Photocatalytic degradation of biological recalcitrant pollutants: a green chemistry approach

Design and development of an environmentally friendly and non-toxic photocatalysts system for the complete mineralization of persistent organic pollutants is an emerging and hottest challenge throughout the globe. However, poor visible light harvesting capacity, faster rate of recombination of photogenerated electron and hole pairs, low charge transfer and agglomeration of photocatalysts in aqueous medium are some of the major bottleneck in this study area. This review paper presents the comprehensive details about the findings of the photocatalytic degradation of biological recalcitrant pollutants using non-metallic graphitic carbon nitride (g-C3N4) and ZnO photocatalysts system. The basic mechanism of photocatalysis and photocatalytic degradation of phenolic compounds has been presented. The structural manipulation, challenges and application of g-C3N4 photocatalysts by doping with non-metallic elements and molecules, formation of heterojunction photocatalytic system by g-C3N4 with carbon quantum dots (CQDs) and ZnO photocatalyst have been discussed. In addition, detailed information regarding important roles of CQDs, metalloporphyrins photosensitizer and supporting carrier materials like hydroxyapatite in enhancement of photocatalytic activity has been focused.