Antibiotic adsorption from aqueous media by using silica aerogels derived from amine-bridged silsesquioxane networks

Amine-functionalized silica adsorbents are an important class of materials efficiently employed in separation applications of pharmaceutical effluents. This study aimed to develop a series of novel amine-substituted silica aerogels by using a six-functional bridged aminosilane and test their effectiveness as adsorbents in removing ciprofloxacin molecules. The aerogels were produced by co-gelation of amine and methyl functional alkoxysilanes with tetraethyl orthosilicate, followed by evaporative drying. The degree of amine-methyl functionalization was altered by changing the molar content of silanes. Structural variations induced by the change in amine-methyl content were evaluated using FTIR, SEM, N2 porosimetry, and SAXS analyses. The findings revealed a porous structure that can be tuned from macroporous to microporous profile. Increasing amine content led to an enhancement in the apparent surface area values up to 705 m2/g, which in turn proved to be beneficial physically and chemically for the adsorption behavior of the samples. Adsorption studies confirmed that the equilibrium and kinetic data fit the Langmuir and pseudo-second-order kinetic models, respectively and the process is spontaneous and endothermic. The rich amine-methyl functionality and large surface area endowed the aerogels with excellent adsorptive performance, achieving a high capacity of 101 mg/g and reusability up to nine cycles.