Sulfonamide antibiotics embedded into zeolite Y: A spectroscopic and theoretical approach to the study of host-guest and guest-guest interactions

INTRODUCTION The use of large amounts of persistent sulfonamide antibiotics ensures that they remain in the aquatic bodies, exerting their selective pressure for long periods of time [1]. A highly dealuminated zeolite Y has been proposed to irreversibly remove high amount of sulfonamides (up to 25 g for 100 g zeolite) with very favourable kinetics (adsorption higher than 90% in less than 1 min) from water [2]. The embedding of sulfonamides inside zeolite pores was revealed by unit cell parameter variations and structural modifications obtained by X-ray structure analysis carried out using the Rietveld method on the exhausted zeolite [2]. A combined experimental and computational study of the interactions of three sulfonamides - sulfadiazine, sulfamethazine, and sulfachloropyridazine – embedded into the cages of high silica zeolite Y is here proposed. RESULTS AND DISCUSSION For all host-guest systems, multidimensional and multinuclear (1H, 13C, 29Si) SS-NMR measurements evidenced the close vicinity of aromatic rings with zeolite framework. Host-guest and guest-guest interactions were also elucidated by in situ FTIR spectroscopy and confirmed by ab initio computational modelling. Single molecules of sulfamethazine and sulfachloropyridazine were stabilized inside the zeolite cages by the vicinity of methyl and amino groups, respectively. Sulfadiazine was present both in monomeric and dimeric form. REFERENCES [1] K. Kummerer, Chemosphere 75 (2009) 435. [2] I. Braschi, S. Blasioli, L. Gigli, C. E. Gessa, A. Alberti, A. Martucci, DOI 10.1016/j.jhazmat.2010.01.006.