Abstract
The unavailability of clean drinking water is one of the significant health issues in modern times. Industrial dyes are one of the dominant chemicals that make water unfit for drinking. Among these dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable and can cause a severe threat to human health and environmental safety. It is usually released in natural water sources, which becomes a health threat to human beings and living organisms. Hence, there is a need to develop an environmentally friendly, efficient technology for removing MB from wastewater. Photodegradation is an advanced oxidation process widely used for MB removal. It has the advantages of complete mineralization of dye into simple and nontoxic species with the potential to decrease the processing cost. This review provides a tutorial basis for the readers working in the dye degradation research area. We not only covered the basic principles of the process but also provided a wide range of previously published work on advanced photocatalytic systems (single-component and multi-component photocatalysts). Our study has focused on critical parameters that can affect the photodegradation rate of MB, such as photocatalyst type and loading, irradiation reaction time, pH of reaction media, initial concentration of dye, radical scavengers and oxidising agents. The photodegradation mechanism, reaction pathways, intermediate products, and final products of MB are also summarized. An overview of the future perspectives to utilize MB at an industrial scale is also provided. This paper identifies strategies for the development of effective MB photodegradation systems.
Highlights
Dyes are the coloured aromatic organic compounds that absorb light and impart color to the visible region [1,2]
Figure shows the effect of irradiation time on the photodegradation of methylene blue (MB), which which displays the absorptive intensity of MB at 664 nm, and it gradually decreases with displays the absorptive intensity of MB at 664 nm, and it gradually decreases with the the reaction time
The presence of MB in natural water is harmful to humans and harms microbes and aquatic life due to its toxic nature
Summary
Dyes are the coloured aromatic organic compounds that absorb light and impart color to the visible region [1,2]. Dyes are applied to the substrates to give them permanent colour, which can resist fading upon exposure to water, light, oxidizing agents, sweat, and microbial attack [5] Due to these advantages, various dyes are used in different industries such as textiles, food, rubber, printing, cosmetics, medicine, plastic, concrete, and the paper industry for multiple purposes [6,7,8]. Various dyes are used in different industries such as textiles, food, rubber, printing, cosmetics, medicine, plastic, concrete, and the paper industry for multiple purposes [6,7,8] These industries generate a tremendous amount of wastewater containing carcinogenic and toxic dyes that pollute water, which becomes unfit for human consumption [9].
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