Recent Advances in Advanced Oxidation Processes for Degrading Pharmaceuticals in Wastewater-A Review

A large variety of pharmaceutical compounds have recently been detected in wastewater and natural water systems. This review highlighted the significance of removing pharmaceutical compounds, which are considered indispensable emerging contaminants, from wastewater and natural water systems. Various advanced oxidation processes (AOPs), including UV-H2O2, Fenton and photo-Fenton, ozone-based processes, photocatalysis, and physical processes, such as sonolysis, microwave, and electron beam irradiation, which are regarded as the most viable methods to eliminate different categories of pharmaceutical compounds, are discussed. All these AOPs exhibit great promising techniques, and the catalytic degradation process of the emerging contaminants, advantages, and disadvantages of each technique were deliberated. Heterogeneous photocatalysis employing metal oxides, particularly anatase TiO2 nanoparticles as catalysts activated by UV light irradiation, was reviewed in terms of the electron-hole separation, migration of the charge carriers to the catalyst surfaces, and redox potential of the charge carriers. This brief overview also emphasized that anatase TiO2 nanoparticles and TiO2-based nanomaterials are promising photocatalysts, and a combination of photocatalysis and other AOPs enhanced photocatalytic degradation efficiency. Finally, the challenges of applying anatase TiO2-based photocatalysis in environmental remediation and wastewater treatments to degrade pharmaceutical compounds, including mass spectroscopic analysis and a biological activity test of by-products of the emerging contaminants resulting from photocatalysis, are summarized.