(12g) Aqueous Organics Degradation in Visible Light and Ozone Integrated Process with WO3 catalysts

Yongbing Xie¹, Jin Yang², Hongbin Cao^1,2*

¹Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, China

²School of Chemical Engineering & Technology, Tianjin University, Tianjin, 300072, China

*Corresponding author: hbcao@ipe.ac.cn

Semiconductors can trigger a super synergy between photocatalysis and ozonation, and the combined process is very effective in organics mineralization¹. Ultraviolet light (UV) was mostly applied in this combined process with TiO₂ catalyst, but this cannot use solar energy. It is very meaningful to develop a visible light sensitive catalyst to adopt the green solar energy for wastewater treatment. In this paper, three tungsten oxides (WO₃) with different phases and exposed facets were synthesized and applied in the visible light photocatalytic ozonation process.

The three materials were synthesized with hydrothermal and calcination methods, and named with H-100 (hexagonal phase with [100] facet exposed), M-002 and M-100 (monoclinic phase with [002] and [100] facet exposed), respectively. The activities of the materials were evaluated upon oxalic acid degradation and cephalexin mineralization, and M-100 showed the highest activity (Fig. 1a).

Fig 1. Oxalic acid degradation (a), band structures (b) and charge separation of different WO₃ materials (c).

To explain this, different optical and electronic properties were characterized. The band gaps (Eg) were calculated from UV-Vis DRS, and the valence bands (VB) were obtained by valence band XPS, and the results are finally shown in Fig. 1b. More negative CB position indicates the electrons with stronger reducing ability and thus favors ozone reduction². M-100 with higher CB position is favor to reduce ozone molecule to generate reactive radicals. Electrochemical Impedance Spectroscopy (EIS) results indicated that the H-100 material has the highest charge transfer ability (Fig 1c), this is very important in photocatalysis but not in photocatalytic ozonation. Other operating parameters of this process were also optimized to achieve a better performance.

References

1. J.D. Xiao, Y.B. Xie and H.B. Cao, Chemosphere, 2015, 121, 1-17.
2. J.D. Xiao, Y.B. Xie, F. Nawaz, S. Jin, F. Duan, M.J. Li and H.B. Cao, Applied Catalysis B: Environmental, 2016, 181, 420-428.