Removal of iopamidol, an iodinated X-ray contrast medium, by zero-valent aluminum-activated H₂O₂ and S₂O₈²⁻

Activation of H₂O₂ (HP) and S₂O₈²⁻ (PS) with zero valent aluminum (ZVA, 1 g/L) nanoparticles was investigated for the treatment of the X-ray contrast medium and micropollutant iopamidol (IOPA; C₁₇H₂₂I₃N₃O₈; ≈777 g/mol) at pH 3. IOPA (2.6 μM) degradation was followed in different water matrices (distilled water, tap water, raw surface water and tertiary treated sewage effluent). Both oxidants could be activated with ZVA resulting in a dramatic enhancement of IOPA degradation due to accelerated hydroxyl and sulfate radical formation. The ZVA/PS (0.5 mM) treatment was more effective than ZVA/HP (0.25 mM) oxidation resulting in 95% IOPA removal after 120 min. IOPA and dissolved organic carbon (DOC) abatements were inhibited when IOPA was treated in real water and wastewater. After 120 min treatment, IOPA removals decreased from 95% (PS/ZVA) and 41% (HP/ZVA) in distilled water to 29% (PS/ZVA) and 13% (HP/ZVA) in surface water, respectively. IOPA could not be removed with the PS/ZVA process in treated sewage, although DOC removal was still substantial (28%). For the HP/ZVA combination, 24% DOC accompanied with 20% IOPA removal was achieved after 120 min in the same wastewater sample. Changes in acute toxicity were followed during PS/ZVA treatment of IOPA in distilled and surface water. These results exhibited a fluctuating trend depending on the sensitivity of the test organism (Vibrio fischeri and Pseudokirchneriella subcapitata) and water matrix. A genotoxic activity analysis was also conducted and the UmuChromo assay indicated that the original and treated IOPA solutions were not genotoxic but cytotoxic. The potentials and differences of PS/ZVA and HP/ZVA treatment of an iodinated contrast medium could be demonstrated in this study.