Preparation, characterization, adsorption, and antibacterial assessments of silane-functionalized zeolites

In this study, the preparation and comparative analysis of two adsorbents based on silane-modified natural and synthetic zeolites for binding silver ions from aqueous solutions and evaluating their potential application as antibacterial agents against two strains of bacteria were conducted. (3-aminopropyl)triethoxysilane (APTES) was used for modification, and its presence in the resulting samples was confirmed by thermal analysis, BET surface area measurements, and infrared spectroscopy. Kinetic analysis showed that the silver adsorption process followed the Lagergren pseudo-second-order model, while the data were best described by the Freundlich isotherm, indicating multilayer adsorption on a heterogeneous surface. The maximum adsorption capacities for silver ions were 89.49 mg/g for natural zeolite and 61.19 mg/g for synthetic Beta zeolite. Natural zeolite exhibited a higher silver-binding capacity, leading to the conclusion that exchangeable cations in the structure of the starting material played a key role in silver binding and that ion exchange was the dominant mechanism. Both materials demonstrated good antibacterial properties against gram-negative Escherichia coli and the gram-positive Staphylococcus aureus. These findings highlighted the potential of APTES-modified zeolites as efficient adsorbents for silver ion removal and as antibacterial agents, paving the way for applications in water purification and antimicrobial technologies.