Iodide-mediated selective photocatalytic treatment of phenolic pollutants

Photocatalysis is a promising approach for environmental remediation. However, the intensively studied •OH and h+-based oxidation processes often miss the target pollutants due to their poor selectivity. The potential formation of toxic degradation byproducts from the oxidation of matrix species is a real concern in photocatalytic treatment. Here, we describe an innovative application of iodide-based photocatalytic process towards efficient degradation of phenolic pollutants even in complex water matrixes. Due to the presence of iodide, the degradation rate of our target pollutant, bisphenol A (BPA), was enhanced by 29 times on g-C3N4, and as much as 130 times on CdS. With evolved reactive iodine species (RIS) as oxidants, the iodide-based photocatalysis could selectively oxidize phenolic pollutants, thus, avoiding the inhibition by ubiquitous anions and organics in wastewater. Quenching experiments and measurements of RIS demonstrated that the diiodide (•I2-) was the dominant oxidant for degradation of phenolic pollutants, while iodine atom (•I) and triiodide (I3-) play minor roles. This work sheds light on the practical application of iodide-based photocatalysis for water treatment.