Improvement of (transition metal-modified) activated carbon regeneration by H₂O₂-promoted catalytic wet air oxidation

Oxidative regeneration of activated carbon (AC) exhausted with phenolic compounds is still a challenging issue due to the frequent porosity loss. Addition of low H₂O₂ amount is investigated as a way to promote catalytic wet air oxidation (CWAO) of adsorbed pollutants and thereby to recover absorbent properties. Commercial AC and transition metal (iron or copper)-modified counterparts are tested in repeated adsorption/batch peroxide-promoted CWAO of phenol. Cycles are operated in both fixed bed and slurry reactors to vary the initial pollutant distribution in between the two phases. Influence of metal location is also studied by adding iron salt to the pollutant solution prior to perform peroxide-promoted oxidation on bare carbon. Regeneration results are analyzed through a detailed analysis of both the solid and the liquid phases during the oxidative treatment. It is proved that a convenient H₂O₂ dosage can increase the lifetime of adsorbent in adsorption-oxidation cycles, but coupling with (un)supported metal oxide does not provide significant gain.