Activation of sulfite autoxidation with CuFe2O4 prepared by MOF-templated method for abatement of organic contaminants.

Copper ferrite (denoted as CuFe2O4MOF), prepared via a complexation reaction to obtain bimetal-organic frameworks (Cu/Fe bi-MOFs), followed by a combustion process to remove the MOF template, is employed as a heterogeneous activator to promote sulfite autoxidation for the removal of organic contaminants. At pH 8.0, more than 80% of the recalcitrant organic contaminant iohexol (10 μM) can be removed within 2 min by the activation of sulfite (500 μM) with CuFe2O4MOF (0.1 g L-1). CuFe2O4MOF exhibits more pronounced catalytic activity in accelerating sulfite autoxidation for iohexol abatement compared to that fabricated by hydrothermal and sol-gel combustion methods. Radical quenching studies suggest that the sulfate radical (SO4•-) is the main reactive species responsible for iohexol abatement. The performance of CuFe2O4MOF/sulfite for iohexol abatement can be affected by several critical influencing factors, including the solution pH and the presence of humic acid, Cl-, and HCO3-. The effect of the ionic strength and the results of the attenuated total reflectance-Fourier transform infrared (ATR-FTIR) analysis indicate that sulfite autoxidation in the presence of CuFe2O4MOF involves an inner-sphere interaction with the surface Cu(II) sites of CuFe2O4MOF. X-ray photoelectron spectroscopy (XPS) characterization suggests that the surface Cu(II)-Cu(I)-Cu(II) redox cycle is responsible for efficient SO4•- production from sulfite. Overall, CuFe2O4MOF can be considered an alternative activator for sulfite autoxidation for potential application in the treatment of organic-contaminated water.