Biochar-based Downflow Fixed-Bed Adsorption Systems for Water Treatment: Process Optimization, Reusability, and Techno-Economic Evaluation

Adsorption processes have emerged as promising solutions for water treatment, particularly when utilizing bioderived materials, due to their environmental sustainability. Nevertheless, a key challenge of this approach lies in the regeneration of spent materials. This study investigates the possibility of using biochar in a fixed-bed adsorption system for water treatment, focusing on its potential reuse following an environmentally friendly regeneration process and evaluating its feasibility for large-scale applications. Rapid small-scale column tests were conducted to optimize process parameters for removing sulfamethoxazole while using a high concentration to prove the concept and evaluate process efficiency. Under optimal conditions, the column maintained its operational capability after treating 33 L, achieving a saturation time of up to 130 h. The adsorption behavior was explored using kinetic models, analyzing breakthrough curves to reveal dynamic performance. The Clark model demonstrated the highest degree of fit to the data, making it a reliable tool for predicting adsorption efficiencies. The reusability of the adsorbent was evaluated through a sustainable regeneration approach, enabling effective reusability for up to 5 cycles. The applicability of the proposed treatment method was further validated on real water samples, demonstrating a significant reduction in turbidity and the concentration of detected substances in the samples. Finally, a techno-economic assessment estimated a treatment cost of €0.89/m3, supporting the economic feasibility of the approach. This research highlights the efficiency and scalability of the proposed process as a viable, cost-effective water treatment solution for large-scale applications.