Harnessing coal fly ash and sludge as low-cost industrial by-product adsorbents for pharmaceutical removal in wastewater: Trends, challenges, and prospects

Pharmaceutical contamination of water sources presents serious risks to environmental sustainability and public health, requiring the development of affordable and effective wastewater treatment methods. Common treatment technologies often fail to fully remove pharmaceutical residues and are hindered by high energy use, operational costs, and the production of harmful by-products. Recently, research has increasingly focused on repurposing industrial wastes such as fly ash and sludge as low-cost, high-surface-area adsorbents for removing pharmaceuticals. This review thoroughly examines pharmaceutical pollutants, including their sources, environmental impacts, and concentration levels in wastewater. It assesses both traditional and emerging removal methods, with a particular emphasis on adsorption. The potential of raw and modified industrial waste materials as sustainable adsorbents is critically analyzed, considering key factors influencing adsorption, such as pH, temperature, initial concentration, as well as adsorption kinetics and isotherms. The review also emphasizes how these materials can be integrated into the circular economy by repurposing them for water purification. Recommendations for future research include enhancing adsorbent stability, reusability, and selectivity through modifications like magnetization, acid treatment, chitosan addition, and zeolitization, along with verifying their scalability. The results reinforce the importance of waste-based adsorbents in achieving sustainable water management.