Synthesis and evaluation of new organofunctionalized silica materials obtained by sol-gel methods applied to ethinylestradiol adsorption

The presence of micropollutants in the environment has been detected in a number of springs in Brazil and in several other countries. Despite the low concentrations of these compounds in aquatic environments, they are capable of causing biological effects on aquatic organisms. Thus, new methods for removing these contaminants need to be pursued. This work reports the synthesis and characterization of a xerogel based on an inorganic core of rigid silica obtained by the sol-gel method, and four adsorbents were synthesized from the organofunctionalization of a silica network, with the ligands cyclohexylamine (CyA), aniline (PhA), benzylamine (BnA) and 2-picolylamine (AMPy), which showed high potential for application as an adsorbent for the emerging contaminant ethinylestradiol. The materials were characterized using IR, ¹³C and ²⁹Si NMR, CHN, TGA, SEM, and BET techniques, which show that adsorbents were formed and that they are particulate, non-porous, and thermally stable up to approximately 548 K. Adsorbent properties were studied, observing the optimum pH value of 5.5 and the equilibrium time in 60 minutes. The experimental data for the adsorption isotherms were closely modeled on the Langmuir and Freundlich models, as a spontaneous process that fits both models and showing adsorption capacity values between 1.05 and 1.46 mmol g⁻¹. The regeneration conditions with acetonitrile were tested; reuse was studied for six cycles and showed very satisfactory results.