Ceramic raw materials from the State of Maranhao, Brazil. Part 1: chemical and mineralogical characterization and technological properties of clays from Sao Luis, Rosario, Pinheiro and Mirinzal

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Barrier and Mechanical Properties of Clay-Reinforced Polymeric Nanocomposites

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fontes de potássio não trocável e potássio total em quatro solos do Estado do Ceará

The mineralogical composition of the soil plow layer (0-20 cm) was analyzed for the following soil suborders (according to the Brazilian soil taxonomy): Neossolo Quartzarênico. Argissolo Vermelho-Amarelo, Cambissolo Háplico and Latossolo Vermelho-Amarelo which samples were collected from different regions of the Ceará State. The present study had the objectives of identifying potential sources of both total and non-exchangeable potassium forms for plants located at the different soil fractions. Then highest content of K occurred in the Cabissolo Háplico soil, including both the total and non-exchangeable K forms. In the Neossolo Quartzarênico. Argissolo Vermelho-Amarelo and Latossolo Vermelho-Amarelo, the highest contents of both forms of potassium were impregnated at the sand fraction. The amount of potassium found in the both sand and silt fractions has its origin in the orthoclase mineral which was detected in the mineralogical analysis. In the clay fractio, the origin of the potassium is illite and a inter-stratified mineral (mica+montmorillonite). As compared with the total content, the amount of non-exchangeable potassium is low for all the four soils. It was more concentrated at clay fraction of the Cambissolo soil. The potassium content sequence in the soil was the following: Cambissolo Háplico > Argissolo Vermelho-Amarelo > Neossolo Quartzarênico > Latossolo Vermelho-Amarelo. The results showed that the distribution of the forms of potassium among the soils differ as a function of the nature of the dominating minerals detected in the mineralogical analysis (illite and orthoclase) which was discussed above.

Voltammetry of mercury (II) based on an organo-clay modified graphite electrode

Organo-clay complex of ligand-hexadecyltrimethylammonium with montmorillonite was made for the purpose of application as a preconcentration agent in a chemically modified carbon paste electrode for determination of mercury (II) in aqueous solution. It was found out that the adsorption of Hg(II) by organo-clay complex is independent of the pH of the solution. It was also found out that the adsorption of the remaining metals Cd(II), Ps(II), Cu(II), Zn(II), and Ni(II) was dependent on the changes in pH solutions and increased when it varies from 1 to 8. The resultant material was characterized by cyclic and differential pulse anodic voltammetry using a modified graphite paste electrode in different supporting electrolytes. The mercury response was evaluated with respect to pH, electrode composition, preconcentration time, mercury concentration, possible interferences and other variables.

Comparison of the nanoparticles performance in the photocatalytic degradation of a styrene-butadiene rubber nanocomposite

Much has been talking about the advantages of polymeric nanocomposites, but little is known about the influence of nanoparticles on the stability of these materials. In this sense, we studied the influence of both oxides of zirconium and titanium, known to have photocatalytic properties, as well as the influence of synthetic clay Laponite on the photodegradation of styrene-butadiene rubber (SBR). SBR nanocomposites were prepared by the colloidal route by mixing commercial polymer lattices and nanometric anatase TiO2, monoclinic ZrO2 or exfoliated Laponite clays colloidal suspensions. To better understand the degradation mechanisms that occur in these nanocomposites, the efficiency of different photocatalysts under ultraviolet radiation was monitored by FT-IR and UV-vis spectroscopies and by differential scanning calorimetric. It was observed that TiO2 and ZrO2 nanoparticles undoubtedly acted as catalysts during the photodegradation process with different efficiencies and rates. However, when compared to pure SBR samples, the polymer degradation mechanism was unaffected. Unlike studies with nanocomposites montmorillonite, exfoliated laponite clay effectively acts as a photostabilizer of polymer UV photodegradation. Copyright © 2012 Wiley Periodicals, Inc.

PLA and Montmorilonite Nanocomposites: Properties, Biodegradation and Potential Toxicity

The concern related to solid waste increases efforts to develop products based on biodegradable materials. At present, PLA has one of the highest potentials among biopolyesters, particularly for packaging. However, its application is limited in some fields. In order to optimize PLA properties, organo-modified montmorilonites have been extensively used to obtain nanocomposites. Although PLA nanocomposites studies are widely reported in the literature, there is still few information about the influence of organoclays on de biodegradation process, which is a relevant information, since one of the main purposals related to the final disposal of biopolymers as PLA is composting. Besides, in the last years some research has been conducted in order to evaluate the potential toxicity of montmorilonite, unmodified or organo-modified. Since the use of montmorilonite is expanding in different applications, human exposure and risk assessment are important issues to be investigated. In this context, this review intends to compile available information related to common organoclays used for PLA nanocomposites, its properties, biodegradation analysis and potential toxicity evaluation of nanocomposites, focused on montmorilonite as filler. Two issues of relevance were pointed out. The first is food safety and quality, and the second consideration is the environmental effect. © 2013 Springer Science+Business Media New York.

Influência dos diferentes cátions metálicos (Cu 2+ , Ni 2+ , Pb 2+ , Cd 2+ ) na formação do hidrogel bentonita – poli (vinil álcool)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização de argilas e biomassa da cana-de-açúcar e utilização como adsorventes na remoção de BTX

Pós-graduação em Química - IBILCE

O papel da argila na estabilização térmica de nanocompósitos: um estudo da ordem local e a média distância

Pós-graduação em Química - IQ

Análise pedoestratigráfica das formações Rio Claro e Piraçununga, no Centro-Leste do Estado de São Paulo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

CARACTERÍSTICAS DAS ROCHAS DA FORMAÇÃO CORUMBATAÍ UTILIZADAS NA INDÚSTRIA DE REVESTIMENTO CERÂMICO.

A Formação Corumbataí é atualmente utilizada com sucesso pela indústria de revestimento cerâmico no pólo de cerâmica de Santa Gertrudes. Este engloba os municípios de Santa Gertrudes, Rio Claro, Cordeirópolis, Limeira, Piracicaba e Araras. De acordo com os estudos geológicos realizados, as argilas da Formação Corumbataí foram divididas em cinco litofácies cerâmicas, sendo elas: maciça, laminada, intercalada I, intercalada II e alterada. De acordo com suas características químicas, são consideradas como argilas com teores médios de elementos fundentes, com os valores da soma dos óxidos alcalinos (Na2O + K2O) variando de 2,9% na litofácies alterada até valores de 4,3% na litofácies intercalada I. Os argilominerais predominantes são a illita e a caulinita (presentes em todas as litofácies), além da montmorillonita que ocorre com freqüência nas litofácies intercalada I e II e laminada. Outros minerais importantes são: quartzo, feldspato do tipo albita, hematita e calcita. Os resultados cerâmicos possibilitaram enquadrar as litofácies cerâmicas dentro do Grupo BIIb na Classificação de Revestimentos Cerâmicos (BII – valores de resistência à flexão da ordem de 180-300 Kgf/cm2; b – valores de absorção de água (Abs) de 6 a 10%), porém, alguns valores de Abs ficaram acima de 10% nas litofácies intercalada I, intercalada II e na alterada.

Estudo eletroquímico do sistema microestruturado montmorilonita-8- hidroxiquinolina na presença de íons metálicos

Pós-graduação em Química - IBILCE

Materiais híbridos argila-poli(metil metacrilato) obtidos através do método grafting

Pós-graduação em Química - IQ

Preparation of a clay-modified carbon paste electrode based on 2-thiazoline-2-thiol-hexadecylammonium sorption for the sensitive determination of mercury

A montmorillonite from Wyoming-USA was used to prepare an organo-clay complex, named 2-thiazoline-2-thiol-hexadecyltrimethylammonium-clay (TZT-HDTA-clay), for the purpose of the selective adsorption of the heavy metals ions and possible use as a chemically modified carbon paste electrode (CMCPE). Adsorption isotherms of Hg 2+, Pb 2+, Cd 2+, Cu 2+, and Zn 2+ from aqueous solutions as a function of the pH were studied at 298 K. Conditions for quantitative retention and elution were established for each metal by batch and column methods. The organo-clay complex was very selective to Hg(II) in aqueous solution in which other metals and ions were also present. The accumulation voltammetry of Hg(II) was studied at a carbon paste electrode chemically modified with this material. The mercury response was evaluated with respect to the pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. A carbon paste electrode modified by TZT-HDTA-clay showed two peaks: one cathodic peak at about 0.0 V and an anodic peak at 0.25 V, scanning the potential from -0.2 to 0.8 V (0.05 M KNO 3 vs. Ag/AgCl). The anodic peak at 0.25 V presents excellent selectivity for Hg(II) ions in the presence of foreign ions. The detection limit was estimated as 0.1 μg L -1. The precision of determination was satisfactory for the respective concentration level. 2005 © The Japan Society for Analytical Chemistry.