Removal of the ionophore antibiotic narasin using vegetal materials as bioadsorbents

Abstract

The occurrence of ionophore antibiotics, particularly narasin (NAR), in the environment, has recently become a matter of concern because of their widespread use, high eco-toxicity, and environmental persistence. This study assessed the adsorption–desorption characteristics of NAR onto a variety of low-cost by-products using batch-type experiments. Fourier transform infrared (FTIR) spectroscopy was performed on all samples, whereas solid-state ¹³C CP/MAS NMR analyses were undertaken on the six most effective adsorbents as well as on the three least efficient ones. The results show that, at low concentrations of antibiotic added (5–10 µmol L⁻¹), adsorption remained low, not exceeding 25.33%. At the three lowest concentrations (5–20 µmol L⁻¹), alfa, palm, and cactus fibers, as well as calcined coffee grounds exhibited adsorption rates always ≥65.12%. At concentrations ≥20 µmol L⁻¹, adsorption increased in bioadsorbents with higher organic matter content, reaching up to 100% for eucalyptus bark at 100 µmol L⁻¹. Adsorption data were adjusted to different models, with Freundlich presenting the best fit. No desorption was observed at low concentrations for most bioadsorbents, except for cactus and Mediterranean tapeweed fibers, as well as for raw and calcined coffee grounds, while it increased with higher concentrations (above 20 µmol L⁻¹), but generally remained below 10%, except for calcined coffee grounds and cactus fiber, where it reached 10.48% and 14.64%, respectively, at 100 µmol L⁻¹ of NAR added. All these results indicate that NAR is strongly retained on the tested bioadsorbents, suggesting that the ecological risks associated with this pollutant can be mitigated using these bioadsorbents.