1,721,065 research outputs found
Sustainable Pathways for the Synthesis of Calcium Sulfate Hemihydrate
No full textCalcium sulfate, and especially its hemihydrate form (bassanite), is crucial in the construction industry, primarily used as a hydraulic binder in cements, mortars, and wallboards. Because of the rapid transformation of bassanite into thermodynamically stable gypsum (calcium sulfate dihydrate) upon contact with water, natural deposits are scarce, rendering it one of the most extensively produced inorganic materials worldwide. Currently, bassanite is derived from mined or waste gypsum through a thermal dehydration process, which is energy-intensive and costly. As sustainability has become a key target for industrial processes and products, a series of studies aiming to increase the energy efficiency and reduce the carbon footprint of bassanite production was published recently. Two primary approaches are pursued: conversion of gypsum and direct precipitation of bassanite from solution. In both cases, organic solvents, (specific) additives and/or elevated temperatures have been used to control the activity/availability of water in the reaction medium and thus direct phase selection towards bassanite. This review offers a comprehensive overview of alternative bassanite production methods, critically examining their benefits, potential downsides, and overall impact on
the sustainability of industrial-scale use
A high-throughput approach for assessing antiscaling performance during mineral precipitation from seawater and hard water
No full textThe undesired precipitation of minerals from solution poses challenges in various industrial and domestic applications, including water treatment, desalination, dishwashers and boilers. To mitigate this, threshold inhibitors - small quantities of water-soluble additives—are commonly employed to inhibit the precipitation of inorganic phases. However, concerns about the persistence of traditional additives like phosph(on)ates) in natural environments and stricter regulations warrant the development of more sustainable alternatives. We present a high-throughput approach using a UV-Vis spectrophotometer and automated data analysis to assess the scale inhibiting potential of numerous candidates and their combinations. The robustness and versatility of this method were validated by measuring the kinetics of alkaline-earth metal carbonates precipitating from simulated hard waters and seawaters across an extended range of experimental parameters. This approach allows for straightforward evaluation and quantification of each antiscaling additive’s effectiveness and operational range, enabling direct comparison of different additives and blends of additives. Moreover, it facilitates the study of scaling processes in both bulk solutions and at liquid/solid interfaces. By providing a rapid and reliable means of screening potential additives and formulations, our versatile toolbox will expedite the identification of effective scale inhibitors, thereby contributing to the advancement of sustainable practices in various industries reliant on water treatment and mineral precipitation control.A.E.S.V.D. and A.F.M. acknowledge project PROYEXCEL_00771 - SMART-water, with funding from the Consejería de Universidad, Investigación e Innovación, the competent authority in R&D of the Junta de Andalucía.Peer reviewe
Towards sustainable solution-driven recycling of gypsum
No full textGypsum (CaSO₄·2H₂O) is a crucial mineral across sectors such as construction, agriculture, and biomedicine. Despite its potentially full recyclability, a shortage looms due to limited mining in Europe and decreasing production of flue gas desulfurization (FGD) gypsum, a byproduct of coal power plants. With current EU consumption at 24 MT/a (17 MT mined, 7 MT FGD), a deficit of 10-35 MT/a is projected by the 2030s as CaSO₄ becomes a critical raw material [1]. Meanwhile, substantial CaSO₄ waste is produced in various industries (e.g., phosphogypsum, red gypsum), but its recycling remains limited (10% in Germany, 5% in the EU) due to contamination and separation challenges.
This contribution introduces a sustainable, efficient wet-chemical method for converting gypsum to bassanite (CaSO₄·0.5H₂O), and thus recycling gypsum, under mild conditions (T 4 M) [2]. The optimal conversion conditions (T > 80°C, c[NaCl] > 4 M) enable rapid (<5 min) and reversible transformation (Fig. 1). Upon cooling, gypsum re-forms, offering a temperature-dependent control over phase transition. Unlike conventional thermal dehydration (150-200 °C), this approach promotes the dissolution of gypsum, allowing contaminants to be separated via selective precipitation or adsorption. Additionally, the wet-chemical process facilitates the physical removal of impurities from gypsum matrices, making it advantageous for recycling gypsum waste from sources such as demolition or urban mining, where it is often mixed with other materials.
Our approach presents a sustainable pathway for recovering high-purity bassanite from contaminated gypsum waste, aligning with EU goals for resource conservation and waste reduction
Dataset associated with Project PID2020-114355GB-I00 PALYTECH, concerning Objective 2.1. Potentiometric titrations of palygorskite suspensions
No full textProject PID2020-114355GB-I00 PALYTECH, on surface titration of palygorskite suspensionPeer reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Towards solution-driven recycling of gypsum
No full textGypsum (CaSO₄·2H₂O) is a crucial mineral across sectors such as construction, agriculture, and biomedicine. Despite its potentially full recyclability, a shortage looms due to limited mining in Europe and decreasing production of flue gas desulfurization (FGD) gypsum, a byproduct of coal power plants. With current EU consumption at 24 MT/a (17 MT mined, 7 MT FGD), a deficit of 10-35 MT/a is projected by the 2030s as CaSO₄ becomes a critical raw material [1]. Meanwhile, substantial CaSO₄ waste is produced in various industries (e.g., phosphogypsum, red gypsum), but its recycling remains limited (10% in Germany, 5% in the EU) due to contamination and separation challenges.
This contribution introduces a sustainable, efficient wet-chemical method for converting gypsum to bassanite (CaSO₄·0.5H₂O), and thus recycling gypsum, under mild conditions (T 4 M) [2]. The optimal conversion conditions (T > 80°C, c[NaCl] > 4 M) enable rapid (<5 min) and reversible transformation. Upon cooling, gypsum re-forms, offering a temperature-dependent control over phase transition. Unlike conventional thermal dehydration (150-200 °C), this approach promotes the dissolution of gypsum, allowing contaminants to be separated via selective precipitation or adsorption. Additionally, the wet-chemical process facilitates the physical removal of impurities from gypsum matrices, making it advantageous for recycling gypsum waste from sources such as demolition or urban mining, where it is often mixed with other materials
Gypsum Gardens: Self-Assembled Tubular Structures of Calcium Sulfate with Relevance for the Detection of Extraterrestrial Life
No full textForm is a common and intuitive criterion to distinguish between the realm of living species and the inanimate nature. However, there are in fact no strict boundaries in terms of morphology, as exemplified by so-called chemical gardens, which form by self-assembly in purely inorganic systems and yet closely mimic the appearance of trees and other plants. While such structures have been reported for a broad range of compositions–most notably silicates of various types of metal cations as well as prominent (bio)minerals like calcium carbonate or phosphate–one important material has been missing in the comprehensive list of these chemobrionic systems: calcium sulfate. In the present work, we succeeded in preparing well-developed CaSO4-based chemical gardens by addition of a concentrated solution of sodium sulfate to solid crystals of calcium chloride. The formed structures were characterized in detail with respect to their growth behavior, mineralogy, and texture. We find hollow tubular architectures consisting of oriented gypsum crystals and delineating smooth curvatures with multiple branching sites. Beyond the sheer beauty of these self-assembled mineral structures, the results of our study bear deep implications for the detection and interpretation of potential past life on Mars, where abundant deposits of calcium sulfate exist. In addition, the current picture of geochemical environments on the early red planet is fully consistent with the experimental conditions used in the present work, rendering the formation and presence of chemical gardens on Mars plausible.Parts of this work were funded by BASF SE in the framework of a collaboration with the University of Regensburg. AESVD acknowledges funding within the project PROYEXCEL_00771 (SMART-water) by the Consejería de Universidad, Investigación e Innovación, the competent authority in R&D of the Junta de Andalucía. CP has received funding from a Marie Sklodowska-Curie action (No. 101021894, CARS-CO2) within the Horizon 2020 programme. Raman micro-spectroscopy analyses were performed at the Isterre MicroAnalytical Platform (IMAP, Université Grenoble Alpes), which has been funded by grants from the European Research Council (Synergy Grant MEET, No. 856555), the region of Auvergne-Rhône-Alpes (2020 AURA P3 – CPER 2015/2020), and CNRS-INSU.Peer reviewe
Illitization of montmorillonite in ammonium solutions under hydrothermal conditions
No full textIn diagenetic solutions, ammonium may be incorporated into smectites as an exchangeable cation and become fixed within the interlayer space of illites and other white micas. To study the potential impact of NH4+ on the smectite-to-illite transformation reaction, a series of hydrothermal experiments were carried out at 100, 150 and 200 °C, spanning reaction duration from 15 to 90 days, and two NH4+ concentrations (0.1 and 0.2 M). The solids resulting from these alteration experiments were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and transmission and analytical electron microscopy (TEM and AEM). The XRD analysis revealed that, under the specified experimental conditions, smectite incorporates NH4+ in the structure, leading to the formation of non-swelling layers, resulting in partial transformation to illite layers and producing packets of disordered illite/smectite (I/S). In addition, a minor XRD peak at ∼10 Å suggests the formation of discrete illite crystals. The FTIR spectra demonstrated the uptake of NH4+, with deformation bands observed at 1400 and 1430 cm−1, corresponding to exchangeable NH4+ in smectite and fixed NH4+ in high-charge layers, respectively. TEM analysis revealed that smectite particles exhibited wavy stacks comprising a few layers with abundant defects and lateral discontinuities. The interlayer spacing in these particles ranged from 12 to 15 Å and became thinner and more plate-like with increasing temperature and time. Moreover, they contained inclusions of 10–10.3 Å layers, either as discrete layers or in packets of several layers, indicating the formation of disordered mixed-layer illite-smectite. Lateral transitions from 12 to 15 Å to 10 Å layers were frequently observed and interpreted as reaction fronts due to local rearrangement. At 150 and 200 °C, isolated packets of 10 Å layers were identified as discrete illite crystals that precipitated directly from solution. Analysis of the chemical composition of individual particles revealed an increase in octahedral charge (MgVI for AlVI substitution) in smectite particles, followed by increase in tetrahedral charge in I/S particles. Interlayer NH4+ played a stabilizing role in the high-charge layers and favored the smectite-to-illite conversion process.Financial support was obtained from MINECO (CGL2011-22567, CGL2014-55108P), with contribution of FEDER funds.Peer reviewe
Dissolution of palygorskite. Dataset associated with Project PID2020-114355GB-I00 PALYTECH, concerning Objective 1. Dissolution of palygorskite in acidic, neutral, and alkaline conditions
No full textResearch supported by Grant PID2020-114355GB-100 funded by MCIN/AEI/ 10.13039/501100011033 and by ÒERDF a way of making EuropeÓ.Peer reviewe
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