Performance of the catalytic ozonation process with pumice in removal of humic acids from aqueous solutions

Aims: This study was conducted to evaluate the feasibility of applying pumice as a catalyst in the ozonation process for removal of humic acids from aqueous solutions. Materials and Methods: The molecular structure and chemical composition of pumice were determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD). The catalytic ozonation experiments were performed in a semi-batch reactor and the mass of ozone produced was measured by means of iodometric titration methods. Concentration changes in humic acid were determined using a spectrophotometer, at an absorption wavelength of 254 nm. To evaluate the performance of catalytic ozonation in humic acid removal, effects of different parameters including pH, contact time, pumice dosage, and t-butyl alcohol (TBA) were examined. Results: The catalytic ozonation results showed that the use of pumice as a catalyst increased the decomposition of humic acid eight times, and the removal efficiency increased as the pH changed from 4 to 12 and catalyst dosage changed from 0.25 to 10 g/l. The catalytic ozonation with considerable efficiency (90%) removed humic acid in less time (10 minutes) than the sole ozonation process (SOP). Moreover; the results indicated that the catalytic ozonation process (COP), compared to conventional SOP, was less affected by the radical scavenger. Conclusions: Due to the low cost, easy access, and remarkable performance of pumice as a catalyst, it can be used in conventional sole ozonation processes for removing organic pollutants.