Review of the performance and energy requirements of metals modified TiO₂ materials based photocatalysis for phenolic compounds degradation: A case of agro-industrial effluent

The waste effluent generated by agro-industries and oil refineries has a high level of phenolic compounds (PhCs) even after the secondary treatment, and is considered one of the major polluters of rivers and streams across the edible oil and petroleum producing countries. Photocatalytic technology based on TiO₂ or modified TiO₂ materials has proven to be both technically and economically feasible for the treatment of such effluents. It has a few significant, enduring problems that must be resolved first, such as inefficient use of visible light by TiO₂, its broad bandgap, and its rapid electron-hole pair recombination. TiO₂ photocatalyst-based photocatalysis has several advantages, such as the ability to fully mineralize organic pollutants into byproducts that are environmentally friendly, high reaction rates, operation at room temperature and pressure, low cost, and chemical and thermal stability of TiO₂. However, to transfer this technology to industrial scale require a thorough analysis of its performance and energy requirements especially, when applied for photodegradation of PhCs from agro-industries. This review critically examined various methods for enhancing the degradation of PhCs using metal modified TiO₂ materials based photocatalysis. It is also described how different strategies will impact the overall visible-light efficiency and energy requirements of the TiO₂ photocatalyst. Furthermore, the most significant modifications to the TiO₂ photocatalysts for enhancing the degradation of PhCs were identified. Finally, estimates and comparisons of each strategy's energy needs, energy savings and treatment costs for various modifications were carried out and presented. The industry should be encouraged to promote the advancement of TiO₂-based photocatalysis by being aware of the technical challenges and energy demands during its development.