Mechanism Study On Degradation Of P-nitrophenol By Fenton Reagent

Phenolic compounds are considered as typical toxic bio-refractory pollutant which can cause considerable damage to the ecosystem and human health. The Fenton reagent that uses Fe2+to react with H2O2generate OH radicals with powerful oxidizing ability has been extensively applied for the degradation of phenolic compounds.In this thesis, the degradation of p-nitrophenol in aqueous solutions by the Fenton reagent was performed, especially specific kinetic analysis on the molar ratio of H2O2and Fe+, the change of Fe2+/Fe3+and H2O2. The research showed that p-nitrophenol degradation followed pseudo first··order kinetics and the decomposition rate of H2O2increased with Fe2+adding. When the initial concentration of Fe2+and H2O2were0.3mmol/L and3mmol/L and pH=3respectively, the degradation efficiency reached the highest around95%.The organic intermediates were qualitatively and quantitatively analyzed by GC-MS and HPLC instruments. Hydroquinone, catechol, p-benzoquinone, phenol,4-nitrocatechol,2,4-dinitrophenol,’. fumaric acid, acetic acid and oxalic acid were detected during the degradation of p-nitrophenol. Hydroquinone and4-nitrocatechol were the main products of p-nitrophenol oxidation and both reached the top around3min and then started to decrease steadily after160min of operation.Using the pulse radiolysis technology, the reactions of p-nitrophenol with OH radicals were studied originally. The results showed that a majority of OH radicals attacked the aromatic ring preferentially forming4-nitrodihydroxycyclohexadienyl radical due to its electrophilic species, while a small number of OH radicals reacted with NO2group, which accompanied by NO2group elimination forming protonated durosemiquinone under acidic conditions.