Efficient biochar regeneration for a circular economy: Removing emerging contaminants for sustainable water treatment

Biochar is widely known as a highly effective adsorbent for water treatment, capable of removing a wide range of pollutants. However, its saturation point limits its long-term use, but regeneration can extend its applicability. This study aims to develop a sustainable method for removing pollutants from water that aligns with the concept of the circular economy. Biochar derived from forest residue was used to remove emerging pollutants such as fipronil (FIP), venlafaxine (VEN), sulfamethoxazole (SMX) and trimethoprim (TRM). A comparative analysis of the adsorption of the studied pollutants onto biochar was performed by analyzing the kinetics, where it was found that SMX exhibited the lowest adsorption efficiency, prompting further optimization experiments. Under optimal conditions, adsorption isotherms were used to investigate the pollutant removal mechanisms. The results showed that biochar exhibited high adsorption capacities for FIP, VEN, SMX and TRM, which were 3.77, 2.09, 2.71 and 3.88 mg/g, respectively. Regeneration treatments were applied to remove adsorbed contaminants after biochar saturation. Among them, heat-activated persulfate showed the most effective regeneration, maintaining biochar's adsorption capacity after five cycles with no significant loss. Eventual morphological, structural and chemical alterations post-regeneration were assessed using different characterization techniques. The findings of this research highlight the potential of biochar for sustainable water treatment, supporting the circular economy by extending its life cycle through effective regeneration.