Hidrogeneoftalato de potássio como molécula modelo para estudos de adsorção sobre TiO2

Este trabalho teve por objetivo utilizar o hidrogenoftalato de potássio como molécula modelo para estudos de adsorção em TiO2. Os resultados de adsorção do hidrogeneoftalato sobre TiO2 se ajustaram aos modelos de adsorção propostos por Langmuir e Freundlich, sendo que o modelo de Freundlich descreveu melhor o fenômeno. A adsorção foi função da temperatura e a capacidade de adsorção aumentou de 2,4 para 4,5 mg.g-1 quando se elevou a temperatura de 20 para 30ºC.The aim of the work was to use the potassium hYdrogenphthalate as molecule model for adsorption studies on TiO2. The results of adsorption of the hydrogenphthalate on TiO2 were fitted to the models proposed by Langmuir and Freundlich, but the model of Freundlich described better the phenomenon. The adsorption was a function of the temperature and the capacity of adsorption increased from 2,4 to 4,5 mg.g-1 when the temperature was increased from 20 to 30 ºC.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Evaluation of pure and Ag-doped TiO2 films in the photocatalytic activity of phenol

Pure TiO2 films, modified by the addition of Degussa P25 powder and Ag-doped were synthesized using sol-gel route and immobilized in borosilicate support at different withdrawing rates and dipping time. They were characterized by X-ray diffractometry, scanning electronic microscopy and high-resolution field-emission gun scanning electronic microscopy. Their photocatalytic activities under UV irradiation were examined using phenol. The higher activities were achieved through the Ag-doped films deposited with 0.4 mm s-1 and two dipping. Approximately 90% of the organic contaminant was photodegradated after 24 h of irradiation.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Polishing of water treated by a biological process with heterogeneous photocatalysis

Effluent from a vegetal extraction plant situated in the region of Botucatu, state of São Paulo, Brazil was treated by combining a biological process and heterogeneous photocatalysis. The biologically pretreated effluent was polished by heterogeneous photocatalysis on a laboratory scale, using TiO2 in suspension as catalyst. The heterogeneous photocatalysis experiments were carried out with natural pH (~7.5) and pH adjusted to 3 and 4. An analysis was made to ascertain how the addition of potassium persulfate inhibited the recombination of the e-/h+ pair and incremented the generation of hydroxyl radicals. Coagulation-flocculation to remove the catalyst in suspension reduced the effluent 's initial turbidity of more than 4000 NTU to 2 NTU in 30 min. The photocatalysis reduced the sample 's initial TOC (Total Organic Carbon) from about 40 mg L-1 (in O2 demand) to approximately 3 mg L-1 in 180 min, rapidly removing the odors from the sample and disinfecting the water.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Synthesis, characterization and determination of the metal ions adsorption capacity of cellulose modified with p-aminobenzoic groups

This paper describes the synthesis and characterization of p-aminobenzoic modified cellulose (Cell-PAB), as well as the separation and preconcentration of Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II) ions from an aqueous medium using a Cell-PAB bath and the column technique. The quantity of p-aminobenzoic groups attached to the cellulose surface, i.e., 1.81±0.04 mmol/g, was determined by elemental analysis. The FT-IR spectra of Cell-PAB revealed characteristic bands of p-aminobenzoic groups, indicating the desired functionalization of the cellulose surface. The adsorptive capacities for the metals (Ns) Cd, Cu, Ni, Pb and Zn (Ns) were, respectively, 1.72 ± 0.02, 1.96 ± 0.02, 1.88 ± 0.04, 2.01 ± 0.03 and 1.93 ± 0.03 mmol/g. Metal separations performed in flow experiments using a column packed with 1 g of Cell-PAB and 5 mL of 1.5 mol/L HCl solution as eluent achieved an almost 100% metal ions recovery rate

Determination of Cu, Ni and Pb in aqueous medium by FAAS after pre-concentration on 2-aminothiazole modified silica gel

This work describes the synthesis and characterization of 2-aminothiazole modified silica gel (SiAT), and the results of a study of the adsorption and pre-concentration (in batch and using a flow-injection system coupled to an absorption atomic spectrometer) of Cu(II), Ni(II) and Pb(II) in aqueous medium. The adsorption capacities for each metal ions in mmol g-1 were: Cu(II)= 1.18, Ni(II)= 1.15 and Pb(II)= 1.10. The results obtained in the flow experiments showed a recovery of practically 100% of the metal ions adsorbed in a mini-column packed with 100 mg of SiAT, using 100 µL of 2.0 mol L-1 HCl solution as eluent. The sorption-desorption of the metal ions made possible the application of a flow-injection system for the pre-concentration and quantification by FAAS of metal ions at trace level in natural water samples digested and not digest by an oxidizing UV photolysis

Mechanisms of phase formation along the synthesis of Mn-Zn ferrites by the polymeric precursor method

Considering the wide application of crystalline Mn-Zn ferrites microparticles, understanding synthesis routes that allow the achievement of such materials is a constant need. In this work, Mn-Zn ferrites, Mn(1-x)ZnxFe2O4 (0.15 <= x <= 0.30), were synthesized by the polymeric precursor method in well-cohtrolled steps and the mechanisms of phase formation under different thermal treatments were studied. Such investigation was performed by means of thermal analysis (TG/DTA), synchrotron X-ray powder diffraction (SXPD) (including in-situ and anomalous scattering experiments) and scanning electron microscopy (SEM). The ferrite precursor powders present the spinel as single crystalline phases whose cell parameters increase as Mn is substituted by Zn, indicating possible Fe deficiencies into the structure. The crystallization degree of these samples is also affected by the Mn substitution and reaches a maximum for x=0.25. Further thermal treatments in air at 700 degrees C and 1100 degrees C lead to additional events also related to the Zn content, such as carbonates elimination and crystallization of the contaminant phase hematite. Thermal treatments under N-2 atmosphere at 700 degrees C allow the achievement of powders with only the spinel phase, especially for x=0.25 for which highly crystalline and homogeneous ferrite is obtained despite the Fe deficiency determined by anomalous scattering SXPD. Finally, thermal treatments at 1100 degrees C under N-2 atmosphere jeopardize the stability of the spinel structure and lead to hematite precipitation. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Determination of Cu, Ni and Pb in Aqueous Medium by FAAS after Pre-Concentration on 2-Aminothiazole Modified Silica Gel

This work describes the synthesis and characterization of 2-aminothiazole modified silica gel (SiAT), and the results of a study of the adsorption and pre-concentration (in batch and using a flow-injection system coupled to an absorption atomic spectrometer) of Cu(II), Ni(II) and Pb(II) in aqueous medium. The adsorption capacities for each metal ions in mmol g -1 were: Cu(II)= 1.18, Ni(II)= 1.15 and Pb(II)= 1.10. The results obtained in the flow experiments showed a recovery of practically 100% of the metal ions adsorbed in a mini-column packed with 100 mg of SiAT, using 100 μL of 2.0 mol L -1 HCl solution as eluent. The sorption-desorption of the metal ions made possible the application of a flow-injection system for the pre-concentration and quantification by FAAS of metal ions at trace level in natural water samples digested and not digest by an oxidizing UV photolysis