polybasic acid-assisted sol-gel route to silica and ag-doped silica nanoparticies

Quasi regular silica nanoparticles are synthesized and post-treated for a facile homogeneous doping with metallic silver. The nanoparticles are obtained through a simple alkali-mediated sol-gel route in presence of tartaric acid and conventional ultrasonic agitation. Gelation in presence of both mechanical agitation and ultrasonic dispersion has lead to the formation of well-dispersed silica nanoparticles having an average particle size of less than 10 nm. In addition, tartaric acid was used to interfere in the hydrolysis stage that has lead to the formation of silica nanocubes probably by forming templates at the early stages of formation of the amorphous hydrous silica colloid. Unlike the acid hydrolysis route that produces irregular-shape grains or micro-sized agglomerates. TEM images in this study show that the combined application of tartaric acid template and ultrasonic agitation during gelation enhanced the formation of well dispersed silica nanocubes. XRD measurements showed that post-treatment of silica wet gel with metallic silver into the silica grains by sonication in silver ion solution and later reduction has successfully loaded the silica particles with silver to a good extent on the expense of regularity and dispersion of obtained nanoparticles. Samples were also characterized by FT-IR

Alkoxide-based sol-gel synthesis of MgO-ZrO2- SiO2 compositions

Using acetylacetone-complexed zirconium alkoxide and tetracthylsilane. the sol-gel technique was followed to prepare five different compositions within the MgO-ZrOr SiO2 system, primarily as amorphous powders. XRD analysis showed the formation enstatitc and zirconia on mild thermal treatment. The results of XRD and Raman spectra indicated that the obtained zirconia powders are of tetragonal phase at room temperature and was thermally stable over the temperature range of 1000-1300 °C. The powders showed aggregates of nanosize zirconia crystallites as shown by some SEM photos

Isolation of aeromonas species from diarrheal patients in Ismailia Governorate

In order to know the prevalence of Aeromonas species as a causative agent of diarrhea in Ismailia, three hundred and fifty stool samples and rectal swabs were collected from infants and children under the age of 5 years visiting El Kilo 11 Clinic suffering from acute diarrhea in the period from May 2004 to September 2004. Stool samples were collected from control group of fifty healthy infants and children of matched age and sex. It was found that 29 diarrheal samples were positive for Aeromonas species with prevalence of 8.28%. None of control samples were positive for Aeromonas. In most cases it was found that the infection is water or food borne. Aeromonas strains show high degree of antibiotic susceptibility

Preparation and characterization of some phosphate salts from crude phosphoric acid

Monosodium phosphate, MSP, di - sodium phosphate, DSP, and trisodium phosphate, TSP, samples were prepared both from partially purified and solvent extracted phosphoric acid fractions. Chemical analysis and preliminary tests showed that the degree of purity of the prepared samples from the solvent extracted acid were in good agreement with the standard samples. TGA confirmed the above findings. The x-ray diffraction patterns and IR- spectra showed that the prepared MSP [b,c], DSP [c] and TSP [c]possessed the same crystalline structures and specific IR absorption bands as the standard sample [S]. Preparations from partially purified phosphoric acid using step filtration and back-acidification, indicated that the orthophosphates obtained had satisfactory purity, but it was slightly less than those of samples produced from solvent extracted acid

Purification of wet-process phosphoric acid by solvent extraction

The purification of wet-process phosphoric acid [WPA] by di-isopropyl ether [DIPE] was studied. The partition coefficient, K, of WPA between water and DIPE at different temperatures was determined. The average value amounted to 4.7 X 10-2 at 25, decreasing as the temperature increased from 25 to 55. The extraction of WPA is apparently more favorable around room temperature. It was also found that the extraction of phosphoric acid in the organic layer increased the greater solvent/acid weight ratio. The batch-wise extraction and stripping of phosphoric acid from 200 ml crude acid yielded 39 g of pure phosphoric acid, 154.7 g of pure Na2HPO4, 7H2O and 215.2 g of pure Na3PO4, 8H2O beside 75 g of a precipitated cake during the chemical treatment of the raffinate

Toxicity of O,S,S,-trialkyl phosphorodithioates to the rat

A series of O, S, S-trialkyl phosphorodithioates was synthesized and examined for acute and delayed toxicity to rats. There was a wide variability in the toxicity of these compounds, with oral LD50 values ranging from 7.9 to 156.4 mg/kg and the time frame for the death occurred from 1-8 days. Two types of response have been observed, acute cholinergic and delayed toxic response. Signs of delayed intoxication, i.e., weight loss, diarrhea, uncontrolled urination and red staining around mouth and nose were apparent in rats treated with the lower molecular weight compounds. The atropine-2-PAM antidotal treatment gave variables results with O, S, S-trialkyl phosphorodithioates, i.e., from complete protection, partial protection [as evidence by prolongation in mean time to death], and no protection. Overall results indicated that two different mechanisms, cholinergic and non-cholinergic, have been involved in intoxication by O, S, S-trialkyl phosphorodithioates