Application of magnetic activated carbon as a catalyst in catalytic ozonation process (COP) for removal and mineralization of humic acid from aqueous solution

Humic acid (HA) is a natural organic matter, which is naturally present in raw water sources due to the decomposition of dead animals and plants. Therefore, the catalytic properties of a carbonaceous nanocomposite in the catalytic ozonation process (COP) of HA were investigated, and the results were compared with those obtained from the single ozonation process (SOP). Magnetic carbonaceous nanocomposite, as a novel catalyst, was applied to optimize the conditions for the removal of HA in the COP, and the influential parameters such as pH, retention time, catalyst dosage, and addition of radical scavengers were all evaluated. This is an experimental study in which the removal of HA by a COP was investigated in a cylindrical glass reactor (a useful volume of 250 mL) with a semi-continuous flow. Catalyst raw material was the granular activated carbon (GAC) that has been stabilized on Fe3O4 nanoparticles by the calcination method. The results revealed that by increasing the retention time, pH, and catalyst dosage, HA and TOC removal efficiencies by both process (SOP and COP) was increased. The highest removal efficiencies of HA and TOC in the COP process were 95% and 87.67%, respectively while their removal efficiencies in the SOP process were 76.8% and 67.1% under the conditions including pH of 9, contact time of 60 min, and HA concentrations of 15 mg/L. The highest removal of the HA by the SOP and catalyst adsorption was obtained to be 76% and 5.8% after 60 min, respectively; however, it was observed to be 95.7% in the COP, in the same contact time. The presence of tert-butanol alcohol (TBA) did not significantly affect the removal of the HA in the COP. Practically, this study revealed that the magnetically activated carbon catalyst could be potentially employed in the COP for the treatment of the water having average concentrations of HA substances.