Dual functional materials capable of integrating adsorption and Fenton-based oxidation processes for highly efficient removal of pharmaceutical contaminants

Abstract

Pharmaceutical contaminants have shown widespread presence in water/wastewater threatening environmental and human health. Existing literature shows that adsorption can efficiently bind pharmaceuticals preventing their transfer into the treated water. However, adsorption only diverts these contaminants from one phase to another requiring the treatment of contaminant-laden adsorbents. Fenton oxidation (H2O2-based) has shown good potential for the degradation of pharmaceuticals. But, the practical use of Fenton oxidation is often limited by its higher chemical demands and low contact of oxidizing species with target contaminants. Efforts to overcome these practical obstacles aim to develop efficient heterogeneous catalysts which also benefit from their strong contaminant adsorption capacity. This is the first review that focuses exclusively on dual-functional materials that can effectively adsorb pharmaceutical pollutants (separation-based removal) and promote Fenton oxidation simultaneously (degradation-based removal) in aqueous systems. The dual functionality enables the integration of adsorption and Fenton-based processes (heterogeneous Fenton, photo-Fenton and photocatalysis) to efficiently remove pharmaceuticals. This integration can be achieved using a single material having both functions or by compositing/impregnating different materials. The properties of these materials have important consequences on their treatment efficiency, stability, and regeneration ability. These processes and materials are critically evaluated to illustrate their potential, associated challenges and their key solutions. Some of these challenges originate from the tested materials while others are inherent to the treatment process and the prospects for improvement exist at their intersection. Future research should aim to rationally improve the catalytic and adsorption properties of these materials and explore their practical implementation in wastewater treatment technologies.