New insight into wastewater treatment by activation of sulfite with photosensitive organic dyes under visible light irradiation

In this work, an advanced oxidation process relying on sulfite radical (SO3−) and superoxide anion radical (O2−) for contaminated water stream treatment was proposed. SO3− was generated from NaHSO3 which was activated by photosensitive organic dye (POD) under visible light irradiation. The organic pollutants such as organic dyes and carbamazepine (CBZ) in aqueous solution could be degraded in this vis/POD/HSO3− system. SO3− and O2− were identified as the major reactive oxygen species (ROS) in the investigated system for the degradation of organic pollutants by the results of quenching experiments and electron spin resonance (ESR) analysis. Moreover, the co-existing inorganic anions (such as SO42−, NO3−, and Cl−) and inorganic cations (such as K+, Mg2+, and Ca2+) and humic acid in water body showed little influence on the degradation reaction. The degradation pathway of rhodamine B (RhB) induced by SO3− and O2− in the vis/RhB/HSO3− system was clarified on the basis of the identification of intermediates by high performance liquid chromatography-mass spectrometry (HPLC-MS). This study is the first report on the activation of sulfite by photosensitive organic dyes under visible light irradiation for the abatement of micropollutants in water treatment, which may lead to a new advanced oxidation process relying on sulfite activation for wastewater treatment.