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Chlorhexidine acetate-loaded silver-kaolinite (CA-Ag-Kaol) was prepared and characterised, and its application as an antibacterial agent was studied. CA-Ag-Kaol was prepared by the adsorption of chlorhexidine acetate (CA) (0.5 mmol/L) on Ag (50% of the Cation Exchange Capacity (CEC) of kaolinite) on kaolinite. Kaolinite (Kaol), silver-kaolinite (Ag-Kaol), CA-modified kaolinite (CA-Kaol) and CA-Ag-Kaol were characterised by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field-emission scanning-electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, zeta potential analysis and dispersion behavior measurements. The modification of kaolinite with cationic silver and chlorhexidine ions did not change the structure of kaolinite, and the characterization of the kaolinite samples revealed the successful loading of cationic silver and chlorhexidine ions on the kaolinite. The antibacterial assay of the samples was carried out against Escherichia coli ATCC 11229, Pseudomonas aeruginosa ATCC 15442, Staphylococcus aureus ATCC 6538 and Enterococcus faecalis ATCC 29212 using the disc diffusion technique (DDT) and the minimum inhibition concentration (MIC) technique. Based on the antibacterial assay, CA-Ag-Kaol showed better antibacterial activity than Ag-Kaol and CA-Kaol, and it performed well in both distilled water and a 0.9% saline solution. Gram-positive bacteria were more susceptible to the antibacterial behavior of Ca-Ag-Kaol than Gram-negative bacteria. In conclusion, silver-kaolinite that has been loaded with chlorhexidine acetate can be used as an effective antibacterial agent because of its high antibacterial activity against wide spectrum of bacteria in solutions containing electrolytes (saline solution). [ABSTRACT FROM AUTHOR]

This paper discusses the formation of cetylpyridinium bromide (CPB), a cationic surfactant quaternary ammonium compound (QAC), immobilized on kaolinite with different initial CPB concentrations ([CPB] i ) and their effect on the antibacterial activity against Escherichia coli . The CPB-immobilized kaolinites were characterized by a CHNS analyzer, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), zeta potential (ZP) analysis and the amount of CPB adsorbed on kaolinite. The antibacterial assay of the samples was studied through the disk diffusion technique (DDT) against E. coli as a model bacterium. The amount of CPB adsorbed on kaolinite did not affect the structure of the parent kaolinite but affected the overall charge of the kaolinite and eventually affected their antibacterial activity. CPB-immobilized kaolinite with [CPB] i above the critical micelle concentration (CMC) possessed antibacterial activity because of reversal of the charge from negative to positive on the kaolinite surfaces, as proven by ZP analysis, which could allow the action of CPB molecules against bacteria cells. This was due to the bilayer formation of surfactant molecules via hydrophobic bonding of their long hydrocarbon chains on the kaolinite surfaces at surfactant concentrations above the CMC value. Therefore, one of the important factors in producing antibacterial agents from surfactant immobilized kaolinite (organo-clay) is by loading excess surfactant on the clay above its CMC level to ensure bilayer formation of surfactant molecules on clay surfaces. [ABSTRACT FROM AUTHOR]