Search Results (550)

Fly ash (FA), a major by-product of coal combustion, has long been regarded as a challenging industrial solid waste. Its inherent abundance of alkaline-earth oxides positioned it as a promising candidate for CO₂ sequestration through mineral carbonation. This study systematically investigated the effects of key operational parameters, including time, stirring rate, ultrasonic treatment, and solid-to-liquid ratio, on the leaching efficiency of calcium ions and subsequent CO₂ fixation. Ultrasonic treatment, a solid-to-liquid ratio of 1:7, a stirring speed of 600 rpm, and 7% monoethanolamine (MEA) collectively enhanced the calcium leaching efficiency (χ_e) to 16.7%, thereby supplying a substantial reservoir of calcium ions for CO₂ fixation. Additionally, the CO₂ injection into fly ash slurry and the slurry spraying into CO₂ gas were investigated to optimize reactor configurations. The latter method demonstrated superior performance, attaining a CO₂ fixation efficiency of 7.23%. This corresponds to a carbonation conversion efficiency (ηc) of approximately 44.5%, indicating that nearly half of the leached calcium ions were successfully converted into stable carbonates. Advanced characterization techniques (SEM-EDS, XRD, FTIR) confirmed the formation of stable carbonates and highlighted the role of additives in enhancing reactivity. The environmental benefit of this approach is addressing fly ash wastes and transforming fly ash into a CO₂ fixation material. These findings provided critical insights for calcium leaching and CO₂ fixation of fly ash. Full article

The increasing demand for lithium-ion batteries (LIBs) has intensified the need for efficient lithium (Li) recovery from secondary sources. This study focuses on anti-solvent crystallization for the recovery of high-purity lithium hydroxide monohydrate (LiOH·H₂O) from a Li-rich leachate, derived from the flue dust of a pilot-scale pyrometallurgical process for LIB material recycling. To optimize product yield and purity, a series of experiments were performed, focusing on the influence of parameters such as solvent type, organic-to-aqueous (O/A) volumetric ratio, crystallization time, stirring rate, and anti-solvent addition rate. Acetone was identified as the most effective anti-solvent, producing rectangular cuboid crystals with approximately 90% Li recovery and around 95% purity, under optimized conditions (O/A = 4, 3 h, 150 rpm, and solvent flow rate of 5 mL/min). The flow rate influenced crystal morphology and impurity entrapment, with 5 mL/min favoring nucleation-dominated crystallization regime, producing ~20 μm of well-dispersed crystals with reduced impurity incorporation. SEM-EDS, surface washing, and gradual dissolution of obtained LiOH·H₂O crystals revealed that the impurities sodium (Na), potassium (K), aluminum (Al), calcium (Ca) and chromium (Cr) were crystallized as conglomerates. It was found that Na, K, Al, and Ca primarily crystallized as highly soluble conglomerates, while Cr was crystallized as a lowly soluble conglomerate impurity. In contrast Zn was distributed throughout the crystal bulk, suggesting either the entrapment of soluble zincate species within the growing crystals or the formation of mixed Li-Zn phase. Therefore, to achieve battery-grade purity, further purification measures are necessary. Full article

Hydrophobic nanofiber membranes derived from the biopolymer alginate were fabricated by electrospinning followed by metal ion crosslinking, and their potential as oil-water separation membranes was primarily investigated. Sodium alginate (SA) was co-electrospun with polyethylene glycol and subsequently crosslinked using calcium chloride and group IV metal ions (zirconium or titanium). Metal ion crosslinking changed the surface wettability of the nanofiber membranes, as confirmed by water contact angle measurements. Both zirconium- and titanium-crosslinked SA nanofiber membranes exhibited effective gravity-driven oil–water separation with complete water blocking. Although hydrophobic modification reduced direct water affinity, the resulting membranes retained residual adsorption capability toward methylene blue, indicating the presence of accessible internal polar sites. The adsorption behavior varied depending on the crosslinking ion. In addition, titanium-crosslinked membranes showed an auxiliary UV-assisted dye removal contribution under irradiation, arising from photoactive Ti species. These findings demonstrate that metal ion crosslinking provides a practical route for tuning the functional properties of alginate nanofiber membranes, with oil-water separation as the primary application and dye adsorption/photocatalysis as secondary functionalities. Full article

Potato starch offers the unique potential of mineral enrichment through the presence of phosphorylated amylopectin chains. This property was utilised in a straightforward dual modification of native potato starch by combining mineral enrichment with dry heat treatments (DHT). DHT itself (110–130 °C, 3–6% moisture, 2 h) affords potato starches with lower viscosity and gelatinisation temperatures and higher contents of digestible starch. Prior ion exchange with Na⁺, K⁺, Mg²⁺, and Ca²⁺ enhanced the versatility of dry heat treatments. This study demonstrates the fine-tuning of functional properties (rheology) of these novel, dual-modified starches. Of special interest are magnesium and calcium due to their nutritional value and their valency, allowing ionic cross-linking. The present study contributes to the understanding of starch–ion interactions in DHT, clearly highlighting the role of specific ion effects, as per the Hofmeister series (K⁺ > Na⁺ and Ca²⁺ > Mg²⁺), in addition to the reversible ionic cross-linking effect of divalent cations. This knowledge is of use for potential substitution of chemically modified starches in food products, serving relevant trends and needs of today’s food industry for clean-label starches. Full article

The aim of the study was to investigate the synergistic effect of conditioned medium (CM) and two types of calcium phosphate biocements on the osteogenic properties of a composite material through rat bone marrow-derived mesenchymal stem cells (MSCs). Briefly, MSCs were cultured for 7 and 17 days in extracts derived from the two biocement types. These extracts were supplemented with 5% (v/v) of concentrated CM. The CM was obtained from rat bone marrow MSC cultures after a 48 h conditioning period. The results showed that the addition of CM had a significant positive impact on the osteoblastic differentiation of MSCs, particularly in the extracts from the tetracalcium phosphate/monetite/calcium sulfate hemihydrate biocement (designated as CAS cement) compared to the other tested cement extract (designated C cement). After 17 days of culturing, a notable increase in cell viability and alkaline phosphatase (ALP) activity, as well as the upregulation of osteoblastic-related gene expression, was found. This enhancement in osteogenic activity was likely driven by the growth factors and bioactive molecules present in the CM. The study concluded that supplementing the biocement extracts with only 5% of 10X concentrated CM is sufficient to significantly influence and improve the in vitro characteristics, cell behavior, gene expression, and synthesis of cell products. It was demonstrated that, especially in the CAS supplemented with CM (CAS + CM) extract system, the improvement in osteogenic properties was due to the synergistic effect between the higher concentration of calcium ions in extracts released from the calcium sulfate hemihydrate-containing cement and the bioactive molecules supplied by the CM. Full article

Magnetite (Fe₃O₄) nanoparticles are biocompatible, non-toxic, and easily functionalized. Coating them with mesoporous silica (mSiO₂) offers high surface area, pore volume, and tunable surface chemistry for drug loading. In this study, Fe₃O₄ magnetic nanoparticles were synthesized and coated with mSiO₂ shells enriched with calcium ions (Ca²⁺), aiming to enhance bioactivity for bone regeneration and tissue engineering. Different synthesis routes were tested to optimize shell formation Their characterization confirmed the presence of a crystalline Fe₃O₄ core with partial conversion to maghemite (Fe₂O₃) post-coating. The silica shell was mostly amorphous and the optimized samples exhibited mesoporous structure (type IVb). Calcium incorporation slightly altered the magnetic properties without significantly affecting core crystallinity or particle size (11.68–13.56 nm). VSM analysis displayed symmetric hysteresis loops and decreased saturation magnetization after coating and Ca²⁺ addition. TEM showed spherical morphology with some agglomeration. MTT assays confirmed overall non-toxicity, except for mild cytotoxicity at high concentrations in the Ca²⁺-enriched sample synthesized by a modified Stöber method. Their capacity to induce human periodontal ligament cell osteogenic differentiation, further supports the potential of Fe₃O₄/mSiO₂/Ca²⁺ core–shell nanoparticles as promising candidates for bone-related biomedical applications due to their favorable magnetic, structural, and biological properties. Full article

The overuse of chemical fertilizers can result in elevated concentrations of nitrogen (N) and phosphorus (P) in soil, potentially impacting rock weathering processes and carbon flux in karst regions. This study analyzed the impacts of chicken dung fertilizer and compound fertilizer on the weathering of carbonate rocks within the water-soil-rock system, yielding the following results: (1) The peak concentrations of various ions in the compound fertilizer system (Ca²⁺: 36.8 mg/L, Mg²⁺: 4.3 mg/L, N: 284.2 mg/L, P: 920.6 mg/L, HCO₃⁻: 16,170.3 mg/L) were generally superior to those in the chicken manure fertilizer system (15.4 mg/L, 1.9 mg/L, 306.9 mg/L, 27.9 mg/L, and 4576.5 mg/L, respectively), with a difference of approximately fourfold between the two systems; (2) Nitric acid generated by nitrification in fertilizers and phosphoric acid in compound fertilizers modify the chemical equilibrium of rock weathering, enhance dissolution, and influence the dynamics of HCO₃⁻; (3) Nitrogen and phosphorus in compound fertilizers are predominantly eliminated through ion exchange and adsorption. Calcium-phosphate precipitates are generated on the limestone surface within the 20 cm soil column, exhibiting a greater degree of weathering compared to the chicken manure fertilizer treatment; (4) analyses utilizing XRD, FT-IR, XPS, SEM, and additional approaches verified that substantial weathering and surface precipitation transpired on limestone throughout the 20 cm compound fertilizer column. Full article

We investigated the roles and regulation of contractile and sodium ion transporter proteins in the pathogenesis of diarrhea in the acute ulcerative colitis. Acute ulcerative colitis was induced in male Sprague-Dawley rats using dextran sulfate sodium (DSS) in drinking water for seven days. The effects of nobiletin, a citrus flavonoid, were also examined. Increased myeloperoxidase activity, colon mass, and inflammatory cell infiltration were associated with damage to goblet cells and the epithelial cell lining indicating the development of acute ulcerative colitis. SERCA-2 calcium pump expression remained unchanged, whereas the phospholamban (PLN) regulatory peptide was reduced and its phosphorylated form (PLN-P) increased, suggesting a post-translational increase in SERCA-2 activity in the inflamed colon. Higher levels of IP3 were associated with a decrease in the Gαq protein levels without altering phospholipase C expression, suggesting that IP3 regulation is independent of Gαq protein signaling. In addition, the expression of sodium/hydrogen exchanger isoforms NHE-1, NHE-3 and carbonic anhydrase-1 and sodium pump activity were decreased in the inflamed colon. Nobiletin treatment of colitis selectively reversed the inflammatory and oxidative stress markers, including superoxide dismutase and catalase without restoring the expression of ion transporters. This study highlights alterations in the expression of ion transporters and their regulatory proteins in acute ulcerative colitis. These changes in the ion transporters are likely to reduce NaCl absorption and alter contractility, thereby contributing to the pathogenesis of diarrhea in the present model of acute ulcerative colitis. Nobiletin selectively ameliorates acute colitis in this model. Full article

This study systematically investigates the engineering characteristics of lead-contaminated red clay stabilized by calcium lignosulfonate and ordinary Portland cement composite binders. A series of experiments were conducted to evaluate the effects of lignosulfonate contents (0%, 0.25%, 0.5%, 1%, 2%), cement content (4%, 6%, 8%, 10%), and lead ion concentration (0%, 0.1%, 1%) on the mechanical properties, permeability characteristics, and leaching behavior. Key findings include the following. (1) Based on the highest mean UCS values observed in this study, the best-performing formulations were 1% lignosulfonate + 4% cement for uncontaminated soil, 0.5% lignosulfonate + 4% cement for 0.1% lead, and 0.25% lignosulfonate + 10% cement for 1% lead. (2) The permeability coefficient initially decreases and then increases with lignosulfonate addition, with maximum reductions of 65.9% and 44.4% for 0.1% and 1% lead contamination under their respective best-performing formulations under these specific test conditions. (3) The leaching concentration of 0.1% lead-contaminated soil met the national standard (<5 mg/L). Critically, however, the 1% lead-contaminated soil failed the TCLP test, with a leaching concentration of 37.3 mg/L, vastly exceeding the regulatory limit. This constitutes a treatment failure for environmental safety purposes, rendering the concurrent mechanical strength improvement irrelevant. (4) Microstructural and X-Ray Diffraction analyses (SEM and XRD) suggest that lignosulfonate improves soil structure by promoting the formation of C-S-H gel and ettringite (3CaO·Al₂O₃·3CaSO₄·32H₂O), whereas high lead concentrations inhibit ettringite formation. This research provides a theoretical foundation for the multi-criteria evaluation and application of lignosulfonate–cement composites in lead-contaminated soil remediation. Full article

Orange peel is suitable for reuse due to the quantity and variety of bioactive compounds it contains, such as pectins, sugars and hesperidin. This study designed a scheme for reusing orange peel extract (OPE) using membrane technologies. Initially, a 100 kDa ceramic membrane was used to separate the pectins and hesperidine from acids and sugars and obtain a clarified product. In the subsequent stage, two ultrafiltration membranes of 25 and 5 kDa were tested, improving the results in terms of product transmittance and obtaining permeates whose physical–chemical parameters are compatible with those established by the European Fruit Juice Association. These membranes did not achieve complete separation of monosaccharide sugars from disaccharides. Finally, a 200 Da nanofiltration membrane was used, which completely reduced the sucrose and pectin content, concentrating glucose and fructose by 40%, values higher than those obtained with the GR90PP membrane. In addition, calcium and magnesium ions were completely rejected. Color changes in the permeate and concentrate streams could be appreciated due to the high concentration produced when working in batches. The nanofiltration (NF) process obtained lower yields (approximately 30%) compared to ultrafiltration (approximately 85%). Full article

Coal gasification slag (CGS), an industrial solid waste produced during high-temperature (1200–1600 °C) coal gasification, was utilized as the primary raw material, combined with minor additions of coal gangue and calcium oxide, to synthesize ceramsite filter via high-temperature sintering (900–1160 °C) for phosphorus-containing wastewater treatment. The resulting ceramsite was evaluated for compressive strength, apparent porosity, water absorption, mineral phase composition, hydrolysis properties, and phosphorus removal performance. Experimental results revealed that increasing sintering temperature and calcium oxide content shifted the dominant crystalline phases from anorthite and hematite to gehlenite, anorthite, wollastonite, and esseneite, promoting the formation of porous structures. This transition increased apparent porosity while reducing compressive strength. Under optimal conditions (1130 °C, 20 wt.% CaO, 1 h sintering), the ceramsite (CM-20-1130) exhibited an apparent porosity of 43.12%, compressive strength of 3.88 MPa, apparent density of 1.084 g/cm³, and water absorption of 33.20%. The high porosity and abundant gehlenite and wollastonite phases endowed CM-20-1130 with enhanced hydrolysis capacity. Static phosphorus removal experiments demonstrated a maximum phosphorus removal capacity of 2.77 mg/g, driven by the release of calcium and hydroxide ions from gehlenite and wollastonite, which form calcium-phosphate precipitates on the ceramsite surface, enabling efficient phosphorus removal from simulated wastewater. Full article

Addressing the significant pressure for carbon emission reduction in the cement industry, the development of novel cement materials capable of achieving “in situ carbon sequestration” has become an important research focus. This study introduces nesquehonite (MgCO₃·3H₂O, NQ) as a functional admixture into the Portland cement system, systematically investigating its effects on the cement hydration process, the evolution of hydration products, and its carbon sequestration efficiency. Through designed penetration resistance tests and hydration tests with a high water-to-solid ratio, this research utilized X-ray diffraction analysis to determine the phase composition and content of hydration products at different ages. This was combined with scanning electron microscopy to observe microstructural evolution and Nano Measure software 1.2.5 for ettringite crystal size measurement, analyzing the impact of NQ on the early hydration process of P.I cement. The results indicate that the incorporation of NQ significantly alters the early hydration of P.I cement. The Mg²⁺ and CO₃²⁻ ions released upon its dissolution interact with Ca²⁺ and OH⁻ in the pore solution, effectively promoting the early precipitation of carbon sequestration products such as calcium carbonate and minor magnesium-containing carbonates. The addition of 10% NQ hindered the crystallization of Ca(OH)₂ before 6 h but promoted its formation after 24 h. Mechanical property tests revealed that a sample with an optimal 3% NQ dosage not only increased the paste’s penetration resistance but also enhanced the compressive strength of the 1-day hardened sample by 8.37% compared to the plain sample, without a decrease and even a slight increase at 28 days. This enhancement is closely related to the microstructural strengthening effect induced by the carbonation products. This study confirms the feasibility of using NQ to steer the cement hydration pathway towards a low-carbon direction, revealing its dual functionality in regulating hydration and sequestering carbon within cement-based materials. The findings provide a new theoretical basis and technical pathway for developing high-performance, low-carbon cement. Full article

Calcium ions, primarily introduced through flotation reagents and mineral dissolution, progressively accumulate a considerable amount due to the process of water recycling, significantly impacting the flotation behavior of minerals. In this paper, the adsorption of calcium ions on a calcite surface was initially studied by surface characteristic analysis, and then further evaluated for its influence on the separation of scheelite from calcite using single mineral flotation and atomic force microscopy (AFM) measurements. The results indicate that calcium ions significantly reduce the hydrophobicity of calcite surface induced by sodium oleate (NaOL) adsorption, while enhancing the adsorption of sodium silicate (SS). In addition, SS forms a strong chemical adsorption on calcite, rendering the surface negatively charged. However, the surface charge diminishes under the combined influence of calcium and silicate ions. AFM measurements further reveal that the adhesion forces between scheelite and calcite are weakened by silicate adsorption. Nevertheless, these forces are markedly restored in the presence of calcium ions, thereby considerably reducing the selectivity of SS and hindering effective particle separation. These findings align with the results of mixed binary flotation, confirming that calcium ions indeed interfere with the separation of scheelite from calcite. Full article

Plant-derived nanocellulose particles, such as cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs), are becoming increasingly popular for a wide range of applications. In particular, when they are employed as rheology modifiers and/or fillers, a choice between CNFs and CNCs is often not obvious. Here, we present the results of a comparative study on the rheological properties of suspensions and gels of carboxymethylated CNFs and CNCs with the same surface chemistry, surface density of charged groups, and thickness. We demonstrate that, at the same weight concentration, CNF suspensions have much higher viscosity and storage modulus, which is due to their longer length providing many entanglements. However, when comparing at the same nanoparticle concentration relative to C*, the situation is reversed: viscosity and storage modulus of CNCs appear to be much higher. This may be due in particular to the higher rigidity and intrinsic strength of highly crystalline CNCs. The gel points for CNF and CNC suspensions (without crosslinker) were compared for the first time. It was found that in the case of CNFs, the gel point occurs at a 3.5-fold lower concentration compared to that of CNCs. Hydrogels were also obtained by crosslinking negatively charged nanocellulose particles of both types by divalent calcium cations. For the first time, the thermodynamic parameters of the crosslinking of carboxymethylated CNFs by calcium ions were determined. Isothermal titration calorimetry data revealed that, for both CNFs and CNCs, crosslinking is endothermic and driven by increasing entropy, which is most likely due to the release of water molecules surrounding the interacting nanoparticles and Ca²⁺ ions. The addition of CaCl₂ to suspensions of nanocellulose particles leads to an increase in the storage modulus; the increase being much more significant for CNCs. Physically crosslinked hydrogels of both CNFs and CNCs can be reversibly destroyed by increasing the shear rate and then quickly recover up to 85% of their original viscosity when the shear rate decreases. The recovery time for CFC networks is only 6 s, which is much shorter than that of CNC networks. This property is promising for various applications, where nanocellulose suspensions are subjected to high shear forces (e.g., mixing, stirring, extrusion, injection, coating) and then need to regain their original properties when at rest. Full article

This study explored the chloride binding characteristics and mechanisms of sulphoaluminate cement (SAC) by isolating its principal mineral component, anhydrous calcium sulphoaluminate (${\mathrm{C}}_4{\mathrm{A}}_3\stackrel{\mathrm{-}}{\mathrm{S}}$), as the research object. Chloride ingress was investigated under external penetration and internal incorporation conditions, with gypsum dosage varied at molar ratios of 1:0, 1:1, and 1:2 relative to ${ \mathrm{C}}_4{\mathrm{A}}_3\stackrel{\mathrm{-}}{\mathrm{S}}$. Through chloride binding experiments and hydration product analysis performed by XRD and TG, the following findings were obtained: under external chloride exposure, the binding capacity increased with rising solution concentration and immersion time. External chloride binding was attributed to SO₄²⁻/Cl⁻ ion exchange in AFm to generate Friedel’s salt and was complemented by physical adsorption of chloride in AH₃ gel. Under internal chloride incorporation, binding capacity increased progressively with curing age. Internal chloride binding involved the direct participation of Cl⁻ in hydration reactions to form Friedel’s salt in addition to the chemical reaction of AFm and the physical adsorption of AH₃. Gypsum dosage critically regulates the AFm/AFt ratio, which in turn governs chloride binding efficiency under both external and internal chloride scenarios (e.g., after immersion in 1 mol/L NaCl solution, the bound chloride content for ${\mathrm{C}}_4{\mathrm{A}}_3\stackrel{\mathrm{-}}{\mathrm{S}}$/gypsum ratios of 1:0, 1:1, and 1:2 was 50.94, 27.28, and 13.47 mg/g, respectively). Full article