# Insights into CoFe2O4/Peracetic Acid Catalytic Oxidation Process for Iopamidol Degradation: Performance, Mechanisms, and I-DBP Formation Control

## TL;DR

This study shows that CoFe2O4 nanoparticles with peracetic acid efficiently remove a type of X-ray contrast chemical and reduce harmful by-products formed during water disinfection.

## Contribution

The study identifies a new catalytic oxidation method using CoFe2O4 and peracetic acid to degrade iodinated contrast media while minimizing harmful iodinated by-products.

## Key findings

- CoFe2O4/PAA achieved over 90% degradation of iopamidol within 40 minutes.
- The metastable intermediate ≡Co(II)-OO(O)CCH3 was identified as the main reactive species for oxidation.
- CoFe2O4/PAA reduced monoiodoacetic acid formation potential by over 57% compared to UV/chlorine treatment.

## Abstract

In chlorination disinfection treatment, residual iodinated X-ray contrast media (ICMs) are the precursors to iodinated disinfection by-products (I-DBPs). This study employed CoFe2O4 nanoparticle catalytic peracetic acid oxidation (CoFe2O4/PAA) to remove iopamidol (IPM) and control I-DBP formation. The experimental results demonstrated that over 90% of the IPM degradation was achieved in 40 min. The metastable intermediate (≡Co(II)-OO(O)CCH3), rather than the alkoxyl radicals, was identified as the dominant oxidation species (ROS). The electron transfer pathways between the metastable intermediate and IPM were oxygen-atom transfer and single-electron transfer. The monoiodoacetic acid formation potential (MIAAFP) was investigated. In ultraviolet-activated ClO− (UV/chlorine), a portion of I− generated through IPM dehalogenation underwent conversion to reactive iodine species (RIS), consequently elevating the MIAAFP. In CoFe2O4/PAA, the MIAAFP was less than 43% of that in UV/chlorine, which can be attributed to the complete conversion of I− into iodate IO3− without generating RIS. CoFe2O4/PAA is thus a promising treatment for removing ICMs and controlling I-DBP formation due to the efficient degradation of ICMs while avoiding the generation of RIS.