Optimized CWPO phenol oxidation in CSTR reactor catalyzed by Al/Fe-PILC from concentrated precursors at circumneutral pH

The catalytic wet hydrogen peroxide oxidation of phenol catalyzed by an Al/Fe-PILC clay catalyst has been optimized in CSTR reactor. In order to get it more cost-effective, the process was optimized by simultaneous maximization of pollutant's degradation and mineralization, whereas minimizing H2O2 consumption under very mild conditions of the covariates pH (4.5-11.3), temperature (5.0-25.9 °C) and input concentrations of phenol ranging 8.45-33.1 mg C/dm3 (expressed as TOC concentration); such a set of conditions resembled those typical in surface waters. A central composite statistical experimental design was developed, followed by optimization via response surface methodology with H2O2 dose (50.0-146.5% of the stoichiometric required for full oxidation) and catalyst concentration (0.5-3.0 g/dm3) as experimental factors. Covariate's analysis showed that input TOC concentration and temperature were the most influencing ones, whereas pH did not result significant on any of the recorded responses within the assessed range (4.5-11.3). Optimal multi-response performance was achieved (65% of phenol degradation and 31% of TOC removal; 650 mg H2O2/dm3 in output stream) under stationary state with residence time of 135 min, room temperature (18 ± 1.0 °C) and neutral pH by using 1.77 g/dm3 of the clay-catalyst and tiny stoichiometric excess of the oxidizing agent (108% of the stoichiometric dose).