Dye sensitization and surface adsorption co-driven visible- light photocatalysis of methylene blue by environmental- friendly hydroxyapatite

This study aimed to develop an efficient, stable, and environmentally-friendly photocatalyst for degrading methylene blue (MB) under visible irradiation. Bio-compatible and nanorod-like hydroxyapatite (HAP) was synthesized using a chemical co-precipitation method, showing that HAp achieved a degradation efficiency of 99.41% within 90 min for 10 mg/L MB with an optimal catalyst dosage of 2 g/L, which was ascribed to the active radicals such as h + , 1 O 2 , and ·O 2 - induced by photo-sensitization of MB dyes and surface adsorption of HAP. It is shown that HAp exhibits good structural stability and re-usability. And a degradation pathway for MB involving stepwise demethylation, ring opening, and subsequent mineralization was also proposed. This research is believed to promote the practical applications of hydroxyapatite in photocatalytic treatment of dye wastewater.