Dendritic bifunctional nanotraps inside SBA-15 for highly efficient removal of selected nonsteroidal anti-inflammatory drugs from wastewater

Large-pore mesoporous SBA-15 materials were functionalized with dendritic bifunctional ligands to achieve efficient adsorption of nonsteroidal anti-inflammatory drugs (NSAIDs) in aqueous solution mainly through a combination of anion-exchange ability of quaternary ammonium cations and pi-pi interaction capability of oxygen activated phenyls. The synthesis of such a dendritic ligand starts from propylamine on SBA-15 followed by consecutive amine-epoxy reactions with resorcinol diglycidyl ether (RDGE) and methylamine, and then amination of terminal epoxy with trimethylamine. The results from Fourier-transform infrared spectroscopy, nitrogen adsorption-desorption measurements and elemental analysis reveal that the bifunctional dendritic nanotraps have been created successfully inside the mesochannels of SBA-15 (DNT@SBA-15). Adsorption kinetics for NSAIDs was very rapid following a pseudo-second-order kinetic model, and adsorption isotherms were fitted well by the Langmuir isotherm model. Notably, DNT@SBA-15 demonstrated remarkably high adsorption capacities for NSAIDs, with maximum values of 1037.3 mg g(-1) for ibuprofen, 821.3 mg g(-1) for naproxen and 781.3 mg g(-1) for diclofenac at pH 7.0. The adsorption was presumed to be governed by a dual-interaction mechanism including electrostatic and van der Waal's interactions. This study demonstrates that the developed dendritic anion-exchanger can be a promising material for removing NSAIDs adsorption from environmental water.