Recent advances in industrial photoreactors: A review from design to large-scale applications

This review critically examines the evolution, current challenges, and potential prospects of photocatalysis in treating pharmaceutical wastewater, particularly in the context of industrial-scale applications. Pharmaceutical contaminants, including active pharmaceutical ingredients, antibiotics, and hormones, exhibit different persistence characteristics, clearly demonstrating the ineffectiveness of existing treatment methods and thus the need for advanced oxidation processes. Photocatalysis using TiO2, ZnO, and other materials has shown potential in degrading these persistent pollutants using light, activating semiconductor materials before transforming or degrading organic contaminants into reactive oxygen species through oxidation and catalyst degradation. The challenges of mass transfer, light penetration, catalyst deactivation, and economic barriers, such as challenges posed by large reactor settings and profitability, have proven challenging in transitioning from laboratory-scale set-ups to pilot and ultimately industrial-scale reactor configurations. Improvements in immobilized and slurry photocatalysts, the development of existing reactor designs, and the combination with solar power have increased the future potential for large-scale applications. However, some technical and economic barriers still prevent the actual and real application of photocatalysis, including low quantum efficiency, catalyst deactivation, and high operational costs. This review will also cover the progress made in designing photocatalytic materials to improve functionality and design, as well as developing reactors to improve scale-up, cost, and efficiency for the first practical application of photocatalysis in the remediation of the contaminated environment.