The present study aimed to investigate the mineralogical and morphological properties of two South African clays, namely bentonite and kaolin. These clays are mined in specific regions of the country ...but have not been fully characterized in terms of their properties for potential application in a number of industries. Bentonite was found to have a larger specific surface area, pore size, and more interchangeable cations than kaolin. The bentonite was also identified as Na-bentonite due to the huge Na content present in the clay. The powder X-ray diffraction (PXRD) patterns revealed that both clays are crystalline, together with the Fourier-transform infrared (FTIR) spectrophotometer results; presumably, some impurities of quartz could be present in the clay materials. The most prevalent functional groups present include Al-OH, Si-O-Mg, Si-O, and Si-O-Al groups. The surface charge of bentonite was consistently negative across all pH values, indicating its potential for adsorption applications. On the other hand, kaolin exhibited a negative charge at pH values greater than 2.4. The scanning electron microscopy (SEM) images provided visual evidence of the presence of pores in the clay structures, which supported the Brunauer–Emmett–Teller (BET) results classifying both bentonite and kaolin as mesoporous and macroporous materials. The particle size analysis revealed a broad distribution for bentonite and a bimodal distribution for kaolin. Overall, the clays revealed interesting features that can be useful for application in several industries, for example, in the treatment of wastewater. Further research and development can explore their potential to address environmental challenges, particularly the application of bentonite and kaolin in water treatment processes to remove toxic metal ions.
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•Reuse of Sicilian volcanic residues as precursors for alkali-activated materials.•TGA, TG coupled to FT-IR and X-ray µCT have been used to define the influence of ...reactants.•Multidisciplinary approach for the optimization of the mix design.
Insights on thermal behavior and microstructures of AAMs based on Sicilian volcanic precursors (i.e., volcanic ash, “ghiara” and pumice) have been performed. A multidisciplinary approach by means of thermogravimetric analysis coupled to Fourier Transform Infrared Spectroscopy and X-ray Computed Microtomography has been used with the aim to define the influence of reactants involved in the process. The obtained results show: i) the increase of metakaolin shifts the gas emission toward lower temperatures; ii) the positive relation between mass loss and liquid/solid ratio; iii) the influence of particle size of precursors on the pore development.
In the present study the stability of the phases pertaining to the Cu–Fe–S–O–H compositional system is investigated using the Eh-pH prevalence diagrams. Calculations were performed under the PHREEQC ...formalism, simultaneously accounting for all concurrent equilibria. Accordingly, point-to-point mass balance diagrams were realised, changing initial parameters to explore the dependence of the system on the temperature, and on the metal-to-sulfur ratio. Among the most relevant results, discussed in comparison with the previous existing literature mainly driven by calculation performed under the so-called line method approximation, the occurrence of large field of stability of the ternary species (and, among them, of delafossite, CuFeO2) and the net change of some boundaries in the stability fields of the binary species, due to competing equilibria. The results have been discussed on the light of the occurrence of these minerals in cuprous and ferrous mineralizations, and in the perspective of possible application in Corrosion Science.
•New thermodynamic modelling in the Cu–Fe–S–O–H system.•Eh-pH at temperature higher than room temperature.•Revised predominance field for ternary phases in the Cu–Fe–S–O–H.•Cu–Fe–S–O–H is not just the sum of Cu–S–O–H and Fe–S–O–H.
To maintain high-level economic development, protect the ecological environment, and achieve carbon peaking and carbon neutrality goals, the construction of green mines has become a critical issue in ...China. In this study, the importance of mineral resources to human society is discussed, and the construction experiences and sustainable development directions of green mines are summarized, which can provide valuable references for the global mining industry. The entry and management process in China was introduced to help understand green mines’ construction objectives and tasks. Moreover, based on the successful construction cases of green mines, four typical green mine models are concluded: the green technology mining model, operation modernization mining model, stability mining model, and ecological restoration mining model. In addition, the key construction elements of green mines are concluded, for example, the mining environment, mining methods, comprehensive utilization of resources, energy conservation, emission reduction, scientific and technological innovation and intelligence, and enterprise-land stability, which provided the directions and guidance for green mine construction.
The pyroclastic rocks belonging to the Late Eocene-Miocene volcanic activity that occurred in Sardinia between 38 and 15 Ma ago were widely used as construction materials in several Romanesque ...churches of the easternmost Logudoro area, as well as in large parts of the Sardinia territory. In this work, the ancient Cathedral of Nostra Signora di Castro (twelfth century) was taken as a representative case study. There is no historical or archaeological evidence of ancient quarries. Based on the geochemical, petrographic, and volcanological data on several samples from an extensive field area (approximately 150 km
2
), a geographical zoning of the volcanics has been recognised. In the Oschiri sector, there are three different sub-zones, which can be identified with different volcanic rocks: less fractionated rocks (Differentation Index ∼70-78); intermediately fractionated rocks (D.I. ∼76-79); and more fractionated rocks (D.I. ∼77-82). To identify the origin of the ignimbrite rocks of the Church of Nostra Signora di Castro, two statistical methods were used: stepwise linear discriminant and canonical analysis. Moreover, to define the geochemical transformation processes induced by the alteration, a comparative study of concentrations of major and trace elements measured by XRF and SEM-EDX analyses on the surface portion and the innermost areas of the stone was made.
The laser-induced breakdown spectroscopy (LIBS) technique was used for analyzing the composition of an ancient Roman mortar (5th century A.D.), exploiting an experimental setup which allows the ...determination of the compositions of binder and aggregate in few minutes, without the need for sample treatment. Four thousand LIBS spectra were acquired from an area of 10 mm2, with a 50 µm lateral resolution. The elements of interest in the mortar sample (H, C, O, Na, Mg, Al, Si, K, Ca, Ti, Mn, Fe) were detected and mapped. The collected data graphically shown as compositional images were interpreted using different statistical approaches for the determination of the chemical composition of the binder and aggregate fraction. The methods of false color imaging, blind separation, and self-organizing maps were applied and their results are discussed in this paper. In particular, the method based on the use of self-organizing maps gives well interpretable results in very short times, without any reduction in the dimensionality of the system.
Archeological mortars are often composed of highly inhomogeneous materials and detailed analysis in most cases can be quite difficult. In this work, a Laser-Induced Breakdown Spectroscopy (LIBS) ...equipment with microscopic-scale spatial resolution was used to image the distribution of elements on real archeological samples of mortars and construction material used in the foundations of the Smederevo Fortress (Republic of Serbia). A double-pulse Nd:YAG at the fundamental wavelength (λ = 1064 nm) and a CCD spectrometer coupled with a commercial microscope were used to generate the plasma and acquire the LIBS spectra. Thanks to the combined use of an unsupervised clustering algorithm and the calibration-free procedure, the results obtained show that it is possible to obtain a good discrimination between materials of different composition, allowing a quick classification for further mineral-petrographic investigations.
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•Elementary imaging on highly inhomogeneous samples.•LIBS mapping application on historical mortar samples.•Performed CF-LIBS analysis on average spectrum, to estimate the elemental composition of the different zones of the sample.
This paper deals with the stones used as building materials in the centre of Pisa during the Middle Age. Most of the stones are quarried from the nearby mountains, Monte Pisano and Monti d’Oltre ...Serchio, but there are also other ones, coming from Apuan Alps, Elba Island, western Tuscan coast, and from other quarries opened in the Western Mediterranean area. Our goal is to enrich the classic concept of street photography by inserting, in an interpretative context, the analysis and the observation of the geoenvironment in which we are immersed, daily, for the journey home-office, home-school or just for a simple walk. The tools we have are the eyes, the light and an instrument: the camera. Five stops along a city route allow to describe the main types of stones that have been used to construct and ornate the buildings since the 10th and 11th centuries, when Pisa acquired its traditional fame as one of the four historical Maritime Republics of Italy. Monte Pisano marble is the most important stone in the medieval phase of construction of the city of Pisa, often used together with black limestones to give the typical decorative alternate bands, black and white, of the Pisan Romanesque style. Other types of stones were also used, such as Quartzites, Agnano breccia, Panchina, Macigno sandstone as well as Apuan marble, granitoid rocks from Elba Island and Sardinia, and some rocks from ancient quarries of the western Mediterranean area, such as precious marbles from Greece and Turkey.
Abstract
In this work, marbles from Castagneto Carducci (Livorno province, Tuscany), which originated by contact metamorphism of the
Calcare Massiccio Fm.
, an Early Jurassic limestone belonging to ...the Tuscan Sequence, were studied for determining their chemical, mineralogical and petrographic characteristics, and the main physical and mechanical properties. Forty marble samples were sampled and analysed; they are from two inactive quarries on the NW and NE slopes of the Mt. Romitorino, and from natural outcrops in the vicinity of the quarries. The analysed rocks are marbles with high calcite content (> 98% by weight). Optical microscopy observations showed Castagneto Carducci marbles generally have a heteroblastic/granoblastic texture with crystal boundaries from curved-right to lobate. The maximum grain size of the calcite crystals ranges from 0.2 mm to 0.6 mm. The determination of the main physical and mechanical properties of the analysed marbles showed that these rocks are characterised by low porosity and, in general, good physical and mechanical properties.
This paper aims to ascertain the provenance of white and greyish marbles used for decorating the Heliocaminus Baths, one of the most ancient thermal complexes inside the Hadrian's Villa at Tivoli ...(Italy).
Fifteen marble samples have been macroscopically described and investigated by means of mineralogical and petrographic observations of thin sections, XRF chemical analyses of major and some trace elements, and stable isotope ratio analysis of carbon and oxygen.
The collected data show that the majority of the marbles analysed come mainly from the Apuan Alps basin (Carrara) and subordinately from several Greek (Mt. Penteli and Thasos Islands) and Turkish (Afyon and probably Ephesus districts) quarrying areas.
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