Temperature dependence of hydroxyl radical formation in the hv/Fe3+/H2O2 and Fe3+/H2O2 systems.
The thermal enhancement of the formation of *OH by the hv/Fe(III)/H2O2 system (including the Fe(III)/H2O2 system) was quantitatively investigated with reaction temperatures ranging from 25 to 50 degrees C. A temperature dependent kinetic model for the hv/Fe(III)/H2O2 system, incorporating 12 major reactions with no fitted rate constants or activation energies, was developed, and successfully explained the experimental measurements. Particularly, the thermal enhancement of Fe(OH)2+ photolysis which is the most significant step in the hv/Fe(III)/H2O2 system was effectively explained by two factors; (1) the variation of the Fe(OH)2+ concentration with temperature, and (2) the temperature dependence of the quantum yield for Fe(OH)2+ photolysis (measured activation energy=11.4 kJ mol(-1)). Although in both the hv/Fe(III)/H2O2 and Fe(III)/H2O2 systems, elevated temperatures enhanced the formation of *OH, the thermal enhancement was much higher in the dark Fe(III)/H2O2 system than the hv/Fe(III)/H2O2 system. Furthermore, it was found that the relative thermal enhancement of the formation of *OH in the presence of *OH scavengers (tert-butyl alcohol) was magnified in the Fe(III)/H2O2 system but was not in the hv/Fe(III)/H2O2 system.
School of Chemical Engineering, College of Engineering, Seoul National University, San 56-1, Sillim-dong, Gwanak-gu, Seoul 151-742, South Korea.
Changha
C
Lee
Jeyong
J
Yoon
D002851:Chromatography, High Pressure Liquid; D006861:Hydrogen Peroxide / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D010782:Photolysis; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
C045076:Fenton's reagent; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; D007501:Iron