Destruction of cresols by Fenton oxidation process

The present study was used to probe the treatment of simulated wastewater containing cresols by Fenton process. Experiments were conducted in a batch reactor to examine the effects of operating variables like pH, hydrogen peroxide concentration (H2O2) and ferrous ion concentration (Fe2+) on chemical oxygen demand (COD) removal. The progress of the degradation reaction was monitored by the decrease in COD content in the treated solution. The optimal reacting conditions were experimentally determined and it was found to be [H2O2]=31.64 mM, [Fe2+]=0.90 mM for o- and p-cresol while 0.72 mM for m-cresol at pH=3.0±0.2. The degradation efficiency for cresol isomers was as high as 82% within 120 min at optimum conditions. A pseudo-first-order kinetic model was adopted to represent the Fenton oxidation for cresols. The mineralization rate for cresols obeys the following sequence: m->p->o-. Maximum degradation occurred at 30 °C for the temperature range of 20–50 °C studied. The global activation energy for the first-order reaction was estimated to be in the range of 12.90–16.25 kJ/mol. Air/nitrogen did not play an active role in completely mineralizing the organic intermediates at the experimental conditions adopted. Irrespective of the position of methyl group in o-, m- or p-position, the maximum dissolved organic carbon (DOC) removal efficiency was 42%. Only 2/5th of cresol was mineralized to CO2 by Fenton process. The results showed that the cresols were completely oxidized and degraded into lower molecular weight aliphatic acids. Among the acids, acetic and oxalic acids were identified as the major products formed during the degradation.