The extensive use of pharmaceuticals has raised growing concerns regarding their presence in surface waters. High concentrations of sulfamethoxazole (SMX) and lincomycin (LIN), as commonly prescribed antibiotics, persist in various wastewaters and surface waters, posing risks to public health and the environment. Biochar derived from accessible biowaste, like activated sludge biomass, offers a sustainable and eco-friendly solution to mitigate antibiotic release into water systems. This study investigates the effectiveness of H₃PO₄-modified activated sludge-based biochar (PBC) synthesized through microwave (MW) heating for the adsorption of SMX and LIN antibiotics. The synthesis parameters of PBC were optimized using a central composite design considering MW power, time, and H₃PO₄ concentration. Characterization results validate the efficacy of the synthesis process creating a specific surface area of 365 m²/g, and well-developed porosity with abundant oxygen-containing functional groups. Batch and dynamic adsorption experiments were piloted to assess the adsorption performance of PBC in single and binary antibiotic systems. Results show that PBC exhibits a higher affinity for SMX rather than LIN, with maximum adsorption capacities of 45.6 mg/g and 26.6 mg/g, respectively. Based on kinetic studies chemisorption is suggested as the primary mechanism for SMX and LIN removal. Equilibrium studies show a strong agreement with the Redlich-Peterson isotherm, suggesting a composite adsorption mechanism with a greater probability of multilayer adsorption for both antibiotics. Hydrogen bonding and π-π electron sharing are suggested as the prevailing adsorption mechanisms of SMX and LIN on the modified biochar. Furthermore, a dynamic adsorption system was replicated using a fixed bed column setup, demonstrating effective removal of SMX and LIN from pure water and real wastewater samples using PBC-loaded hydrogel beads (PBC-B). These findings serve as crucial support for upcoming studies concerning the realistic application of sludge-based biochar in the removal of antibiotics from water systems.

Per- and poly-fluoroalkyl substances (PFAS) are synthetic chemicals widely used in everyday products, causing elevated concentrations in drinking water and posing a global challenge. While adsorption methods are commonly employed for PFAS removal, the substantial cost and environmental footprint of commercial adsorbents highlight the need for more cost-effective alternatives. Additionally, existing adsorbents exhibit limited effectiveness, particularly against diverse PFAS types, such as short-chain PFAS, necessitating modifications to enhance adsorption capacity. Biochar can be considered a cost-effective and eco-friendly alternative to conventional adsorbents. With abundant feedstocks and favorable physicochemical properties, biochar shows significant potential to be applied as an adsorbent for removing contaminants from water. Despite its effectiveness in adsorbing different inorganic and organic contaminants from water environments, some factors restrict its effective application for PFAS adsorption. These factors are related to the biochar properties, and characteristics of PFAS, as well as water chemistry. Therefore, some modifications have been introduced to overcome these limitations and improve biochar's adsorption capacity. This review explores the preparation conditions, including the pyrolysis process, activation, and modification techniques applied to biochar to enhance its adsorption capacity for different types of PFAS. It addresses critical questions about the adsorption performance of biochar and its composites, mechanisms governing PFAS adsorption, challenges, and future perspectives in this field. The surge in research on biochar for PFAS adsorption indicates a growing interest, making this timely review a valuable resource for future research and an in-depth exploration of biochar's potential in PFAS remediation.