Silica-Based Porous Adsorbents for Efficient 17α-Ethinylestradiol Removal: Role of Organic Functionalization and Water Matrices

Three silica-based porous adsorbents, MCM-41 (pure silica), vinyl-MCM-41 (hybrid silica), and Ph-PMO (periodic mesoporous phenylene-silica), were tested to evaluate the effect of organic functionalities on removing the hormone disruptor 17α-ethinylestradiol (EE2) from water. Different adsorbent dosages were tested in ultrapure water spiked with 200 μg L^-1 EE2, and the results revealed that adsorbent concentrations higher than 500 mg L^-1 did not significantly enhance the EE2 removal efficiency. Both materials containing organic functionalities (using a dose of 500 mg L^-1) were tested in ultrapure water, phosphate buffer at pH 5, 7, and 9, and wastewater effluent to evaluate the pH impact and the effect of different water matrices on their adsorption performance. An increase in pH significantly improved the EE2 adsorption capacity of Ph-PMO, reaching 94 ± 2% at pH 9, while it decreased the adsorption efficiency of vinyl-MCM-41 to 14 ± 7% at the same pH. Following a comprehensive characterization of the materials, including assessments of chemical stability across varying pH conditions, point of zero charge, hydrophobicity, and textural properties such as specific surface area, pore volume, and pore diameter, the findings suggest that the homogeneous distribution of organic functionalities in Ph-PMO enhances surface interactions, such as π-π stacking and hydrophobic interactions, with the EE2 hormone. Ph-PMO demonstrated superior performance in wastewater effluents, and kinetic studies showed rapid EE2 adsorption across all matrices, reaching equilibrium within 5 min. This study highlights the potential of Ph-PMO for the advanced-stage removal of EE2 from water effluents.