Emerging Biopharmaceuticals in Wastewater: A Classification of Treatment Approaches Based on Photo, Electro and Electro-Photo Catalytic Methods

Abstract

There is an emerging family of biopharmaceutical contaminants present in wastewater that includes a sizeable number of molecules originated in the partial metabolism of medicines used for both animal and human treatment. These contaminants represent a health hazard that need to be addressed. For this purpose, Advanced Oxidation Processes (AOPs) are suitable techniques in which highly oxidizing hydroxyl free radicals are generated by chemical or photochemical or electrochemical or photoelectrochemical methods that can indiscriminately attack and degrade them oxidatively into safer and simpler mineralized products such as water, carbon dioxide, and inorganic ions. Effectiveness and efficiencies of degradation depend upon the type of AOPs by which •OH is generated, operating conditions, and the chemical and physical properties of the contaminants. In this study, we review the general approaches of AOPs with a focused study on heterogeneous photocatalytic methods that are applicable for removing various classes of emerging biopharmaceuticals that are growing rapidly in modern-day-wastewaters. We present a classification of the AOPs based on the mechanistic pathways by which •OH radicals are generated. In addition to highlighting the removal effectiveness and degradation mechanisms of biopharmaceuticals by titanium dioxide based photocatalytic methods, a summary of early trends and recent advances in the advanced oxidation of biopharmaceuticals in wastewater is presented.