scholarly journals On the structural formula of smectites: a review and new data on the influence of exchangeable cations

2021 ◽  
Vol 54 (1) ◽  
pp. 251-262
Author(s):  
Emilia García-Romero ◽  
Adrián Lorenzo ◽  
Andrea García-Vicente ◽  
Juan Morales ◽  
Javier García-Rivas ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Structural Formula ◽  
Exchangeable Cations ◽  
Correct Position ◽  
Octahedral Sheet ◽  
Structural Formulae ◽  
Cation Substitutions ◽  
Trioctahedral Smectites ◽  
Octahedral Cations

The understanding of the structural formula of smectite minerals is basic to predicting their physicochemical properties, which depend on the location of the cation substitutions within their 2:1 layer. This implies knowing the correct distribution and structural positions of the cations, which allows assigning the source of the layer charge of the tetrahedral or octahedral sheet, determining the total number of octahedral cations and, consequently, knowing the type of smectite. However, sometimes the structural formula obtained is not accurate. A key reason for the complexity of obtaining the correct structural formula is the presence of different exchangeable cations, especially Mg. Most smectites, to some extent, contain Mg2+ that can be on both octahedral and interlayer positions. This indeterminacy can lead to errors when constructing the structural formula. To estimate the correct position of the Mg2+ ions, that is their distribution over the octahedral and interlayer positions, it is necessary to substitute the interlayer Mg2+ and work with samples saturated with a known cation (homoionic samples). Seven smectites of the dioctahedral and trioctahedral types were homoionized with Ca2+, substituting the natural exchangeable cations. Several differences were found between the formulae obtained for the natural and Ca2+ homoionic samples. Both layer and interlayer charges increased, and the calculated numbers of octahedral cations in the homoionic samples were closer to four and six in the dioctahedral and trioctahedral smectites, respectively, with respect to the values calculated in the non-homoionic samples. This change was not limited to the octahedral sheet and interlayer, because the tetrahedral content also changed. For both dioctahedral and trioctahedral samples, the structural formulae improved considerably after homoionization of the samples, although higher accuracy was obtained the more magnesic and trioctahedral the smectites were. Additionally, the changes in the structural formulae sometimes resulted in changing the classification of the smectite.

Nickel-bearing clay minerals: I. Optical spectroscopic study of nickel crystal chemistry

Clay Minerals ◽  
1985 ◽  
Vol 20 (3) ◽  
pp. 367-387 ◽  
Author(s):  
A. Manceau ◽  
G. Calas ◽  
A. Decarreau
Keyword(s):  
Clay Minerals ◽  
Crystal Chemistry ◽  
New Caledonia ◽  
Ore Deposits ◽  
Octahedral Sheet ◽  
Al Content ◽  
Intermediate Phases ◽  
Optical Evidence ◽  
Trioctahedral Smectites ◽  
Nickel Crystal

AbstractNickel crystal chemistry was systematically studied in various phyllosilicates, mainly the natural phases selected from the ‘garnierites’ of the supergene ore deposits of New Caledonia. Minerals which do not usually occur in New Caledonian parageneses were synthesised, as they could represent intermediate phases of genetic importance. In the kerolite-pimelite series, a linear relationship occurred between the ratioI(13,20)/I(02,11)of thehkbands and Ni-content. Diffuse reflectance spectra were used to derive the crystal chemical parameters of Ni. These confirmed its divalent character and its occupation of octahedral sites; the resulting structural distortion was slight and could not be detected in some minerals. There was no optical evidence for Ni atoms in 4-fold coordination. The two main parameters which showed significant variations among the studied phases were site distortion and crystal field stabilization energy (CFSE). Site distortion was at a maximum in trioctahedral smectites and sepiolite. CFSE depended on the mineralogy, crystallinity and chemical composition (Al-content) of the phase. Finally, clay minerals are classified according to the increasing stability of Ni in the octahedral sheet, which has been tentatively related to the geochemical distribution of this element. Secondary minerals are usually enriched vs. primary ones and among them are nepouite and kerolite which exhibit a high CFSE in contrast to sepiolite.

Theoretical Study of Octahedral Substitution Effect in Delaminated Pyrophyllite: Physicochemical Properties and Applications

2021 ◽  
Author(s):  
Carla Romina Luna ◽  
Walter Guillermo Reimers ◽  
Marcelo Avena ◽  
Alfredo Juan
Keyword(s):  
Dft Calculations ◽  
Physicochemical Properties ◽  
Electronic Properties ◽  
Theoretical Study ◽  
Substitution Effect ◽  
Isomorphic Substitution ◽  
Octahedral Sheet ◽  
Octahedral Substitution

We have studied, using DFT calculations, some geometrical and electronic properties of delaminated pyrophyllite (D-P) and the corresponding layers that resulted from three isomorphic substitution on the octahedral sheet (Mg2+,...

Crystal chemistry and nomenclature of rhodonite-group minerals

2019 ◽  
Vol 83 (6) ◽  
pp. 829-835 ◽  
Author(s):  
Nadezhda V. Shchipalkina ◽  
Igor V. Pekov ◽  
Nikita V. Chukanov ◽  
Cristian Biagioni ◽  
Marco Pasero
Keyword(s):  
Crystal Chemistry ◽  
Structural Formula ◽  
Structure Type ◽  
Mineral Species ◽  
Triclinic Space Group ◽  
Space Group ◽  
International Mineralogical Association ◽  
Mineralogical Association ◽  
General Chemical

AbstractThis paper presents the nomenclature of the rhodonite group accepted by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA). An overview of the previous studies of triclinic (space group P$\bar{1}$) pyroxenoids belonging to the rhodonite structure type, with a focus on their crystal chemistry, is given. These minerals have the general structural formula VIIM(5)VIM(1)VIM(2)VIM(3)VIM(4)[Si5O15]. The following dominant cations at the M sites are known at present: M(5) = Ca or Mn2+, M(1–3) = Mn2+; and M(4) = Mn2+ or Fe2+. In accordance with the nomenclature, the rhodonite group consists of three IMA-approved mineral species having the following the general chemical formulae: M(5)AM(1–3)B3M(4)C[Si5O15], where A = Ca or Mn2+; B = Mn2+; and C = Mn2+ or Fe2+. The end-member formulae of approved rhodonite-group minerals are as follows: rhodonite CaMn3Mn[Si5O15]; ferrorhodonite CaMn3Fe[Si5O15]; and vittinkiite MnMn3Mn[Si5O15].

scholarly journals Sensory and Physicochemical Evaluation of Acacia and Linden Honey Adulterated with Sugar Syrup

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4845
Author(s):  
Zsanett Bodor ◽  
Zoltan Kovacs ◽  
Mahmoud Said Rashed ◽  
Zoltán Kókai ◽  
István Dalmadi ◽  
...  
Keyword(s):  
European Union ◽  
Physicochemical Properties ◽  
Profile Analysis ◽  
Electronic Tongue ◽  
Medical Product ◽  
Sensory Profile ◽  
High Price ◽  
Sugar Syrup ◽  
Physicochemical Evaluation

Honey is produced by honeybees and is used as a food and medical product. Adulteration of honey has been a problem for several years now because of the relatively high price of honey on the market according to its valuable composition. The aim of our study is to determine the physicochemical properties of authentic Hungarian linden and acacia honeys (pure samples or manipulated ones blended with sugar syrup) as well as commercially available blends of European Union (EU) non-European Union (non-EU) honeys. Authentic linden and acacia were blended with sugar syrup at 10%, 20% and 50% concentration levels, and physicochemical properties were determined according to the methods of the International Honey Commission. Our objectives also included testing of the performance of electronic sensory techniques (electronic tongue (ET) and electronic nose (EN)) in the detection of adulteration, and the results are compared to the sensory profile analysis. The results provide good average recognition and prediction abilities for the classification of adulterated and authentic honeys (>90% for ET and higher than >80 for EN). Misclassifications were found only in the case of honey with 10% added sugar syrup. The methods were also able to reveal adulteration of independently predicted samples.

Classification of traditional Chinese pork bacon based on physicochemical properties and chemometric techniques

Meat Science ◽  
2016 ◽  
Vol 117 ◽  
pp. 182-186 ◽  
Author(s):  
Xin Guo ◽  
Feng Huang ◽  
Hong Zhang ◽  
Chunjiang Zhang ◽  
Honghai Hu ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Chemometric Techniques

Modelling the Axial-Flow Compressors for Calculating Starting of Turbojet Engines

1985 ◽  
Author(s):  
Yan De-You
Keyword(s):  
Excellent Agreement ◽  
Axial Flow ◽  
Structural Formula ◽  
Experimental Results ◽  
Low Speed ◽  
Structural Formulae ◽  
Axial Flow Compressors

This paper provides a method of modelling the axial-flow compressors in the low speed starting regime of an engine from windmilling to idling. A structural formula for the model is established by means of reference (1). A method of step-by-step regression is provided by the author for determining the coefficient matrices of the structural formulae. Excellent agreement was obtained between the computational and experimental results.

scholarly journals Physicochemical Properties of Honey from Marche, Central Italy: Classification of Unifloral and Multifloral Honeys by Multivariate Analysis

2014 ◽  
Vol 9 (11) ◽  
pp. 1934578X1400901 ◽  
Author(s):  
Cristina Truzzi ◽  
Silvia Illuminati ◽  
Anna Annibaldi ◽  
Carolina Finale ◽  
Monica Rossetti ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Physicochemical Properties ◽  
Robinia Pseudoacacia ◽  
Central Italy ◽  
Physicochemical Characterization ◽  
Castanea Sativa ◽  
Principal Component ◽  
Pattern Recognition Methods ◽  
Multifloral Honey

The purpose of this study was the physicochemical characterization and classification of Italian honey from Marche Region with a chemometric approach. A total of 135 honeys of different botanical origins [acacia ( Robinia pseudoacacia L.), chestnut ( Castanea sativa), coriander ( Coriandrum sativum L.), lime ( Tilia spp.), sunflower ( Helianthus annuus L.), Metcalfa honeydew and multifloral honey] were considered. The average results of electrical conductivity (0.14 – 1.45 mS cm−1), pH (3.89 – 5.42), free acidity (10.9 – 39.0 meqNaOH kg−1), lactones (2.4 – 4.5 meqNaOH kg−1), total acidity (14.5 – 40.9 meqNaOH kg−1), proline (229–665 mg kg−1) and 5-(hydroxy-methyl)-2-furaldehyde (0.6–3.9 mg kg−1) content show wide variability among the analysed honey types, with statistically significant differences between the different honey types. Pattern recognition methods such as principal component analysis and discriminant analysis were performed in order to find a relationship between variables and types of honey and to classify honey on the basis of its physicochemical properties. The variables of electrical conductivity, acidity (free, lactones), pH and proline content exhibited higher discriminant power and provided enough information for the classification and distinction of unifloral honey types, but not for the classification of multifloral honey (100% and 85% of samples correctly classified, respectively).

Synthesis and crystallogenesis of ferric smectite by evolution of Si-Fe coprecipitates in oxidizing conditions

Clay Minerals ◽  
1987 ◽  
Vol 22 (2) ◽  
pp. 207-223 ◽  
Author(s):  
A. Decarreau ◽  
D. Bonnin ◽  
D. Badaut-Trauth ◽  
R. Couty ◽  
P. Kaiser
Keyword(s):  
Crystal Growth ◽  
Structural Evolution ◽  
Structural Formula ◽  
Atomic Ratio ◽  
Local Order ◽  
Chemical Formula ◽  
Octahedral Sheet ◽  
Smectite Layer ◽  
Apparent Concentration ◽  
Dioctahedral Smectite

AbstractSilico-ferric coprecipitates, with chemical formula, were aged in suspension at 75°, 100° and 150°C and the structural evolution of solids with time studied by XRD, TEM, and IR, Mössbauer and EXAFS spectroscopy. The initial Si-Fe coprecipitate was found to be amorphous but showed local order similar to that of a smectite layer. At 75°C only a weak structural evolution of the silico-ferric product towards a smectite-like structure was observed. Experiments performed at 100° and 150°C led to synthesis of a ferric smectite with structural formula. During syntheses a highly soluble silico-ferric complex appeared; the Si/Fe atomic ratio of this complex was 3, and the apparent concentration of Fe3+in solution reached 27 mm/l. These syntheses prove that the crystallization of a dioctahedral smectite, containing only Fe3+atoms in the octahedral sheet, is possible under strictly oxidizing conditions. However, crystal growth of a ferric smectite under these conditions is slow and only syntheses carried out at sufficiently high temperatures give convincing results.

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