Methylene Blue Degradation by Nano Tungsten Trioxide Photocatalyst

Compared with titanium dioxide, tungsten trioxide (WO₃) nano-powder can efficiently photocatalytically degrade methylene blue due to its narrow band gap, which can only absorb ultraviolet light. However, the technical problem of photocatalytic degradation of methylene blue by tungsten trioxide is to select catalysts with high catalytic activity.

The preparation of nano tungsten trioxide photocatalyst by hydrothermal method is as follows: 3.0000g sodium tungstate is weighed, 0.0010g CTAB is dissolved in 30mL distilled water, stirred evenly, the above solution 3mL is dripped into HCl with 5mL concentration of 3mol L-1, stirred for 0.5h, the yellow solution is moved into stainless steel reactor lined with PTFE, placed in oven at 100 ℃ for 24h, and centrifuged after extraction. The yellow precipitation was obtained. The precipitation was washed repeatedly with distilled water and acetone for 3 to 4 times. Tungsten trioxide photocatalyst was prepared by drying in oven at 80 ~7h and then burning in muffle oven at 300 ~3h.

Different monoclinic WO₃ samples with different qualities were added to 5 ml 10 mg/L methylene blue dye solution. After irradiation under sunlight for 3 hours, the decolorization rate gradually increased with the increase of catalyst quality. When the dosage of catalyst was 0.0080g, the decolorization rate was the highest, 97.15%, with an average of 95.36%.

The results showed that the decolorization rate of monoclinic WO₃ sample to methylene blue was 95.36% under sunlight and 76.78% under ultraviolet light. Compared with ultraviolet lamp, B solar light is better as light source. At the same time, the catalyst can be recycled repeatedly. The decolorization rate of WO₃ samples is maintained above 90% each time after recycling for five times. The phase of monoclinic WO₃ samples used repeatedly remains unchanged, which shows that WO₃ as a photocatalyst has stable performance and cost effect.

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