Characterization of a brazilian smectite by solid state NMR and X-ray diffraction techniques

Abstract

As técnicas de difração de raios-X (DRX), análise térmica diferencial (ATD) e ressonância magnética nuclear no estado sólido com rotação no ângulo mágico (RMN-MAS) de 27 Al e 29 Si foram utilizadas para o monitoramento das etapas de fracionamento de uma amostra de esmectita brasileira, previamente moída, originária de Campina Grande, Paraíba, e utilizada como matéria-prima para a preparação de catalisadores ácidos. As frações foram obtidas por tratamentos físico e químico. As análises de DRX das frações areia e silte mostraram que ambas possuem predominantemente quartzo e feldspato, respectivamente. Os resultados de DRX da fração argila, saturada com K + e aquecida, confirmaram tratar-se de argilomineral do grupo 2:1, enquanto a análise da fração argila, saturada com Mg 2+ e glicolada, confirmou a presença de esmectita. Os resultados de RMN-MAS de 27 Al e 29 Si evidenciaram ser a fração areia constituída por cerca de 79% de quartzo; a fração silte possui 55% de quartzo, e a fração argila, rica em esmectita com baixa substituição isomórfica de Si por Al, contém 38% de quartzo.X-ray diffraction (XRD), differential thermal analysis (DTA) and 27 Al and 29 Si solid state MAS-NMR techniques were used to monitor the fractionation steps of a brazilian smectite, previously crushed, from Campina Grande, Paraíba. The sand, silt and clay fractions were obtained by physical and chemical treatments. The XRD analysis of sand and silt fractions showed that both fractions had predominant quartz and feldspar, respectively. The XRD results of the K + saturated and heated clay fraction confirmed that the natural clay belongs to the 2:1 clay-mineral group, whereas the analysis of the Mg 2+ saturated and glycolated clay fraction confirmed the presence of a smectite group clay. The MAS-NMR results of 27 Al and 29 Si showed that the sand fraction contains 79% of quartz and the silt fraction contains 55% of quartz, while the clay fraction is rich in smectite with low isomorphic replacement of Si by Al, and contains 38 % of quartz.

An environmentally friendly preparation of iodohydrins from alkenes mediated by clay-minerals

“…The diffractogram of all clays exhibited a peak at 2θ = 6.0º (14.7 Å), corresponding to the 001 plane of the smectite clay-mineral group. As the Brazilian clays F-101 and F-117 belong to the same region of other clays studied in the literature, 9 the 001 peak related indicates the presence of smectite group (S). All clays showed a strong reflection corresponding to 3.33 Å (2θ = 26.7º) and a minor one at 3.25 Å (2θ = 27.4º), suggesting that quartz (Q) was the predominant mineral in them.…”

“…All clays showed a strong reflection corresponding to 3.33 Å (2θ = 26.7º) and a minor one at 3.25 Å (2θ = 27.4º), suggesting that quartz (Q) was the predominant mineral in them. 9 The K-10 and F-117 clays also have others clay minerals: K-10 has mica, KSF has kaolite and F-117 has both mica and kaolinite. The 001 peak was very broad in KSF.…”

Characterization of natural Brazilian clays and their utilization as catalysts in the coiodination of alkenes with water and alcohols

“…11 In addition, this sample shows a peak at 3.30 Å (2 = 27.05º) corresponding to -quartz. 12 On the other hand, the XRD patterns of the natural clay F-117 show several peaks: 8.76 Å (2 = 10.15º) and 6.46 Å (2 = 13.69º) suggesting the presence of mica and kaolinite respectively and 3.18 Å (2 = 28.06º) indicating the presence of -quartz. In addition, the broad weak peak corresponding to smectite in F-117 clay suggests that this clay mineral is not the main component and its structure is disarranged.…”

“…The 27 Al NMR spectrum of F-101 clay shows a broad peak at 56.4 ppm due to tetrahedral Al ions and another one at -5.1 ppm which can be attributed to octahedral Al sites. In a previous paper, it was observed that tetrahedral Al sites were not present in the structure of this clay 12 as it was expected to be from the composition of feldspar, which was not detected by XRD as it presents low crystallinity. 11 On the other hand, the F-117 clay presents a peak at 61.4 ppm attributed to tetrahedral Al sites.…”

Remoção de metais pesados de efluentes industriais por aluminossilicatos

“…Técnicas como difração de raios-X, análise térmica diferencial e gravimétrica, microscopia eletrônica de transmissão e de varredura, análise química e ressonância magnética nuclear no estado sólido 28 permitem a identificação e classificação dos diversos minerais. Atualmente, as argilas cristalinas são agrupadas em sete grupos sistemá-ticos, apresentados na Tabela 2.…”