High Alkali Content Research Articles

Geochemistry and Zircon U–Pb Chronology of Jinchanshan Gold-Hosted Granitoids, Inner Mongolia: Implications for Petrogenesis and Geodynamic Evolution

Jinchanshan is a medium-sized, granitoid-hosted gold deposit located in the Kalaqin area of Inner Mongolia. Mineralization predominantly occurs in the contact zone between biotite granites and quartz porphyry rocks, associated with the Jinchanshan minor intrusion, suggesting a genetic link to the granitoid-hosted gold deposit. In this study, the petrography, geochemistry, and LA-ICP-MS zircon U–Pb chronology of these two granitoid samples were studied. The results indicate that the zircon U–Pb age of the biotite granites is 127.9 ± 3.0 Ma, while that of the quartz porphyry is 121.4 ± 1.5 Ma, both dating back to the Early Cretaceous. The average SiO2 content of the granites is 66.64%, and the rocks have high total alkali (K2O + Na2O) content, averaging 9.13%. The average K2O content is 4.39%, with a K2O/Na2O ratio of 0.93. The quartz porphyry rocks are enriched in SiO2 (74.41%–76.85%) and have high Na2O + K2O content (8.67%–9.59%), but are low in MgO (0.03%–0.09%), CaO (0.44%–1.02 %), and TiO2 (0.08%–0.12%). Most samples of the biotite granite and the quartz porphyry rocks exhibit high-K peraluminous and medium-K calc-alkaline characteristics, respectively. Both rock types are enriched in Rb, Th, U, K, Zr, Hf, and Gd and relatively depleted in Ba, Sr, P, Ti, Nb, Ta, and Eu, with a pronounced negative Eu anomaly. The biotite granites show high ∑LREE/∑HREE ratios (6.1–6.9), while the quartz porphyry rocks exhibit lower ratios (2.0–4.2). Both granitoid types have elevated FeOT content and FeOT/(FeOT + MgO) ratios, indicating that the Jinchanshan granitoids are A-type granites. The zircon U–Pb ages, combined with the regional tectonic settings, suggest that these granitoids formed during large-scale metallogenic events in the Early Cretaceous, within the Yanshanian post-orogenic extensional tectonic regime. This is consistent with the lithospheric thinning and extensional processes in Eastern China during this period.

Rubidium (Rb) enrichment processes in a highly evolved granitic system: Insights from the petrology and geochemistry of the Guobaoshan Rb deposit in eastern Tianshan, NW China

Highly fractionated granitoids are closely associated with Rb mineralization, yet the mechanisms that control Rb enrichment and details about the enrichment process have not been well constrained. The Guobaoshan Rb deposit in eastern Tianshan, NW China, is one of the largest granite-related Rb deposits; it preserves a series of gradual lithofacies ranging from biotite granite and muscovite granite to Rb-rich amazonite granite and pegmatite, and provides an excellent opportunity to constrain the Rb enrichment processes in granitic systems. The large Guobaoshan Rb deposit hosts 281,000 tons of Rb2O at a grade of 0.12% mainly in its amazonite-bearing granite and amazonite granite lithofacies. In this contribution, we integrate geochronology, bulk-rock geochemistry, and analysis of Nd and zircon Hf isotopes to characterize the evolution of the Guobaoshan granitic pluton and the mechanisms that generated Rb enrichment. The zircon U-Pb age of the biotite granite and columbite U-Pb age of the amazonite granite are 244.8 ± 1.8 Ma (1σ, mean square of weighted deviates [MSWD] = 1.1) and 241.9 ± 2.3 Ma (1σ, MSWD = 1.0), respectively. In situ Rb-Sr analysis of orthoclase, mica, and albite from the amazonite-bearing granite, amazonite granite, and pegmatite yields ages of 249.1 ± 7.3 Ma (2σ, MSWD = 1.6), 245.5 ± 16.8 Ma (2σ, MSWD = 0.63), and 245.8 ± 9.8 Ma (2σ, MSWD = 3.3), respectively. Together, these ages demonstrate that the Guobaoshan granitic pluton formed during the Triassic and underwent a protracted magmatic evolution. The Guobaoshan granitic pluton is characterized by high concentrations of SiO2, alkalis, and Al2O3, and low concentrations of MgO, Fe2O3, CaO, P2O5, and TiO2, with an Al saturation index (A/CNK) of 1.01−1.14. It is enriched in Rb, but depleted in Ba, Sr, P, and Eu, has low total rare earth element (REE) contents (83.1−221 ppm), and is characterized by significantly negative anomalies (Eu/Eu* = 0.01−0.44). The biotite granite is enriched in light rare earth elements (LREEs), whereas the muscovite granite, amazonite-bearing granite, amazonite granite, and pegmatite are depleted in LREEs, and exhibit a marked tetrad effect (TE1.3 = 1.05−1.50). These geochemical characteristics, combined with the non-CHARAC (charge-radius−controlled) ratios of Zr/Hf, Nb/Ta, Y/Ho, and K/Rb, are indicative of melt-fluid interaction during the evolution of the Guobaoshan magma. Given that the biotite granite is the least-evolved rock, its petrological and geochemical characteristics suggest that it is an I-type granite. The slightly variable εHf(t) and consistently negative εNd(t) values indicate that the magma from which the Guobaoshan granitic pluton crystallized was likely sourced from the Mesoproterozoic crust, with limited mantle contributions. The coeval ages and coherent geochemical variations and mineral compositions of these rocks suggest that they formed via fractional crystallization of plagioclase, mica, quartz, and K-feldspar in the same magmatic system. This is supported by fractional crystallization simulations using the rhyolite-MELTS software package. Based on the petrological, mineralogical, and geochemical characteristics of the muscovite granite, amazonite-bearing granite, amazonite granite, and pegmatite, as well as simulations using rhyolite-MELTS, high degrees of fractional crystallization of granitic magma and interaction of this evolving magma with F-rich fluids are suggested to have been the key mechanisms that caused enrichment of Rb, while the melt-fluid interaction was more critical for Rb mineralization.

Self-protected Chlorella@Mn catalyst with excellent resistance to alkali/alkaline earth metal for NOx reduction by NH3

In the selective catalytic reduction of NOx by NH3 (NH3-SCR), conventional Mn-based denitration catalysts often suffered from susceptibility to poisoning by alkali and alkaline earth metals, this paper presented an innovative self-protected Chlorella@Mn denitration catalyst. Remarkably, in the presence of high concentrations (2 wt%) of alkali and alkaline earth metal oxides, the Chlorella@Mn catalyst sustained a NOx conversion exceeding 96 % at 175 °C. At an even higher concentration (4 wt%), NOx conversion above 90 % at 175 °C, surface analysis revealed that POMn sites acted as sacrificial sites, binding to the alkali and alkaline earth metals, the Chlorella@Mn catalyst surface naturally carried a spectrum of acidic species (such as SO42−, PO3−, SiO32−), proficient in capturing alkali/alkaline earth metal effectively, elements such as S, P, and Si formed bonds with K, Na, Ca, and Mg. The synergistic protection of the active sites and the surface elements avoided the deactivation of the catalyst. The detrimental effects of high concentrations of alkali and alkaline earth metals were primarily due to promoting an excessively high valence state of Mn on the catalyst surface and the reduction or loss of NH3 adsorption and activation at Brønsted acid sites. This research provided valuable insights for advancing the development of low-temperature denitration catalysts with improved resistance to alkali and alkaline earth metal poisoning.

Age and petrogenesis of the Madi intrusion in the Huashi area, northern margin of the North China Craton: Implications for magma evolution and Nb–Ta mineralization

Although the mineralization of rare earth elements (REEs) and rare metals is intimately associated with the extreme fractionation of granitic magmas, the metallogenic intrusions of many granite-hosted Nb–Ta deposits have undergone fluid–melt interaction. Nevertheless, the precise mechanisms by which fluid–melt interaction influences mineralization remain poorly understood. The present investigation examines the issues of the fluid–melt interaction in highly fractionated granites with Nb–Ta mineralization, utilizing data from the newfound Huashi deposit in the northern margin of the North China Craton (NNCC). The Huashi Nb–Ta–Rb–Li deposit hosted in the Madi intrusion consists of two lithologies that have evolved continuously, namely medium–fine grained granite (MGG) in the lower section and alkali-feldspar granite (AG) at the top. The ages of the MGG and AG were determined using LA–ICP–MS columbite U–Pb dating, yielding values of 182.9 ± 1.7 Ma and 184.7 ± 1.3 Ma, respectively. The Madi intrusion has high SiO2, Al2O3, and total alkali contents, along with low CaO, MgO, MnO, and TFe2O3 contents and high Al2O3 / (CaO + Na2O + K2O) (A/CNK) values, classifying it as highly peraluminous granite with a high-K calc-alkaline affinity. Additionally, the intrusion also exhibits enrichment in Rb, U, Th, and Nb alongside significant depletion in Sr, Ba, Ti, Eu, and P, with a noticeable tetrad effect of REEs. The investigation of mica and feldspar minerals in the Madi intrusion using electron probe microanalysis (EPMA) indicates that the mica is mainly zinnwaldite, while the plagioclase belongs to albite. In summary, the Madi intrusion exhibits a highly I-type fractionated granite affinity. The extreme fractionation, intense fluid–melt interaction, and hydrothermal alteration of the intrusion contribute to the formation of the Huashi deposit.

Influence of Steel Slag as a Partial Replacement of Aggregate on Performance of Reinforced Concrete Beam

Amidst the global pursuit of sustainable alternatives in concrete production, this study explores the viability of incorporating by-products or waste materials as aggregates to support the concrete construction industry, with a specific emphasis on steel slag. The objective of this study is to evaluate the effectiveness of steel slag as a partial replacement for fine and coarse aggregates in concrete production. The experiment involved casting 30 cubes and 10 beams, replacing fine aggregate from 0 to 60%. Flexural and compressive strength tests at 7 and 28 days followed the ACI method. Results revealed that a 30% replacement of fine aggregate with steel slag led to higher compressive strength at both 7 and 28 days, while a 45% replacement showed superior flexural strength at 28 days. Further chemical analysis and optimization are recommended for deeper insights. The study concludes with marginal improvements in compressive and flexural strength with steel slag partial replacement, identifying 30% for fine aggregate and 45% for coarse aggregate as optimal replacements. In addition, the mineral composition of steel slag exhibits significant variability, with compounds, including silicon dioxide (SiO2), iron oxide (Fe2O3), manganese oxide (MnO), aluminum oxide (Al2O3), and calcium oxide (CaO). Chemical analysis indicates high silicate content and minimal alkali content, contributing to enhanced strength during concreting. Higher steel slag replacement reduces workability, confirmed by slump tests. However, all mixes maintain a true slump, and unit weight increases with steel slag aggregate replacement. Compressive strength improves incrementally with higher steel slag content, echoing prior research. In addition, flexural strength rises with steel slag replacing both coarse and fine aggregates, suggesting enhanced performance in reinforced concrete structures. These findings highlight steel slag’s potential as a sustainable alternative in concrete production, aiming to advance its application in the construction industry, promoting environmental sustainability and economic viability.

Comprehensive Assessment of A-Type Granite from South Sinai, Egypt: Geochemistry, Zircon Geochemistry, and Geochronology

The A-type granites are an important component of the Earth's continental crust and play a significant role in understanding crustal evolution and tectonic processes. This study presents a comprehensive assessment of A-type granites from Ataitir El Dehami granites (ADG) that located at the north-western part of Wadi Seih area in South Sinai, using geochemistry, zircon geochemistry, and geochronology characteristics. The geochemical analysis reveals that ADG are characterized by high silica content, relatively high FeO*, and high alkali concentration consistent with the A-type granites that derived from the melting of tonalite sources. Zircons from Ataitir El Dehami granites have high REE contents with Ce enrichment and depletion of Eu, which, together with the high U/Yb ratios, suggest that the studied granites were generated from melting of continental crust rocks. Zircon U-Pb geochronological data indicates that the granite emplacement occurred around 575 to 603 Ma throughout continuous exhumation pulses. The isotopic analyses also indicate that the presence of inherited zircon grains (735± 9Ma). The present data suggest that the studied granites were formed in a post-collisional setting, and represent the transition stage from convergence to extension that occurred at 600 Ma.

Inverted Glasses As Ductile Lithium Ion Conductors for Solid State Batteries

Inorganic electrolytes for solid state batteries with Li metallic anodes must combine properties such as high ionic conductivity, chemical stability, and resistance to failure due to propagation of Li dendrites. Abundance of experimental evidence suggests that cracking of the solid electrolytes due to pressure exerted by lithium plating into the material defects is the primary source of failure [1]. This is due to inherent brittleness of the ceramic ionic conductors, i.e. their inability to reduce stress by means other than fracture. Unlike ceramics, plastic deformation in glass can be achieved via shear and (or) by densification. Both mechanisms can be operational in glasses with reduced content of glass formers relative to the content of glass modifiers – i.e. inverted glasses. Using the example of lithium phosphorous oxynitride, Lipon, we demonstrate how these two mechanisms are capable of accommodating applied stress while avoiding creation of new surfaces by cracking. We investigate the resistance to fracture in Lipon-like glasses and the underlying connection to their composition via instrumented nano-indentation, Raman spectroscopy, and numerical simulations. We observe enhancement of isochoric shear with increase of Li content, similarly to the reports of increased plasticity in sodium aluminoborate glases with high alkali content [2]. Nano-indentation demonstrates that Lipon is extremely resistant to fracture, compared to other inorganic solid electrolytes [3].[1] Porz, T. Swamy, B.W. Sheldon, D. Rettenwander, T. Fromling, H.L. Thaman, S. Berendts, R. Uecker, W.C. Carter, Y.-M. Chiang, Mechanism of lithium metal penetration through inorganic solid electrolytes. Adv. Energy Mater. 7, 1701003 (2017)[2] Sellappan, T. Rouxel, F. Celarie, E. Becker, P. Houizot, R. Conradt, Composition dependence of indentation deformation and indentation cracking in glass. Acta Mater. 61, 5949–5965 (2013)[3] Kalnaus, A. Westover, M. Kornbluth, E.J. Herbert, N.J. Dudney, Resistance to fracture in the glassy solid electrolyte Lipon. J. Mater. Research, 36, 787-795 (2021)

Petrology and geochemistry of Mount Lurus lavas: evidence for alkaline to subalkaline transition in the rear arc of Java, Sunda Arc

Abstract Mount Lurus, a small Quaternary volcanic center in the rear of Java Island, Sunda arc, has erupted both alkaline and subalkaline lavas in a short span of active period. Furthermore, this small volcanic edifice, together with its neighboring alkaline volcanic center of Ringgit-Beser, corresponds to a shallower slab depth (∼160 km) than Muria in Central Java (270 km). We report the mineralogical and geochemical characteristics of Lurus lavas and compare them to the Ringgit-Beser lavas. All Lurus lavas show typical characteristics of island arcs with elevated Ba, Sr, Pb, and K and negative anomalies of Nb and Ti. The older Lurus edifice (Old Lurus) produces alkaline lavas with high alkalinity, which are trachyandesite and phonotephrite in composition. The younger Lurus (Young Lurus) generates calc-alkaline lavas with basaltic andesite composition. Both groups have plagioclase, clinopyroxene, olivine, and opaque minerals as phenocrysts phase. Leucite is found in one sample of Old Lurus with the lowest SiO2 content (48.92 wt%) and highest alkali content (5.38 wt%). Old Lurus lavas tend to show higher contents of incompatible elements (Pb, Ba, Nd, and Rb) than Young Lurus. The mineralogical and compositional differences between these lavas suggest that these magmas are sourced from at least three magma chambers of distinct composition: highly potassic magma chamber (comparable to the evolved-K series of Ringgit-Beser) and hydrous-potassic magma which fed Old Lurus edifice; and calc-alkaline magma chamber which fed Young Lurus edifice.

Mechanical Properties and Mesoscopic Numerical Simulation of Local Weakening in High-Performance Concrete after 10 Years of Alkali Solution Immersion

The natural environment in the high-altitude regions of Northwest China is extremely harsh, characterized by numerous salt lakes. The high concentrations of chloride salts, sulfates, and alkali metal ions in these areas can induce alkali–silica reactions (ASRs) in concrete. These reactions generate harmful gel within the concrete, causing expansion and cracking, which significantly impacts the durability of concrete structures. This study investigates the evolution of the mechanical properties in high-performance concrete (HPC) under long-term ASR by incorporating different admixtures and varying the equivalent alkali content. A three-dimensional random aggregate mesoscopic model was used to simulate static compression tests under various operational conditions. Non-destructive testing methods were utilized to determine the expansion rate, internal, and surface damage variables of the concrete. The experimental results indicate that the 10-year expansion rate differs from the 1-year rate by approximately 1%, and under long-term ASR mitigation measures, the internal damage in the HPC is minimal, though the surface damage is more severe. As the equivalent alkali content increases, the compressive strength of the concrete cubes decreases, initially rising before falling by 5–15% over time. The HPC with only air-entraining agent added exhibited better mechanical performance than the HPC with both air-entraining and corrosion inhibitors added, with the poorest performance observed in the HPC with only a corrosion inhibitor. A relationship was established between the surface and internal damage variables, with the surface damage initially increasing rapidly before stabilizing as the internal damage rose. Numerical simulations effectively describe the damage behavior of HPC under static uniaxial compression. Comparisons with actual failure morphologies revealed that, in the cube compression tests, crack propagation directly penetrated both coarse and fine aggregates rather than circumventing them. The simulations closely matched the experimental outcomes, demonstrating their accuracy in modeling experiments. This study discusses the compressive mechanical properties of concrete under prolonged ASR through a combination of experimental and simulation approaches. It also delves into the impact of surface damage on the overall mechanical performance and failure modes of concrete. The findings provide experimental and simulation support for the concrete structures in regions with high alkali contents.

Mesozoic crustal growth and recycling along the Southern margin of Eurasia: Magmatic rocks from the Sanandaj-Sirjan Zone of Iran

The Sanandaj-Sirjan Zone of western Iran is characterized by significant Mesozoic magmatic activity (from the early Jurassic to the late Cretaceous), with Cenozoic rocks being less common. Granitoids are prevalent in this zone, displaying A-, I-, and S-type geochemical characteristics. Despite several studies on these granitoids, there are still some questions regarding their sources– especially the S- and A-type granitoids – and the crustal growth and recycling in this zone, which require further studies using isotopes. This study focuses on the Aligoodarz, Kolah-Ghazi, and Golpayegan granitoids from the central SaSZ to better understand crustal growth and recycling in the Sanandaj-Sirjan Zone. The Aligoodarz and Kolah-Ghazi granitoids are identified as S-type granites, showing strong peraluminous signatures. Geochemical evidence suggests a mixture of melts from sub-crustal metasedimentary and meta-igneous sources, with factors such as source diversity and disequilibrium melting contributing to their formation. in contrast, the Golpayegan granitoids exhibit high total alkali (Na2O + K2O) contents and high field strength elements, indicating alkaline magmatic affinity. Their geochemical signatures suggest derivation from an enriched portion of an Indian MORB-like protolith. Golpayegan syenites share similarities with within-plate A1 granites, suggesting they are related to anorogenic silica-oversaturated granitoids. Golpayegan A-type granites probably originated from high-degree fractionation of alkali basic magmas. Golpayegan gabbros may be derived from a MORB or OIB-like mantle source, with characteristics indicating the presence of garnet in the mantle source and potentially deep melting from a mantle plume. Newly compiled zircon UPb data from the Sanandaj-Sirjan Zone show a complex magmatic chronology spanning from approximately 180 million years ago to the Eocene epoch, revealing peaks of magmatic activity at various intervals. Distinct phases of A-, I-, and S-type magmatism are identified, and synthesis of zircon UPb ages and HfO isotope data reveals the simultaneous occurrence of S-type and I-type magmas during specific periods. Furthermore, our study explores the tectonic settings underlying these magmatic processes and proposes scenarios involving subduction, continental rifting, and asthenospheric upwelling to elucidate the geological dynamics of the SaSZ.

Zircon U-Pb Dating, Geochemistry, Lu-Hf Isotope Characteristics, and Geological Significance of Volcanic Rocks in Zhenghe Fozi Mountain National Geopark, Fujian, China

Fozi Mountain National Geopark is located in Zhenghe County in the northern region of Fujian Province, where the volcanic rocks of the Zhaixia Formation of the Shimaoshan Group are exposed. Zircon U-Pb dating and geochemical analysis were carried out to constrain its age and tectonic environment. The results show that three zircon U-Pb dating samples have attained ages of 99.2 ± 1.0 Ma, 99.6 ± 0.8 Ma, and 99.7 ± 2.0 Ma. Volcanic rocks in the core scenic area of Fozi Mountain were formed during the Late Cretaceous period. Elemental analysis showed that these volcanic rocks were dominated by the shoshonite series. They include gray dacite porphyry, grayish-white breccia tuff, volcanic agglomerate, and gray tuffaceous sandstone. These rocks were characterized by high silicon, high alkali content, and rich potassium levels. Lu-Hf isotope analysis of zircons revealed that their εHf(t) values varied from −8.7 to −6.8. The corresponding TDM2 values were primarily distributed in the range of 1.71 Ga to 1.59 Ga. These findings indicated that the magma primarily originated from the partial melting of the Mesoproterozoic crystalline basement, accompanied by a small number of mantle-derived materials. Tectonic environment analysis indicated that these rocks were formed in the post-orogenic intraplate extensional environment, which was associated with the back-arc extension or lithospheric thinning caused by the subduction of the paleo-Pacific plate beneath the Eurasian plate. The formation of these volcanic rocks was attributed to post-orogenic magmatism.

Electro-oxidation of 5-hydroxymethylfurfural in a low-concentrated alkaline electrolyte by enhancing hydroxyl adsorption over a single-atom supported catalyst

Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), a sustainable strategy to produce bio-based plastic monomer, is always conducted in a high-concentration alkaline solution (1.0 mol L−1 KOH) for high activity. However, such high concentration of alkali poses challenges including HMF degradation and high operation costs associated with product separation. Herein, we report a single-atom-ruthenium supported on Co3O4 (Ru1-Co3O4) as a catalyst that works efficiently in a low-concentration alkaline electrolyte (0.1 mol L−1 KOH), exhibiting a low potential of 1.191 V versus a reversible hydrogen electrode to achieve 10 mA cm−2 in 0.1 mol L−1 KOH, which outperforms previous catalysts. Electrochemical studies demonstrate that single-atom-Ru significantly enhances hydroxyl (OH−) adsorption with insufficient OH− supply, thus improving HMF oxidation. To showcase the potential of Ru1-Co3O4 catalyst, we demonstrate its high efficiency in a flow reactor under industrially relevant conditions. Eventually, techno-economic analysis shows that substitution of the conventional 1.0 mol L−1 KOH with 0.1 mol L−1 KOH electrolyte may significantly reduce the minimum selling price of FDCA by 21.0%. This work demonstrates an efficient catalyst design for electrooxidation of biomass working without using strong alkaline electrolyte that may contribute to more economic biomass electro-valorization.

A single-step crystallization process to remove potassium from sodium aluminate solution

The high concentration of potassium in sodium aluminate solution seriously threatens the seed precipitation process and reduces the quality of alumina products, but the separation of potassium is quite difficult due to the similar chemical properties between potassium and sodium ions. In this work, a novel single-step double salt crystallization (SDSC) process with low energy consumption was proposed to remove potassium from the concentrated sodium aluminate solution using sodium sulfate, and the corresponding removal performance, kinetics and mechanism were studied. The potassium concentration decreases with the increase of additive dosage and reaction temperature, while the high caustic alkali concentration hinders the potassium removal. At 70 °C, the SDSC process exhibits a rapid crystallization and reaches an equilibrium within 60 min because of the low activation energy and weak bonding of 3 K2SO4·Na2SO4·9H2O. Under the optimum conditions, the potassium removal efficiency can achieve 85.68 %, and the potassium concentration is reduced from 120 g∙L−1 to 24.54 g⋅L−1. Finally, a cyclic utilization pathway was obtained to economically and effectively remove potassium from the sodium aluminate solution.

Study and Characterization of Algerian Spart Cellulosic Fibers (Lygeum spartum): Effect of Alkali and Acid Treatments on Their Physicochemical and Morphological Properties for Papermaking

Recently, non-wood plants have increasingly gained attention, due to their versatile advantages like cost and fast-growing period. The purpose of this study was to examine the effectiveness of different treatments on Algerian Spart fibers (Lygeum spartum) using sodium hydroxide at various concentrations (8, 10, 15, and 22% NaOH), and sulfuric acid at 30% for 2h at 100 °C. Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses were used to characterize the microstructural changes in the treated fibers. The results of FTIR confirmed the presence of cellulose in the raw fibers with a crystallinity index of 49.4%. The FTIR and XRD studies showed that an 8% NaOH treatment eliminated the amorphous constituents and improved the crystallinity index. Also, SEM micrographs confirmed the removal of impurities; for the acid treated fibers a pseudo-lignin was formed and deposited on fibers surfaces in the form of spherical droplets. Moreover, a decrease in the yield of cellulose at high alkali concentrations was noticed. The results suggest the possibility of exploitation of Spart fibers and their application in papermaking and as a reinforcement in composite materials.

The Influence of Retreated Lithium Slag with a High Content of Alkali, Sulfate and Fluoride on the Composition and the Microstructure of Autoclaved Aerated Concrete.

In this paper, the possibility of retreated lithium slag (RTLS) with a high content of alkali, sulfate and fluoride as a partial replacement for fly ash (FA) to produce autoclaved aerated concrete (AAC) was investigated. The influence of the RTLS dosage on the AAC performance were examined. The composition and microstructure of hydrates as well as the microstructure of the RTLS-FA-based AAC compositions were determined by XRD, FTIR, TG-DSC and SEM. The results illustrated that the incorporation of RTLS changed the crystal structure and the microstructure of the tobermorite. With increased RTLS contents, the morphology of tobermorite was changed, and the grass-like tobermorite gradually transformed into network-like tobermorite. The newly formed tobermorite improved the mechanical performance of the AAC. Compared with the RTLS10, the content of tobermorite in the RTLS30 increased by 8.6%.

Geochemistry, Rb-Sr whole rock age and Sr-Nd isotopic constraints on the Variscan A1-type granite from Azegour area in the Marrakech High Atlas (Moroccan Meseta) and their geodynamic implications

In the northern part of the Marrakech High Atlas (MHA), along the southern Variscan segment of the Western Meseta, a Variscan granitic intrusion crops out, intruding metasediments and meta-volcanosedimentary rocks of Early Cambrian to Ordovician age. A new whole-rock Rb-Sr isochron age of 268 ± 9 Ma for the granite, combined with a previously published whole-rock Rb-Sr radiometric dating (271 ± 3 Ma), reveals a post-kinematic (tectonic) character with regard to the main Variscan deformational event, belonging within the tectonic context of the Moroccan Variscan orogenic belt. Geochemically, the Azegour intrusion is metaluminous to peraluminous and exhibits a calc-alkaline affinity with a ferruginous composition. The massif shows an extremely differentiated character (SiO2 = 77.53–78.14 per cent), K2O and high total alkali contents, FeOt/(FeOt + MgO) and Ga/Al ratios, which have typical characteristics of an A-type granite. In addition, the granite contains high concentrations of LREE (LaN/SmN= 7.9–13.67) relative to HREE (LaN/YbN= 4.81–11.61) and a well-defined Eu negative anomaly (Eu/Eu* = 0.44–0.75). The granitic samples exhibit a strong enrichment of the most incompatible elements (RbN/YbN = 69.84–159.98) and a strong depletion of Ba, Sr, Eu, Nb, P and Ti. These characteristics are similar to those of A1-type granites. The absence of mineralogy typical of an S-type granite, combined with its weakly peraluminous character [A/CNK (molar Al2O3/CaO+Na2O+K2O) = 1,013–1,045], suggest that there is little or no significant involvement of supracrustal sources in the petrogenesis of the intrusion studied. Despite the strongly differentiated character of Azegour granitic rocks samples, their multi-element patterns shows many similarities to those of I-type granitoids, which has led to postulate that the parental liquids of A1-type were derived from partial melting of mafic magmas. The representative samples studied show less depleted εNd(t = 270 Ma)values of –0.94 to –4.85 and lower positive to slightly negative εSr(t = 270 Ma) values of –1.45 to 9.32. The isotopic data suggest that the Azegour granite was emplaced 270 myr ago, apparently generated by partial melting of a mafic/intermediate magma source in the lower crust as a result of the underplating of the asthenosphere mantle-derived Oceanic Island Basalt-like magmas. Alternatively, their isotopic signatures also can be attributed to the interaction and/or hybridisation of basaltic liquids derived from the mantle with these lower crust materials. The generated parental magma probably occurred at deep structural levels and involved fractional crystallisation processes by the separation of a mineralogical association composed of plagioclase + potassium feldspar ± biotite ± amphibole ± sphene ± apatite. The whole-rock Rb-Sr age of 268 ± 9 Ma, whole-rock geochemistry and Sr-Nd isotopic compositions of εNd(t = 270 Ma) and εSr(t = 270 Ma), combined with fieldwork data, suggest that the Azegour granite was emplaced.

Anion Exchange Membrane with Pendulous Piperidinium on Twisted All-Carbon Backbone for Fuel Cell.

As a central component for anion exchange membrane fuel cells (AEMFCs), the anion exchange membrane is now facing the challenge of further improving its conductivity and alkali stability. Herein, a twisted all-carbon backbone is designed by introducing stereo-contorted units with piperidinium groups dangled at the twisted sites. The rigid and twisted backbone improves the conduction of hydroxide and brings down the squeezing effect of the backbone on piperidine rings. Accordingly, an anion exchange membrane prepared through this method exhibits adapted OH- conductivity, low swelling ratio and excellent alkali stability, even in high alkali concentrations. Further, a fuel cell assembled with a such-prepared membrane can reach a power density of 904.2 mW/cm2 and be capable of continuous operation for over 50 h. These results demonstrate that the designed membrane has good potential for applications in AEMFCs.

Aging behaviour assessment of cellulosic fibres in alkaline media: A green technology approach in construction materials

With the increasing demand for buildings, the utilisation of green materials represents a novel approach toward achieving sustainable development goals. Cellulose-based materials, such as jute, exemplify eco-friendly substances for civil engineering applications. The present study aims at studying the aging behavior of jute fibers in an alkaline environment. For this purpose, three alkali environments (NaOH, KOH, Ca(OH)2) with three different concentrations were selected. Samples were treated at three different periods (7 d, 14 d, and 28 d) to assess the impact of treatment on the fiber properties. This study introduces a pioneering concept of the alkali treatment of jute-based fibres to evaluate tensile strength and weight loss, marking the first of its kind. This approach incorporates various characterisation techniques, including Differential Scanning Calorimetry (DSC), Thermo-Gravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM) to assess the treatment process. In our experimental procedures, we evaluated key parameters such as the type of alkali, alkali concentration, and curing time for their influence on tensile strength. Subsequently, we applied Response Surface Methodology (RSM) in conjunction with bagging techniques to develop mathematical models based on the acquired data. Results demonstrated varied tensile strengths based on alkali type, concentration, and treatment duration. Fibres treated with 15 g/L concentration of NaOH exhibited an increase in tensile strength from 7 days (79.66 MPa) to 28 days (225.05 MPa). The highest tensile strength of jute fibres treated with KOH was observed with 15 g/L concentration at 14 days (237.58 MPa). For Ca(OH)₂ treatments, the highest tensile strength was observed with 30 g/L concentration at 14 days (111.28 MPa). It was also observed that prolonged exposure to very high alkali concentrations could adversely affect the tensile strength, as observed in the case of 30 g/L concentration of NaOH at 28 days (84.73 MPa). Among the various alkali materials tested, NaOH and KOH demonstrated greater effectiveness compared to Ca(OH)2. According to RSM analysis, the time of sample curing was found to be the most significant factor in tensile strength, with a P-value of 0.009. On average, the tensile strength changes by 54 %, 52 %, and 35 % for NaOH, KOH, and Ca(OH)₂, respectively, when the curing time shifts from 7 days to 28 days.

The alkali–silica reaction of seawater-mixed mortar

The application of seawater concrete is receiving increasing attention due to the advantage of using seawater in alleviating water scarcity. One concern with seawater concrete applications is the potential for alkali–silica reaction (ASR) due to the elevated alkali concentration. In this paper, the ASR risk induced by mixed seawater in cement mortar incorporating non-reactive or reactive aggregates (RAs) was studied through short-term and long-term experiments. Experimental results indicate that seawater only increased ASR in the presence of RAs due to the high alkali concentration. Replacing cement with 70% ground granulated blast-furnace slag (GGBS) prevented expansion, although very few ASR products may be observed. SEM results indicated that seawater decreases the (Na + K)/Si ratio and increases the Ca/Si ratio of ASR products slightly. Compared with cement mortar, C–S–H in GGBS blended cement mortar has a higher (Na + K)/Si ratio, which indicates its higher alkali binding capacity.

Novel flame-retardant aluminum-based hydrolyzed material

Al is the most abundant metallic element in the Earth's crust, and its theoretical capacity of hydrolyzing hydrogen production is high (1244mL/g). How to destroy Al2O3 films and control reaction rate are the key to control hydrolysis. Herein, we designed an activity-controlled and flame-retardant Al based hydrolytic composite by analyzing the mechanism of Al2O3 film breaking. The results show that the addition of anion is an important factor to improve film breaking. Among them, the system with CaH2 and NaF showed the best modification effect in deionized water (vmax = 265 mL/(s·g), Cmax = 1075 mL/g), and the mean hydrogen conversion was 97.79%. It is generally believed that the synergistic pitting effect of H− and F− is the heart of the continuation of the hydrolysis reaction. However, by studying the mechanism of pitting, we noticed that Ca(OH)2, Al(OH)3 and F− can provide an in-situ high concentration alkali field, which plays the crucial role for hydrolysis of Al. Meanwhile, the ignition test of the composite material shows that it is flame retardant. Then, the proposed novel hydrolysis film breaking mechanism of in-situ high concentration alkali field can also provide an idea for the further development of hydrolyzed hydrogen production materials.