Heterogeneous photocatalysis (HPC), an eco-friendly technique utilized in Advanced Oxidation Processes (AOPs), is gaining recognition as an effective method for purifying water contaminated with organic and biological pollutants within environmental systems. In this transformative process, the photocatalysts’ performance hinges on three key factors: light harvesting, separation and transfer of photogenerated charge carriers, and surface reactivity.
When it comes to HPC-based AOPs, light harvesting plays a pivotal role. The photocatalytic reaction is initiated by the absorption of photons from the light source, which energizes the photocatalyst material. Typically, semiconductors such as titanium dioxide (TiO2) are employed due to their exceptional light-harvesting properties. These catalysts possess a bandgap energy that allows them to absorb photons in the ultraviolet (UV) range, thereby inducing electron excitation from the valence band to the conduction band.
The efficient separation and transfer of photogenerated charge carriers is crucial for the overall catalytic performance of the system. Once photons are absorbed by the photocatalyst, electron-hole pairs are generated. These charge carriers must be swiftly separated to prevent recombination, which can hinder the catalytic process. Surface defects or doping with elements like nitrogen or metal nanoparticles aid in enhancing the separation efficiency, leading to improved photocatalytic efficiency.
Surface reactivity significantly influences the degradation capacity of the photocatalyst. Upon contact with the pollutant molecules present in water, the active sites on the photocatalyst’s surface facilitate chemical reactions that break down these pollutants into harmless byproducts. Factors such as surface area, crystallinity, and the presence of reactive surface species directly impact the catalyst’s reactivity. Maximizing the surface area through techniques like nanoparticle deposition or nanostructuring can enhance the catalytic activity by providing more active sites for pollutant adsorption and reaction.
Furthermore, advances in HPC-based AOPs have led to the development of various techniques and modifications to optimize the photocatalytic process. These include doping with different elements, creating heterojunctions, utilizing novel materials, and employing co-catalysts. These strategies aim to enhance light absorption, promote efficient charge separation, and improve surface reactivity, thereby increasing the overall efficiency of the system.
In conclusion, heterogeneous photocatalysis based on Advanced Oxidation Processes demonstrates promising potential for water purification from organic and biological pollutants. Its effectiveness relies on optimizing light harvesting, efficiently separating and transferring photogenerated charge carriers, and maximizing surface reactivity. With ongoing research and technological advancements, HPC-based AOPs hold great promise for addressing water pollution challenges, contributing to a cleaner and healthier environment.
