Evaluation and Optimization of Azithromycin Removal by Raw and Alkali-Modified Peanut Shells Using Taguchi-Based Experimental Design Approach

Advanced treatment methods for removing antibiotics are cost-intensive. Subsequently, the goal of environmental and economic sustainability has switched attention towards bio-adsorbents. This study evaluated the effectiveness of raw and alkali-modified peanut shell powder as a cost-effective, novel adsorbent for removing azithromycin, one of the most widely used drugs worldwide. Prepared adsorbents were characterized by FTIR and SEM equipped with EDX. Experiments designed using a Taguchi-based approach were performed with a synthetic azithromycin solution to optimize initial concentrations, adsorbent dose, pH, and time. The results showed 63% removal with raw adsorbent at pH 11, an initial concentration of 20 mg/L, a time of 45 min, and an adsorbent dose of 0.4 g/L. With the modified adsorbent, an attractive 85% (maximum) removal was achieved at pH 11, an initial concentration of 30 mg/L, a time of 60 min, and an adsorbent dose of 0.4 g/L. Based on analysis of variance (ANOVA), pH and initial concentration are identified as the most influential factors for azithromycin removal. The improved adsorption performance of modified peanut shells (q_max = 192.1 mg/g compared to 159.2 mg/g for raw PS) was due to increased surface heterogeneity, enhanced electrostatic interactions, and greater accessibility of oxygen-containing functional groups, as confirmed by kinetic, isotherm, and surface analysis.