Sustainable activated carbon from copper pod tree leaves for efficient tetracycline removal and regeneration

The persistence of tetracycline (TC) in water poses environmental risks, including antibiotic resistance, necessitating effective removal. This study explores the synthesis and application of activated carbon from copper pod tree leaves for TC adsorption. The adsorbent was produced through orthophosphoric acid activation at low temperature and characterized using multiple techniques. FESEM revealed a porous structure favorable for adsorption, while EDS confirmed the presence of carbon, oxygen, and phosphorus. FTIR identified hydroxyl and carbonyl groups facilitating hydrogen bonding with TC, enhancing adsorption. XRD confirmed the adsorbent's amorphous nature, while BET revealed a high surface area (865.06 m²/g). XPS further identified C-O and C = O bonds, further supporting adsorption. Kinetic experiments showed that the adsorption fitted to pseudo-second-order kinetics (R² = 0.9765), indicating chemisorption as the dominant mechanism. The isotherm modeling results indicated that the Langmuir model provided an excellent fit to the experimental data (R² = 0.9952), demonstrating a high monolayer adsorption capacity of 103.32 mg/g. Thermodynamics confirmed spontaneity and endothermicity with a ΔH° of 50.75 kJ/mol. The prepared adsorbent effectively removed TC across natural water matrices, retaining high performance after five regeneration cycles.