scholarly journals Computer Simulations to Predict the Adsorption and Cation Exchange at Mineral Surfaces

2018 ◽  
Author(s):  
Sen Yang ◽  
Sen Yang ◽  
Qian Wang ◽  
Qian Wang ◽  
Chang Zhu ◽  
...  
Keyword(s):  
Cation Exchange ◽  
Computer Simulations ◽  
Mineral Surfaces

scholarly journals Interactions between Cationic Dye Toluidine Blue and Fibrous Clay Minerals

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 708
Author(s):  
Qingfeng Wu ◽  
Kristen Carlson ◽  
Qi Cheng ◽  
Xisen Wang ◽  
Zhaohui Li
Keyword(s):  
Cation Exchange ◽  
Toluidine Blue ◽  
Electrostatic Interactions ◽  
Cationic Dyes ◽  
Strong Interactions ◽  
Cationic Dye ◽  
Mineral Surfaces ◽  
Dynamic Simulations ◽  
Experimental Conditions ◽  
Maya Blue

Interactions between cationic dyes and negatively charged mineral surfaces have long attracted great attention from clay mineralogists, environmental scientists, and chemical engineers. In this study, the interactions between a cationic dye toluidine blue (TB) and palygorskite and sepiolite were investigated under different experimental conditions. The results showed that in addition to cation exchange, the specific surface area (SSA) of the minerals, particularly the formation of dimer molecules on the surface of both minerals, also accounted for the much higher TB uptake in comparison to their cation exchange capacities (CEC). The TB molecules were sorbed to the external surfaces, as no d-spacing expansion was observed in X-ray diffraction analyses. FTIR analyses showed strong interactions between the C=N or N-(CH3)2 group and the mineral surfaces, suggesting net electrostatic interactions if either of these functional groups bears a positive charge. Results from molecular dynamic simulations suggested dense monolayer TB formation on palygorskite because of its limited SSA and large CEC values. In comparison, a loosely dimeric formation was revealed on sepiolite for its large SSA and limited CEC values. Therefore, palygorskite is a better carrier for the sorption of cationic dyes, as evidenced by Maya blue paintings.

EFFECTS OF SOME CHEMICAL TREATMENTS ON K/Ca CATION EXCHANGE SELECTIVITY OF LAYER SILICATES

1972 ◽  
Vol 52 (2) ◽  
pp. 151-161 ◽  
Author(s):  
M. A. ARSHAD ◽  
P. M. HUANG ◽  
R. J. ST. ARNAUD
Keyword(s):  
Cation Exchange ◽  
Amorphous Materials ◽  
Mineral Surfaces ◽  
Layer Silicates ◽  
Chemical Treatments ◽  
Soil Clays ◽  
Mineral Components ◽  
Ca Ions ◽  
Oxalate Extraction ◽  
Exchange Selectivity

The effects of chemical treatments commonly employed to remove amorphous materials, on the K/Ca cation exchange selectivity (CES) of montmorillonite, kaolinite, chlorite, vermiculite, biotite, muscovite, and soil clays were studied. The K/Ca CES values for biotite and muscovite decreased appreciably upon peroxidation. Both the Na–dithionite–citrate–bicarbonate and boiling 0.5 N NaOH dissolution treatments resulted in a substantial increase in the K/Ca CES of biotite and muscovite. This was attributable to increases in the wedge-zone sites resulting from partial K-depletion of these minerals. Furthermore, the release of structural cations and their subsequent precipitation on mineral surfaces appears to have resulted in the "preferential occupation" of Ca-adsorbing sites and thus contributed to the lower selectivity of Ca ions. However, these two treatments affected the K/Ca CES of illite slightly. Acid NH4-oxalate extraction reduced the K/Ca CES values for all layer silicates investigated except chlorite for which the reverse was true. Selectivity of Ca and the CEC of illite were substantially increased by this treatment. The data suggested that the naturally occurring amorphous inorganic and organic constituents may have higher selectivity towards Ca relative to K. However, the degree of variation in the K/Ca CES seems to be further controlled by the amount, nature, and composition of amorphous materials and the mechanisms by which they are associated with the crystalline mineral components.

Computer simulations of cations order-disorder in 2:1 dioctahedral phyllosilicates using cation-exchange potentials and monte carlo methods

2014 ◽  
Vol 114 (19) ◽  
pp. 1257-1286 ◽  
Author(s):  
Erika J. Palin ◽  
Martin T. Dove ◽  
Simon A. T. Redfern ◽  
Joaquín Ortega-Castro ◽  
Claro Ignacio Sainz-Díaz ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Cation Exchange ◽  
Computer Simulations ◽  
Monte Carlo Methods

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

Scanning Electron Microscope Study of Bacteria on Mineral Surfaces

1976 ◽  
Vol 34 ◽  
pp. 130-131
Author(s):  
V.K. Berry
Keyword(s):  
Oxidation Reaction ◽  
Electron Microscope Study ◽  
Elemental Sulfur ◽  
Thiobacillus Ferrooxidans ◽  
Physical Contact ◽  
Metal Sulfides ◽  
Low Grade ◽  
Mineral Surfaces ◽  
Mineral Surface ◽  
Scanning Electron Microscope Study

There are two strains of bacteria viz. Thiobacillus thiooxidansand Thiobacillus ferrooxidanswidely mentioned to play an important role in the leaching process of low-grade ores. Another strain used in this study is a thermophile and is designated Caldariella .These microorganisms are acidophilic chemosynthetic aerobic autotrophs and are capable of oxidizing many metal sulfides and elemental sulfur to sulfates and Fe2+ to Fe3+. The necessity of physical contact or attachment by bacteria to mineral surfaces during oxidation reaction has not been fairly established so far. Temple and Koehler reported that during oxidation of marcasite T. thiooxidanswere found concentrated on mineral surface. Schaeffer, et al. demonstrated that physical contact or attachment is essential for oxidation of sulfur.

Multislice calculations for quasi-periodic and non-periodic objects

1990 ◽  
Vol 48 (4) ◽  
pp. 138-139
Author(s):  
R. Herrera ◽  
A. Gómez
Keyword(s):  
Electron Diffraction ◽  
Computer Simulations ◽  
Periodic Table ◽  
Amorphous Materials ◽  
Space Group ◽  
Essential Step ◽  
Shape Effects ◽  
Atomic Scattering ◽  
Diffraction Patterns ◽  
Periodic Continuation

Computer simulations of electron diffraction patterns and images are an essential step in the process of structure and/or defect elucidation. So far most programs are designed to deal specifically with crystals, requiring frequently the space group as imput parameter. In such programs the deviations from perfect periodicity are dealt with by means of “periodic continuation”.However, for many applications involving amorphous materials, quasiperiodic materials or simply crystals with defects (including finite shape effects) it is convenient to have an algorithm capable of handling non-periodicity. Our program “HeGo” is an implementation of the well known multislice equations in which no periodicity assumption is made whatsoever. The salient features of our implementation are: 1) We made Gaussian fits to the atomic scattering factors for electrons covering the whole periodic table and the ranges [0-2]Å−1 and [2-6]Å−1.

Computer simulations for the TEM bend contour technique

1996 ◽  
Vol 54 ◽  
pp. 134-135
Author(s):  
Vladimir Yu. Kolosov ◽  
Anders R. Thölén
Keyword(s):  
Computer Simulations ◽  
Real Space ◽  
Advantages And Disadvantages ◽  
Short Overview ◽  
Diffraction Contrast ◽  
Beam Method ◽  
Convergent Beam ◽  
Contour Technique

In this paper we give a short overview of two TEM applications utilizing the extinction bend contour technique (BC) giving the advantages and disadvantages; especially we consider two areas in which the BC technique remains unique. Special attention is given to an approach including computer simulations of TEM micrographs.BC patterns are often observed in TEM studies but are rarely exploited in a serious way. However, this type of diffraction contrast was one of the first to be used for analysis of imperfections in crystalline foils, but since then only some groups have utilized the BC technique. The most extensive studies were performed by Steeds, Eades and colleagues. They were the first to demonstrate the unique possibilities of the BC method and named it real space crystallography, which developed later into the somewhat similar but more powerful convergent beam method. Maybe, due to the difficulties in analysis, BCs have seldom been used in TEM, and then mainly to visualize different imperfections and transformations.

Assessing "Dissimilarity From the Group": Evidence From Computer Simulations

2005 ◽  
Author(s):  
Natalie J. Allen ◽  
David Stanley ◽  
Helen Williams ◽  
Sarah J. Irwin
Keyword(s):  
Computer Simulations
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