Response surface modelling of methylene blue adsorption onto Ceratonia siliqua leaves

This study investigates the application of Ceratonia siliqua L. leaves as a sustainable and low-cost biosorbent for the removal of methylene blue from aqueous solutions. A Box-Behnken design combined with response surface methodology was employed to model and optimise the adsorption process. The developed quadratic model exhibited excellent statistical performance (R2 = 0.9988), confirming the reliability and predictive accuracy of the experimental design. Numerical optimisation identified the optimal operating conditions as an adsorbent dose of 29.23 mg, a solution pH of 10.36, and a contact time of 7.39 min, with an overall desirability value of 0.99. Regeneration experiments performed over five adsorption–desorption cycles demonstrated good reusability, with NaOH achieving the highest regeneration efficiency (81% efficiency retained after five cycles). These findings highlight the potential of C. siliqua leaves as an environmentally friendly, cost-effective, and reusable material for wastewater treatment applications.