Niobium pentoxide / silica nanocomposites with hierarchical pore structure as methylene blue and doxycycline adsorbent

Abstract

Nanocomposites formed by niobium pentoxide dispersed in a silica matrix, with pores modulated by the addition of a soluble polymer (polyethylene glycol 10000), were calcined at different temperatures and applied to remove methylene blue (MB) and doxycycline (DOX) from water. The temperature of calcination changed the morphology of the niobium pentoxide nanoparticles inserted in the silica matrix and the textural characteristics of the nanocomposites, influencing their adsorption properties. The adsorption of the two contaminants used as models was sensitive to the pH variation of the solution, being optimal at pH 11 and 9 for the removal of MB and DOX, respectively. The effect of ionic strength corroborated by the zeta potential and FTIR analyses of the nanocomposite, before and after adsorption, showed that the adsorption of MB (exothermic process) is due only to electrostatic interaction, while the adsorption of DOX (endothermic process) is due to electrostatic and n-π interactions. Both removal processes were spontaneous. The use of the nanocomposites for the adsorption of the two contaminants is efficient and economical since they can be regenerated and reused.