Trace Ce(III) boosted acidic peroxone (O3/H2O2) process for efficient water treatment: Essential role of oxalic acid complexation

The peroxone (O 3 /H 2 O 2 ) process has long suffered from inefficient performance for water decontamination at acidic pHs. Herein, we find the evident capability of trace Ce(III) to boost the acidic peroxone process. In contrast to the negligible degradation (∼6% in 60 min) of oxalic acid (OA) as a recalcitrant compound in the O 3 /H 2 O 2 system, efficient removal of OA (∼95 %) was achieved by introducing trace Ce(III) (0.30 µM). OA was identified as an effective ligand activating Ce(III) by forming the Ce(III)-OA complex, which served as the catalytic active component to accelerate the decomposition of O 3 and H 2 O 2 to produce •OH and promote the co-degradation of refractory pollutant atrazine and ibuprofen. The remarkable catalytic activity of trace Ce(III) for peroxone reaction resulted from the efficient interconversion of Ce(III/IV) relying on both the favorable electron transfer from the ternary Ce(III)-OA-hydroperoxo complex to O 3 and the rapid reduction of Ce(IV) back to Ce(III) mainly by H 2 O 2 . Furthermore, the catalytic performance of Ce(III) for peroxone process outperformed Fe(II), Cu(II), and Co(II). This study puts forward an effective method to extrapolate the applicability of the peroxone (O 3 /H 2 O 2 ) process to the acidic range and enlightens the development of Ce-catalyzed peroxone processes.