Search Results (70)

Titanium alloys are widely employed in structural and electrochemical applications owing to their excellent mechanical properties and inherent corrosion resistance. However, their stability in harsh acidic environments, such as those encountered in energy storage systems, remains a critical issue. In this study, composite ceramic coatings were synthesized on a Ti6Al4V alloy using plasma electrolytic oxidation (PEO) in silicate-, phosphate-, and sulfate-based electrolytes, with and without the addition of α-alumina nanoparticles. The resulting coatings were comprehensively characterized to assess their surface morphology, chemical and phase compositions, and corrosion performance. Thus, the corrosion current density decreased from 9.7 × 10⁴ for bare Ti6Al4V to 143 nA/cm² for the coating fabricated in phosphate electrolyte with alumina nanoparticles, while the corrosion potential shifted anodically from –0.68 to +0.49 V vs. silver chloride electrode in 5 M H₂SO₄. Among the tested electrolytes, coatings produced in the phosphate-based electrolyte with Al₂O₃ showed the highest polarization resistance (113 kΩ·cm²), outperforming those fabricated in silicate- (71.6 kΩ·cm²) and sulfate-based (89.0 kΩ·cm²) systems. The composite coatings exhibited a multiphase structure with reduced surface porosity and the incorporation of crystalline oxide phases. Notably, titania–alumina nanoparticle composites demonstrated significantly enhanced corrosion resistance. These findings confirm that PEO-derived composite coatings provide an effective surface engineering strategy for enhancing the stability of the Ti6Al4V alloy in aggressive acidic environments relevant to advanced electrochemical systems. Full article

Phosphogypsum represents a gypsum-based solid waste originating from phosphoric acid production, which can be exploited for road filling after cement modification. This study delved into the composition design of high-volume phosphogypsum road base materials, aiming to ascertain their feasibility for subgrade filling, and refine the mix ratio. The main content of phosphogypsum was set at three high-proportion intervals of 86%, 88% and 90%, while the total content of inorganic curing agent was fixed at 0.5% of the total material. Within such a total amount, the proportion of bentonite was preserved at 20%, whereas the proportion of waterproofing agent was configured at three gradients of 20%, 25% and 30%, with the remaining part supplemented by powdered sodium silicate. Merged with trace amounts of inorganic curing agents, particularly the waterproofing agent component, the composite cementitious system comprising cement and ground granulated blast-furnace slag (GGBS) was leveraged to augment the key road performance and water stability of high-volume phosphogypsum-based materials. Material strengths were observed to be distinguishable under an array of phosphogypsum contents, which could be explained by the varying proportions of cement, GGBS and waterproofing agent. The test samples and microscopic products were dissected via XRD and SEM, demonstrating that the hydration products of the materials were predominantly C-S-H gel and ettringite crystals. Full article

The formation of acidic goaf water in abandoned coal mines poses significant environmental threats, especially in karst regions where the risk of groundwater contamination is heightened. This study investigates the geochemical processes responsible for the generation of acidic water through batch and column leaching experiments using coal mine surrounding rocks (CMSR) from Yangquan, China. The coal-bearing strata, primarily composed of sandstone, mudstone, shale, and limestone, contain high concentrations of pyrite (up to 12.26 wt%), which oxidizes to produce sulfuric acid, leading to a drastic reduction in pH (approximately 2.5) and the mobilization of toxic elements. The CMSR samples exhibit elevated levels of arsenic (11.0 mg/kg to 18.1 mg/kg), lead (69.5 mg/kg to 113.5 mg/kg), and cadmium (0.6 mg/kg to 2.6 mg/kg), all of which exceed natural crustal averages and present significant contamination risks. The fluorine content varies widely (106.1 mg/kg to 1885 mg/kg), with the highest concentrations found in sandstone. Sequential extraction analyses indicate that over 80% of fluorine is bound in residual phases, which limits its immediate release but poses long-term leaching hazards. The leaching experiments reveal a three-stage release mechanism: first, the initial oxidation of sulfides rapidly lowers the pH (to between 2.35 and 2.80), dissolving heavy metals and fluorides; second, slower weathering of aluminosilicates and adsorption by iron and aluminum hydroxides reduce the concentrations of dissolved elements; and third, concentrations stabilize as adsorption and slow silicate weathering regulate the long-term release of contaminants. The resulting acidic goaf water contains extremely high levels of metals (with aluminum at 191.4 mg/L and iron at 412.0 mg/L), which severely threaten groundwater, particularly in karst areas where rapid cross-layer contamination can occur. These findings provide crucial insights into the processes that drive the acidity of goaf water and the release of contaminants, which can aid in the development of effective mitigation strategies for abandoned mines. Targeted management is essential to safeguard water resources and ecological health in regions affected by mining activities. Full article

Vitreous carriers of essential nutrients should release elements in response to plant demand, minimizing over-fertilization risks. This study focused on designing and characterizing sulfate-bearing slow-release fertilizers based on four glass series (41SiO₂∙6(10)P₂O₅∙20K₂O–33(29)MgO/CaO/MgO + CaO) with increasing sulfate content. Structural analysis identified a network dominated by ${\mathrm{Q}}_{\mathrm{Si}}^2$ units, with some ${\mathrm{Q}}_{\mathrm{Si}}^3$ species and isolated ${\mathrm{Q}}_{\mathrm{P}}^0$ units. This fragmented structure resulted in high solubility in acidic environments while maintaining water resistance. Such dual behavior is a direct consequence of the delicate balance between depolymerized silicate chains and isolated orthophosphate units, which ensure rapid ion exchange under acidic conditions while preventing uncontrolled leaching in neutral media. Nutrient leaching depended on SO₃ content, affecting matrix rigidity, and on the type of alkaline earth modifier and P₂O₅ content. Dissolution kinetics showed an initial rapid release phase, followed by stabilization governed by silicate hydrolysis. Thermal analysis linked network flexibility to dissolution behavior—CaO promoted an open structure with high SiO₂ release, MgO increased rigidity, while their co-addition reduced ion diffusion and silica dissolution. The thermal behavior of the glasses provided indirect insight into their structural rigidity, revealing how compositional variations influence the mechanical stability of the network. This structural rigidity, inferred from glass transition and crystallization phenomena, was found to correlate with the selective dissolution profiles observed in acidic versus neutral environments. These results reveal complex interactions between composition, structure, and nutrient release, shaping the agricultural potential of these glasses. Full article

Water deficit is a notable environmental stress, which leads to negative impacts on crop growth, resulting in yield decline. In the current experiment, the exogenous application of potassium silicate (KSi) and L-cysteine (Cys) was investigated on the productivity, qualitative, and biochemicals of Cape gooseberry fruits subjected to drought stress condition in a 2-year field experiment (2022 and 2023). Our findings indicated that deficit irrigation reduced yield, the membrane stability index, titratable acidity, and the ascorbic acid content of fruits in comparison to the untreated plants in both years. Nonetheless, MDA, H₂O₂, and antioxidant enzyme activities were meaningfully enhanced as a consequence of water deficit conditions. The application of KSi and Cys alleviated water deficit stress by reducing MDA accumulation and provided significantly greater content of total soluble solids, soluble carbohydrate, proline, total soluble protein, total phenols, and flavonoids. KSi and Cys have a positive influence on H₂O₂ accumulation by boosting the actions of antioxidant enzymes. Furthermore, higher values of Cys induced the production of proline, APX, PPO, and PAL activities, which contributed to decreasing the damaging effects of plant drought stress and led to an enhanced yield rate. Overall, the foliar application of KSi and Cys by improving antioxidant components, antioxidant enzyme activity, and proline accumulation had a positive impact on the productivity and quality of Cape gooseberries cultivated under standard and shortage irrigation levels. Full article

Chitosan and collagen are natural polymers widely used in biomaterials science; however, their inherent low stability and solubility present several challenges to obtain formulations suitable for potential clinical applications. In this study, tannic acid (TA) was employed as a cross-linker to improve the properties of thin films made from chitosan and collagen. In addition, potassium silicate (PS) was added as an inorganic filler, to produce innovative biocomposite films. The impact of TA and PS on physicochemical (i.e., material homogeneity, surface free energy, degradation, and stability roughness of surface), antioxidant, hemocompatibility, as well as cellular responses was evaluated. The results demonstrated that the incorporation of TA significantly enhanced the physicochemical properties of the chitosan/collagen-based films. The addition of 5% PS resulted in an increase in surface free energy and a decrease in roughness parameters. Furthermore, both surface free energy and cellular responses improved with the increased TA concentration in the biocomposite firms. Meanwhile, the hemolysis rate remained below 5%, indicating the potential suitability of these materials for medical applications, such as coatings or scaffolds for bone or skin wound healing. Full article

Phosphogypsum, a byproduct of phosphate fertilizer production, accumulates in large quantities annually, posing significant environmental challenges due to harmful components such as fluorine, heavy metals, and acidic salts. To mitigate these issues, phosphogypsum is often combined with cement and single modifiers such as sodium silicate, hydrated lime, and defluorinating agents for use in pavement applications. However, concerns about the durability of unmodified or singly modified high-content phosphogypsum have hindered its widespread adoption. To address this issue, this study explored the use of sodium silicate, hydrated lime, and defluorinating agents as composite modifiers to enhance the durability of cement-stabilized phosphogypsum. The mechanisms of modification by individual and composite additives were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Durability was evaluated through three-point bending fatigue, freeze–thaw, and drying shrinkage tests on both unmodified and modified cement-stabilized phosphogypsum. The results demonstrated that the composite modification of sodium silicate, hydrated lime, and defluorinating agents significantly improved the material’s density, strength, and stability by enhancing hydration products and stabilizing fluoride ions. The modified material exhibited superior fatigue and freeze–thaw resistance, with reduced mass loss and slower strength decline compared to unmodified phosphogypsum. Additionally, the modified material showed improved drying shrinkage performance due to enhanced hydration. However, caution is recommended when using these materials in regions with high moisture content and significant temperature fluctuations. Full article

Maps of (baseline) δ¹³C and δ¹⁵N values of primary producers or consumers near the base of food webs provide crucial information for interpreting patterns in the isotopic composition of consumers that occupy higher trophic levels. In marine systems, understanding how oceanographic variables influence these values enables the creation of dynamic isoscapes across time and space, providing insights into how ecosystems function. The San Jorge Gulf (SJG) in the southwest Atlantic Ocean (45° S–47° S) is an area of particular importance, as it is located on one of the most productive continental shelves in the world, supporting large fisheries and marine mammal and seabird populations. We reconstructed spatial variation in zooplankton δ¹³C and δ¹⁵N values across SJG and investigated their relationship with physical and chemical oceanographic conditions. During cruises in the austral spring of 2016 and 2017, we collected medium-sized copepods whose isotopic composition integrate short-term (days to weeks) variation in oceanographic conditions recorded by phytoplankton at the base of the food web. We also collected data on water column depth, surface and bottom temperatures, water column stability, and macronutrient (nitrate, phosphate, and silicic acid) concentrations. The results revealed significant variation in both δ¹³C and δ¹⁵N values of up to 7-8‰ over a relatively small spatial scale (200–300 km). Copepod δ¹³C values were lower at the center of the SJG, showing an inverse correlation with water column stability, surface nitrate concentration, and water column depth. δ¹⁵N values showed a strong and negative relationship with surface nitrate concentration and water column stability, increasing from south to north in the SJG. δ¹⁵N values also showed a positive relationship with surface silicic acid concentration. These spatial patterns in nutrient dynamics and copepod carbon and nitrogen isotope values are interpreted in the context of the dominant northward current and temporal development of the frontal systems in the SJG. Full article

This article presents the results of a thermodynamic analysis of the oxidation soda conversion reactions of minerals in ilmenite concentrates in the temperature range of 373–2273 K. The thermodynamic parameters of pseudorutile, pseudobrukite, and the new minerals, zhikinite and spessartine, were calculated for the first time. It has been established that the most important criterion relating to the stability of titanium minerals and related elements, as well as the reaction properties of the structural oxides of metals and silicon, is their degree of oxidation. Oxides of silicon (IV) and manganese have the best reactivity in solid-phase oxidizing alkaline environments (VI). Modeling this process scientifically substantiates the mechanism involved in the destruction of minerals in ilmenite concentrates in the low-temperature region in the presence of atmospheric oxygen and sodium oxide of soda ash, which are decomposed through the absorption of heat and the evaporation of moisture during the dehydration of hydrated minerals of iron and manganese and the dehydration of the soda–ilmenite batch. Tests conducted during pilot metallurgical production at the Institute of Metallurgy and Enrichment (PMP of JSC) confirmed the feasibility of processing high-chromium and siliceous rutile leucoxene ilmenite concentrates, which are unsuitable for traditional pyro- and hydro-metallurgical enrichment methods, through single-stage oxidation soda roasting, followed by the leaching of easily soluble sodium salts of iron and associated impurities with water and a dilute hydrochloric acid solution. The proposed energy-saving method ensures the production of high-purity (>98%) synthetic rutile while eliminating the formation of strong deposits on the lining of roasting units. Full article

Background/Objectives: The aim of this work was to prepare and characterize gastroretentive floating combination tablets (GRCTs) containing 500 mg of amoxicillin trihydrate (AMX) and 125 mg of levofloxacin (LVX) that provide sustained drug release and stability at gastric pH levels for the eradication of resistant Helicobacter pylori. Method: GRCTs were prepared with low-density excipients and hydrophilic swellable polymers, including hydroxypropyl methylcellulose (HPMC) of various viscosities, polyethylene oxide (PEO), and carboxymethylcellulose (CMC), by the direct compression method. The prepared GRCTs were investigated and optimized in terms of pH stability, tablet hardness, floating lag time and total floating time, drug release rate, gel strength. Results: AMX and LVX in GRCT were stable at the HP eradication target pH above 4.0. The effervescent GRCT composition (AMX/LVX/HPMC [4000 cP]/CMC/microcrystalline cellulose/citric acid/sodium bicarbonate/calcium silicate/silicon dioxide/magnesium stearate = 500/125/50/50/125/40/60/30/10/10, w/w) yielded acceptable hardness (>6 kp), reduced floating lag time (<5 s), a long floating duration (>12 h), and sustained release rates of AMX and LVX (>90% until 12 h). This optimized GRCT had a gel strength of 107.33 ± 10.69 g and pH > 4.0, which maintained the tablets’ shape and AMX stability for 12 h. Conclusions: Collectively, the formulated effervescent GRCTs combining AMX and LVX represented a promising candidate dosage form for eradicating resistant H. pylori. Full article

Increasing the biological effectiveness of probiotic preparations requires the development of new stable forms in the gastrointestinal tract. Live bacteria immobilized on a sorbent belong to the latest, fourth generation of probiotics, which ensures a prolonged effect. This study is devoted to developing a new method of preparing active lactobacilli on a natural mineral carrier, a tuff containing zeolite of the clinoptilolite group, which is among the most common authigenic silicate minerals that occur in sedimentary rocks and is known as a safe ion-exchange and adsorbing detoxicant. Among the characterized lactobacilli, strains of L. plantarum, L. acidophilus, and L. crispatus possessed a high level of acid formation and stability in gastrointestinal fluids. The protective effect of the clinoptilolite-containing tuff was registered when the samples were incubated in gastric juice. The optimal technological conditions for immobilization and lyophilization were determined, and the preservation of the viability and probiotic properties of bacteria was confirmed during 8 months of storage. The release of bacteria from the carrier occurred gradually over 12 h. The data obtained show how promising the new preparation is, combining the ability to detoxify harmful intestinal metabolites and the prolonged release of probiotics. Full article

The preservation of cultural heritage, particularly historical stone structures, represents a very challenging matter due to several environmental and anthropogenic factors. Vicenza stone, a calcareous rock known for its historical significance and widespread use in architectural masterpieces, requires significant attention for conservation. In fact, as the demand for sustainable and effective preservation methods intensifies, the exploration of innovative consolidation strategies becomes essential. To this end, inorganic consolidants, based on alkaline silicate formulations and nano-silica, were explored for their promising performance in enhancing the surface properties and chemical stability of Vicenza stone. In particular, the durability of treated and untreated Vicenza stone samples was evaluated by means of accelerated weathering tests such as freeze–thaw cycles, salt crystallization and simulation of acid rain. The experimental results revealed that Vicenza stone is very resistant to the effects of freeze–thaw cycles and acid rain; both the accelerated weathering tests did not show significant differences between treated and untreated VS samples. A different behavior was detected for the test for resistance to salt crystallization, whose findings led us to deduce that, for this kind of degradation, it is possible to observe a more beneficial effect of the consolidation treatments on the stone durability. Full article

With the application of CO₂ fracturing, CO₂ huff and puff, CO₂ flooding, and other stimulation technologies in shale reservoirs, a large amount of CO₂ remained in the formation, which also lead to the serious corrosion problem of CO₂ in shale reservoirs. In order to solve the harm caused by CO₂ corrosion, it is necessary to curb CO₂ corrosion from the cementing cement ring to ensure the long-term stable exploitation of shale oil. Therefore, a new latex was created using liquid polybutadiene, styrene, 2-acrylamide-2-methylpropanesulfonic acid, and maleic anhydride to increase the cement ring’s resistance to CO₂ corrosion. The latex’s structure and characteristics were then confirmed using infrared, particle size analyzer, thermogravimetric analysis, and transmission electron microscopy. The major size distribution of latex is between 160 and 220 nm, with a solid content of 32.2% and an apparent viscosity of 36.8 mPa·s. And it had good physical properties and stability. Latex can effectively improve the properties of cement slurry and cement composite. When the amount of latex was 8%, the fluidity index of cement slurry was 0.76, the consistency index was 0.5363, the free liquid content was only 0.1%, and the water loss was reduced to 108 mL. At the same time, latex has a certain retarding ability. With 8% latex, the cement slurry has a specific retarding ability, is 0.76 and 0.5363, has a free liquid content of just 0.1%, and reduces water loss to 108 mL. Moreover, latex had certain retarding properties. The compressive strength and flexural strength of the latex cement composite were increased by 13.47% and 33.64% compared with the blank cement composite. A long-term CO₂ corrosion experiment also showed that latex significantly increased the cement composite’s resilience to corrosion, lowering the blank cement composite’s growth rate of permeability from 46.88% to 19.41% and its compressive strength drop rate from 27.39% to 11.74%. Through the use of XRD and SEM, the latex’s anti-corrosion mechanism, hydration products, and microstructure were examined. In addition to forming a continuous network structure with the hydrated calcium silicate and other gels, the latex can form a latex film to attach and fill the hydration products. This slows down the rate of CO₂ corrosion of the hydration products, enhancing the cement composite’s resistance to corrosion. CO₂-resistant toughened latex can effectively solve the CO₂ corrosion problem of the cementing cement ring in shale reservoirs. Full article

To investigate the influence of deashing on fusion characteristics, a combined method of water and acid washing with different sequences (water washing followed by acid washing, and acid washing followed by water washing) was used to treat the biochar of bamboo shoot shells (BBSSs). The results show that deashing decreased the K content of the biochar from 50.3% to 1.08% but increased the Si content from 33.48% to 89.15%. The formation of silicates and aluminosilicates from alkali metal oxides with silicon was an inevitable result of ash phase transformation at the high temperatures used to improve the fusion temperature (>1450 °C). The thermochemical behavior of ash mainly occurs at 1000 °C. The deashing treatment significantly reduced the reaction intensity during the high-temperature process. This significantly increased the thermal stability of the ash. The adjustment of the washing sequence had a slight impact on the chemical compositions, but the differences in ash micromorphology were obvious. Deashing treatments with different washing sequences can significantly improve ash fusion properties effectively and reduce the risk of scaling, slagging, and corrosion. This study provides a new and reasonable strategy for the deashing of biochar to commercially utilize bamboo shoot shell resources. Full article

A method for the determination of trace levels of silicon from biological materials by inductively coupled plasma mass spectrometry (ICP-MS) has been developed. The volatility of water-soluble silicon species, hexafluorosilicic acid (H₂SiF₆), and sodium metasilicate (Na₂SiO₃) was investigated by evaporating respective solutions (50 µg/mL silicon) in nitric acid (HNO₃), nitric acid + hydrochloric acid (HNO₃ + HCl), and nitric acid + hydrochloric acid + hydrofluoric acid (HNO₃ + HCl + HF) at 120 °C on a hot-block to near dryness. The loss of silicon from H₂SiF₆ solutions was substantial (>99%) regardless of the digestion medium. Losses were also substantial (>98%) for metasilicate solutions heated in HNO₃ + HCl + HF, while no significant loss occurred in HNO₃ or HNO₃ + HCl. These results show that H₂SiF₆ species were highly volatile and potential losses could confound accuracy at trace level determinations by ICP-MS if digestates prepared in HF are heated to eliminate HF. Among the various matrices comprising major elements, sodium appeared to be effective in reducing silicon loss from H₂SiF₆ solutions. Excess sodium chloride (NaCl) matrix provided better stability, improving silicon recoveries by up to about 80% in evaporated HF digestates of soil and mine waste samples, but losses could not be fully prevented. To safely remove excess acids and circumvent the adverse effects of excess HF (e.g., risk of high Si background signals), a two-step digestion scheme was adopted for the preparation of biological samples containing trace silicon levels. A closed-vessel digestion was performed either in 4 mL of concentrated HNO₃ and 1 mL of concentrated HCl or 4 mL of concentrated HNO₃, 1 mL of concentrated HCl and 1 mL of concentrated HClO₄ on a hot plate at 140 °C. Digestates were then evaporated to incipient dryness at 120 °C to remove the acids. A second closed-vessel digestion was carried out to dissolve silicates in 0.5 mL of concentrated HNO₃ and 0.5 mL of concentrated HF at 130 °C. After digestion, digestates were diluted to 10 mL. The solution containing about 5% HNO₃ and 5% HF was directly analyzed by ICP-MS equipped with an HF-inert sample introduction system. The limit of detection was about 110 µg/L for ²⁸Si when using the Kinetic Energy Discrimination (KED) mode. The method was used to determine silicon in various plant and tissue certified reference materials. Data were acquired for ²⁸Si using KED and standard (STD) modes, and ⁷⁴Ge and ¹⁰³Rh as internal standard elements. There was not any significant difference between the accuracy and precision of the results obtained with ⁷⁴Ge and ¹⁰³Rh within the same measurement mode. Precision, calculated as relative standard deviation for four replicate analyses, varied from 5.3 (tomato leaves) to 21% (peach leaves) for plant and from 2.2 (oyster tissue) to 33% (bovine liver) for tissue SRM/CRMs. Poor precision was attributed to material heterogeneity and the large particle size distribution. An analysis of lung tissue samples from those with occupational exposure to silica dust revealed that tissues possessed substantial levels of water-soluble silicates, but the most silicon was present in the particulate matter fraction. Full article