Synchronous photosensitized degradation of methyl orange and methylene blue in water by visible-light irradiation

In this work, a novel method that homogeneous degrading methyl orange (MO) with methylene blue (MB) as a photosensitizer under visible-light irradiation is proposed. MO can be efficiently degraded at a wide concentration range, and its degradation rate is significantly promoted by increasing MB concentration. The result of EPR, LC-MSMS, TOC and ion chromatography reveals that the degradation mechanism of MO consists two parts: 1O2 mediated Type II pathway and Type I photosensitization of involving direct electron transfer between 3MB* and MO. Furthermore, benefitting from the self-degradation of MB, synchronous removal of MO and MB in water can be realized by controlling the initial MB concentration in system, thus avoiding the problems faced by heterogeneous photocatalytic such as solid-liquid separation. Therefore, this cost-effective and easy method possesses great potential in the application of eliminating MO and MB from wastewater as well as provides a new strategy for sustainable water treatment.