Hierarchically porous carbon from coffee husk: Pore development and antibiotic adsorption behavior

A hierarchically thermally porous carbon was produced from coffee husk using a two-step thermal method (carbonization and subsequent activation), aiming to correlate pore development with adsorption performance. Textural and structural properties were analyzed using SEM and N₂ adsorption-desorption, revealing a highly developed porous network and a BET surface area of approximately 535 m² g⁻¹ , consistent with abundant accessible adsorption sites. The porous carbon was tested for tetracycline adsorption from aqueous solution. The adsorbent demonstrates high removal efficiency under the investigated conditions over a broad pH range (2−12) and a maximum adsorption capacity of 14.545 mg g⁻¹ under the investigated conditions. Kinetic fitting indicates pseudo-second-order behavior, while equilibrium is best represented by the Freundlich model, suggesting a heterogeneous surface typical of biomass-derived carbons. Reusability testing shows the porous carbon retains adsorption performance over five consecutive cycles, indicating regeneration feasibility. The results highlight that coffee husk can be valorized into a low-cost, biomass-derived adsorbent with practical relevance for antibiotic removal from water.