Degradation of 1,4-dioxane from industrial wastewater by solar photocatalysis using immobilized NF-TiO2 composite with monodisperse TiO2 nanoparticles

• Solar photocatalysis of 1,4-dioxane using NF-TiO2-monodisp.TiO2 films was studied.
• Kinetics of 1,4-dioxane degradation in various water matrices were investigated.
• 1,4-Dioxane was successfully removed from real wastewaters from chemical industry.
• Degradation pathways of 1,4-dioxane by immobilized photocatalysis were proposed.

The degradation of 1,4-dioxane was accomplished by solar photocatalysis using an immobilized nitrogen and fluorine co-doped titanium dioxide (NF-TiO2) composite with monodisperse TiO2 nanoparticles. The effect of different wastewater matrices was studied, and the treatment of an industrial effluent contaminated with 1,4-dioxane was carried out. Compared to the degradation rate in a synthetic solution (kdioxane = 0.34 ± 0.02 h−1), 1,4-dioxane removal decreased in the industrial wastewater (kdioxane = 0.27 ± 0.01 h−1) due to the presence of inorganic constituents, whereas, the increase of the effluent pH to 6.9 produced only a slight decrease of the photocatalytic efficiency (kdioxane = 0.31 ± 0.01 h−1). In the photocatalytic treatment of the industrial effluent, almost complete degradation of 1,4-dioxane (≤100%) was achieved along with 65% and 50% removal of COD and TOC, respectively. Moreover, remarkably similar results (about 50% of COD removal in 6 h) were achieved using both the immobilized lab-made catalyst and the commercial P25-TiO2. In the chromatographic study of metabolites, ethylene glycol diformate, ethylene glycol monoformate, and formic acid were identified as major reaction intermediates, and thereby, the main reaction pathways have been proposed. The progressive decrease of the partial oxidation efficiency down to about 0.2 and the moderate increase of the mean oxidation state of carbon in the solution (up to +0.5) indicate that a complete mineralization of the contamination from the current industrial effluent could be feasible using this supported catalyst.

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