Degradation of Rhodamine B in a photocatalytic reactor containing TiO2

This study was led by Xiaojun Han (School of Chemistry and Chemical Engineering, Harbin Institute of Technology).

With the rapid development of urbanization and industrialization, environmental problems are becoming more and more serious. Dye wastewater is considered as one of the biggest challenges because of its high toxicity. Organic dyes have mutagenic, teratogenic and carcinogenic properties, and threaten human health and life while inhibiting plant photosynthesis, which poses a risk to ecosystems. Traditional organic pollutant treatment methods include physical methods, biological methods, and chemical methods. This method has weaknesses such as poor efficiency, high energy consumption, and incomplete processing, so it is necessary to develop new waste treatment methods. In 1972, Fujishima carried out the pioneering work of the photocatalytic decomposition of water to produce hydrogen using TiO₂ as a photocatalyst. After that, photocatalytic technology was developed to be applied in sewage treatment because of its advantages in superior mineralization ability, fast reaction rate and no secondary pollution. TiO₂ is a common photocatalytic material due to its high catalytic activity, non-toxicity, excellent chemical stability and low cost. To convert TiO₂ photocatalytic technology from the experimental research stage to practical application, it is important to design photocatalytic reactors with simple structure, convenient assembly and outstanding maintenance performance.

In recent years, photocatalytic technology has been combined with various advanced oxidation (AOP) processes to improve photocatalytic performance. TiO₂The coupling of photocatalytic based technologies with classical AOPs such as Fenton oxidation, plasma oxidation and ozone oxidation reportedly improves the handling of organic pollutants. Nanobubbles (NB) are very small gas bubbles with unique physical properties, which make nanobubbles a superior aeration method for many applications. Nanobubbles have been widely used in wastewater treatment because of their long residence time, large specific surface area, and free radical generation capabilities. Yu et al. designing UV/NBs/P25-TiO₂ photocatalytic reactor to degrade methyl orange in water. The results showed that the photocatalytic performance of TiO₂ coupling with nanobubbles was improved by 11.6% compared to without bubbles. But TiO₂ the photocatalyst needs to be re-separated and recovered after photocatalytic degradation, which is unfavorable for photocatalytic reactor designs. Therefore, a photocatalyst is still needed for the assembly of a photocatalytic reactor.

Here, the photocatalytic reactor is assembled using Ti nets coated with TiO₂ nanotube arrays to degrade organic pollutants. The coupling reactor with nano-bubble technology showed extraordinary photocatalytic degradation capabilities, with a degradation efficiency of Rhodamin B (RhB) of 95.39% after irradiation treatment. Other organic pollutants including methylene blue, tetracycline and oxytetracycline hydrochloride can all be decomposed using this photocatalytic reactor, with degradation efficiencies of 74.23%, 68.68% and 64.10%, respectively. Therefore, this work provides a strategy to develop photocatalytic and nano-bubble coupling technologies to treat wastewater.

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Degradation of Rhodamine B in a photocatalytic reactor containing TiO₂ nanotube arrays coupled with nanobubbles

https://doi.org/10.1016/j.asems.2023.100054