Adsorption of the antibiotic minocycline on cerium(IV) oxide: Effect of pH, ionic strength and temperature

Abstract

Adsorption of the antibiotic minocycline (MC) on cerium(IV) oxide, CeO 2, has been studied in batch experiments by performing adsorption isotherms/kinetics under different conditions of pH, supporting electrolyte concentration, and temperature. CeO 2 was composed by nanoparticles whose grain size was around 9 nm. The adsorption of MC on the studied material is strongly dependent on pH, increasing as pH decreases. The adsorption mechanism, controlled by diffusion processes, is strongly related to electrostatic attractions and H-bond formations mainly between dimethylamino, amide, carbonylic and phenolic groups of the antibiotic and the functional groups of CeO 2 nanoparticles. On the other hand, the adsorption capacity at constant pH increases as ionic strength decreases and as temperature increases. The analysis of thermodynamic parameters suggests that the adsorption on CeO 2 is endothermic and not spontaneous in nature. Ceria nanoparticles might act as an alternative adsorbent for pollution control.