMEFS for Fe@KSC-800 as air cathode,carbon black modified stainless steel electrodes are organisms anode,the degradation performance of the AO7 under different resistances?0?,200?and 1000??conditions were compared.The results show when the external resistance is 0??short-circuit connection?,the two-electrode AMEFS obtained the best degradation of AO7.Further simplifying the configuration,a single electrode AMEFS was constructed using Fe@KSC-800 as both biological anode and air cathode,and its degradation performance of AO7 was studied.It was found that the system's degradation efficiency of pollutants was equivalent to that of a two-electrode AMEFS with short-circuit connection?98%vs.96%?,as compared to the electro-Fenton system,the degradation efficiency was improved by nearly 10%.Even when the AO7 concentration was as high as 50 mg L^-1,the degradation efficiency can also achieve about 93%.And single electrode AMEFS has good stability.After repeated testing for 6 cycles,the degradation efficiency does not decrease at all.