Recent advances in nano-Fenton catalytic degradation of emerging pharmaceutical contaminants

The voluminous anthropogenic activities and non-regulated discharge of emerging pharmaceutical pollutants have led to deterioration of water quality characteristics and shortage of potable water. One of most ubiquitous problems is that the pharmaceutical pollutants are slowly developing resistance in pathogens, which increases the risks manifold. Conventional water treatment methods and technologies have been known to be inadequate for elimination of recalcitrant and emerging pollutants. Advanced oxidation processes have been exploited to the most for mineralizing the pollutants with some limitations especially toxic metal based catalysts and secondary pollution. However Fenton-based systems are considered to be safer as they utilize non-toxic chemicals. Homogeneous Fenton processes suffer from limitations as limited pH operational range, generation of Fe containing sludge etc. have shifted focus to heterogeneous systems. This review focusses on removal of pharmaceutical pollutants by homogeneous and heterogeneous Fenton, electro-Fenton, sono-Fenton, photo-Fenton and photoelectro-Fenton processes using nano-catalysts. Various types of new pharmaceutical pollutants, their emergence, characteristics and toxicity have been discussed to have an insight into quantity and variety. New Fenton-like catalysts have been designed and used for degradation of pollutants and high mineralization is also achieved in a wide pH-range. In addition Fenton catalysts capable of showing high mineralization using solar light have been prepared by various methods with and without iron based materials. In addition in this review we have also focused on complexities related to removal of pharmaceutical effluents and how they are addressed by Fenton systems. The review aims to assist researchers and engineers to gain fundamental understandings and critical view of Fenton process and its optimization processes, and hopefully with the knowledge it could bring new opportunities for the optimization and future development of Fenton process. The key advances in Fenton catalysts are innovations in design of ligands, junction designing for effective radical generation, reaction engineering, hydro-dynamical effects and complete mineralization. The combinations and coupling of biological oxidation, semiconductor photocatalysis with Fenton process for high performance pharmaceutical pollutants removal in pilot-scale experiments have been discussed and evaluated. (C) 2019 Elsevier B.V. All rights reserved.