Electrochemical abatement of diclofenac with various electrode systems for water treatment applications

Abstract

Treating pharmaceutical wastewater is one of the biggest challenges of the present century and is widely detected in surface and groundwater. The release and accumulation of biologically active Diclofenac (DCF) pharmaceutical waste into natural water bodies and groundwater harms aquatic and human life. It is often detected in aquatic environments due to the high consumption of DCF worldwide. Conventional technologies with different physical and biological treatment methods are inefficient in their effective removal and leave traces of DCF untreated. Anodic oxidation is a promising technology for the degradation of an organic pollutant. An electrochemical method of generating radicals is cost-effective and environmentally cleaner and achieves complete mineralization/scission of the DCF to CO₂, water, and inorganic ions. Oxidative reactive species such as hydroxyl radical, hydrogen peroxide, ozone, hypochlorous acid, and other inorganic radicals are generated in situ subjected to the type of water matrices present. The concurrent generation of different reactive species and their simultaneous presence (radicals and other active components) brings the complete degradation of DCF. The electrodes and electrolytic systems present the crucial parameters in generating highly reactive intermediates at the electrode surface. An inexpensive electrode material that meets the requirement of high electroactivity and is chemically stable under reactions is necessary for the successful large-scale implementation of DCF wastewater treatment. Different electrodes such as boron-doped diamond, carbon-based, and metal oxides and their efficiency in the electro-mineralization process of DCF are discussed. The DCF oxidation mechanism via C-N scission, decarboxylation, and hydroxylation process is illustrated comprehensively with different chemical structure formations.