Navegando por Assunto "Palygorskita"

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Acesso aberto (Open Access)
Beneficiamento de uma argila tipo paligorskita da bacia de S. Luis-Grajaú, região de Alcântara, MA, e sua utilização como adsorvente de fósforo
(2014-03) RODRIGUES, Gabriela Monice Arruda; NEVES, Roberto de Freitas; ANGÉLICA, Rômulo Simões
This study used a sample from the basin of S. Luís-Grajaú, Maranhão state, Brazil,consisting of a mixture of predominantly palygorskite and dolomite, approaching the existence of this new occurrence, suggesting a processing method and its application as phosphorus adsorbent, once dolomite is a pH soil corrector while palygorskite has the function of nutrients carrier. First, chemical and mineralogical characterizations were performed by X-ray diffraction, X-ray fluorescence, scanning electron microscopy and separation of sand, silt and clay fractions. Sedimentation and phosphorus adsorption experiments were also performed, with determination of kinetic curve. After the X-ray diffraction analysis, results show that the sample consists mainly of palygorskite and dolomite. Illite, chlorite and quartz are also determined. It was also possible to see that the different types of disaggregation used show no significant differences in the diffraction patterns of the samples. The sand-silt-clay separation, although it is only based on the size of the material, showed a reasonable efficiency for material separation, as the sedimentation tests, where it was noticed that after 24 h, dolomite had disappeared from the supernatant. Determination of the kinetic curve revealed that the adsorption period of 2 h is not sufficient for phosphorus adsorption, requiring 24 h to reach the reaction equilibrium. Sorption tests showed efficiency higher than 91% of the initial phosphorus in solution, and the maximum quantity adsorbed per gram of sample was 0.607 mg. The correlation with the adsorption isotherm models studied, showed better results for Langmuir-Freundlich isotherm, with correlation coefficient of 0.9993, which can be attributed to the fact that adsorption occurs in more than one layer.
Acesso aberto (Open Access)
Beneficiamento de uma argila tipo palygorskita da Bacia de São Luis-Grajaú, região de Alcântara (MA) e sua utilização como adsorvente de fósforo.
(Universidade Federal do Pará, 2012-09-04) ARRUDA, Gabriela Monice; NEVES, Roberto de Freitas; http://lattes.cnpq.br/9559386620588673
The estimated contribution of the industry minerals in Brazil is about 70% of National Mineral Production Value. These minerals are important because of its diverse applications. Among them, in clay minerals group, there is palygorskite, which presents the requirements to join special clays group, once their occurrence is restricted. Thus, this new mineral occurrences deserve attention and further study. Adding to this, there is the fact in the Amazon region, as well as in most areas of tropical and temperate zones, the acidity is an important factor in land degradation and represent one of the major problems faced by agriculture. Acid soils have several limitations, which hinders the use of nutrients, requiring the addition of fertilizers, always aiming maximum efficiency. In this context, this study used a sample from the Bacia de São-Luis-Grajaú, Maranhão State, consisting of a mixture which is predominantly palygorskite and dolomite, approaching the existence of this new occurrence, suggesting a processing method and its application as phosphorus adsorbent, once dolomite is a pH soil corrector, while palygorskite has the function of nutrients carrier. First, chemical and mineralogical characterizations were performed, by XRD, XRF, SEM and separation of sand, silt and clay fractions. Sedimentation and phosphorus adsorption experiments were also performed, with determination of kinetic curve. After the analysis of XRD, results shown that the sample consists mainly of palygorskite and dolomite. Illite, chlorite and quartz are also presented. It was also possible to see that the different types of disaggregation used showed no significant differences in the diffractograms of the samples. The sand-silt-clay separation, although only based on the size of the material, showed a reasonable efficiency for material separation, as the sedimentation tests, where it was noticed that after a 24 hours period, dolomite had disappeared from the supernatant. Determination of kinetic curve revealed that the adsorption period of 2 hours is not sufficient for phosphorus adsorption, requiring 24 hours to reach the reaction equilibrium. Sorption tests showed efficiency higher than 91% of the initial phosphorus present in solution, and the maximum quantity adsorbed per gram of sample was 0.607 mg. The correlation with the adsorption isotherm models studied, showed better results for Langmuir-Freundlich isotherm, with correlation coefficient of 0.9993, which can be attributed to the fact that adsorption occurs in more than one layer.
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.