Environmental problems caused by human intervention in nature are some of the most critical challenges facing human societies. It is essential to use suitable adsorbents to remove pollutants. The abundance, natural abundance and low cost of fine soil have made it a good candidate for removing environmental pollutants. In this research, removal of safranin dye by natural and acidic-organic-treated fine soil with sulfuric acid and ethanolamine was studied. The characteristics of natural and acidic-organic-treated fine soil were confirmed using X-ray diffraction, Fourier-transform infrared spectroscopy, Brunauer–Emmett–Teller and scanning electron microscopy techniques. The adsorbents were placed in contact with different concentrations of safranin dye solution separately. After that, the effects of adsorbent amount (0.4–3.2 g L−1), contact time (0–60 min), adsorbate concentration (5–20 ppm) and pH (3–11) were evaluated regarding the optimum safranin adsorption process. The greatest adsorption capacity of fine soil was calculated as 1250 mg g–1. The experimental results were evaluated using thermodynamic and kinetic models. The data showed that the process follows the Langmuir isotherm model and pseudo-second-order kinetic model. The intraparticle diffusion model estimated the possible mechanism of dye adsorption. Overall, it can be deduced that natural fine soil is an efficient remover of human pollutants.

This study examines the effects of the chemical composition of the clay fraction of various soil horizons on radiation shielding parameters. X-ray fluorescence (XRF) analysis did not reveal significant differences in the concentration of the most abundant oxides (Al2O3, SiO2, Fe2O3) among the various horizons. Consequently, the mass attenuation coefficient did not vary among the horizons in terms of the photon energies studied (15 keV–10 MeV). The mean free path (MFP), half-value layer (HVL) and tenth-value layer (TVL) did not differ for energies up to 100 keV. However, at higher energies, these parameters were mainly influenced by the differences in the densities of the soil horizons. The effective atomic number did not differ across the horizons for the various photon energies, nor did the mass attenuation coefficient. It is shown that slight differences in the chemical composition of the clay fraction of soil horizons do not affect radiation shielding parameters (MFL, HVL, TVL) for low photon energies (<500 keV). Density is more important for radiation shielding than the chemical composition of the various horizons of the same soil type for higher energies (>100 keV); hence, compacting the clay fraction might be more efficient for radiation shielding purposes at higher energies.

This work aims to characterize and study the properties of an Algerian diatomaceous earth (Sig-Mascara) as a catalyst carrier. A commercial product of diatomite was characterized by granulometric analysis, X-ray fluorescence, X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis/differential scanning calorimetry and scanning electron microscopy/energy-dispersive X-ray spectroscopy methods. To purify the diatomite and remove the impurities (iron oxides, clay minerals, quartz and organic matters), the <63 μm fraction of the diatomite was separated out. The 15Ni/Ds-700 catalyst has lower SiO2, Al2O3 and CaO contents compared with the original diatomite. The NiO content of the catalyst is 15 wt.%, indicating successful impregnation. According to the nitrogen sorption–desorption results, the specific surface area of the purified diatomite particles (<63 μm) increased from 26.47 to 46.33 m2 g–1 compared to crude diatomite. The 15Ni/Ds-700 catalyst was applied in the dry reforming of methane to obtain synthesis gas (CO and H2). The results showed that the catalyst was relatively stable during catalytic measurements for 6 h, although the conversion rate value was low (12%).

The zeolitic rocks of Akrotiri, on Santorini Island (Aegean Sea, Greece), can be grouped according to the zeolite minerals present. The first group includes zeolitic rocks that contain only clinoptilolite, the second group contains clinoptilolite and mordenite and the third group contains only mordenite. Clinoptilolite accounts for up to 56 wt.% and mordenite for up to 69 wt.% of the rocks. All samples contain feldspars (8–36 wt.%), clay minerals (6–8 wt.%), quartz (3–6 wt.%), opal-CT (2 wt.%), amphibole (2–4 wt.%) and amorphous materials (4–7 wt.%). The studied samples were classified chemically as andesites or dacites. The ammonium-exchange capacity of the studied samples was 104–158 meq 100 g–1. According to Commission Implementing Regulation (EU) No. 651/2013, zeolitic rocks that contain ≥80 wt.% clinoptilolite, ≤20 wt.% clay minerals and are free of fibrous minerals and quartz can be used as feed additives in animal husbandry. Zeolites with fibrous habit (mordenite, erionite, secondarily roggianite and mazzite) and SiO2 minerals such as quartz, cristobalite and tridymite can be dangerous to both humans and animals. The mineralogical study showed that, due to their low clinoptilolite content and the presence of both quartz and fibrous mordenite, the studied zeolitic rocks do not conform with European Regulation No. 651/2013. As a result, their use as feed additives and nutrition supplements is prohibited.

This study examines the origin and distribution of clay minerals of the pedological horizons of Kori Ouallam watershed (south-western Niger). It is based on field sampling campaigns and a series of laboratory analyses. A total of 49 samples were analysed, 28 from surface horizons (0–10 cm depth) and 21 from pedological profiles (0–1 m depth). The samples were analysed by X-ray diffraction on bulk and clay (<2 μm) fractions, X-ray fluorescence spectrometry, laser granulometry, organic matter and calcium carbonate content, macroscopic observations (binocular loupe) and scanning electron microscopy equipped with an energy-dispersive spectrometry system. The pedological horizons are characterized by low organic matter contents (<1%) and no calcium carbonate. The particle-size distribution shows net textural differentiation, with a predominance of sandy loam to sandy clay loam textures in the upper horizons and clay loam to clay in the deep horizons. The main major oxides were SiO2 (46.3–89.0%), Al2O3 (5.0–24.2%) and Fe2O3 (1.0–27.9%). Kaolinite (64–98%) is the predominant clay mineral at all horizons, associated with low to moderate proportions of illite (1–34%) and traces of chlorite. Kaolinite is essentially inherited from the parent rock, whereas illite results from chemical alteration by bisialitization of the primary minerals initially rich in potassium feldspar contained in the parent rock. However, soil texture and organic matter vary independently with clay mineralogy. An extended study of all of the pedological facies that make up south-western Niger, combined with supplementary analyses, would further improve our understanding of clay mineralogy in the Sahelian zone.

In sediments, clay minerals are mainly detrital. Formed by continental weathering, they are carried by surface transport predominantly by rivers, glaciers and, to a lesser extent, winds to the adjacent sedimentary basins and then are redistributed by oceanic currents. In a sedimentary core, the variability in the clay mineral assemblages reflects either variable physical and chemical weathering conditions in the watershed, typically with a significant link to climatic conditions, or changes in the mineral source, the latter being associated with various transport agents. When different sources are involved, a combination of mineralogical and geochemical proxies allows us to trace the detrital provenance, but they also indirectly provide valuable information on transport pathways and palaeocurrents. This manuscript reviews several examples from the literature and ongoing research on clay mineral variability in marine or lacustrine sedimentary records and interprets them in terms of: (1) climate control at different timescales, from the Neogene to the Quaternary; and (2) transport paths. Examples are selected to review the various clay-derived proxies in existence.