Synthesis, characterization, and application of modified silica in the removal and preconcentration of lead ions from natural river water

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Attachment of 2,2-bipyridine onto a silica gel for application as a sequestering agent for copper, cadmium and lead ions from an aqueous medium

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparative analysis of root surface smear layer removal by different etching modalities or erbium:yttrium-aluminum-garnet laser irradiation. A scanning electron microscopy study

The purpose of this study was to evaluate the effect of erbium:yttrium-aluminum-garnet (Er:YAG) laser (2.94 mu m) irradiation on the removal of root surface smear layer of extracted human teeth and to compare its efficacy with that of citric acid, ethylenediamine tetra-acetic acid (EDTA), or a gel containing a mixture of tetracycline hydrochloride (HCl) and citric acid, using scanning electron microscopy (SEM). Thirty human dentin specimens were randomly divided into six groups: G1 (control group), irrigated with 10 ml of physiologic saline solution; G2, conditioned with 24% citric acid gel; G3, conditioned with 24% EDTA gel; G4, conditioned with a 50% citric acid and tetracycline gel; G5, irradiated with Er:YAG laser (47 mJ/10 Hz/5.8 J/cm(2)/pulse); G6, irradiated with Er:YAG laser (83 mJ/10 Hz/10.3 J/cm(2)/pulse). Electron micrographs were obtained and analyzed according to a rating system. Statistical analysis was conducted with Kruskal-Wallis and Mann-Whitney tests (P < 0.05). G1 was statistically different from all the other groups; no statistically significant differences were observed between the Er:YAG laser groups and those undergoing the other treatment modalities. When the two Er:YAG laser groups were compared, the fluency of G6 was statistically more effective in smear layer removal than the one used in G5 (Mann-Whitney test, P < 0.01). Root surfaces irradiated by Er:YAG laser had more irregular contours than those treated by chemical agents. It can be concluded that all treatment modalities were effective in smear layer removal. The results of our study suggest that the Er:YAG laser can be safely used to condition diseased root surfaces effectively. Furthermore, the effect of Er:YAG laser irradiation on root surfaces should be evaluated in vivo so that its potential to enhance the healing of periodontal tissues can be assessed.

Clinical and Microbiologic Follow-Up Evaluations After Non-Surgical Periodontal Treatment With Erbium:YAG Laser and Scaling and Root Planing

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Flame AAS determination of metal ions in fuel ethanol after preconcentration on acid carboxymethylcellulose (CMCH)

This paper describes the preparation of acid carboxymethylcellulose (CMCH), and the results of a study on the adsorption and preconcentration (using batch and flow-through column methods) of Cd(II), Cu(II), Cr(III), Fe(III), Ni(II) and Zn(II) in ethanol medium. The adsorption capacities for each metallic ion were (in mmol g(-1)) Cd(II) = 0.92; Cu(II) = 1.45; Cr(III) = 1.70; Fe(III) = 1.60; Ni(II) = 1.30; and Zn(II) = 1.10. By means of the flow-through method, a recovery of ca. 100% of the metallic ions adsorbed in a column packed with 2 g of CMCH was found when 5.0 mL of 1.0 mol L-1 hydrochloric acid were used as eluent. An enrichment factor of 20 (100 mt solution containing 50 mu g L-1 of the metallic ions, concentrated to 5.0 mt) was obtained by this preconcentration procedure. The sorption-desorption procedure applied allowed the development of a preconcentration and Flame AAS quantification method of metallic ions in fuel ethanol at trace levels.

Determination of metal ions in natural waters by flame-AAS after preconcentration on a 5-amino-1,3,4-thiadiazole-2-thiol modified silica gel.

5-amino-1,3,4-thiadiazole-2-thiol groups attached on a silica gel surface have been used for adsorption of Cd(II), Co(II), Cu(II), Fe(III), Ni(II), Pb(II) and Zn(II) from aqueous solutions. The adsorption capacities for each metal ion were (in mmol.g(-1)): Cd(II)= 0.35, Co(II)= 0.10, Cu(II)= 0.15, Fe(III)= 0.20, Hg(Il)= 0.46, Ni(II)= 0.16, Pb(II)= 0.13 and Zn(II)= 0.15. The modified silica gel was applied in the preconcentration and quantification of trace level metal ions present in water samples (river, and bog water).

The chelation of metal ions by the acylpolyamine toxins from the web-spider Nephilengys cruentata: effects in the intoxication/detoxification of preys

Orb-web-spiders present a series of different strategies for prey capture, involving the use of different types of silk for web building, the use of adhesive traps in the webs, the secretion of toxic compounds to the spider's preys in the adhesive coating of the capture web and the biosynthesis of a wide range of structurally related acylpolyamine toxins in their venoms. The polyamine toxins usually block neuromuscular junctions and/or the central nervous system (CNS) of Arthropods, targeting specially the ionotropic glutamate receptors; this way these toxins are used are as chemical weapons to kill / paralyze the spider's prey. Polyamine toxins contain many azamethylene groups involved with the chelation of metal ions, which in turn can interact with the glutamate receptors, affecting the toxicity of these toxins. It was demonstrated that the chelation of Ni+2, Fe+2, Pb+2, Ca+2 and Mg+2 ions by the desalted crude venom of Nephilengys cruentata and by the synthetic toxin JSTX-3, did not cause any significant change in the toxicity of the acylpolyamine toxins to the model-prey insect (honeybees). However, it was also reported that the chelation of Zn+2 ions by the acylpolyamines potentiated the lethal / paralytic action of these toxins to the honeybees, while the chelation of Cu+2 ions caused the inverse effect. Atomic absorption spectrometry and Plasma-ICP analysis both of N.cruentata venom and honeybee's hemolymph revealed that the spider's venom concentrates Zn+2 ions, while the honeybee's hemolymph concentrates Cu+2 ions. These results are suggesting that the natural accumulation of Zn+2 ions in N. cruentata venom favors the prey catching and/or its maintenance in the web, while the natural accumulation of Cu+2 ions in prey's hemolymph minimizes the efficiency of the acylpolyamine toxins as killing/paralyzing tool.

The structure of a native L-amino acid oxidase, the major component of the Vipera ammodytes ammodytes venomic, reveals dynamic active site and quaternary structure stabilization by divalent ions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Collision of positronium with atoms, molecules and ions using a modified coupled-channel framework

Scattering of positronium (Ps) from atoms (H, He, Ne, Ar), molecule (H(2)) and ion (He(+)) have been investigated using a coupled-channel (CC) formalism with a regularised non-local exchange potential. The advantage of using such a regularized exchange potential in the close-coupling formalism and the normalizability aspect of the solution at low energies with a minimum effective coupling are discussed. Results for the elastic and total scattering cross-sections, resonance and binding energies in Ps-H, and pick-off annihilation results in Ps-He are found to be in excellent agreement with measurements and variational predictions. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Effect of citrate ions on the electrochemical behaviour of low-carbon steel in borate buffer solutions

The electrochemical behaviour of cold-rolled low carbon steel was studied on both active and passive potential regions in borate buffer solutions with and without the addition of sodium citrate (NaCit). In the active region anodic charges increased significantly and RCT values decreased with citrate, due to the formation of soluble complexes. In the passive potential region the film formed at +0.4 V in borate buffer solution with and without 0.010 M NaCit is probably enriched by Fe3O4 oxide, while films formed at +0.8 V are probably enriched by gamma-Fe2O3. The equivalent circuit [R-s(R(CT)Q)] fitted all experimental impedance data. (C) 2003 Elsevier Ltd. All rights reserved.

Influence of cerium (IV) ions on the mechanism of organosilane polymerization and on the improvement of its barrier properties

In this work, the effect of cerium (IV) ammonium nitrate (CAN) addition on the polymerization of bis-[triethoxysilyl]ethane (BTSE) film applied on carbon steel was studied. The electrochemical characterization of the films was carried out in 0.1 mol L(-1) NaCl solution by open-circuit potential measurements, anodic and cathodic polarization curves and electrochemical impedance spectroscopy (EIS). Morphological and chemical characterization were performed by atomic force microscopy (AFM), contact angle measurements, infrared-spectroscopy, nuclear magnetic resonance and thermogravimetric analysis. The results have clearly shown the improvement on the protective properties of the Ce(4+) modified film as a consequence of the formation of a more uniform and densely reticulated silane film. A mechanism is proposed to explain the accelerating role of Ce(4+) ions on the cross-linking of the silane layer. (C) 2008 Elsevier Ltd. All rights reserved.

Removal of metal ions from aqueous solution by chelating polymeric hydrogel

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)