Potential of Cost-Effective Phosphoric Acid-Based Geopolymer as Photocatalyst for Dye Wastewater Degradation

Abstract

Well recent study confirmed that surface Brønsted acid sites could evidently improve the formation of free hydroxyl radicals of semiconductors and thus enhanced the photocatalytic degradation activity. However, the intentional introduction of Brønsted acid sites on semiconductor surface was complex and expensive. In this study, the potential of low-cost phosphoric acid-based geopolymer (PAG) as photocatalyst for the degradation of dye was investigated for the first time. To this end, a batch of metakaolin-based PAGs with different P/Al ratios were prepared, and the photocatalytic degradation of Direct Blue-86 (DB-86) over PAGs was studied. Results showed that the process of phosphoric acid-activated geopolymerization endowed PAGs with redox ability by photoinduced holes and electrons, which suggested PAGs had photocatalytic activity. The photocatalytic degradation rate increased with increasing P/Al ratios, because the enhancement of the surface Brønsted acid deriving from non-tetrahedral P-OH groups improved the generation of free hydroxyl radicals. The PAGs reported here would be a promising candidate for dye wastewater treatment since the low-cost catalyst produces outstanding catalytic performance for their special structure.