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Study On The Performance And Mechanism Of Peroxymonosulfate Activated By Ordered Mesoporous Metal Oxide

Posted on:2018-08-19Degree:MasterType:Thesis
Country:ChinaCandidate:S F FengFull Text:PDF
GTID:2321330518973549Subject:Civil engineering
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Nowadays,large kinds of organic pollutants were discharged into the water environment,which leads to the trace pollutants show the diversity,toxicity and durability.The long-term accumulation of organic pollutants in water environment poses a potential hazard to ecosystems and human health.Ordered mesoporous metal oxides have been prepared by nanocasting method with mesoporous materials like SBA-15 and KIT-6 as hard templates and innovatively used as peroxymonosulfate(PMS)activator for the degradation of typical organic pollutants.The structural properties were characterized by TEM,XRD,BET and XPS.The catalytic activity of ordered mesoporous metal oxides was evaluated through the establishment of reaction kinetic model and the effects of different background conditions on catalytic performance were also studied.In addition,the possible activation mechanisms of PMS by ordered mesoporous metal oxides were proposed.Finally,the stability and reusability of ordered mesoporous metal oxides was explored to illustrate the potential of practical applications.Results showed that ordered mesoporous Co3O4 fabricated using SBA-15 and KIT-6 as the hard template showed excellent catalytic performance toward PMS and the sequence of catalytic activity in PMS solution abided by the order of Co3O4-KIT6 > Co3O4-SBA15 > nanoCo3O4.The superior catalytic performance of Co3O4-KIT6 was ascribed to the combination of multiple unique characteristics,including the large specific surface area,high pore volume,high Co2+ content and high density of surface active sites.Several factors played important roles in controlling the degradation of chloramphenicol.Higher catalyst dosage,higher PMS concentration,neutral p H and higher reaction temperature favored the removal.The balance among Co2+/Co3+,O2-/O2 and PMS decomposed in solution ensured the continuous generation of hydroxyl and sulfate radicals,and the latter made the predominant contribution for the degradation of chloramphenicol.Considering its outstanding catalytic activity,excellent reusability and long-term stability,ordered mesoporous Co3O4 should be an ideal catalyst for environmental application.Fe-doped ordered mesoporous Co3O4 possessed the superparamagnetism and reduced the leaching concentrations of metal ions especially cobalt ions.In addition,ordered mesoporous structure was destroyed with the increase of Fe-doping content.Compared with ordered mesoporous Co3O4,the catalytic activity of ordered mesoporous Co3O4/CoFe2O4 in PMS solution decreased,but still superior than that of spinel CoFe2O4 and Co3O4.As the Fe-doping content increased,the catalytic activity of ordered mesoporous Co3O4/CoFe2O4 decreased.The best catalytic performance was obtained at pH 9.0.The low concentration of Cl-can inhibit the degradation of ciprofloxacin.The high concentration of Cl-accelerated the removal.Compared with Cl-,HCO3-presented the completely opposite trend on the degradation of ciprofloxacin.Ordered mesoporous Co3O4/CoFe2O4 displayed excellent stability,and can be easily separated through external magnetic field and maintain high catalytic activity.Piperazine group in the molecule of ciprofloxacin was easily attacked by SO4-·,however,the core fluoroquinolone structure in quinolone group was relatively stable.The catalytic activity of ordered mesoporous MnFe2O4 synthesized with KIT-6 as the hard template was far superior than that of spinel MnFe2O4,which can be attributed to its unique structural characteristics.Data fitting showed that the Orange ? degradation could be described by the pseudo-first-order kinetics under all conditions.Ordered mesoporous MnFe2O4 presented stable and excellent catalytic activity in wide pH range of 5~9.Both the increase of catalyst dosage and reaction temperature favored the enhancement in catalytic efficiency.However,the degradation of Orange ? tended to have a decline trend after an initial ascent as the PMS concentration increased.Ordered mesoporous MnFe2O4 was reusable over five consecutive cycles and negligible leaching of metal ions was observed during catalytic reaction.The balance among Mn2+/Mn3+,Fe2+/Fe3+ and PMS decomposed in solution was considered as the proposedactivation mechanism,and the generation of SO4-· played the dominant role in the degradation of Orange ?.
Keywords/Search Tags:ordered mesoporous metal oxides, heterogeneous activation, sulfate radicals, advanced oxidation, organic pollutants
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