Reaction of Ozone with Hydrogen Peroxide (Peroxone Process) : A Revision of Current Mechanistic Concepts Based on Thermokinetic and Quantum-Chemical Considerations

• The reaction of ozone with the anion of H2O2 (peroxone process) gives rise to (OH)-O-center dot radicals (Staehelin, J.; Hoigne, J. Environ. Sci. Technol. 1982, 16, 676-681). Thermokinetic considerations now suggest that the electron transfer originally assumed as the first step has to be replaced by the formation of an adduct, HO2- + O-3 -> HO5- (Delta G degrees = -39.8 kJ mol(-1)). This decomposes into HO2 center dot and O-3(center dot-) (Delta G degrees = 13.2 kJ mol(-1)). HO2 center dot is in equilibrium with O-2(center dot-) + H+ and O-2(center dot-) undergoes electron transfer to O-3 giving rise to further O-3(center dot-). The decay of O-3 into (OH)-O-center dot is now discussed on the basis of the equilibria O-3(center dot-) reversible arrow O-2 + O center dot- and O center dot- + H2O reversible arrow (OH)-O-center dot + OH-, excluding HO3 center dot as the intermediate originally assumed. To account for the observation of the peroxone process being only 50% efficient, the decay of HO5- into 2 O-2 + OH- (Delta G degrees = -197 kJ mol(-1)) is proposed to compete with the decay into HO2 center dot; and O-3(center dot-).

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

ADVANCED OXIDATION PROCESSES

HYDROXYL RADICALS

PULSE-RADIOLYSIS

KINETICS

WATER

DECOMPOSITION

OZONATION

BROMIDE

DENSITY

IONS

Chemistry

Kemi

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