Regeneration by Wet Oxidation of an Activated Carbon Saturated with p-Nitrophenol

The regeneration of a commercial activated carbon (AC) was studied using the wet air oxidation (WAO) process in the temperature range 150−180 °C and an oxygen partial pressure of 0.718 MPa. p -Nitrophenol (PNF) was used as the adsorbate. First, the oxidation process of PNF was studied. In the absence of AC, it was independent of the initial concentration of PNF at the conditions used in this work. The temperature and oxygen partial pressure exerted positive effects on the oxidation process. The activation energy of the PNF oxidation process and the reaction order with respect to oxygen were 134.8 kJ mol -1 and 0.55, respectively. The desorption process of PNF from the saturated AC was studied in the aforementioned temperature range. It was found to occur during the heating period, with an equilibrium being reached. The regeneration process was studied at these same temperatures, yielding an activation energy for PNF oxidation of 99.1 kJ mol -1 . The isotherms of the virgin and regenerated AC and the phenol, methylene blue, and iodine indices indicated that the WAO regeneration produced notable modifications in the porous structure of the carbon, diminishing its adsorption capacity. Nevertheless, at a regeneration temperature of 170 °C, 80% of the adsorption capacity of AC can be recovered.