Adsorption behavior of tetracycline and methylene blue onto microwave-assisted pine bark biochar

Abstract

The widespread occurrence of antibiotics and synthetic dyes in aquatic environments poses serious environmental challenges due to their persistence and potential ecological impacts. This study evaluated the adsorption performance of tetracycline (TC) and methylene blue (MB) onto pine bark-derived biochar prepared via microwave-assisted pyrolysis. Optimal adsorption was achieved at pH 7 for TC and MB, with equilibrium attained within 120 min. The adsorption kinetics of both pollutants were best described by the pseudo-second-order model, while the Langmuir isotherm provided the best fit to the equilibrium data, suggesting predominantly monolayer adsorption on homogeneous adsorption sites. The maximum adsorption capacities were 36.36 mg.g⁻¹ for TC and 163.93 mg.g⁻¹ for MB. These findings highlight the potential of microwave-assisted pine bark biochar as an efficient, sustainable, and cost-effective adsorbent for the removal of antibiotic and dye contaminants from aqueous systems.