Efficient abatement of an iodinated X-ray contrast media iohexol by Co(II) or Cu(II) activated sulfite autoxidation process

摘要

Efficient abatement of an iodinated X-ray contrast media iohexol by an emerging sulfite autoxidation advanced oxidation process is demonstrated, which is based on transition metal ion-catalyzed autoxidation of sulfite to form active oxidizing species. The efficacy of the combination of sulfite and transition metal ions (Ag(I), Mn(II), Co(II), Fe(II), Cu(II), Fe(III), or Ce(III)) was tested for iohexol abatement. Co(II) and Cu(II) are proven to show more pronounced catalytic activity than other metals at pH 8.0. According to the quenching studies, sulfate radical (SO4 center dot-) is identified to be the primary species for oxidation of iohexol. Increasing dosages of metal ion or sulfite and higher pH values are favorable for iohexol abatement. Inhibition of iohexol abatement is observed in the absence of dissolved oxygen, which is vital for the production of SO5 center dot- and subsequent formation of SO4 center dot-. Overall, activation of sulfite to produce reactive radicals with extremely low Co(II) or Cu(II) concentrations (in the range of mu g L-1) in circumneutral conditions is confirmed, which offers a potential SO4 center dot--based advanced oxidation process in treatment of aquatic organic contaminants.