Abstract
This study examined the photocatalytic degradation efficiency under high UV photon flux (intensity normalized by photon energy) irradiation; the incident UV photon flux was einstein made by a super high-intensity UV apparatus. A comparative study between high photon flux photocatalytic process and routine low photon flux photocatalytic process for methylene blue degradation has been made in aqueous solution. The experimental results showed that under the best conditions of high UV photocatalytic reaction 99% decolorization and 95% TOC removal of 20 mg L−1methylene blue could be achieved in 30 s and 120 s of UV irradiation time, respectively. To the best of our knowledge, photocatalytic decolorization and photocatalytic degradation of dyes in such a short time has not been reported. Aiming at the low photonic efficiency in high photon flux photocatalytic process, we found that reducing the density of excited electron-hole appropriately could improve initial apparent photonic efficiency effectively. The TOC experiments under high UV photon flux showed a faster mineralization rate and a different mineralization process compared to that under low UV photon flux.
Highlights
Heterogeneous photocatalytic oxidation has potential applications for the treatment of waste water with dilute concentration of organic compounds because it effectively oxidizes a large number of chemical pollutants [1]
The photocatalytic degradation of methylene blue (MB) was investigated in high UV photon flux photocatalytic process (HUP) and low UV photon flux photocatalytic process (LUP)
It was found that high UV photon flux is effective for accelerating the photocatalysis rate
Summary
Heterogeneous photocatalytic oxidation has potential applications for the treatment of waste water with dilute concentration of organic compounds because it effectively oxidizes a large number of chemical pollutants [1]. If TiO2 photocatalysis is to have a commercial future as a method for water purification, reaction time must compare favorably with those of its competitors (UV/H2O2, UV/O3, photo Fenton, etc.). On this basis, many studies have been conducted to improve the photocatalytic reaction rate such as the doping of some elements or compounds into TiO2 [4], increasing the external surface area [5], improving photocatalytic reactor design [6], and so forth. Light photon flux (intensity normalized by photon energy) is one of the most parameters in photocatalytic reaction, and high UV intensity could compensate for the low photocatalytic efficiency of TiO2 itself [7]. The high photon flux UV irradiation can effectively lessen the photocatalytic reaction time [12]; it is important to improve the understanding of the high UV intensity photocatalytic reaction and to increase UV light efficiency of the reaction
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