Tuning adsorption capacities of hybrid mesoporous silica nanospheres and adsorption mechanism study for sulfamethoxazole and diclofenac removal from water

Abstract

The functionalization of mesoporous silica nanospheres and mesoporous hybrid core–shell magnetic silica nanospheres has been carried out through post-synthetic procedures, and these materials have been tested as adsorbents for the removal of sulfamethoxazole (SMX) and diclofenac (DF) from water. The effects of the silica material and the types of functionalities anchored on the silica surface have been investigated. Additionally, the unreacted silanol groups on the silica surface have been capped with hydrophobic trimethylsilyl groups to modify the hydrophilic-hydrophobic properties of the materials. The materials have been characterized by textural, spectroscopic, and microscopic techniques. The maximum adsorption capacity and kinetics of adsorption were determined using adsorption and kinetic theoretical models. The experimental results indicate that both the surface area and the presence of specific functionalities on the silica surface, including zwitterionic groups like hydroxide choline and methyl p-toluene sulfonate choline, have a significant impact on the material's adsorption capacity. The adsorption studies revealed that the highest adsorption capacity (qt) for DF (80.7 mg L-1) and SMX (27.2 mg L-1) was achieved with PTS-Chol-MSN, which consists of mesoporous silica nanospheres possessing a larger surface area, unprotected silanol groups and the methyl p-toluene sulfonate choline functionality on its surface. The mechanism of drug adsorption involves physical and chemical adsorptions with the presence of H-bonding and π-π stacking interactions.