Revealing the degradation intermediates and pathways of visible light-induced NF-TiO2 photocatalysis of microcystin-LR

Abstract The effect of using only visible light to induce nitrogen- and fluorine-doped titanium dioxide (NF-TiO 2 ) photocatalysis of degradation products of microcystin-LR (MC-LR), the most common problematic cyanotoxin, was explored by looking at the intermediate degradation products. Although the degradation mechanisms and products of conventional UV-based TiO 2 photocatalysis of MC-LR have been well elucidated, the same is not true for visible light-based TiO 2 photocatalysis. The results of LC/MS 2 (and in one case LC/MS 3 ) indicated that the intermediates are not drastically altered in comparison to traditional TiO 2 photocatalysis using UV light. The data hint that the degradation is driven by hydroxyl radicals, as is UV-based TiO 2 photocatalysis, although the mechanism for producing hydroxyl radicals is unclear since studies indicate drastically slower kinetics for visible light-based photocatalysis of MC-LR. Notably, the data indicate that visible light-induced NF-TiO 2 photocatalysis degraded the portion of MC-LR that is responsible for biological toxicity. As a result of this, it was concluded that doping TiO 2 with nitrogen and fluorine is an effective method for increasing utilization of visible light while degrading MC-LR in water, although it should still be noted that degradation kinetics are still slower than UV-based TiO 2 photocatalysis.