Evaluation of Activated Carbon Prepared from Pistachio Shell as an Adsorbent for the Removal of Tetracycline Antibiotics from Aqueous Solution: Kinetic and Isotherm Study

Introduction: In recent decades, antibiotics have received much attention as emerging contaminants in aqueous environments. Tetracycline is one of the most widely used antibiotics all over the world and has been detected in aqueous environments at high concentrations. Antibiotic residues in aqueous environments may have toxic and adverse effects on the biological balance of aquatic ecosystems, leading to antibiotic resistance in microorganisms. Therefore, the treatment and removal of these pollutants from aqueous environments are essential. Materials and Methods: In this study, tetracycline antibiotic was removed using activated carbon prepared from hard pistachio shell as adsorbent in this treatment process, and the effect of various variables such as initial antibiotic concentration, solution pH, adsorbent level, and reaction time were investigated. The analysis of adsorption kinetics, isotherms, and the structural properties of the adsorbent was performed using scanning electron microscopy (SEM) and isoelectric point of zero charge (pHpzc). Results: The results showed that maximum efficiency of antibiotic removal under optimum conditions at the initial concentration of 20 mg/L, pH of 5, adsorbent level of 0.35 mg/L, and reaction time of 45 minutes was equal to 99.8%. The adsorption process of tetracycline antibiotics follows second-order kinetic model (R2= 0.9973) and Langmuir isotherm (R2= 0.995). Conclusion: This study showed that the adsorption process using activated carbon prepared from hard pistachio shell has high efficiency in terms of the removal of tetracycline antibiotics and can be used as an adsorbent to replace expensive adsorbents.