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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]

Abstract: Quaternary ammonium compound (QAC)-zeolites A, X and Y were prepared and characterized and their antibacterial activity was studied against Bacillus subtilis. The presence of QAC molecules on the zeolites has been proven by Infrared (IR) Spectroscopy. The antibacterial activity of these materials was determined by Minimum Inhibition Concentration (MIC) technique. From MIC values, QAC-zeolite X has highest antibacterial activity than that of zeolites A and Y due to the higher amount of QAC adsorbed onto zeolites X. To sum up, zeolite X was found to be a good support system for antimicrobial agents of QAC against B. subtilis. [Copyright &y& Elsevier]

Zeolites P in sodium (NaP) and potassium (KP) forms were used as adsorbents for the removal of calcium (Ca2+) and zinc (Zn2+) cations from aqueous solutions. Zeolite KP was prepared by ion exchange of K+ with Na+ which neutralizes the negative charge of the zeolite P framework structure. The ion exchange capacity of K+ on zeolite NaP was determined through the Freundlich isotherm equilibrium study. Characterization of zeolite KP was determined using infrared spectroscopy and X-ray diffraction (XRD) techniques. From the characterization, the structure of zeolite KP was found to remain stable after the ion exchange process. Zeolites KP and NaP were used for the removal of Ca and Zn from solution. The amount of Ca2+ and Zn2+ in aqueous solution before and after the adsorption by zeolites was analysed using the flame atomic absorption spectroscopy method. The removal of Ca2+ and Zn2+ followed the Freundlich isotherm rather than the Langmuir isotherm model. This result also revealed that zeolite KP adsorbs Ca2+ and Zn2+ more than zeolite NaP and proved that modification of zeolite NaP with potassium leads to an increase in the adsorption efficiency of the zeolite. Therefore, the zeolites NaP and KP can be used for water softening (Ca removal) and reducing water pollution/toxicity (Zn removal). [ABSTRACT FROM AUTHOR]

Excessive nitrate discharge into aquatic environment is a serious concern as it gives huge impacts on aquatic life as well as corrupts ecosystem and water sources. The effective treatment of nitrate-containing wastewater is essential for the sake of health and environmental protection. In this study, the adsorption of nitrate was carried out using porous rice husk silica functionalized with branched polyethyleneimine (RSi-bPEI). A series of experiments were conducted to measure several adsorption conditions, adsorption isotherms, kinetics, selectivity and reusability. Experimental results demonstrated that the functionalization with branched PEI (bPEI) has significantly improved the adsorption about 40% higher. The ideal conditions for the nitrate adsorption onto RSi-bPEI is at pH = 4, 0.5 g L−1 dose, 50 mg L−1 concentration and about 120 min adsorption time. The pseudo-second-order and Langmuir equations were the most suitable models to describe the nitrate sorption from aqueous solution with high correlation coefficient (0.99). The monolayer adsorption capacity was found to be 94.49 mg g−1 for RSi-bPEI and 47.46 mg g-1 for RSi. The reusability test manifested RSi-bPEI has good regeneration capacity, hence can be an ideal adsorbent for practical wastewater treatment. [ABSTRACT FROM AUTHOR]