A Comprehensive Review on Light-Driven Detoxification of Emerging Pollutants by Scalable Photocatalytic Systems

In modern society, due to rapid urbanization and industry growth, different types of pollutants are accumulating in the environment and making it polluted. The excessive discharge of organic toxins into water bodies is a major contributor to environmental pollution and poses significant health risks to society and the environment. Organic toxins from various chemical and textile industries pollute our water resources, forming breeding centers for different disease pathogens and adversely affecting the natural water cycle. Therefore, to protect and sustain life on the planet, it should be our prime mandate to preserve, manage, and remediate our limited available water resources. Organic pollutant decomposition is a difficult task due to their complex nature; therefore, it is important to understand the structures of different pollutants to decompose them perfectly. This review highlights the classification of various pollutants, their structural properties, and their possible detoxification processes through the advanced photocatalytic processes. In addition, the elaboration for the decomposition mechanism of the different toxins, ranging from azo dyes, phenols, pesticides, and nitrogen-based compounds to halo-compounds, has been explained. This review also briefly explains the underlying charge transfer mechanism used by different photocatalysts, such as metal oxide semiconductors and 2D-layered nanostructures. A brief description of this mechanism is mentioned in the review, along with the fundamental principle, the role of active redox radicals, such as superoxides and hydroxyl ions, in facilitating the photocatalytic degradation process. Lastly, the creation of robust and scalable photocatalytic systems for practical environmental applications is discussed along with the knowledge gaps and future research goals. This review provides invaluable insight into developing the advanced photocatalyst materials for the targeted pollutants.