Kinetics of microwave-enhanced oxidation of phenol by hydrogen peroxide

Abstract

Aqueous solutions of phenol were oxidized by hydrogen peroxide assisted by microwave (MW) irradiation. A simple kinetic model for the overall degradation of phenol in the presence of excess H 2 O 2 is proposed in which the degradation rate of phenol is expressed as a linear function of the concentrations of phenol and H 2 O 2 . A detailed parametric study showed that the degradation rate of phenol increased with increasing [H 2 O 2 ] until saturation was observed. Phenol degradation followed apparent zero-order kinetics under MW radiation or H 2 O 2 oxidation. However, after 90 min of irradiation, the observed kinetics shifted to pseudo first order. The overall reaction rates were significantly enhanced in the combined MW/H 2 O 2 system, mainly because microwave could accelerate H 2 O 2 to generate hydroxyl radical ( $ OH) and other reactive oxygen intermediates. The observed synergetic effects of the MW/H 2 O 2 process resulted in an increased in the net reaction rate by a factor of 5.75. When hydrogen peroxide is present in a large stoichiometric excess, the time required to achieve complete mineralization is reduced significantly.

Nanocrystalline N-DopedTiO2Powders: Mild Hydrothermal Synthesis and Photocatalytic Degradation of Phenol under Visible Light Irradiation

“…The maximum photodegradation is observed at pH = 4, and it can reach 81% after 10 h of visible light irradiation. The similar results were also reported in [40]. Figure 8 shows the zeta potential of N-doped TiO 2 in phenol aqueous solution at different pH values.…”

Microwave‐Assisted Solvothermal One‐Pot Synthesis of RuO2 Nanoparticles: First Insights of Its Activity Towards Oxygen and Chlorine Evolution Reactions

“…Particularly, this incorporation generates the oxidation of the acetaldehyde formed during the microwave irradiation, and EG excess in the precursor solution (eqs. 4 and 7) due to reactive oxygen intermediates ( 1 O 2 , HO − 2 , HO • 2 , • OH) during the disproportion of the peroxide to H 2 O and O 2 , which is enhanced at the final calcination. Additionally, the average crystallite size determination by Scherer equation was 38 nm, achieving a lower crystallite size than other synthesis method based in solvothermal method ,…”

Pentachlorophenol removal from aqueous solutions by microwave/persulfate and microwave/H2O2: a comparative kinetic study

“…MW/H 2 O 2 /TBA results show that OH 0 is activation initiator and isn’t dominant radical (its role was only 3%). Based on following equations, MW is able to dissociate H 2 O 2 to many radicals as well as OH 0 [ 6 , 28 , 38 ]. Also according to Hong et al results in MW/H 2 O 2 system, O 2 is dominant radical [ 9 ].…”