Research On Photo-electrical Process Of High-salt And Refractory Industrial Wastewater

With the rapid development of industry,the producing wastewater has become one of the major sources of pollution and difficulties for treating wastewater.The influence of pharmaceutical chemicals on public health and environment has gotten increasing concern not only due to their acute toxicity but also their genotoxicity.mutagenic effects,poor biodegradability and refractory.In fact.the conventional wastewater treatment processes,such as sedimentation,filtration,coagulation/flocculation,have insufficient efficacy in removing these pharmaceutical residues and their metabolites.Photoelectrocatalytic(PEC)technology is characterized by simple process,mild reaction conditions,fast degradation rates,wide application range and without secondary pollution.It has become one of the research hotspots of water treatment technologies and one of the most notable environmental protection technologies.In this paper,we chose antibiotics of Berberine chloride form(BCF)as the target pollutant.We started this study from three aspects:combinations of electrochemical(EC)and photocatalytic(PC),construction and performance research of two-dimensional(2-D)and three-dimensional particle electric(3-D)PEC reactor.Besides,we determined the optimum conditions and explored mechanisms of the PEC reaction.The effects of five photoelectric combinations on BCF degradation were studied,and we concluded that a synergistic effect existed between PC and EC.When the ultraviolet lamp was placed inside the reactor and belowed the reaction level under the suspension two-dimensional PEC system,the PEC activity was best.The main mechanism was considered that generate hole(h+)directly oxidized and superoxide radicals(OZ-),sulfate radical(SO4-)and hydroxyl radicals(OH)indirectly oxidized BCF.Besides,h+ and OH were the major reactive oxygen species(ROS)in the very beginning,SO4-and O2-played important roles after a period of time.We have simulated the ESR signals and the value of g was 2.0046.Six-line spectra with an intensity ratio of 1:1:1:1:1:1(hyperfine splitting constants AN=1.554mT,AH=2.306 mT),Four-line spectra with an intensity ratio of 1:2:2:1(AN=AH=1.491 mT),and three-line spectra with an intensity ratio of 1:1:1(AN= 1.479 mT,)were observed,which may be assigned to C-centered-radical,OH and DMPO(N-centered-radical).respectively.In addition,we constructed a highly efficient and stable 3-D PEC system through the Fe2O3/graphite and TiO2-coated glass bead layers.This system had an enhancedPEC ability in acid condition and even after 6 times cycle test,the system still remained excellent reusability and stability.Under the ultraviolet light irradiation,more photo-generated electrons and holes were generated of TiO2 and Fe2O3,which increased the concentration of charge carriers.The photocurrent was enhanced for using both TiO2 and Fe2O3,suggesting the using of TiO2 and Fe2O3 suppress the recombination of photogenerated electron-hole pairs.When positive bias was applied,these electrons continued to transfer from the CB of TiO2,Fe2O3 and the work electrode to counter electrode,which further increased the lifetime of the photo-charge carriers.The photo-excited electrons and holes reacted with O2 and H2O forming the O2-and OH.Meanwhile,a lot of electrons were beneficial to the reduction of Fe3+ and the Fe3+/Fe2+ cycle reaction efficiency on catalyst surface could promote the Fenton reaction,increase the amount of OH and is another responsible for the efficient mineralization of the pollutants.