In this study, we developed well-validated, Pitzer ion-interaction-approach-based thermodynamic models for solution behavior and solid–liquid equilibrium in 17 binary nitrate systems [of the type 1-1 (HNO₃-H₂O, LiNO₃-H₂O, NaNO₃-H₂O, KNO₃-H₂O, RbNO₃-H₂O, CsNO₃-H₂O, and NH₄NO₃-H₂O), of the type 2-1 (Mg(NO₃)₂-H₂O, Ca(NO₃)₂-H₂O, Ba(NO₃)₂-H₂O, Sr(NO₃)₂-H₂O, and UO₂(NO₃)₂-H₂O), 3-1 (Cr(NO₃)₃-H₂O, Al(NO₃)₃-H₂O, La(NO₃)₃-H₂O, Lu(NO₃)₃-H₂O), and 4-1 (Th(NO₃)₄-H₂O)] from low to very high concentrations at T = 25^oC. To parameterize the models for the binary systems, we used all available raw experimental osmotic coefficients data (φ) for the entire concentration range of solutions, including the supersaturation zone. To construct the models, we used different versions of the standard molality-based Pitzer approach. The predictions of the newly developed models presented here are in excellent agreement with experimental osmotic coefficient data, as well as with recommendations on mean activity coefficients given in the literature for binary solutions from low to very high concentrations. It was established that, for seven of the systems under study, the application of the extended approach with four parameters (β⁰, β¹, β², and C^φ) and variation of the a₂ term in the fundamental Pitzer equations leads to the lowest values of the standard model–experiment deviation. The Deliquescence Relative Humidity (DRH), thermodynamic solubility product (expressed as ln K^o_sp), and standard molar Gibbs free energy of formation (D_fG^o_m) of 18 nitrate solid phases have been determined on the basis of evaluated binary parameters and using m(sat) solubility data. The models for nitrate systems described in this study are of high importance, especially for the development of strategies and programs for nuclear waste geochemical storage.

Acknowledgement: This study is funded by the European Union–NextGenerationEU, project № BG-RRP-2.013-0001.

Designing earth-abundant and durable catalysts for the oxygen evolution reaction (OER) is vital for sustainable energy conversion and carbon-neutral technologies. Herein, we present a modular design strategy to construct an efficient sulfide/oxide heterostructured electrocatalyst through a facile sulfidation treatment of natural ilmenite. The resulting catalyst integrates high intrinsic activity, good electrical conductivity, and long-term operational stability. Benefiting from the synergistic coupling between FeS₂ and TiO₂, it requires only an overpotential of 230 mV to achieve a current density of 10 mA cm^-2 and retains its performance over extended electrolysis in alkaline media, showing nearly 20-fold higher OER activity than pristine ilmenite at 300 mV. Comprehensive structural and electrochemical analyses reveal that the superior performance originates from an accelerated surface self-reconstruction process, where lattice-sulfur leaching promotes the in situ generation of FeOOH species that serve as the genuine active phase. Meanwhile, the residual FeS₂ modulates surface electronic structures, facilitating charge transfer and enhancing conductivity, while the TiO₂ scaffold maintains mechanical integrity and prevents corrosion. This synergistic interplay ensures efficient charge separation, fast reaction kinetics, and excellent durability. This work establishes a scalable and eco-friendly route to convert natural minerals into high-efficiency heterostructured catalysts, providing a sustainable materials platform for renewable-energy conversion and storage applications.

Extrusion-based 3D printing is an emerging additive manufacturing (AM) technique that enables the layer-by-layer fabrication of complex ceramic structures from flow-optimized pastes. This study explores the potential of locally sourced Talakag clay obtained from Tikalaan, Talakag, Bukidnon, Philippines, as a sustainable material for ceramic additive manufacturing. The clay was blended with zeolite, silica, and feldspar to enhance printability and structural performance. The raw materials were physically processed through crushing, pulverizing, and sieving, followed by paste formulation containing 71% solids and 29% liquid. Carboxymethyl cellulose (CMC) was incorporated as a binder to improve viscosity control, homogeneity, and extrusion behavior. Printing trials using the DeltaWASP 2040 Clay printer revealed that the optimized paste extruded smoothly at 3–3.5 bar, producing continuous, dimensionally accurate, and structurally stable layers. Post-printing evaluations confirmed good surface smoothness, geometrical precision, and mechanical integrity. The presence of micro/nanomineral components in Talakag clay contributed to the enhanced rheological and cohesive properties of the paste, supporting its feasibility for 3D ceramic fabrication. This study demonstrates that locally available mineral resources can serve as cost-effective and eco-friendly raw materials for advanced ceramic technologies. Overall, Talakag clay and its composites exhibit strong potential for sustainable extrusion-based additive manufacturing, paving the way for future innovations in functional ceramic materials and green manufacturing within the context of micro/nanomineral-based materials science.

The escalating global energy demand necessitates innovative approaches to harness solar energy and convert it into sustainable chemical fuels. This research investigates the design and optimization of nanomineral-modified electrodes for enhanced photocatalytic hydrogen production through direct water splitting. Specifically, we employ layered nanoclays and transition metal oxides (titanium oxide, iron oxide, and tungsten oxide) as electrode modifiers to improve charge separation, reduce electron–hole recombination, and extend light absorption into the visible spectrum. The synergistic integration of nanomineral films with metal oxide photocatalysts addresses critical limitations in current solar-to-hydrogen systems, including poor charge carrier mobility and limited photocurrent generation.

Our methodology employs a multi-stage approach: synthesis of layered nanomineral films via sol–gel and hydrothermal techniques; controlled decoration of these nanomineral surfaces with metal oxide nanoparticles to establish heterostructures; systematic characterization using X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopy; and evaluation of photocatalytic performance in a custom-designed photoreactor under simulated solar radiation.

Preliminary results demonstrate that nanomineral-modified metal oxide electrodes exhibit significantly enhanced photocurrent density and hydrogen evolution rates compared to unmodified counterparts. This approach promises improved solar-to-hydrogen conversion efficiency by facilitating electron transfer, creating favorable band alignments, and increasing the reactive surface area for water oxidation. The outcomes will establish design principles for next-generation photoelectrochemical devices and contribute to scaling sustainable hydrogen production for energy applications.

The solubilities of the Na₂SeO₄-FeSeO₄-H₂O system have been investigated by the physicochemical analysis method. Crystallization of a new double salt Na2SeO4.FeSeO4.2H₂O has been established. TG and DTA measurements indicate that the double salt loses the crystallization water in three steps in the temperature interval from 87 ^oC to 148^oC. The Pitzer ion interaction model has been used for thermodynamic analysis of the experimental solubility data obtained. The simulation has been materialized by i) determination of the Pitzer binary parameters for the binary solutions, ii) determination of the Pitzer mixing parameters, and iii) calculation of the solubility isotherm of the Na₂SeO₄-FeSeO₄-H₂O system. The binary parameters of interionic interaction for Na2SeO4(aq) and FeSeO4(aq) are taken from our previous studies. The ternary parameters θ(Na,Fe) and (Na,Fe,SeO4) and the thermodynamic solubility product (as lnK^o_sp) of the double salt have been calculated on the basis of experimental data on the solubility reported in this study. The experimentally obtained and the calculated solubilities are in very good agreement. The standard molar Gibbs energy of the synthesis reaction D_rG^o_m of the double salt Na2SeO4.FeSeO4.2H₂O from the corresponding simple salts Na2SeO4.10H₂O and FeSeO4.6H₂O and the standard molar Gibbs energy of formation D_fG^o_m of simple salts and double salt have been determined. The experimental data and the model described in this study are of high importance, especially in the development of nuclear waste storage technology, as well as for production and purification of selenate solutions and solid phases.

Acknowledgement: This study was financed by the European Union-NextGenerationEU, project № BG-RRP-2.013-0001

In the Philippines, nickel extraction plays a pivotal role in industrial development by supplying essential raw materials for the global transition to clean energy, metallurgical applications, and advanced technologies. However, the operation of the surface nickel mines generates substantial quantities of mine silt and mine tailings that require proper management to prevent long-term environmental impacts. This study explores the potential of converting nickel mining waste into non-fired ceramics using locally available Claver clay in Surigao del Norte, Philippines, where multiple nickel laterite mining companies operate. X-ray fluorescence showed that Claver clay contains 72.5% combined silica and alumina, confirming its alluminosilicate-rich nature and strong natural binding properties. X-ray diffraction identified mineral phases of rectorite and phyllosilicates, while Fourier-transform infrared spectroscopy (FTIR) revealed characteristics of H-OH and Si-O bonds, suggesting polymeric network formation. Particle size distribution (PSD) analysis demonstrated reduced particle sizes after mechanochemical treatment for both nickel mine silt and Claver clay, while scanning electron microscopy (SEM) showed more cemented and agglomerated morphological structures in the blended samples, suggesting enhanced particle cohesion using Claver clay as a natural binder. The unconfined compressive strength test revealed a 245% increase in strength, from 1.53 MPa for the non-fired mining waste bulk sample to 5.28 MPa for the Claver clay-mixed nickel mining waste sample prepared at a 1:1 ratio. The results highlight a viable route for valorizing nickel mining silt into an eco-efficient ceramic product using locally available materials.

Thaumasite, along with ettringite, is responsible for sulfate attack in concrete based on Portland cement [1]. Chemically represented as Ca₃[Si(OH)₆](CO₃)(SO₄)·12H₂O, thaumasite exhibits a columnar crystal structure comprised of stacked silicon hydroxide and calcium hydroxide polyhedra. The hydroxide columns are interconnected through a network of hydrogen bonds (H-bonds), facilitated by H₂O molecules, sulfate ions, and carbonate ions occupying the intercolumnar spaces within the crystal.

Here, we use the classical molecular dynamics (MD) simulation technique together with the ClayFF-MOH force field [2, 3] to quantitatively investigate the mineral–water interfaces. Water structuring at the (100) and (001) surfaces for thaumasite and ettringite shows that the affinity of thaumasite for water is greater. However, the total amount of H₂O molecules on the surface is the same for both minerals. Investigation of the (hkl) solid–water interfacial energies confirms that thaumasite is more soluble than ettringite. The (001) surface of thaumasite is more susceptible to dissolution than its (100) surface. Due to the smaller number of H₂O molecules in the structure of thaumasite, the density of the H-bonding network is lower at the thaumasite (001) surface. Dissolution of structural H₂O from the thaumasite (001) surface is most likely, as intracrystalline H-bonds between structural hydroxyls and H₂O molecules are the weakest. The MD simulations also demonstrate that the solid (100) interface between the thaumasite and ettringite crystals is stable, confirming the assumption that epitaxial growth of thaumasite on the ettringite surface is possible. Thus, our MD results establish the mechanism governing AFt phase dissolution/formation, which is critical for enabling accurate thermodynamic models of cement systems.

References

[1] Köhler, S., Heinz, D. and Urbonas, L., Cem. Conr. Res. 36 (2006) 697-706.

[2] Cygan, R., Greathouse, J. and Kalinichev, A., J. Phys. Chem. C 125 (2021) 17573-17589.

[3] Tararushkin, E., Pisarev, V. and Kalinichev, A., Cem. Conr. Res. 156 (2022) 106759.

Strontium (Sr) is an alkaline earth metal that substitutes for calcium (Ca) in minerals and could be incorporated into biogenic carbonates and sediments precipitated from water. In the case of the geochemical anomaly of high Sr levels in rocks and sediments, this study determined the origin and spreading among environmental components. The three floodplain zones in the Tula region (Russia) with the suggested high levels of Sr were selected for environmental study. The details of the mineral presence of Sr in typical environment components were found and discussed. The sedimentary rocks as the probable sources of Sr were analyzed by scanning electron microscopy, photon-counting computed tomography, and X-ray diffraction. The levels of Sr were analyzed in components of floodplain ecosystems: substrates, buttercup and shells of the several species of freshwater molluscs. It could be assumed that the strontium-containing mineral in the studied rocks from Zone 1 was celestine (SrSO₄). The highest level of Sr in water (>20 mg/L) was in the underground spring (brook) in Zone 2, which was higher than the established drinking sanitary limit of 7 mg/L. The obtained values in buttercup (Ranunculus repens) were of the same order of magnitude as in plants—hyperaccumulators Alstonia scholaris or Vicia cracca. This indicates the high abundance of Sr in the studied zones, which is reflected in its enrichment in typical aquatic vegetation. The sediments from the studied zones showed an excess of Sr (2635 mg/kg) in the brook at st. 5 and swamp at st. 6 (3336 mg/kg). These values are significantly higher in comparison with the sediments from another regions. The highest levels in shells of freshwater molluscs were found for Zone 3 (10000-12000 mg/kg) on the Ista river. It was concluded that in general, the levels of Sr decreased in the case of high turbidity and low water mineralization.

The waste management of wind turbine components is challenging, as they are composed of glass or carbon fibers embedded in highly durable polymer matrices. A potential method for recycling wind turbine blades involves their conversion into melted or vitrified slag using thermal plasma-based systems. However, the suitability of melted slag as the geopolymer binding material remains underexplored. Therefore, this study focused on the resistance of slag obtained after wind turbine blade vitrification to alkaline and acidic activation solutions, subsequently assessing the effectiveness of adding such specific waste for the synthesis of geopolymers.

The composition and microstructure of the slag and geopolymer were analyzed using X-ray diffraction, FTIR, and SEM-EDS analytical tools. The results revealed that the vitrified slag contains both amorphous and crystalline anorthite phases, with the content of the amorphous phase decreasing as the distance from the plasma reactor increases.

According to SEM-EDS and FTIR analysis, the leaching of calcium was observed in slag exposed to an acidic environment, although dissolution was also observed in an alkaline solution. The impact of as-derived vitrified slag on the microstructure and mechanical strength of geopolymer was investigated to evaluate its potential application in geopolymer materials.

The study demonstrates that plasma vitrification of wind turbine blade waste produces a partially amorphous slag with potential for geopolymer applications. The reactivity and microstructure of the resulting materials suggest that this slag can serve as a supplementary precursor in sustainable binder systems.

Acknowledgment: This research was carried out with the financial support of European Union Structural Funds for the project “Testing an R&D idea - The Potential of Waste in the Synthesis of Climate-Neutral Geopolymers (ANGeoS)”.

Advancements in micro/nanomineral-based materials are driving innovations in sustainable ceramics. This study explores the potential of locally sourced diatomaceous earth from Kapatagan, Lanao del Norte, Philippines, as a micro/nanoporous siliceous additive for improving the performance and sustainability of commercial ceramic wall tiles. The Kapatagan diatomaceous earth (KDE) exhibited notable physicochemical characteristics, including 52.49% water absorption, 19.28% fired shrinkage, 0.92 g/cm³ bulk density, and 48.79% apparent porosity. Scanning electron microscopy revealed the presence of intricate, porous diatom frustules that retained micro/nanostructured features even after sintering. X-ray diffraction (XRD) analysis indicated the presence of hematite and quartz in the raw KDE, with the transformation of phases to cristobalite and quartz upon sintering at 1150 °C.
Incorporating 5 wt.% KDE into a standard wall tile body (T5), sintered at 1235 °C, led to an increase in water absorption (0.48%) and apparent porosity (0.80%), while reducing fired weight (66.92 g) and bulk density. The microstructural evolution of T5 showed modified interparticle porosity, causing a slight decrease in the modulus of rupture (6.03 MPa). The XRD pattern of T5 confirmed quartz and cristobalite as the dominant crystalline phases. A control tile (T0, without KDE) was also fabricated for comparison.
These findings demonstrate the promising role of local diatomaceous earth as a sustainable micro/nanoporous siliceous additive, highlighting its contribution to the emerging field of micro/nanomineral-based materials for advanced and lightweight ceramic applications.