Facile sol–gel synthesis of silica sorbents for the removal of organic pollutants from aqueous media

Abstract

In this work, silica-based adsorbents were prepared by a facile and straightforward sol–gel route. The adsorption capacity of the prepared materials was investigated using methylene blue (MB) and metamizole (sodium dipyrone – DIP) as reference pollutants. We observed that the samples prepared here, regardless of the absence of catalyst, templating agent, or heat treatment step during their preparation, are promising materials for adsorption purposes. The adsorption kinetics was investigated based on the pseudo-first and pseudo-second-order kinetic laws of Lagergren. The most promising sample showed an adsorption capacity of 36.9 mg g−1 (removal capacity of 92.3%) for MB and 8.5 mg g−1 (20.5%) for DIP in aqueous media kept at a pH = 7.0. We observed that the adsorption of these species is strongly associated with the electrostatic interaction between the pollutant molecules and the silica surface. Such an interaction was increased when the pH of the solution increased from 3.0 to 4.5, 7.0, or 9.0. The incorporation of amino groups derived from (3-Aminopropyl)triethoxysilane (APTES) increased the affinity of silica for MB and DIP. These functional groups were incorporated into silica via post-grafting and co-condensation. Furthermore, it was shown that the silica matrices tested here can be easily regenerated by heat treatment in air at 450 °C for periods as short as 15 min, allowing its reuse in subsequent adsorption cycles.

Keywords

• Facile synthesis
• Mesoporous silica
• Organic pollutants
• Water treatment
• Adsorption
• Thermal regeneration