Agro-waste materials: A low-cost approach to ionophore antibiotics mitigation in aquatic environment

Abstract

Ionophore antibiotics, such as lasalocid (LAS), have emerged as significant environmental contaminants due to their extensive use, high toxicity, and persistence. This study evaluated the adsorption-desorption behavior of LAS on fourteen low-cost by-products using batch experiments. To elucidate the adsorption mechanisms, Fourier Transform Infrared (FTIR) spectroscopy was applied to all samples, while solid-state 13C CP/MAS NMR was performed on the most effective adsorbents. Results revealed that materials with pH between 4.5 and 5.5 and comparatively elevated exchangeable calcium and sodium contents (such as acacia and eucalyptus bark, palm and alfa fibers, orange peel, almond shells, and date stones) achieved high LAS adsorption efficiencies (≥96.3 %), regardless of initial concentration. Elevated organic matter content (17–68.4 %) in all the investigated by-products promoted LAS retention, with all samples maintaining ≥48.6 %. Freundlich isotherm provided the best prediction for LAS, indicating heterogeneous, multilayer sorption, while the Langmuir model fit less accurately. Desorption remained below 12 % for all materials, with the most effective adsorbents showing <2 %, suggesting quasi-irreversible retention across a wide pH range (3.7–7.4). These findings highlight the potential of using agricultural by-products as cost-effective and sustainable bio-adsorbents for mitigating emerging pollutants like LAS in aquatic environments, thereby reducing ecological and human health risks