Insights into adsorbent-based pharmaceutical wastewater treatment and future developments toward sustainability

Pharmaceutical compounds have emerged as surface and groundwater contaminants over the last three decades. It is paramount to efficiently remove these contaminants from wastewater, as these molecules pose a severe threat to biodiversity and human health due to the inefficacy of wastewater treatment plants in removing many of these compounds, bioaccumulation in animal tissues, and harmful health effects caused at low concentrations. Although different removal techniques can be effective depending on the target compounds and wastewater characteristics, adsorption has a slight edge due to its low adsorbent and operational costs, high efficacy, and minimal byproducts. However, over the last decade, only a few articles have comprehensively reviewed the removal of pharmaceutical compounds through adsorption. This paper focuses on the environmental impact, detection accuracy, and effectiveness of various adsorbents for different pharmaceutical compounds. It critically analyzes the adsorption isotherms, adsorption kinetics, adsorption thermodynamics, and mechanisms of different adsorbents. Pore filling, electrostatic attraction, hydrophobic interactions, surface complexation (or bond formation), hydrogen bonding, and π-π interactions are the primary mechanisms for target molecule removal during adsorption. The sustainability metrics of different adsorbents are explored for scale-up, as well as effective strategies for managing used adsorbents to support sustainability, covering the gap from the lab scale to the industrial scale.