The effects of solution pH and temperature on the adsorption of fluoride onto bone char made from cattle bones were investigated in this work. It was found that the maximum adsorption took place at pH 3 and the adsorption capacity decreased nearly 20 times augmenting the pH from 3 to 12. This behavior was attributed to the electrostatic interactions between the surface of bone char and the fluoride ions in solution. The adsorption capacity was not influenced by temperature in the range from 15 to 35 °C. A comparison of fluoride adsorption capacities among several adsorbents revealed that the adsorption capacity of the bone char was 2.8 and 36 times greater than those of a commercial activated alumina (F-1) and a commercial activated carbon (F-400). The adsorption capacity is considerably dependent upon the physicochemical properties of the bone char surface and the solution pH.

Silver nanoparticles with a narrow size distribution were synthesized over the surface of two different commercial TiO(2) particles using a simple aqueous reduction method. The reducing agent used was NaBH(4); different molar ratios TiO(2):Ag were also used. The nanocomposites thus prepared were characterized using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), dynamic light scattering (DLS) and UV-visible (UV-vis) absorption spectroscopy; the antibacterial activity was assessed using the standard microdilution method, determining the minimum inhibitory concentration (MIC) according to the National Committee for Clinical Laboratory Standards. From the microscopy studies (TEM and STEM) we observed that the silver nanoparticles are homogeneously distributed over the surface of TiO(2) particles and that the TiO(2):Ag molar ratio plays an important role. We used three different TiO(2)Ag molar ratios and the size of the silver nanoparticles is 10, 20 and 80 nm, respectively. It was found that the antibacterial activity of the nanocomposites increases considerably comparing with separated silver nanoparticles and TiO(2) particles.

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