Search results for "clay mineral"

Enrichment and activation of smectite-poor clay

2011

A new method of smectite clay enrichment has been developed. The method is based on dispersing clay in a phosphate solution and sequential coagulation. The product of enrichment is characterized with X-ray powder diffraction, wavelength dispersive X-ray fluorescence spectrometry, differential thermal analysis and thermogravimetry. Sorption of methylene blue and hexadecylpyridinium bromide on raw and purified clays was studied.

Nature and origin of natural Zn clay minerals from the Bou Arhous Zn ore deposit: Evidence from electron microscopy (SEM-TEM) and stable isotope comp…

2016

International audience; Zn-clay minerals have been found in the non-sulfide deposit of Bou Arhous (High Atlas, Morocco). They occur as white or ochre clays embedding willemite (Zn2SiO4) and are commonly associated to red detrital clays in karstic cavities. Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) with Energy Dispersive X-ray (EDX) analyses were combined in order to characterize the clay minerals and to determine the mechanism of their formation. XRD patterns on oriented and powdered clays and Fourier Transform Infrared (FTIR) spectroscopic analyses suggest that fraipontite is the major Zn clay phase (with some smectite interstrat…

Chemical variations in clay minerals of the Archaean Barberton Greenstone Belt (South Africa)

1996

Abstract Four rock profiles of shales, carbonates and greywacke-type sediments were sampled from the mafic compositional influenced sedimentary Fig Tree Group and from overlying, more felsic related, sedimentary Moodies Group of the Archaean Barberton Greenstone Belt in South Africa. Clay separates of forty sedimentary rocks were examined by XRD and SEM to study the mineralogical, chemical and morphological variations of the constitutive illite and chlorite. The clay minerals showed a significant K-enrichment in the illites and Mg- and Fe-depletions in the chlorites upwards the stratigraphic sequence. Three independent parameters influenced these variations: (1) a change in the origin of th…

High-resolution clay mineralogy as a proxy for orbital tuning: example of the Hauterivian-Barremian transition in the Betic Cordillera (SE Spain).

2012

11 pages; International audience; The response of clay mineral assemblages to potential orbital forcing is tested in Mesozoic hemipelagic marl- limestone rhythmites of the Río Argos section (Betic Cordillera, Southeastern Spain). Along the section, marls are pervasively enriched in kaolinite and illite, whereas limestones are enriched in smectite-rich illite/smectite mixed-layers, suggesting that marl-limestone alternations are produced by cyclic high-frequency fluctuations of continental runoff. Spectral analyses show that clay mineral assemblages evolve accordingly to precession, obliquity and eccentricity cycles. Durations of ammonite zones are assessed at 535 kyr for the Late Hauterivia…

2012

Abstract. Mineral dust is a major fraction of global atmospheric aerosol, and the oxidation of SO2 on mineral dust has implications for cloud formation, climate and the sulfur cycle. Stable sulfur isotopes can be used to understand the different oxidation processes occurring on mineral dust. This study presents measurements of the 34S/32S fractionation factor α34 for oxidation of SO2 on mineral dust surfaces and in the aqueous phase in mineral dust leachate. Sahara dust, which accounts for ~60% of global dust emissions and loading, was used for the experiments. The fractionation factor for aqueous oxidation in dust leachate is αleachate = 0.9917±0.0046, which is in agreement with previous m…

Isotope ratios of nonexchangeable hydrogen in soils from different climate zones

2010

Abstract The fractionation of H isotopes in global precipitation leads to a continuous decrease in 2 H concentrations of precipitation with increasing latitude, altitude and continentality. Thus, the local precipitation, soil and ground water used by plants for photosynthesis or consumed during neoformation of pedogenic clay minerals often have a spatially diagnostic δ 2 H value. We hypothesize that the δ 2 H value of isotopically nonexchangeable H in bulk soil (composed of C-bonded H in soil organic matter (SOM) and the nonexchangeable fraction of O-bonded H in pedogenic clay minerals) is correlated with the mean δ 2 H value of local precipitation water at the place and time of biomass pro…

Past, Present and Future Perspectives on Halloysite Clay Minerals

2020

Halloysite nanotubes (HNTs), clay minerals belonging to the kaolin groups, are emerging nanomaterials which have attracted the attention of the scientific community due to their interesting features, such as low-cost, availability and biocompatibility. In addition, their large surface area and tubular structure have led to HNTs’ application in different industrial purposes. This review reports a comprehensive overview of the historical background of HNT utilization in the last 20 years. In particular it will focus on the functionalization of the surfaces, both supramolecular and covalent, following applications in several fields, including biomedicine, environmental science and catalysis.

CLAYS IN COSMETICS AND PERSONAL-CARE PRODUCTS

2021

Clays are used in various cosmetic formulations, such as sunscreens, toothpastes, deodorants, creams, hair cosmetics, makeups, nail polish, facial masks, and shampoos, among others, to improve the organoleptic and physicochemical characteristics, to increase the stability, or to facilitate elaboration. Together with their technological functionalities, clays are cosmetologically active ingredients with cleaning, anti-aging, anti-wrinkling, and sun-care functionalities. Talc, kaolinite, mica, and some smectites are the clay minerals used most frequently in cosmetic products, but several other phyllosilicates as well as modified and synthetic clays are also used. Sometimes, clays are useful i…

Burial and thermal evolution of the Sicilian fold-and-thrust belt: preliminary results from the Scillato wedge top basin (central-northern Sicily, It…

2016

Wedge top basins are key elements for unravelling the tectonic evolution of fold-and-thrust belts. In detail, their thermal signature and sedimentary fill records modes and time of exhumation of their edges. The Scillato basin is a wedge-top basin located in the central-northern sector of the Sicilian fold-and-thrust belt (western sector of the Madonie Mts). Upper Serravallian-upper Tortonian succession composed by up to 1,200 m thick delta-river to open marine siliciclastic sediments, fills the basin. This succession lies on a deformed substrate made up of thrust sheets composed of Numidian Flysch, Sicilidi and Imerese units stacked with a SW tectonic transport. The basin fill records a po…

Adsorption of anionic dyes onto natural, thermally and chemically modified smectite clays

2014

Abstract The aim of this study was to determine the adsorption capacity of the smectite clays (from the overburden of the lignite deposit in Belchatow) for two anionic dyes, i.e. Reactive Blue 81 (RB-81) and Direct Blue 74 (DB-74). Additionally, the influence of the thermal and chemical (acid and alkali) clay modifications on the amount of bonded dyes was investigated. The adsorption capacity of the clay (natural and modified) was different for studied dyes and depended on the initial concentration and modification type. All the modified clays adsorbed the dyes at pH>pHPZC as the negatively charged surfaces of their particles (in accordance with the formula: AOH ↔ AO- + H+) prevented the…