Water pollution is one of the serious environmental concerns faced by our planet today. One factor contributing to this problem is the rapid development of urbanization and industrialization.
Environmentalists recently focused on dye wastewater due to its high toxicity level to address this concern. According to CNN, one-fifth of water pollution is due to textile dyes. Organic dyes contain mutagenic and carcinogenic and pose risks to human health and the ecosystem. The textile industry mainly releases it by emitting contaminated wastewater into the environment.
Conventional treatment strategies such as physical, biological, and chemical methods are inadequate due to inefficiency, high energy consumption, and partial remediation. Because of this, experts are looking for alternative techniques for better sewage treatment.
Evolution of Photocatalytic Technology
Fujishima and Honda discovered the photocatalytic activity of titanium dioxide and used it for the first time in 1972. Using the property of titanium dioxide as a semiconductor metal oxide, they pioneered the technology by employing this compound as a catalyst in producing hydrogen gas by splitting water. Since their discovery, photocatalytic technology was improved wastewater treatment using its mineralization ability, fast reaction rate, and absence of secondary pollution.
Several attempts have been made to improve the performance of titanium dioxide in photocatalysis. Some experts tried to modify its composition, while some researchers formed heterojunctions with other metals.
To utilize the photocatalytic applications of titanium dioxide, there is a need to design a simple and efficient photocatalytic reactor that is easy to assemble. Advanced oxidation processes (AOPs) have been integrated into photocatalytic technology to enhance performance. Some of these AOPs include ozone oxidation, Fenton oxidation, and plasma oxidation, all proven effective in treating organic pollutants.
Another innovation comes into play in the form of nanobubbles, a long-lasting cavity that contains gas. These extremely small gas bubbles have unique characteristics that differentiate them from ordinary bubbles. In wastewater treatment, nanobubbles were found useful in enhancing the photocatalytic performance of titanium oxide by 11.6% when compared to non-bubble approaches.
However, this technology faces challenges as the reactor design is complicated by the need to re-separate and recover titanium oxide post-degradation. A fixed photocatalyst is needed to assemble the reactor to address this issue.
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New Approach to Enhancing Reactor Design
A group of Chinese researchers developed a photocatalytic reactor integrated with nanobubbles to enhance organic pollutants' degradation in wastewater. The reactor was assembled using titanium mesh coated with titanium oxide nanotube arrays and UV light inside a steel cylinder. These arrays serve as photocatalysts while the nanobubbles increase the dissolved oxygen content.
Upon testing this method, an outstanding photocatalytic performance was observed in the photocatalytic reactor, which had a higher degradation ability after the irradiation treatment. This enhanced ability was evident when applied to organic pollutants such as Rhodamine B, tetracycline, and methylene blue.
The result of this study proves that the combination of photocatalysis and nanobubbles technology presents a promising approach for wastewater treatment.
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