Navegando por Assunto "Minerais de argila"

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Acesso aberto (Open Access)
Adsorção de molibdato em minerais de argilas naturais e modificadas com ácido sulfúrico, ácido húmico e uréia
(2013-03) PEREIRA, Patrícia Magalhães; LEMOS, Vanda Porpino; RODRIGUES, E.; FAIAL, Kelson do Carmo Freitas
Clay sediments from the municipalities Assis Brazil (Acre), were leached with solutions of sulfuric acid, humic acid and urea, to evaluate the retention capacity of molybdate in these materials and to investigate the feasibility of the adsorption processes at solid-solution interfaces. The materials were characterized from data of XRD, FTIR spectra, surface charge and chemical composition. The Langmuir isotherm models, Freundlich and Sips were used to fit the experimental data of adsorption. The minerals identified in the clay sediments were smectite, kaolinite, illite, quartz, albite, calcite and microclineo. The chemical modification leads amorphization of the modified sample with sulfuric acid and delamination along the plane 001 of the modified sample with urea. The settings defined by mathematical parameters (KL,Kf) of the adsorption isotherms, evaluation Ce vs. qe, pH vs. Qe, Qmax (sips) and Kd, indicated that the S10H15 sample is more efficient in the adsorption MoO42- ,with com qMax = 6.83 mg. L-1.
Acesso aberto (Open Access)
Materiais híbridos orgânicos-inorgânicos: argilominerais, óxidos e polímeros
(Universidade Federal do Pará, 2018-03-23) CAVALCANTE, Manoella da Silva; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
The interaction on a nanometric scale of molecular or polymeric species with inorganic substrates constitute the basis for obtaining hybrid materials. The development of these materials represents an emerging and interdisciplinary topic between the frontiers of life sciences, materials and nanotechnology. The combination of these two materials, organic-inorganic, produces a new material with improved properties and structures essentially different from its individual components. Constituted by a continuous phase (matrix), being plastics or cellulose, and an inorganic phase, such as clay minerals or oxides. several papers have been published obtaining these materials with improved properties: traction modules, gas barrier, flame retardants, density, melt strength, electrical conductivity, etc. Capable of making industry flexible and rigid products and in the manufacture of electronic materials (wire and cable coatings manufacture of sensors / actuators), vaccine production, among others. The most clay minerals used in the synthesis of hybrid materials are the species montmorillonite, clay but others can also be used, such as illite and palygorskita. In the state of Maranhão, northeastern Brazil, there are several occurrences of clay minerals, most notably smectite, illite and palygorskite. Among these clay minerals two new occurrences have already been identified and characterized by the UFPA Group of Applied Mineralogy (GMA), such as Bentonite Formosa and Palygorskite, which are abundant in the region and do not yet have an application. In addition to a new occurrence of illite not yet characterized in the region of the municipality of Barão de Grajaú (MA). Another material with great potential for obtaining nanomaterials is the vanadium pentoxide, having intrinsic features such as alignment of the magnetic field, and redox system such as gel elasticity, enabling application in the electronics industry for the manufacture of batteries and electrochromic displays for sensors/actuators. In Brazil, vanadium pentoxide began to be produced in 2014 by Maracás S/A. Currently, its consumption is focused on the production of special steels for the manufacture of aircraft structures and the aerospace industry. At the national level the production and development of hybrid materials and platforms for use in high-tech industry is small. Thus, the development and improvement of nanomaterials is necessary using as starting material and clay minerals national occurrence oxides. Within this context, this thesis aimed to develop a study on application of three clay minerals (Mg-montmorrillonite, illite and Palygorskita) from northeastern Brazil, besides vanadium pentoxide in the processing of hybrid materials using as poly matrix (methylmethacrylate) (PMMA ) and cellulose nanofibers. For this, the methodology of this work was divided into three parts: The first one consisted of the collection or synthesis, treatment and characterization of the individual materials (clay minerals, vanadium pentoxide, methyl poly (methacrylate) and cellulose). The second was to obtain hybrid materials clay mineral-PMMA (AP) and vanadium pentoxide cellulose (VC) and the third one was mainly to evaluate the thermal and mechanical properties of the AP hybrids and the electrochromic properties of the VC films. The characterization of the samples confirmed the predominance of Mg-montmorillonite, Illita and Palygorskita. The natural clay and organophilic fraction were used to obtain 12 samples with common and elastomeric PMMA to perform the physical-chemical tests focusing mainly on flammability and traction. By means of XRD measurements it was possible to verify that there was interaction between the two organic-inorganic phases, and that in the elastomeric PMMA there was a better dispersion of the clay minerals. The tests carried out on these materials indicated that the hybrids exhibit intrinsic thermal and mechanical behavior of each material possibly related to the type of structure present in the inorganic phase, contributing to the increase or decrease of Tg, Tm, flammability and traction. Four V2O5-cellulose films were obtained and characterized. Electrochromic tests were conducted in the films that presented better performance. It was possible to verify that there was interaction between the nanofibers of vanadium pentoxide and cellulose maintaining the electrochromic property of the oxide. Potentiometric measures were found that after 30 and 100 cycles the films remained flexible and maintained their properties. In this way, this work concluded that it is possible to obtain hybrid materials with clay minerals coming from the northeastern region of Brazil and can adapt their thermal and mechanical properties according to their application. The same was observed for the VC films that presented satisfactory results and that can be used in displays and / or flexible sensors.
Acesso aberto (Open Access)
Mineralogia e geoquímica da ocorrência de palygorskita de Alcântara, bacia de S. Luís-Grajaú, Maranhão
(2011-12) AMORIM, Kamilla Borges; ANGÉLICA, Rômulo Simões
The Alcântara Formation (S. Luis-Grajaú Basin, Alcântara region, northern Brazil) is mainly constituted by mudstones, sandstones and limestones. These lithotypes represent a progradacional succession of lagun/washover and tidal channel deposits that overlap huge shoreface deposits. The main purpose of this work is to carry out a mineralogical and geochemical characterization of the clay minerals association related to the pelitic rocks of the Alcantara Formation, specially the known palygorskite occurrences. One geological profile was sampled (eight samples) and described at the Baronesa beach (Alcântara city). The samples were submitted to mineralogical and chemical analysis by means of the following techniques: X-ray diffraction, X-ray fluorescence, thermal analysis (TG-DTA) and scanning electron microscopy. The results showed that the Baronesa Beach profile is mainly composed by sandstones at the base, followed by mudstones with intercalations of limestones. A wide clay mineral assemblage was described in a lagoon environment, with different contents of palygorskite, chlorite, illite, smectite and traces of kaolinite. Small amounts of dolomite, calcite and feldspars were also observed. The genesis of these minerals assemblage are mainly related to arid to semi-arid climatic conditions during the deposition period, with high evaporation rates. Two generations of palygorskite were described: (1) white macroscopic accumulations easily observed in the field and frequently described in the literature; and (2) massive accumulation, as the dominant mineral, in the upper muddy levels of the Baronesa Beach profile. This second generation is described for the first time in this work, and may constitute metric levels with potential economic interest.
Acesso aberto (Open Access)
Mineralogia e geoquímica da palygorskita e argilominerais associados da fácies lagunar da Formação Alcântara, Cretáceo Superior da Bacia de São Luis – Grajaú
(Universidade Federal do Pará, 2012-04-01) AMORIM, Kamilla Borges; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
The Alcântara Formation lithotypes (pelites, sandstones and dolomites) outcrop along the cliffs in the town of Alcântara, Maranhão state, and are characterized by the occurrence of the clay mineral palygorskite mainly in the form of whitish pockets, more specifically in pelitic levels. This unit is represented by shoreface deposits generated by storms processes, covered by lagoon/washover and tidal channel, comprinsing a progradational succession. In this paper, the results of mineralogical characterization of these rocks are presented, in order to understand/define palygorskite origin (autigenic or detrital), discuss the geochemical context of paleoenvironmental conditions of rich-magnesium clay minerals formation and theirs paragenesis, specially the relation between palygorskita and dolomite. Furthermore, this research shows a preliminary assessment of mineral potential of palygorskita occurrence, showing the levels where this mineral is massive and the approximate thickness of the packets. A geological profile was described at Baronesa Beach, where 22 samples were collected in two field stages. After laboratorial preparation, they were submitted to the following instrumental techniques: X-Ray diffraction (XRD), X-Ray fluorescence, thermal analysis (DTA-TAG) and scanning electron microscopy (SEM). The first field stage results and chemical and mineralogical analysis were utilized in the submitted and accepted paper by Cerâmica journal. These data show that Baronesa Brach profile is composed of sandstones, in the base, succeeded by mudstones with dolomites intercalations. In the mudstones, a vast clay mineral assemblage was described, characteristic of lagoonal environment, with variations in the contents of palygoskite, dolomite, chlorite, illite, smectite and traces of kaolinite and feldspars. Two different generations of palygorksite were described: (1) in the form of pockets or macroscopic accumulations in the rich-palygorskite pelitic levels, and (2) in the massive form, as the higher pelitic levels dominant mineral of the Baronesa Beach profile. The second generation, described for the first time in this paper, may constitute metric levels with potential economic interest. In the second field stage, analysis were performed with more detail in pelitic layers, and also, in dolomitic layers. In this stage, it was possible to observe that palygorskite is indeed the dominant clay mineral in pelites, and appear as trace mineral in dolomitic levels. Data reveal that palygorskite contents tend to increase in the upper portions of the profile, showing an inversely proportional relationship with chlorite and illite clay minerals, whose values decrease as palygorskite increases. The relationship between palygorskite and dolomite is also very significant, because when the first mineral is the dominant, dolomite appears as the second most abundant mineral. This relationship is accentuated when SEM data are analysed, because both minerals always occur associated. Palygorskite micromorphological analysis indicate its origin is autigenic, that is, it was formed “in situ”, since its features do not exhibit any wearing or reworking, eliminating any possibility of detrital origin. It is known that palygorskite can be found in association with carbonate rocks and that the appropriated conditions for its formation are semi-arid to arid climate, high Si and Mg activities with Al available, and alkaline pH (~8). These conditions, added to mineralogical assemblage, indicate that Mg concentration in solution was probably enough to precipitate palygorskite, after dolomite formation. Others factors, such as changes in physic-chemical conditions (Si increasing by the consumption of other minerals (chlorite and illite?)), may also have favoured palygorskite precipitation. In addition to the observed results, new XRD data showed that upper horizons of the profile, approximately 4m of pelites, are the ones with the highest palygorskite concentration. This mineral occurrence seems to be very significant, with very high contents in some horizons, revealing prospects of future works related to industry properties of this mineral, to a better quantifying and to possibilities about its economic use.