Photo-oxidation of phenols with ozone.

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Abstract

The aqueous-phase photo-ozonization of phenols in concentrations ranging from 800 ppm to 1500 ppm was carried out by employing two kinds of reactors, one being a bubble column and the other a stirred cell having a gas-liquid free interface. The oxidation of phenols with ozone alone was also performed for comparison.<br> The kinetic data from the stirred cell revealed that both photo-ozonization and ozonization fell into the fast pseudo-first order regime for simultaneous mass transfer and reaction. The intrinsic reaction rate constants for the degradation of various phenolic compounds were determined, based on the chemical absorption theory, from the data of the ozonizations in the bubble column over a wide range of variables.<br> Product distributions were elucidated for removal of phenol and of its primary and secondary oxidation products. The overall reaction pathway was regarded as being comprised of the two successive oxidation series, each of which produced the same smaller molecules. The pH value as well as ultraviolet light intensity exerted negligible influence on the overall reaction pathway, but they enhanced the rate of each oxidation step.<br> Ultraviolet radiation promoted remarkably the efficiency of ozone absorption in the later stage of ozonization rather than the application of higher pH.

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