Fe Oxides–Eggshell Composites: Development, Characterization, and Oxytetracycline Adsorption Test

Abstract

While emerging pollutants are being detected in water bodies globally, a significant amount of solid waste that could be used for effluent remediation is being discarded. This not only reduces the half-life of landfills but also contributes to environmental pollution. Of these, eggshells (ES) are one of the most discarded food waste items worldwide. This paper presents the development and characterization of ES-based adsorbent for the removal of oxytetracycline (OTC), an emerging pharmaceutical pollutant, from aqueous solutions. The sorption of OTC on ES and ES-derived materials has not been previously studied. The ES was modified by removing the organic layer and both materials were used to grow Fe oxides, which can impart magnetic response to allow indirect manipulation or the addition of new sorption sites. Two methodologies were employed to synthesize Fe oxides: alkaline oxidation in the presence of nitrate and impregnation–pyrolysis (IP), which have not been used previously for developing magnetic ES. The materials developed by IP exhibit the highest total specific surface area and display a magnetic response due to the presence of magnetite and maghemite. Moreover, they exhibit a negative zeta potential over a wide range of pH values. All materials were able to adsorb OTC at pH 3, 7, or 9, indicating that ES (the simplest material) and ESIP (composite with good enough magnetic response) are suitable for removing OTC from aqueous solution. ES is recommended when indirect manipulation is not necessary, whereas ESIP is recommended when it is required. In order to explore the potential for reuse of the composite-pollutant materials, their antibacterial capacity against E. coli and E. faecium was evaluated. The findings of the present work contribute to the development of a circular economy by reducing waste generation, minimizing the consumption of natural resources, and reducing greenhouse gas emissions, while improving environmental protection.