Pb(2)CrO(5) nanoparticles were embedded in an amorphous SiO(2) matrix by the sol-gel process. The pH and heat treatment effects were evaluated in terms of structural, microstructural and optical properties from Pb(2)CrO(5)/SiO(2) compounds. X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), energy dispersive spectroscopy (EDS), and diffuse reflectance techniques were employed. Kubelka-Munk theory was used to calculate diffuse reflectance spectra that were compared to the experimental results. Finally, colorimetric coordinates of the Pb(2)CrO(5)/SiO(2) compounds were shown and discussed. In general, an acid pH initially dissolves Pb(2)CrO(5) nanoparticles and following heat treatment at 600 A degrees C crystallized into PbCrO(4) composition with grain size around 6 nm in SiO(2) matrix. No Pb(2)CrO(5) solubilization was observed for basic pH. These nanoparticles were incorporated in silica matrix showing a variety of color ranging from yellow to orange.
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 06/54946-9; This paper describes the synthesis, modification, and application of modified silica for the removal of lead ions from aqueous medium. The modification reaction provided a reduction in surface are from 737 to 399 m(2) g(-1), which was attributed to the 4-amine-2-mercaptopyrimidine molecule attachment onto its surface. The characterization through FTIR spectra demonstrated bands at 3347 cm(-1) assigned to N-H stretching vibrations and the absence of thiol bands at 2600 e 2547 cm(-1) at Si-mod spectrum is an indicative that the attachment occurred via SH groups. The linearization of adsorption isotherm data through the modified Langmuir equation resulted in a maximum adsorption capacity of 2.9 mu mol g(-1). The material was applied in a continuous flow system in the preconcentration of water samples from Parana River and the results were in agreement with metal concentration determined directly through atomic absorption spectrometry with graphite furnace. The method validation was performed through analysis of water standard reference material (1643e), which also presented a 7.2-fold enrichment factor.
This work describes the synthesis and characterization of 2-aminothiazole-modified silica gel (SiAT), as well as its application for preconcentration (in batch and column technique) of Cu(II), Ni(II) and Zn(II) in ethanol medium. The adsorption capacities of SiAT determined for each metal ion were (mmol g(-1)): Cu(II)=1.20, Ni(II)=1.10 and Zn(II)=0.90. In addition, results obtained in flow experiments, showed a recovery of ca. 100% of the metal ions adsorbed in a column packed with 500 mg of SiAT. The eluent was 2.0 mol L-1 HCl. The sorption-desorption of the studied metal ions made possible the development of a preconcentration method for metal ions at trace level in fuel ethanol using flame AAS for their quantification.