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This study deals with the synthesis of zeolite from natural kaolinite using hydrothermal treatment and evaluation of its phase transformation behaviors. The synthesized zeolites were modified with silver ion by using the ion exchange method for the enhancement of antibacterial properties. The characterizations were performed by using X‐ray diffraction spectroscopy, Fourier‐transform infrared spectroscopy, field emission scanning electron microscopy, and energy‐dispersive X‐ray. Disk diffusion technique (DDT) was used for the evaluation of the antibacterial property of the modified zeolites. This study observed the transformation of kaolinite into amorphous metakaolin after calcination treatment at 900°C and the successful reconstruction of amorphous metakaolin into synthesized crystal zeolite in the presence of sodium hydroxide as an activating agent. It was also found that the zeolite type A was produced at 100°C, while sodalites were produced at 120 and 140°C. DDT analysis revealed that the modified zeolites showed significant antibacterial capability against Escherichia coli ATCC 11229 and Staphylococcus aureus ATCC 6538. In general, the present study has proven that the zeolites can be synthesized from natural material and can be modified with silver ion to enhance their antibacterial activity. [ABSTRACT FROM AUTHOR]

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]

• Acid-treated kaolinite is able to be loaded with zinc ions and chlorhexidine. • Growth of isolated water vending bacteria is inhibited by modified kaolinite. • Modified kaolinite at low amount exhibits no cytotoxicity towards fibroblast cells. Access to the portable drinking water is of paramount importance and remains major challenge globally. Water vending machine (WVM) could supplies drinking water to the community but the bacterial growth in WVM is of great health risk requires urgent attention. Chlorhexidine zinc-modified kaolinite (C-Zn-Kao-t 1) was prepared, characterized and studied to inhibit the growth of isolated bacteria from WVM. The material was prepared by attaching chlorhexidine (0.5 mmol/L) on Zn-loaded kaolinite in which the loading capacity of Zn on the kaolinite (Kao-t1) satisfied 50% of cation exchange capacity of the kaolinite. The materials were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray and dispersion behaviour analysis. The C-Zn-Kao-t 1 did not cause any structural changes on the original structure and morphology of the kaolinite. The antibacterial activity of the materials was studied using disc diffusion technique (DDT) and minimum inhibition concentration (MIC) against bacteria isolated from WVM which are Stenetrophomonas maltophilia and Bacillus cereus as well Escherichia coli ATCC 11229 as a comparison. Based on these antibacterial assays, C-Zn-Kao-t1 sample has the highest DDT and the lowest MIC values against all bacteria (accept the MIC value for E. coli) showing its excellent antibacterial activity against bacteria isolated from WVM. Further test on cytotoxicity towards human fibroblast cells in vitro showed that 0.5 mg of the C-Zn-Kao-t1 is cytocompatible towards HSF 1184 cells. This concludes that chlorhexidine modified zinc-kaolinite are not cytotoxic and can be embedded safely in WVM in preventing bacteria contamination. [ABSTRACT FROM AUTHOR]