Search Results (367)

The dewatering of cyanobacteria-laden sludge remains a challenge. Extracellular polymeric substances (EPS) mainly consist of polysaccharides and proteins, which form a stable gel network with water through hydrogen bonding and other interactions. To address this bottleneck, a low-voltage (5 V) electrochlorination system was constructed, employing a Ti/IrO₂/RuO₂ electrode as the anode, iron as the cathode, and calcium chloride dihydrate (CaCl₂·2H₂O) as the electrolyte. The results showed that the active chlorine generated during electrolysis degraded the highly water-retentive loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS), converting them into low-viscosity, easily removable soluble EPS (S-EPS). Moreover, the total contents of polysaccharides and proteins in EPS decreased. Three-dimensional excitation-emission matrix fluorescence spectroscopy revealed that in the EPS of the algal sludge, the relative proportion of humic-like substances increased, while that of protein-like products decreased. At a CaCl₂·2H₂O dosage of 1 g/L, the dewatering performance of the algal sludge was significantly improved: the capillary suction time (CST) of the algal suspension decreased from 10.30 ± 0.1 s to 4.1 ± 0.05 s, the proportion of bound water decreased from 43.5% to 9.8%, and the cake solids content increased to 9.48%. The residual water quality of this process was also favorable, with total phosphorus (TP) and total nitrogen (TN) concentrations stabilized at 0.166 ± 0.040 mg/L and 9.0 ± 1.1 mg/L, respectively. Therefore, this study provides an efficient, low-energy electrochemical pretreatment strategy to overcome the dewatering bottleneck in cyanobacteria-laden sludge, thereby reducing the treatment load and cost of downstream mechanical dewatering. Full article

Calcium sulfate (CaSO₄; CS) is added to dental calcium silicate cement (CSC) to regulate the hydration speed of the tricalcium aluminate phase. However, most commercial CSC products do not specify the CS hydration type, and reports on the role of CS are scarce. Therefore, the effects of the hydration type of the CS compound incorporated into CSC were evaluated. The synthesized CSC clinker was confirmed using XRD, TEM, and FT-IR. Subsequently, a ZrO₂ (5 μm) radiopacifier was added at 20 wt%, and different types of CS compounds (either anhydrite, hemihydrate, or dihydrate) were added at 5 wt%. The hydration type of CS significantly affected the setting time and flowability (p < 0.05). The CS hemihydrate addition group showed the highest flowability, according to the ISO and LVDT methods (p < 0.05). The CS dihydrate addition group showed the lowest flowability, fastest setting time, and highest washout resistance and compressive strength. The 5 wt% addition of CaSO₄ anhydrite significantly increased the setting time (p < 0.05). The CS-containing CSC groups showed cell viability levels similar to those of the CSC control group. These results provide valuable information for optimizing the selection of CS hydration type for manufacturing CSC tailored to specific clinical situations. Full article

Chalcopyrite and molybdenite exhibit similar surface wettability and high floatability, which has long hindered their efficient and selective separation in mineral processing. In this work, the novel chalcopyrite depressant 2-mercapto-5-benzoimidazole sulfonate dihydrate (2MBI5SA) was investigated for its effect on the flotation behavior of chalcopyrite and molybdenite. Compared with the conventional depressant sodium sulfide (Na₂S), 2MBI5SA exhibited stronger selective depression toward chalcopyrite; under conditions yielding a Mo recovery of 81.46% and a Mo grade of 4.46%, the Cu recovery decreased to 13.03%. To clarify the origin of this selectivity, interfacial properties were systematically characterized using adsorption measurements, contact angle measurements, zeta potential measurements, FTIR, XPS, and SEM-EDS, and the adsorption mechanism was further elucidated using SCC-DFTB calculations. The results demonstrate that 2MBI5SA chemisorbs onto the chalcopyrite surface via bidentate coordination, forming a stable adsorption layer that effectively suppresses chalcopyrite flotation. Moreover, structure–function relationship analysis confirmed that introducing hydrophilic and ionizable functional groups into the collector framework can convert a collector into a selective depressant, thereby providing new insights into the rational design of selective organic depressants with potential environmental advantages over conventional highly toxic inorganic depressants. Full article

Purpose: This study aimed to determine whether positive admission urine culture is associated with stone burden, renal involvement, pathogen distribution, and measured urinary biochemical profiles in men and women with calcium oxalate stones. Methods: We retrospectively analyzed adults who underwent percutaneous nephrolithotomy or ureterorenoscopy for upper urinary tract stones between 2016 and 2020. Calcium oxalate stones were defined as stones containing ≥50% calcium oxalate monohydrate and/or dihydrate by Fourier transform infrared spectroscopy. Patients were compared by sex and then stratified by admission urine culture status within each sex. Results: Among 1257 patients, 878 were men and 379 were women. Women had a higher culture-positive rate than men (59.6% vs. 28.2%, p < 0.001), despite lower 24-h urinary calcium, uric acid, sodium, potassium, phosphorus, and chloride. In men, culture positivity was associated with recurrent stones, renal stone location, larger maximum stone diameter, and lower eGFR, but not with measured 24-h urinary parameters. In women, culture positivity was associated with renal stone location, larger maximum stone diameter, lower eGFR, and modestly lower urinary calcium. Escherichia coli predominated among culture-positive women, whereas men showed a broader pathogen distribution. Conclusions: Positive admission urine culture was associated with greater stone burden and renal involvement in calcium oxalate stone disease, without a uniformly higher measured urinary biochemical profile. Culture status may provide clinically relevant phenotypic information alongside measured urinary biochemical assessment, although interpretation is limited by the absence of key CaOx-related urinary parameters such as oxalate, citrate, and supersaturation indices. Full article

The present work investigates the combined effect of precursor source and solvent on the structural, morphological, and optical properties of ZnO thin films prepared by the spin-coating technique. Three precursor sources (zinc acetate dihydrate, zinc chloride, and zinc nitrate hexahydrate) and four solvents (ethanol, 2-methoxyethanol, 2-propanol, and 1-methoxy-2-propanol) were systematically explored. X-ray diffraction analysis confirms that all films crystallize in the hexagonal wurtzite structure, with a pronounced (002) preferential orientation for zinc acetate-derived and most of the zinc chloride-derived films. Scanning electron microscopy reveals that both precursor and solvent strongly influence surface morphology. Zinc acetate yields smoother and more compact films, zinc chloride promotes larger hexagonal grains, and zinc nitrate leads to relatively porous structures. Among the solvents, 2-methoxyethanol produces the most uniform and dense films regardless of the precursor. Optical measurements show that transmittance is highly dependent on synthesis conditions, reaching up to 90% in the visible range for zinc acetate-based films, particularly with 2-methoxyethanol. The optical band gap varies between 3.20 and 3.37 eV, reflecting differences in crystallinity and defect density. Overall, these results highlight the key role of precursor–solvent interactions in tailoring ZnO thin film properties for optoelectronic applications. Full article

This study investigates the mechanochemical synthesis of silver molybdate (Ag₂MoO₄). Three silver precursors (AgCl, AgNO₃, Ag₂SO₄) in combination with sodium molybdate dihydrate as the molybdenum precursor were used. Three corresponding sodium salts, which are also formed as byproducts, were employed as process control agents (PCAs) to investigate the possibility of obtaining fine-grained silver molybdate. Milling was performed in a planetary mill at 600 and 100 rpm, and for 2 h, 15 min, and 5 min. X-ray diffraction analysis (XRD) revealed that AgCl is completely unreactive in this type of reaction, whereas AgNO₃ and Ag₂SO₄ form crystalline Ag₂MoO₄. Additional sample characterization included Fourier transform infrared spectroscopy (FTIR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and simultaneous differential thermal and thermogravimetric analysis (DTA-TGA). The results indicate that the silver molybdate formation reaction is favorable and rapid. Even under the mildest conditions, including the presence of PCA, micron-sized silver molybdate particles were obtained. A greater rotation rate and longer milling time resulted in a decrease in particle size, but also an increase in sodium content. However, unlike the few existing reports on the mechanochemical synthesis of Ag₂MoO₄, which, despite harsh milling conditions, did not yield a phase-pure product, our approach produced well-crystallized and pure silver molybdate even under the mildest synthesis conditions. Full article

Basic calcium phosphate (BCP) and calcium pyrophosphate dihydrate (CPPD) crystals drive the degenerative and inflammatory pathways that lead to crystal arthropathy. Although recent classification criteria and imaging recommendations have improved standardisation for CPPD disease, it remains underdiagnosed in practice. In contrast, BCP disease lacks validated classification criteria and standardised diagnostic descriptors, limiting translational research and clinical recognition. Accurate diagnoses are limited by varied reference standards, operator-dependent techniques, and the absence of validated bedside tools. As the population ages and the burden of crystal disease rises, there will be increased demand for reliable diagnostic tools in clinical practice. This review summarises current and emerging diagnostic tools for identifying BCP and CPPD, with emphasis on bridging the diagnostic gap from research to routine care. Polarised light microscopy remains a highly specific test for the diagnosis of CPPD but is limited by inter-observer variability and access to polarising light microscopes. Imaging tools such as ultrasound, conventional radiography, computed tomography (CT) and dual-energy CT can identify CPPD, although performance varies by anatomical site, disease stage and technical parameters. Ultrasound is a useful bedside tool for identifying BCP disease, whereas CT and DECT also have diagnostic utility but lack validation for routine use. Emerging technologies such as computational polarised light microscopy and Raman spectroscopy are promising techniques, but require further research to evidence their use in clinical practice. Development of clear diagnostic reference standards, classification criteria for BCP disease, and evidence-based multimodal diagnostic pathways are essential to bridge the gap between research and routine clinical diagnosis. Full article

Analytical studies of archeological materials often face challenges, such as the merging of heterogeneous, multidimensional datasets from complementary analytical techniques, and incorporating site- and user-defined parameters. In this study, a data fusion methodology is applied that combines micro-X-ray fluorescence (micro-XRF) spectrometry and handheld Raman spectroscopy to investigate degradation layers and identify pollution sources on two monuments in an urban background: the Temple of Hephaestus and the Byzantine Church of Ag. Theodoroi, in Athens, Greece. A total of 12 samples were collected for laboratory measurements and 32 in situ measurements were conducted. Statistical and unsupervised machine learning tools, namely correlation analysis, Principal Component Analysis and k-means clustering, were applied to the merged datasets. Additionally, selected elements’ ratios were calculated to infer their sources. The black crusts were identified as heterogeneous mixtures of calcium sulfate dihydrate, calcite, and particulate pollutants, with their composition reflecting their preservation state. Vehicular emission indicators were dominant in both sites, while secondary domestic heating pollutant indicators were more prevalent at Ag. Theodoroi. Orientation had a minor role compared to pollutant sources in differentiating degradation patterns. The integrated comparison of the different outputs highlighted the interpretive potential of the approach, particularly in improving the readability of the multivariate structure and supporting the development of targeted conservation strategies for monuments in polluted urban contexts. Full article

Soil hydrophysical properties play a key role in processes such as water movement through soil and also affect the amount of water available to plants, thus influencing the sustainability of water management in lowland agricultural landscapes. This study investigated whether the application of calcium sulfate dihydrate (gypsum, CaSO₄·2H₂O) can improve selected hydrophysical properties of a heavy clay agricultural soil from the Eastern Slovak Lowland (Slovakia). In a controlled laboratory experiment, topsoil samples (0–15 cm depth) were treated with four rates of gypsum application (0.5, 1, 2.5 and 10 g core⁻¹; ≈2–40 t ha⁻¹ equivalents) and then repacked in 100 cm³ cores. Gypsum caused a marked apparent shift from “clay” to “silt” in the particle-size analysis, consistent with flocculation and incomplete dispersion rather than a real textural change. Increasing the gypsum dose also led to a gradual increase in saturated hydraulic conductivity (from 0.68 ± 0.21 to 2.00 ± 0.66 cm d⁻¹). Water retention near saturation changed little, but water content at the wilting point decreased at higher doses, increasing plant-available water (maximum ~59% at 2.5 g core⁻¹). Under laboratory conditions, gypsum improved the hydraulic function of the soil, and, at selected doses, increased water availability related to drought, supporting its potential as a structural amendment for enhancing the sustainable management of heavy clay soils. Full article

Ultra-high-performance concrete (UHPC) matrix faces critical challenges of high carbon footprint and significant autogenous shrinkage. Supersulfated cement (SSC), a potentially lower-carbon binder comprising ground granulated blast-furnace slag and gypsum, offers a promising alternative. This study systematically investigated the effect of gypsum type—phosphogypsum (PG), dihydrate gypsum (DH), and anhydrite (AH)—on the early hydration and shrinkage behavior of UHPC matrix incorporating 30% SSC as Portland cement replacement. A multi-technique approach, including mechanical testing, isothermal calorimetry, XRD, TG-DSC, SEM, LF-NMR, and autogenous shrinkage measurements, was employed. Results demonstrate that gypsum type critically governs sulfate dissolution kinetics, thereby dictating phase assemblage and microstructural evolution. DH provides relatively rapid sulfate dissolution, promoting earlier AFt and gel formation, which is associated with the highest early strengths and a marked reduction in autogenous shrinkage. AH shows a slower but sustained sulfate supply, resulting in comparable 28-day strength with moderate shrinkage reduction. PG yielded the lowest autogenous shrinkage (374 μm/m at 7 d), but it also suffered from severe early-age retardation due to soluble phosphate impurities, as evidenced by the delayed hydration peak and lowest 3 d strength. This behavior is mainly related to strong early-age retardation, delayed hydration, delayed setting, and a prolonged low-stiffness state. These findings suggest that appropriate gypsum selection in SSC enables tailored early-age performance and improved volume stability in the UHPC matrix, offering guidance for utilizing industrial by-products such as phosphogypsum in sustainable high-performance concrete design. Full article

This work presents a comprehensive investigation of the thermal decomposition of nickel oxalate dihydrate as a precursor for the synthesis of porous NiO, with particular emphasis on microstructural formation and evolution. The transformations occurring at successive stages of the reaction were examined using SEM, TEM, N₂ adsorption, TG–DSC–MS, and in situ powder XRD, enabling the mechanisms of pore formation to be elucidated. The decomposition results in the formation of a porous pseudomorph composed of NiO nanoparticles with an average size of approximately 4 nm. This is the first time that the resulting microstructure has been shown to exhibit hierarchical, bimodal porous architecture. During dehydration, macropores are generated as a result of crystal fragmentation into blocks several hundred nanometers in size. Subsequent oxalate decomposition leads to the formation of mesoporous aggregates composed of nanometer-sized particles. The factors governing the parameters of the porous microstructure are analyzed. The resulting NiO, with its hierarchical pore structure, shows significant potential for applications in heterogeneous catalysis, gas sensing, and as electrodes for supercapacitors, lithium-ion batteries, and photoelectrochemical devices, as its macropores facilitate mass transport by reducing diffusion resistance while its mesopores provide a large accessible surface area for adsorption and catalytic reactions. Full article

The presence of impurities directly affects the properties of α-hemihydrate gypsum (α-HH) prepared from phosphogypsum (PG) as a raw material. However, the effect of soluble fluorine impurities on the properties of α-HH by autoclaving remains insufficiently understood. This study investigated the influence of sodium fluoride on the morphology, hydration, and hardening properties of α-HH, using XRD, XPS, SEM, MIP, and tests of setting time, evolution of hydration temperature increase, and strength. The results showed that during the preparation of α-HH, some F⁻ reacted with Ca²⁺ to form CaF₂, which adhered to the surface of the α-HH crystal, hindering the growth and development of the crystal and resulting in small crystals with rough surfaces. When α-HH hydrated, sodium fluoride caused the early, rapid nucleation of dihydrate gypsum (DH) crystals, accelerating the crystallization process of DH. The introduction of sodium fluoride inhibited the early hydration of α-HH and promoted its later hydration. The increase in sodium fluoride content caused the initial setting time of α-HH hydration to first increase and then decrease, while the final setting time continued to decrease. In the absence of sodium fluoride, the average pore diameter of the hardened paste was approximately 617.99 nm. When the NaF content was 0.2%, the DH crystals were prismatic and densely packed, which resulted in a decrease in the average pore diameter to 449.35 nm. When the NaF content was 0.6%, the DH crystals exhibited a plate-like morphology and were loosely interlocked, leading to an increase in the average pore diameter to 1169.58 nm. Based on these results, the sodium fluoride content in PG should be controlled below 0.2%. Full article

The green synthesis of nanomaterials has emerged as a sustainable and environmentally friendly approach, gaining significant attention in recent years for its potential in a wide range of multifunctional applications. Among these materials, zinc oxide nanoparticles (ZnO NPs) stand out due to their remarkable versatility and effectiveness in fields such as industry (food, chemistry, and cosmetics), nanomedicine, cancer therapy, drug delivery, optoelectronics, sensors, and environmental remediation. This study focuses on bioinspired strategies for the facile synthesis of ZnO NPs, employing natural polysaccharide gums as mediators. Acting as both reducing and stabilizing agents, natural gums not only facilitate the eco-friendly production of ZnO NPs but also enhance their stability and functionality. Natural gum-mediated green synthesis typically yields stable, spherical ZnO particles, often in the 10–100 nm range. Typical reaction conditions are the use of zinc acetate dihydrate or zinc nitrate (0.01–0.5 M) as precursors, with low gum concentrations of 0.1–1.0% (w/v) in distilled water, alkaline conditions (pH from 8 to 12), often achieved by adding NaOH, which aids in the reduction and capping by the gum, at reaction temperature between 60 °C and 80 °C, under continuous stirring. The dried precipitate is often calcined at 400 °C to 600 °C to remove organic residues and enhance crystallinity. This approach underscores the potential of biopolymer-assisted synthesis in advancing green nanotechnology for sustainable and practical applications. Utilizing environmentally benign materials such as natural gums for the synthesis of ZnO NPs offers significant advantages, including enhanced eco-friendliness and biocompatibility, making them suitable for a wide range of applications without the involvement of toxic reagents. This review provides an in-depth analysis of the synthesis and characterization techniques employed in the eco-friendly production of ZnO NPs using different natural gums from biological sources and its environmental applications (e.g., pollutant removal and increased agriculture sustainability). Full article

The present study aimed to determine the optional alginate and CaCl₂ concentrations in the encapsulation formulation to produce alginate beads of Stachys byzantina, thereby offering a potential alternative method for its propagation. Stem explants were derived from in vitro cultures grown on Murashige and Skoog (MS) medium supplemented with 10 μM benzyladenine (BA) and were evaluated for their germination and regeneration potential after a short-term storage period (1, 2, and 3 months). Three different sodium alginate concentrations (2%, 2.5% and 3%) were used for the preparation of alginate beads. For the hardening of the alginate beads, calcium chloride dihydrate (CaCl₂·2H₂O) at four concentrations (50, 100, 200 and 400 mM) was employed for 35 min. The combination of 100 mM calcium chloride with sodium alginate at concentrations of 2.0%, 2.5%, or 3.0% resulted in high germination rates, ranging from 73.33% to 76.60%. However, germination rates declined with increased storage duration. Among the formulations, 2.5% sodium alginate consistently supported higher germination over time, with rates of 53.33% and 36.66% observed after 2 and 3 months of storage, respectively. The decline in germination rate was followed by an increase in bead hardness over time. The optimal encapsulation matrix composition was identified as 2.5% sodium alginate with 100 mM CaCl₂, which yielded the highest regeneration rate of explants after 1, 2 and 3 months of cold storage at 4 °C. Full article

The rapid increase in end-of-life lithium-ion batteries demands sustainable recycling routes for lithium recovery. This work presents a novel integrated hydrometallurgical–electrodialysis process designed specifically for recovering lithium from off-specification NMC cathode materials while enabling full reagent recyclability. Selective leaching with oxalic acid was optimised by setting the water-to-oxalic acid dihydrate ratio (H₂O/OA·2H₂O) to 7.3:1 w/w, achieving 81% lithium extraction at room temperature within 2 h while limiting the co-dissolution of Ni, Co and Mn to 0.2%, 1.6% and 1.7% by weight, respectively. The resulting leachate was processed in a four-chamber electrodialysis cell equipped with two Nafion 117 cation-exchange membranes and one Neosepta AMX-fmg anion-exchange membrane operating at −1.6 V versus Ag/AgCl, enabling 96% lithium recovery and 98% oxalic acid recovery. The regenerated oxalic acid stream (41.8 g L⁻¹) was fully restored to its initial concentration and reused in successive cycles without performance loss. Subsequent precipitation of lithium with Na₂CO₃ yielded 99.3%-pure Li₂CO₃. This combined leaching–electrodialysis–precipitation presents a high selectivity, low-waste, circular recovery system, offering a scientifically original approach that integrates reagent regeneration with high-purity lithium production. Full article