Optimizing the Adsorption Conditions for Removing Tetracycline from Water Using ZnCl2-Activated Carbon Derived from Walnut Shell

This study investigates the performance of ZnCl2-activated carbon derived from walnut shell as an adsorbent for eliminating tetracycline from water solutions. The adsorbent was characterized using various analytical techniques. The research evaluates the impact of important variables on the removal efficiency. Furthermore, response surface methodology was applied to optimize the adsorption parameters for tetracycline using the ZnCl₂-activated carbon synthesized from walnut shells. The results of the variance and response surface analyses demonstrated that a quadratic polynomial model provided the best fit for the experimental data. The model predicted that the optimal conditions for removing tetracycline were achieved at a pH of 5.40, with a maximum removal efficiency of 100%. This occurred with a contact time of 100 minutes using an adsorbent mass of 0.09 g. The effects and interactions of the main variables were analyzed using a Pareto chart. The highest adsorption capacity attained was 400 mg/g. After three regeneration cycles, the removal efficiency of tetracycline remained at approximately 95%. The adsorption process adhered to the pseudo-second-order kinetic model.