Treatment of Variable Complex Mixed Dye Wastewater by Photodegradation with a Photocatalyst Gradation Strategy

Photocatalysis is a promising advanced oxidation technology for treating wastewater; however, the complexity, diversity, and variability of actual wastewater make its application difficult at the current level of technology. In this work, a photocatalyst gradation strategy is proposed in which the specific photocatalysts Ag2O, NaBiO3, and BiOCl0.75Br0.25 are combined to treat the specific pollutants methyl orange, methylene blue, and rhodamine B, as well as their mixtures. The photocatalyst ratio is adjusted on the basis of big data analysis to photodegrade variable mixed dye solutions rapidly and efficiently. The results demonstrate positive synergistic effects among the photocatalysts, which can completely decolorize a 30 mg/L mixed dye solution at a ratio of 1:1:1 in 15 min. When big data analysis is applied, mixed dye solutions with random dye ratios are purified sufficiently to meet the standard using a graded photocatalyst combination based on the predictions of the trained model. This work provides a reference strategy for the treatment of complex variable wastewater.