Degradation of Acid Organic 7 by modified coal fly ash-catalyzed Fenton-like process: kinetics and mechanism study

The H2SO4-modified coal fly ash can be reused as Fenton-like catalyst to treat organic wastewater effectively. The BET test shows that the specific surface area of the catalyst (24.4m(2)g(-1)) is smaller relatively, while the existence of Fe2O3 (5.1%, wt%) illustrates the value of H2SO4-modified coal fly ash as catalyst. The degradation of AO7 in the Fenton-like process obeys the pseudo-first-order kinetics, and the apparent activation energy, calculated by Arrhenius equation, was 19.24kJmol(-1). Under the optimal treatment condition (catalyst loading=10gL(-1), [H2O2]=15mM, pH 2.5-5.5, temperature=298K), the removal rate of AO7 is more than 95% at 60min. The catalyst can be used 6 times with the removal rate of AO7 no less than 90%. The decrease in catalytic capacity is caused by the leaching and loss of Fe element. The concentrations of other leached metallic elements are lower than the standard in China. The OH in the Fenton-like process was generated simultaneously by the homogeneous and heterogeneous catalyses, while the heterogeneous catalysis plays a more important role. The degradation path of AO7 in the Fenton-like process is analyzed and proposed as well as per the determination result of GC-MS.