Synthesis and characterization of cethyltrimethyl ammonium bromide and silver supported Nay zeolites for antibacterial applications

Abstract

Microbial resistance to antibiotics and antibacterial agents and limitation of the effectiveness of the current antibacterial agent such as high cytotoxicity and short lifetime necessitates the development of advance and efficient support of the antibacterial agents. This study is about versatile application of NaY zeolite as a support for antibacterial agents cetyltrimethyl ammonium bromide (CTAB) and silver ions (Ag+). The NaY zeolite modified with various concentrations of CTAB and Ag+ were characterized for their structural, morphology and elemental analysis. The antibacterial activity of commercialized NaY (NaY-C) and synthesized NaY (NaY-S) zeolites modified with CTAB; and regenerated NaY (NaY-R), NaY-C and NaY-S modified with Ag+ were investigated. The NaY-S (327.23 ± 17.70 nm) with high crystalline (crystallinity 64-88%) and high purity was synthesized with and without using pre-treated rice husk ash (RHA) by seeding and ageing techniques in hydrothermal condition. The NaY-C (700 nm) and NaY-S were modified with CTAB with varying coverage based on 50-500% of the external cation exchange capacity (ECEC) of the zeolite producing CTAB-NaY and with varying concentrations of Ag+ (100, 600 and 900 mg/L) producing Ag-NaY. Regenerated AgY (AgY-R) zeolite was prepared by decomposition of CTAB-NaY-C (550°C, 5 hours), pre-treated with Na+ and ion exchange with Ag+ (100, 600 and 900 mg/L). The characterization results showed that the structure of the zeolites was preserved after calcination and modification with CTAB or Ag+. The antibacterial activity of the modified NaY zeolites was performed against Gram-negative (Escherichia coli ATCC 11229 and Pseudomonas aeruginosa ATCC 15442) and Gram-positive (Staphylococcus aureus ATCC 6538 and Enterococcus faecalis ATCC 29212) bacteria based on disk diffusion technique (DDT) and minimum inhibitory concentration (MIC) technique in saline solution (0.9 wt.%) and distilled water. Results showed that the amount of CTAB or Ag+ loadings affected the antibacterial activity of the samples as Gram-positive bacteria are more susceptible to CTAB-NaY, whereas Gram-negative bacteria are more susceptible to Ag-NaY. The antibacterial activities of Ag-NaY were proportional to the amount of Ag+ loadings, whereas the size of NaY zeolites did not influence the antibacterial activity of the samples. AgY-C-900 (NaY-C zeolite with 900 mg/L initial concentration AgNO3) showed optimal antibacterial activity compared to other NaY zeolites samples. The CTAB-NaY-C was regenerated to original NaY-R and reused as the support for Ag+ with its structure remained and exhibited good antibacterial activity. Due to the good performance of the antibacterial activities of CTAB-NaY and Ag-NaY, therefore, NaY zeolite could be used as the good support of the antibacterial agents of CTAB and Ag.