Oxidation kinetics of phenol and chlorinated phenols with hydrogen peroxide in a continuous stirred tank reactor

De Avik; K. De Asim
The degradation of phenolic compounds via hydrogen peroxide (H2O2) was investigated using laboratory scale batch reactors. A bench scale continuously stirred tank reactor (CSTR) was used for characterizing the effects of varying experimental concentrations on the degradation rate of phenol as well as 2- and 4-chlorophenols. Results showed that the conversion attained within 15 minutes of reaction accounted for approximately 90% of the total conversion. The drops in pH for phenol, 2-chlorophenol and 4-chlorophenol were 6.6 to 6.38, 5.8 to 4.45 and 5.7 to 4.40 respectively. Concentration of H2O2 measured at different time intervals remained almost constant during reaction. The optimum conversion of substrates could be achieved by maintaining pH at 6.0, 4.55 and 4.5 for phenol, 2-chlorophenol and 4-chlorophenol, respectively. The conversion was amplified with increasing initial concentration of substrates and this phenomenon was observed only when the substrate to H2O2 molar ratio was kept constant. The total conversion under similar reaction conditions was comparable for all three substrates. Though the conversion was in the order of 4-chlorophenol > 2-chlorophenol > phenol, the conversion varied only within 30% for substrate initial concentration of 500 mg/L. The pH after degradation was such that it did not require neutralization for its disposal in any body of water.
Conversion; COD; Phenol; 2-chlorophenol; 4-chlorophenol; H2O2 Oxidation
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