Kinetic and mechanistic investigations of the oxidation of organics by near-infrared light driven thermocatalytic activation of peroxydisulfate with Fe3O4

The utilization of renewable solar energy through near-infrared (NIR)-driven photothermal catalysts offers a potential novel strategy for environmental remediation. In this work, we reported an initial demonstration of the peroxydisulfate (PDS) activation in oxidative degradation of organics (represented by bisphenol A (BPA)) via a unique NIR light-to-heat conversion effect using cost-effective and biocompatible nanoparticles (NPs). The systematical investigation of the photothermal experiments found that Fe3O4 magnetic NPs exhibit great photothermal conversion efficiency (65.4%) and have the capability to quickly elevate the system temperature to 61°C. The increased reaction temperature leads to the homolytic fission of the OO bond for producing sulfate radical (SO4−) and the derivative hydroxyl radical (OH), as confirmed by the radical quenching and electron paramagnetic resonances (EPR) tests, and in turn accelerates the thermocatalytic degradation reaction of BPA. The BPA degradation reaction rate of the NIR/Fe3O4/PDS system is about 25.8 times and 9.4 times of that in the NIR/PDS and Fe3O4/PDS systems, respectively. Both photothermal heating and surface valence states conversion of Fe2+/Fe3+ on Fe3O4 under dark conditions make a contribution to the observed oxidation reactions. Moreover, this NIR light-to-heat activation system exhibits efficient photocatalytic degradation of BPA molecules in deep water by virtue of the deep penetration capability of NIR light in water, highlighting NIR-driven photothermal catalysts hold the excellent potential to be applied in practical water restoration through PDS activation.