Study Of Electro-Fenton Technology Based On Membrane Electrodes In The Treatment Of Heterocyclic Compounds

Electro-Fenton（EF）technology is one of an effective and energy-saving advanced oxidation processes（AOPs）.There are still some issues including low-efficiency,automation and large-scale in the application for the treatment of refractory organic wastewater.This paper is based on the exploration of oxygen transport mechanism and the development of membrane electrode to construct a more efficient,stable and facile-operated EF system.Then,it is performed to do the research on application of the EF technology in the treatment of refractory heterocyclic compound wastewater.First,we explored the mechanism of oxygen mass transfer and introduced dimethyl siloxane（DMS）as oxygen transport layer to the EF cathode.The high oxygen-transport cathode was obtained with excellent electrocatalytic performance,the wider electrochemical working range,the more stable H₂O₂ yield and higher current efficiency.It was revealed that accelerating the oxygen transport process would prevent the"water flooding"process in the EF system,which are also mutually reinforcing.After this modification,the lifetime of cathode was prolonged10.92 times,which could provide a novel idea for the modification of the cathode materials in EF technology.Second,it was prepared a membrane anode（Ti/Ir O₂-Ta₂O₅）with superlong lifetime and acid resisting performance,which was based on titanium membrane,by the traditional process.Compared with other anodes,our anode has superior performance on electrocatalysis,stability and oxygen evolution reation（OER）,which was proper in the application of EF technology.Based on the above-mentioned anode and cathode,a novel dual-membrane homogeneous EF system was successfully constructed.We explored the effect of Ti/Ir O₂-Ta₂O₅ on the dissolved oxygen,gas generartion rate and the ration of H₂/O₂ comparing with other system.It was proved that Ti/Ir O₂-Ta₂O₅ could provide enough oxygen for cathode without aeration.In this system,the anode and cathode have the synergy to degrade tricyclazole pollutant quickly.After the parameter optimization,the best degradation,79.0%removal rate of tricyclazole（TCZ）was achieved in 20 min,which was 6.58 times higher than that in electrochemical oxidation.In the end,the electrocatalytic oxygen cycle process（EOC）between OER and oxygen reduction reaction（ORR）in the electro-Fenton system was first proposed.Third,a multilayer heterogeneous CB-PTFE/Fe₂O₃-NPs membrane electrode comprising nano Fe₂O₃ particles（Fe₂O₃-NPs）catalytic layer,carbon black-Polytetrafluoroethylene（CB-PTFE）reduction layer and PTFE protective layer was prepared.Based on the novel cathode,we also improved the above dual-membrane EF system.To our surprise,the operation of the traditional EF system including p H adjustment,extra aeration and addition of iron ions could be removed.The response surface methodology（RSM）was used to evaluate the system and optimize the parameter including p H value（A）,current density（B）,membrane flux（C）,the mass ratio of CB/Fe（D）.We obtained the FTF degradation equation:FTF_d（%）=72.02-6.99 A+4.50 B-18.90 C-4.61 D-1.89 AB-4.98 AC-1.44 AD+2.89 BC-1.21 BD+1.49 CD-26.04 A²-8.37 B²-14.80 C²-6.93 D².The model equation can accurately forecast the degradation rate of flutriafol（FTF）in this system.It was also tested on the intermediate product（Five intermediate）,toxicity of FTF degradation(EC50 from 46.92 to 168.00 mg·L^-1),which deduced the degradation process of FTF and proved the excellent catalytic performance of the system.Finally,to further strengthen the oxidation of EF technology,the part-time addition of UVC light can effectively accelerate photoelectro-Fenton（PEF）process.It was confirmed that the main functions of UVC light including the direct photocatalysis of aromatic ring compounds,photocatalysis of H₂O₂ and avoidance of·OH loss,the photocatalytic reduction of Fe（III）-carboxylic acid.The system was applied on the degradation of two kinds of BHTs,benzothiazole and 2-hydroxy-benzothiazole,which degradation process was followed by the pseudo-first order kinetic process.The optimized PEF system could obtain 98%mineralization removal of BTHs wastewater.The intermediates,five aromatic ring compounds,carboxylic acids and heteroatoms during the degradation of BTHs were studied,and the degradation pathway of BTHs was proposed.The novel EF system based on the membrane electrodes is constructed on the basis of mass transport,which is extremely simple operation,high-efficiency oxidation,economical and practical process,no secondary pollution,and has a prospect on the large-scale application.