Effect of iron particle formation on the transformation of Al in drinking water distribution system: implications for Al deposition control.

ABSTRACT The capacitive behavior and structural characterization of xenotime located in the Atotonilco el Grande Formation, Hidalgo, Mexico, were investigated. The study area is associated with an extensional rift environment known as the Molango Rift, where tectonic and volcanic processes facilitated the concentration of strategic minerals such as xenotime.Xenotime was characterized using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM–EDS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The identified crystalline phases include xenotime-(Y) (PDF 96-101-1144) and xenotime-(Yb) (PDF 96-152-9051). The xenotime particles exhibit subhedral morphologies, along with mineral phases such as zirconium pyrophosphate (ZrP2O7, PDF 96-153-4358) and pretulite (ScPO4, PDF 96-900-1950), which may be remnants of diffusive metasomatic processes that promoted isomorphic substitution of rare earth elements within a phosphorus- and zirconium-rich matrix. Electrical tests demonstrated that xenotime behaves as a high-pass filter (HPF), with efficient signal response above 100 kHz, suggesting its potential use in high-frequency electronic devices. Thermal characterization revealed high dielectric constants (~500) and two ferroelectric transitions (at 70 °C and 300 °C), indicative of a Class I dielectric material with Class II ferroelectric stability. These findings position xenotime as a promising material for the technology sector, particularly in the development of high-stability capacitors, energy storage devices, and solid-state rectifiers. Furthermore, the study underscores the relevance of rift systems as favorable geological environments for the concentration of strategic critical elements in Mexico, encouraging new exploration strategies for high-tech mineral resources. Key Words: Rift, Rare Earth Elements (REEs), Xenotime mineralization, Metasomatic, Thermal and electrical characterization.

Using the crystal energy theory of isomorphous miscibility, the mixing energies, critical decomposition temperatures, and substitution limits were calculated, and the thermodynamic stability ranges of solid solutions Sr1-x(Na0.5Ln0.5)xMoO4 (where Ln represents rare-earth elements, REEs) were determined. It was shown that both the mixing energies and the critical decomposition temperatures increase systematically with the REE atomic number. A thermodynamic stability diagram and dependencies of solubility limits of the solid solutions were built for concentrations ranging from x = 0 to x = 1.0 with a step of Δx = 0.05. These diagrams allow one to determine the limits of equilibrium substitution at a given decomposition temperature, decomposition temperatures for a specified substitution limit, or the thermodynamically stable composition regions. The results may be helpful for immobilizing radioactive isotopes of REEs, actinides, and strontium-90 in nuclear waste disposal and developing new inorganic materials for phosphors and lasers.

The antagonistic geochemical behaviors of cadmium (Cd) and arsenic (As) in co-contaminated soils complicate their simultaneous remediation. This study aimed to develop a synergistic immobilization strategy by converting Spirulina residue into a magnetic biochar-layered double hydroxide composite (FSRBL). The composite was applied to both acidic red and calcareous black soils, and its effects on Cd and As, immobilization efficiency, and ecotoxicity were evaluated. The results showed that FSRBL effectively transforms Cd and As from mobile fractions to stable residual forms. At a 2.5% application rate, FSRBL achieved remarkable immobilization efficiencies of 39.2% for Cd and 57.5% for As, representing effectiveness 3.55 and 5.97 times higher than that of unmodified biochar, respectively. A dose–response relationship between the application amount of FSRBL and the immobilization efficiency of As and Cd was observed and further quantified using a logistic model. The results indicate that while increased FSRBL application enhances immobilization efficiency, the marginal benefit of each additional unit diminishes as the application rate increases, demonstrating a significant diminishing marginal effect. According to the ecotoxicity assessment experiment, the soil leachate from FSRBL-amended soil remarkably decreased the ecological toxicity to rice (Oryza sativa L.). Mechanistic investigations employing SEM/TEM-EDS, XRD, and XPS revealed that the synergistic immobilization could be ascribed to the multi-component cooperation within FSRBL, which resolved the conflicting pH/Eh requirements for the immobilization of Cd and As: (1) the LDH phase efficiently immobilized As oxyanions through anion exchange and isomorphic substitution; (2) the magnetic Fe phase concurrently immobilized Cd2+ and As oxyanions via redox transformation and coprecipitation, resulting in the formation of precipitates such as Fe/Ca/Cd–As(V). This work demonstrates a feasible approach to upcycle biomass waste into a value-added material for sustainable remediation of Cd–As co-contaminated soil.

Ceria supported noble metals are important commercial catalysts, however, the long-term stability suffering from metal particle sintering still challenges the practical benefits. This work determines the favorable migration pathway of supported Pt particles over CeO2 surface as well as three distinct trends of isomorphous substitution in modulating the metal-support interactions (MSIs), via extensive ab-initio molecular dynamics (AIMD) simulations and density functional theory calculations with on-site Coulomb interaction correction. We find that, while several dopants (Ti, Ge, Sn) enhance the MSI upon contact with metal particles, Ge shows additionally an intriguing MSI weakening effect in the distant region, stemming from the reduction of tetravalence Ge into off-lattice Ge2+ cation (Ge4+ + 2Ce3+ → Ge2+ + 2Ce4+). Integrating with the dynamic bury-and-expose migratory structure inspires us to propose an effective sintering-resistance strategy of constructing dual-stabilization "deeper well and taller wall" migration energetics, simply by manipulating Ge doping content within an estimated threshold (roughly to be one tenth of Pt). Such approach can remarkably stabilize surface Pt particles with migration energy consumption being elevated by 1.80eV and exhibit broad applicability to other supported metals (e.g., Rh/CeO2), giving rise to excellent stability even under harsh experimental conditions of H2 atmosphere at 800°C.

A molecular dynamics study on the impact of isomorphic substitution on the interaction between illite and colloidal alumina in laterite

Microbially induced carbonate precipitation as an innovative technology for achieves efficient Sr2+ bioremediation.

Lithium (Li) is a cornerstone of green technology in reducing carbon emissions. However, conventional Li mining faces potential supply chain disruptions by 2030, underscoring the urgency of exploring clay-type Li deposits with poorly understood occurrence states and extraction mechanisms. This study investigates a drill core from central Yunnan to elucidate the modes of Li occurrence and the genetic mechanisms. The claystone is primarily composed of cookeite, diaspore, and anatase, exhibiting a world-class Li grade of up to 1.94 wt % in whole rock. The occurrence state of Li is constrained by using X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analyses. Fitted XPS Li 1s peaks in samples AN 1.62 and AN 1.58 at 57.0, 56.3, 55.9, and 55.4 eV and 57.2, 56.6, 56.0, and 55.3 eV, respectively, suggest Li occurrence on surfaces, within pseudohexagonal cavities, and in the lattice, forming LiCl, Li2O, LiF, and LiOH species. The 7Li NMR chemical shift at -0.7 ppm indicates that Li predominantly resides in the lattice, while the asymmetry and positive skew of the peaks suggest the coexistence of surficial and structural Li. The genetic mechanisms of these Lis likely involve isomorphic substitution within tetrahedral Al-Si and octahedral Fe/Mg-Al sites. The presence of Al/Mg/Fe-F complexes and F-Li species further suggests the structural Li incorporation. Li exhibits coupled enrichment with Al, Mg, and Fe in cookeite but is decoupled from Al in the diaspore. TOF-SIMS three-dimensional (3D) reconstruction reveals that Li is predominantly concentrated in the O2 sheets of cookeite's TO1T-O2-TO1T structure. Stepwise leaching experiments further constrain Li occurrence, demonstrating that most Li is hosted within the lattice. Calcination at 400 °C promotes Li incorporation into the lattice, while subsequent treatment at 600 °C-200 °C (H2SO4) or 200 °C (concentrated H2SO4) effectively mobilizes Li, particularly in sample AN 1.58, achieving nearly complete extraction.

The Yellow River Basin, as a crucial water and ecological zone, is threatened by environmental contamination from the Bayan Obo tailings dam located just 13 km away. Based on the Microbial-Induced Calcite Precipitation, this research used a combined approach of bio-mineralization and bio-sorption to bio-remediate the rare earth elements (REEs) and their mixed contaminants. Optimal conditions for soil solidification and stabilization are determined through solution pretests. Comparative analyses of adsorption, mineralization, and their combined processes were conducted in soil experiments. Evaluating using the results of speciation analysis. Following bioremediation, the adsorption-mineralization group involving indigenous bacteria, Bacillus oceanicus, exhibited the best performance. In this group, the average comprehensive reduction in exchangeable forms of Zn, Pb, La, and Ce was 52.02%, which is 2.9 times that of the adsorption group and 1.3 times that of the mineralization group under the same environmental conditions. These results indicate that the biogenic carbonates and isomorphic lattice substitutions generated through the bioption and bio-mineralization process contribute to the solidification/stabilization of REEs and their mixed contaminants. This approach holds significant importance for environmental protection and ecological restoration in the Yellow River Basin, particularly in the middle and lower reaches of the Yellow River.

Efficient adsorption of heavy metals using Friedel's salt synthesized from municipal solid waste incineration fly ash leachate.

This work encompasses the study of magnetic, optical, and structural properties of the coordination compounds [Ln(MeDPQ)2Cl3] (Ln ─ Ho3+, Er3+, Dy3+, and Y3+; MeDPQ − 2‐methyldipyrido‐[3,2‐f:2′,3′‐h]‐quinoxaline) and substituted complexes [Ln1‐xDyx(MeDPQ)2Cl3] (Ln = Ho3+, Er3+, and Y3+) based on them. Magnetic measurements within the range 5–300 K revealed single ion anisotropy in [Dy(MeDPQ)2Cl3], with the Curie‐Weiss temperature θ being −3.69 ± 0.03 K. Complexes of Ho3+ and Er3+ exhibited f–f emission in the visible range, while the latter was also emissive in the NIR. Dilution of the Dy3+ complex with diamagnetic Y3+ ions resulted in alterations of magnetic and photophysical properties. The substituted complexes Y0.5Dy0.5 and Y0.9Dy0.1 demonstrated paramagnetic behavior, with θ being 3.06 ± 0.12 K and 9.64 ± 0.23 K, respectively. In both cases, the emission decay times of Dy3+ changed insignificantly, 21.02 ± 0.41 µs and 14.56 ± 0.22 µs, respectively, compared to the value (18.92 ± 0.03 µs) of the individual Dy3+ complex. Additional ligand‐based emission bands were observed in the Ho3+ and Er3+ complexes at room temperature and 77 K and in the substituted complexes Ho0.5Dy0.5 and Er0.5Dy0.5 at room temperature, which were assigned to the exciplex states. The thermal stability of [Er0.5Dy0.5(MeDPQ)2Cl3] was determined to be the same as for the individual complexes, starting to oxidize at 410°C.

With the rapid industrial development, industrial wastewater poses a significant environmental burden. The prevailing chemical precipitation treatment requires excessive chemicals, leading to substantial sludge production, unstable hydroxides, and limited resource utilization. Addressing these challenges, Duan Xue’s team proposed the super-stable mineralizer technique. LDHs replace heavy metal ions by isomorphous substitution, creating a super stable mineralized structure. This approach effectively reduces heavy metal ion migration and bioavailability. With its versatility in treating Ni, Cu, Cr, and Pb, it also proven effective in real wastewater. Moreover, the super-stable mineralized materials selectively convert trace ionic gold into simpler gold, exhibiting exceptional performance in electrolytic water and CO2PR. This innovation offers new possibilities in clean energy and waste resource recycling. In treating highly concentrated heavy metal wastewater, it successfully transforms Cu, Ni, Pb, and other metals into elemental forms, enabling heavy metal resource recovery and expanding the application of treating heavy metal-polluted wastewater. This figure explains mechanism of super-stable mineralization and catalytic application.

With the rising demand for batteries with iron phosphate (LiFePO<sub>4</sub>, LFP) cathodes in electric vehicles, developing sustainable and cost-effective recycling processes is becoming increasingly important. Acid-free leaching with Fe<sup>3+</sup> ions provides an environmentally friendly approach to lithium recovery; however, selectively separating Li<sup>+</sup> over Fe<sup>2+</sup> which is the predominant species in the leachate formed through isomorphous substitution, remains challenging because of their comparable physicochemical and electrochemical characteristics. This study develops a redox-mediated bipolar membrane electrodialysis (Redox-BMED) system for efficiently recovering lithium recovery from acid-free leachates while simultaneously producing of lithium hydroxide (LiOH). Unlike conventional electrodialysis, which relies on water splitting, Redox-BMED utilizes redox reactions to enhance separation performance. The system is evaluated under various conditions, comparing two different membranes (nanofiltration and ion-exchange membranes) and examining the ion selectivity and its stability during long-term operation for 24 h. The Redox-BMED system recovered lithium and successfully produced LiOH (> pH 12) from real leachates obtained from the acid-free leaching of spent LFP batteries. These results highlight Redox-BMED as a promising, environmentally benign electrified platform for lithium recovery in next-generation battery recycling.

Proton exchange membrane water electrolysis is promising for green hydrogen production, but the sluggish oxygen evolution reaction (OER) and the poor stability of iridium-free OER electrocatalysts hinder its application. Herein, non-metallic element germanium (Ge) is doped into rutile RuO2 nanoparticles to synthesize an active and stable Ru-based acidic OER electrocatalyst. The optimized catalyst (Ge0.1Ru0.9O2) exhibits an ultralow overpotential of 161 mV at 10 mA cm-2 and undergoes a long-term stability test of 650 h at 100 mA cm-2, with a decay rate of 0.164 mV h-1. The high performance is attributed to the isomorphic substitution of Ge, which possesses a slightly smaller ionic radius (53 pm) than Ru (64 pm) and the same valence state (4+), and can donate electrons to Ru, and enhance the structural stability. In situ attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS), operando isotropic differential electrochemical mass spectrometry (DEMS), and first-principles calculations reveal that, compared to pristine RuO2, the Ge dopants further unexpectedly facilitate water dissociation and accumulate abundant ─OH group as reactants on electrocatalysts surface. This work gives insights to non-metallic cation doping and interfacial water dissociation for the design of active and robust Ru-based electrocatalysts for acidic water splitting.

The growing global demand for lithium, driven by its pivotal role in battery production, highlights the need for alternative technologies to recover this metal from low-grade and anthropogenic raw materials. This study investigates lithium extraction from aluminosilicate tailings of rare-metal production by sulfate roasting with concentrated sulfuric acid, followed by aqueous and hydrochloric acid leaching. Mineralogical analysis confirmed lithium mainly in muscovite and biotite (isomorphic substitutions) and partly as spodumene within the aluminosilicate matrix. The optimal parameters of thermochemical treatment were determined as 300 °C for 1 h at a liquid-to-solid ratio of 1:6. Subsequent aqueous leaching (90 °C, 1 h, L/S = 6:1) achieved a lithium recovery of 82.3%, while HCl proved less effective. Using response surface methodology (RSM) and a central composite design (CCD), a regression model was developed predicting up to 93.4% lithium extraction at 90 °C, a liquid-to-solid ratio of 10:1, and a leaching duration of 75 min. The calculated values showed good agreement with experimental data obtained at 90 °C, L/S = 10:1, and 30 min leaching, yielding 91.92% lithium recovery. These results confirm the efficiency of the proposed thermochemical approach and provide a scientific foundation for its further development and industrial scale-up.

The enrichment of cadmium (Cd) in farmland soil poses serious risks to agricultural safety and remains challenging to remediate. This study evaluated CaAl-layered double hydroxide (CaAl-LDH) as a highly efficient and stable passivator for Cd-contaminated soil. Laboratory adsorption tests demonstrated that Cd2+ adsorption on CaAl-LDH followed pseudo-second-order kinetics and the Langmuir model, indicating monolayer chemisorption, with a maximum capacity of 469.48 mg·g−1 at pH 6. The adsorption mechanisms include surface complexation, interlayer anion exchange, dissolution–precipitation, and isomorphic substitution. A three-year field trial in Yongkang City, China showed that CaAl-LDH promoted the transformation of Cd in rhizosphere soil from the ion exchange state (F2) to the residual state (F7) and Fe–Mn oxidized state (F5), reducing the exchangeable Cd content by 26.71%. Consequently, Cd content in rice grains decreased by 68.42% in the first year and remained over 37% lower in the second year, consistently below the national food safety limit. Future research should focus on the optimization of material’s stability and application protocol. The results demonstrate that CaAl-LDH provides a cost-effective and sustainable strategy for the in situ passivation remediation of Cd-contaminated farmland, contributing to food safety and sustainable agriculture.

Mg-Al layered double hydroxides derived from secondary aluminum ash for soil remediation contaminated with Cd(Ⅱ) and Cr(Ⅵ).

Abstract Pharmaceutical residues, particularly ciprofloxacin (CIP), are frequently detected in aquatic environments and pose significant risks to ecosystems and human health. This study investigates the visible-light photocatalytic degradation of CIP using Co²⁺-modified Zn₀.₆₆₇Al₀.₃₃₃-layered double hydroxide (LDH) materials, with persulfate (PS) as a co-activator. The hydrotalcite-like compounds Zn₀.₆₆₇Al₀.₃₃₃(OH)₂(CO₃)₀.₁₆₇•0.5H₂O, denoted as nCoZnH, were synthesized by co-precipitation.These were further calcined at 500 °C for 5 hours to obtain nCoZnH500. Both uncalcined and calcined materials were characterized structurally and physicochemically. Results revealed that nCoZnH maintained the typical hydrotalcite layered structure, with Co²⁺ ions effectively incorporated into brucite-like layers through isomorphic substitution of Zn²⁺. Upon calcination, partial retention of the LDH structure was observed, accompanied by the formation of ZnO and Co₃O₄ phases. The BET surface area of nCoZnH500 was markedly higher than that of uncalcined counterparts. Co²⁺ modification also significantly reduced the bandgap energy, thereby enhancing visible-light-induced photocatalytic activity. Among all samples, 1.0CoZnH and 2.0CoZnH500 exhibited the highest degradation efficiencies, 78.0 ± 1.87% and 70.9 ± 2.31%, respectively, for 10 ppm CIP under visible light. Furthermore, the photocatalytic activity of the synthesized materials was influenced by the Co: Al molar ratio, initial CIP concentration, persulfate (S₂O₈²⁻) dosage, and solution pH. The 2.0CoZnH500 sample demonstrated superior stability compared to 1.0CoZnH, with only a 9.1% reduction in the CIP removal efficiency after four consecutive cycles, maintaining a degradation efficiency of 59.7%. These findings indicate that the synergy between Co²⁺ doping and PS activation effectively boosts CIP degradation. The developed materials offer promising potential for the treatment of pharmaceutical wastewater under visible light irradiation.

Accelerated tetracycline hydrochloride mineralisation by Fe@CeO2-x/MgO complex metal oxides via ozone-catalysed interfacial reactions: The role of oxygen vacancies and multivalent metal cycling.

Abstract The catalytic performance of zeolites is intrinsically linked to their structural and chemical properties. This review comprehensively explores how various structural and surface modifications enhance catalytic efficiency and fine‐tune zeolite physicochemical properties. A key approach involves controlling the Si/Al ratio, which profoundly influences acidity and hydrothermal stability. Both bottom‐up (synthesis) and top‐down (post‐synthesis) methods offer pathways to engineer specific acid site densities and introduce beneficial mesoporosity. Beyond composition, advancements in morphological control (2D nanosheets to 3D hollow particles) further enhance catalytic efficiency by effectively addressing diffusion limitations and extending catalyst lifetime. In terms of modulating the acid sites, the review highlights versatile approaches to metal incorporation, including isomorphous substitution for tuning framework acidity and various functionalization techniques–i.e., ion exchange, impregnation, and encapsulation–for creating spatially confined and highly dispersed metal nanoparticles on zeolite surfaces or within their internal sites. Case studies highlight the benefits of modifications in various catalytic reactions, including CO oxidation, methanol‐to‐olefins, and hydrodeoxygenation, demonstrating improved acidity, selectivity, and stability. The review concludes by outlining ongoing challenges related to optimizing synthesis methods to enhance one property without sacrificing others, advocating for integrated research combining advanced characterization with catalytic testing to establish robust structure‐performance relationships of zeolite catalysts.