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.

摘要

最近的研究证实，表面布朗斯台德酸位点可以明显改善半导体的羟基自由基的形成，从而增强光催化降解活性。然而，有意在半导体表面引入布朗斯台德酸位点既复杂又昂贵。在这项研究中，首次研究了低成本磷酸基地质聚合物 (PAG) 作为光催化剂降解染料的潜力。为此，制备了一批具有不同P/Al比的偏高岭土基PAGs，并研究了直接蓝86（DB-86）在PAGs上的光催化降解。结果表明，磷酸活化的地质聚合过程赋予了PAGs通过光致空穴和电子的氧化还原能力，这表明PAGs具有光催化活性。光催化降解率随着 P/Al 比的增加而增加，因为源自非四面体 P-OH 基团的表面布朗斯台德酸的增强改善了自由基的产生。这里报道的 PAG 将是染料废水处理的有希望的候选者，因为低成本催化剂因其特殊结构而产生出色的催化性能。