Photoelectrocatalytic Degradation Of Typical Environmental Pollutants Using RGO Modified TiO₂ Nanotube Arrays

Ti O₂ nanotube arrays?TNAs?possess the advantages of steady chemical property,high specific surface area,low toxicy and high photoelectrocatalytic activity,and have been applied widely in the area of solar energy,environmental pollutant elimination,photocatalytic and photoelectrocatalytic?PEC?degradation.In this study,TNAs were modified with reduced graphene oxide and Ce O₂ and Cu₂ O,etc.The photoelectrocatalytic activity of them were investigated with TBBPA and BPA.RGOCe O₂-TNAs,RGO-Cu₂O-TNAs and RGO-Cr-TNAs were synthesized by anodic oxidation,persistent current,cyclic voltammetry and doping method.The synthesized NTAs sheets were applied in the PEC degradation of TBBPA,and different parameters that would influence the degradation efficiency were investigated.Besides,the EDTAFenton assisted PEC degradation of BPA using RGO-Ce O₂-TNAs as catalyst was also studied.The achievements were summarized as follows:?1?RGO-Ce O₂-TNAs,RGO-Cu₂O-TNAs and RGO-Cr-TNAs all possessed extraordinary PEC degradation ability towards TBBPA,and the degradation efficiency reached 84.8%,91.7% and 91.2% for them,respectively.?2?The optimal annealing temperature for Ce O₂-TNAs,TNAs and Cr-TNAs was 500? due to the fact that the appropriate propotion of rutile and anatase was achieved for catalysis at 500?.?3?The optimized pH values were pH 7,pH 5 and pH 7 for RGO-CeO₂-TNAs,RGOCu₂O-TNAs and RGO-Cr-TNAs,because the p H value could affect the dessolved state of TBBPA and the charge state of TNAs.Beside,production of the active radicals with high oxidizing ability was also affected by p H value.In Acidic condition,TBBPA was more likely to be absorbed on the films,and was more likely to react with the holes and active radicals.Besides,the active radicals were likely to be produced in acidic condition as well.Generally,the degradation process was in favor of netural or weak acidic condition.?4?In the process of PEC degradation of TBBPA using RGO-Cu₂O-TNAs,the effect of scavenger types and amounts were investigated.It was proved that 5% actone in the solution could promote the degradation process in the largest degree by inhibiting the recombination of photogenerated electrons and holes,and then improve the degradation efficiency.?5?In the process of PEC degradation of TBBPA using RGO-Cu₂O-TNAs,the intermediate products of TBBPA in the degradation process were analyzed by a high resolution mass spectrometry.It was found that in the degradation process,the hydroxyl radical?·OH?could attack and replace the Br atom on the benzene ring.Then dehydroxylation emerged and thus the debromination process was completed.Besides,the ·OH could attack the benzene on the isopropyl and replace the ring,leading to a debenzonlation process and producing phenolic compounds of bromine.Thus the TBBPA molecules were decomposited.?6?In the repeated experiments,the RGO-Ce O₂-TNAs proved nice stability in 10 cycled degradation process and the degradation ability of the material was not affected obviously.In the process of PEC degradation of TBBPA using RGO-Ce O₂-TNAs,the degradation efficiencies were in the range of 81.9-89.1%.In the process of EDTA-Fenton assisted PEC degradation of BPA,the degradation efficiencieswere in the range of 82.3-85.7%.?7?In the processof EDTA-Fenton assisted PEC degradation of BPA,besides the parameters mentioned above,the consistence of EDTA-Fenton was also investigated in detail.The consequences proved that when the concentration of Fe2+,H2O₂ and EDTA-2Na were 1m M,20 m M and 5m M separately,the degradation efficiency reached highest,twice of the efficiency without EDTA-Fenton assistance.In the degradation process,the active radicals could be aslo produced by Fe2+-EDTA and Fe3+-EDTA besides the RGO-Ce O₂-TNAs,and thus the degradation efficiency towards BPA was improved.