Adsorptive removal of amoxicillin from aqueous solutions using halloysite nanotubes

This study reports the effective adsorptive removal of amoxicillin from aqueous solutions using halloysite nanotubes as adsorbents. Pharmaceuticals are identified as well-known emerging pollutants which can pose risks to aquatic life and other organisms due to their toxicity. Toxicity may cause long-term effects even if they are present in trace levels. Among them, amoxicillin is the most widely used drug for the treatment of bacterial infections. As they are used extensively, they can be found in different environmental compartments. Studies have shown that drugs cannot be absorbed and digested well by living organisms. In this study, halloysite nanotubes were selected due to their high adsorption capacity, wider porous structure and cost effectiveness. In the study, Langmuir, Freundlich and Temkin isotherm models were used to investigate adsorption isotherms. Also, kinetic studies were evaluated using pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion modules. Langmuir isotherm was found to be the best fitted isotherm for the experimental data, which indicated a monolayer adsorption. Kinetic data were also fitted to pseudo-second-order and Elovich modules. The structural and surface properties of halloysite nanocomposites were characterized by X- Ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The maximum adsorption capacity was 118.75 mg/g and a 70.03% removal efficiency was observed. Unlike other tubular materials, halloysite is an abundantly available natural nanomaterial, which makes it attractive and convenient for technological applications.