Study On Conversion And Removal Characteristics Of Aromatic Hydrocarbons Oxidized By Potassium Ferrate And CuO/TiO₂

Currently, many water sources are polluted by the aromatic hydrocarbon. Althoughthe concentration of aromatic substances in the water is relatively low, the conventionalwater treatment technology could not remove these substances effectively. Due to thestable structure of benzene ring, aromatics substances would be oxidized to a series ofintermediates, which has potential environmental risk and would impact the safety ofdrinking water. The paper used homemade potassium ferrate and CuO/TiO₂as catalystto treat naphthalene, phenanthrene and pyrene in micro-polluted source water, andstudied the effect and influencing factors of different oxidation system transformation toremove aromatic hydrocarbonand in the different source water pH conditions. Thispaper also studied the products and intermediates of different oxidation system totransform and remove phenanthrene, and then explore the mechanism of differentoxidation system to remove phenanthrene. The results showed that:①Hypochlorite oxidation method could stably synthesize potassium ferratecrystals. After measuring the infrared sbsorption spectrum and UV-visible absorptionspectrum of this crystal, the purity of self-made crystals of potassium ferrate was91.81%. CuO/TiO₂photocatalysts was made by the sol-gel method, XRD and UV-Visdiffuse reflectance characterization showed that the average particle size of the catalystwas24.25nm, absorption edge was890nm, indicating that CuO/TiO₂could be activatedby visible light.②The quantitative determination of aromatic hydrocarbon in the experiment wasdone by fluorescence spectrometry, the excitation and emission wavelengths of threesubstances were: naphthalene EX/EM218/332nm, phenanthrene EX/EM250/362nm,and pyrene EX/EM238/372nm. The fluorescence intensity and the concentration of thethree substances had good linear relationship when the concentration range was5.0²50.0ug/l.③The oxidation of the three aromatic hydrocarbon by potassium ferrate wasoccurred during the first5to10minutes. With the amount of potassium ferrateincreased, the removal efficiency of the three aromatic hydrocarbon gradually enhanced.When the concentration of potassium ferrate in the reaction system was10mg/L, theremoval rate of phenanthrene reached98%, pyrene and naphthalene were84%and61%.Further increasing the dosage of potassium ferrate could not improve the removal rate significantly. The main intermediate product of phenanthrene oxidated by potassiumferrate system was9,10-phenanthrene quinine, whose percentage reached82.66%.④When using CuO/TiO₂photocatalytic system to transform and remove thearomatic hydrocarbon, the author found that with the time increased the conversion rateof three aromatic hydrocarbon increased, which indicated that aromatic hydrocarboncould be removed by CuO/TiO₂photocatalyst using long arc xenon lamp as simulatednatural light. With the increase of the amount of catalyst aromatic hydrocarbondegradation first increased and then became smooth. When the amount of CuO/TiO₂inthe reaction system was0.05g/l, the removal efficiency of naphthalene, phenanthreneand pyrene were37.16%,54.75%and44.25%. The intermediates of phenanthreneoxiedated by CuO/TiO₂photocatalytic system were nonanal, pentadecane andnonadecane, diphenyl2,2’-two formaldehyde,9,10-phenanthrenequinone andoterephthalic acid mono（2-ethylhexyl）ester. Due to the strong oxidation ability of·OHradicals, in addition to the direct oxidation products of the starting reactants, someindirect products which had different structure were also produced.⑤The removal efficiencies of naphthalene, phenanthrene and pyreneincreasedoxidated by Potassium ferrate and CuO/TiO₂photocatalyst degradation system, were4.72%,5.13%,4.57%higher than oxidated by pure potassium ferrate. But thecombination of gas chromatography mass spectrometry results showed that the twodifferent oxidation system had different oxidation intermediates. Potassium ferraterapidly oxidated phenanthrene into9,10-phenanthren equinone, and then CuO/TiO₂photocatalytic degrade the intermediates and the remaining part of the phenanthreneinto completely inorganic substance.