| Water pollution in China is becoming increasingly severe in recent years. There are more and more traces of organic pollutants with biotoxicity and being stable in environment have been detected with the developing of analytical technologies. How to protect human being from polluted drinking water has drawn social attention widely. The oxidation mechanisms of polycyclic aromatic hydrocarbons (PAHs) including naphthalene(Nap), phenanthrene(Phe), pyrene(Pyr), benzo[a]pyrene(Bap) degraded in both ferrate oxidation and Cu/TiO2 photocatalytic oxidation systems have been studied, while the previous arts on removal of hint amount of organic pollutants also have been systematically reviewed in this paper. Synergy effect between ferrate oxidation and Cu/TiO2 photocatalytic oxidation has been identified, in which the separation of electron hole pair in TiO2 photocatalytic system is believed to be accelerated by the property of capturing electron of ferrate. Complete degradation of these hard-to-degrade organic pollutants with the synergetic oxidation system of ferrate and Cu/TiO2 photocatalytic oxidation has been proved, which can provide strong technical support to safely oxidize the waste water contaminated by hint amount of organic pollutants.? Ca (ClO)2 was used to prepare potassium ferrate, which is less dangerous and complicated when compared to other traditional preparation methods where chlorine is necessary as raw material in the laboratory. The yield of potassium ferrate is increased by adding cooled and saturated potassium hydroxide solution to the aqueous mixture and by filtrating impurities in batches. The yield of potassium ferrate was 50.16% and the purity was 96%.Compared with other results reported in the similar literatures, the yield and purity were in medium to high level.? CuO/TiO2 photocatalysts was prepared by the sol-gel method and the band gap of CuO/TiO2 of CuO loaded TiO2 photocatalyst is 1.51 eV. The average particle size of the catalyst was 24.25nm, absorption edge was 890nm, indicating a successful visible light modification of TiO2 photocatalyst.? The study showed that most conversion of PAHs in potassium ferrate oxidation system occurred in the first 10?20 minutes. The removal rates of naphthalene, phenanthrene, pyrene and BaP at optimized potassium ferrate dosages were 46.9%,97.9%,72.4% and 83.0% respectively. Dibutyl phthalate, Hexanedioic acid, bis(2-ethylhexyl) ester and Bis(2-ethylhexyl) phthalate were identified as intermediate products of the potassium ferrate oxidation system which were further analyzed by using GC-MS. However, PAHs is not completely converted to inorganic substances in ferrate oxidation process. Furthermore, dibutyl phthalate is identified as environmental hormone substance having great potential environmental risk. Thus, further conversion this intermediate to inorganic substance is particularly important.? The conversion rate of PAHs increased with the reaction time in the CuO/TiO2 photocatalytic oxidation system. The removal rates of naphthalene, phenanthrene, pyrene and BaP were 28.6%,13.6%,11.6% and 51.9% respectively, after 30min reaction. With further analysis using GC-MS, dibutyl phthalate, hexanedioic acid, bis(2-ethylhexyl) ester and other quinone, alderhyde and alkane substances were identified as intermediate products of CuO/TiO2 photocatalytic oxidation system. With adequate reaction time, all PAHs can be completely converted to inorganic substances.? Synergy effect was found when combining potassium ferrate and CuO/TiO2 photocatalytic synergetic oxidation system in which strong oxidation ability of potassium ferrate was believed to promote the generation of H2O2 while the increased generation of ·OH radicals was inspired by CuO/TiO2 photocatalytic. With the synergetic oxidation system of potassium ferrate and CuO/TiO2, the conversion rate of naphthalene, phenanthrene, pyrene and BaP are 52.5%,98.3%,81.6% and 92.7%, respectively, which is better than each single oxidation system. As a result, the TOC removal efficiency is also better than each single oxidation system. By tracking synergetic oxidation process, it was found that potassium ferrate oxidation was maily occurred in the first 20mins in which PAHs is quickly oxidized into intermediates. Afterwards, the intermediates were degraded by ·OH·OOH, R· radicals from CuO/TiO2 photocatalytic system and then were completely oxidized to inorganic substances. The synergetic effect is also shown in shorter reaction time and higher conversion rate, when compare to the independent oxidation systems. |
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