Initial Content Research Articles

Influence of Zr Addition on the Microstructure and Hydrogenation Kinetics of Ti50-xV25Cr25Zrx (x = 0, 5, 7, and 9) Alloys.

Due to the poor activation performance and kinetics of Ti50V25Cr25 alloys, the element Zr was added to improve the phase structure of the alloy and achieve a high-performance hydrogen storage alloy. The Ti50-xV25Cr25Zrx (x = 0, 5, 7, and 9) system alloys were prepared by arc melting. The alloys were analyzed using an X-ray diffractometer (XRD), scanning electron microscope (SEM), and differential scanning calorimeter (DSC). The hydrogen storage capabilities of the alloys were also obtained by the Sievert volumetric method. The results indicated that the alloy with Zr added had a combination of the C15 Laves phase and the BCC phase, whereas the Zr-free alloy had a BCC single phase. The partial replacement of Zr with Ti resulted in an increase in the lattice parameters of the main phase. The hydrogen storage kinetic performance and activation of the alloys both significantly improved with an increasing Zr concentration. The time to reach 90% of the maximum hydrogen storage capacity decreased to 2946 s, 230 s, and 120 s, respectively, with the increases in Zr concentration. The initial hydrogen absorption content of the alloys increased and then decreased after the addition of the element Zr. The second phase expanded with an increasing Zr concentration, which in turn decreased the abundance of the BCC main phase. The Ti43V25Cr25Zr7 alloy showed good cycle stability and hydrogen-desorption performance, and it could absorb 90% of the maximum hydrogen storage capacity in around 230 s. The maximum hydrogen-absorption capacity of the alloy was 2.7 wt%. The diffusion activation energy of hydrogen desorption dropped from 102.67 kJ/mol to 92.62 kJ/mol.

Influence of Quercus alba oak geographical origin on the colour characteristics and phenolic composition of Tempranillo wines

AbstractThis research analyzes the influence of Quercus alba barrels from four different forests of the USA [Missouri (M), Ohio (O), Kentucky (K) and Pennsylvania (P)] on the colour parameters, phenolic composition, and visual and gustatory sensory characteristics of 12 Tempranillo red wines from different wineries after 12 months of aging. Oak origin significantly affected the colour parameters of the wines, except for tonality, and the content of anthocyanins, stilbenes and ellagitannins but had little effect on the rest of the phenolic compounds. Wines aged in K and O barrels showed the highest content of ellagitannins. Wines aged in P barrels had the lowest content of phenolic compounds and colour intensity (CI), while K and O barrels produced the highest levels of ellagitannins. K wines were the best value in the global perception of the taste analysis. The influence of the barrel origin on the phenolic composition of the wines was also evaluated according to their initial phenolic composition. Wines with the highest initial CI and phenol content also showed the highest content of ellagitannins after barrel aging. When aging wines with high CI and phenol content, M barrels provided the wines with the highest content of ellagitannins.

Investigation of wine fermentation of three-leaf cayratia (Cayratia trifolia L.) using Saccharomyces cerevisiae 2.1

Background Cayratia trifolia has been extensively studied for its bioactive components and medicinal properties. This study was carried out to evaluate the fermentation ability of Saccharomyces cerevisiae 2.1 yeast to determine suitable fermentation conditions. Methods The initial sugar content for three-leaf cayratia fermentation and fermentation efficiency were calculated. The temperature for three-leaf cayratia fermentation, incubation time, and preliminary 1 liter of three-leaf cayratia wine fermentation were determined. All treatments showed that the total sugar content decreased after 9 days of fermentation compared to the initial level. Temperature during fermentation has a direct effect on yeast activity. Temperature increases the growth of yeast and speed of enzyme activity. The fermentation time changes depending on temperature, initial soluble solid contents, and yeast strains, leading to changes in the ethanol content after the end of fermentation. Results The results showed that the S. cerevisiae 2.1 was able to ferment at room temperature with an initial pH of 4.5, 24 °Brix, and a yeast density of 107 cells/mL. The appropriate fermentation conditions determined for S. cerevisiae 2.1 were 24 °Brix and incubation at room temperature (28-33°C) with a fermentation time of 11 days. Conclusion In 1-L scale fermentation, three-leaf cayratia wine had 9.46% (v/v) and the fermentation efficiency was 90.34%. The wine produced had a unique color, flavor, and aroma that met the sensory evaluation of the Vietnamese national standard TCVN-3217:79.

Infiltration and Leaching Characteristics of Soils with Different Salinity under Fertilizer Irrigation

Salt and nutrient transport and transformations during water infiltration directly influence saline soil improvement and the efficient use of water and fertilizer resources. The effects of soil initial salinity (18.3 g/kg, 25.5 g/kg, 42.2 g/kg, 79.94 g/kg, and 165 g/kg, respectively, labeled S1 to S5) on the infiltration and leaching characteristics of water, salt, and nitrogen were analyzed via a one-dimensional vertical fertilizer infiltration experiment. Meanwhile, the estimation models of cumulative infiltration and wetting front, including the effect of soil initial salinity, were established. The results showed that, with the increase in soil initial salinity, the cumulative infiltration within the same time decreased, and the migration time of wet front to 45 cm was longer. The time required for S5 to reach the preset cumulative infiltration was more than six times that of S1, and, for the wet front migration to 45 cm, the time requirement for S5 was about four times that of S1. In the established Kostiakov model and wetting front model, the coefficients all decreased with the increase in soil initial salinity, and the test index R2 values both reached 0.999. In the Kostiakov model, coefficient K had a linear relationship with the natural logarithm of initial soil salt content, while index a had a direct linear relationship with initial soil salt content. The cumulative leachate volume decreased with the increase in soil initial salinity, and the corresponding data of S3 and S5 were reduced by 37% and 57.3%, respectively, compared with S1. The electrical conductivity values of S1, S3, and S5 were 15.4, 209.8, and 205.6 ms/cm, respectively, being affected by the initial content in soil, soil moisture transport rate, and exogenous potassium nitrate (KNO3) addition. The NO3−-N concentrations in the leachates of S1, S3, and S5 at the end of leaching were 55.26, 16.17, and 3.2 mg/L, respectively. Based on the results of this study, for soil with high initial salinity, the conventional irrigation amount (2250 m3/ha) of the general soil in the study area could not meet the requirements of leaching salt. These results can provide a reference for the formulation of irrigation and fertilization strategies for soils with different salinity and contribute to the sustainable development of saline soil agriculture and the ecological environment.

Microbial Mechanisms of Removal of Phthalic Acid Esters in Purple Soils Revealed Using Metagenomic Analysis

The removal mechanisms of phthalic acid esters (PAEs) have attracted much attention because of their endocrine-disrupting properties and persistence in environmental media. In order to reveal the removal mechanism of PAEs and involved keystone taxa and functional genes, purple soils were polluted by di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP), respectively, along a gradient of 0, 5, 10, and 20 mg·kg-1 and cultured for 90 days in the dark. The results showed that the degradation dynamics of DBP and DEHP were well-fitted by the first-order kinetic model, and the half-life of DBP and DEHP ranged from 17.0 to 38.2 days. The degradation rate of DBP (5 mg·kg-1) was the fastest, and that of DEHP (20 mg·kg-1) was the slowest. The soil samples of the seventh day and the fifteenth day were analyzed using metagenomic sequencing. NMDS and cluster analysis showed that there was a significant difference between the bacterial community structure of soil samples from the seventh day and the fifteenth day. The relative abundance of Actinobacteria increased from the seventh day to the fifteenth day. The smaller the half-life of DBP or DEHP, the higher the relative abundance of Actinobacteria in the different treatments. In addition, Streptomyces was the dominant genus in all polluted soils. Co-occurrence network analysis elucidated that Pandoraea was a keystone genus of the soil bacterial communities, which could be used to indicate the pollution levels of DBP and DEHP. The results of KEGG annotation demonstrated that Pandoraea was responsible for benzoate degradation, quorum sensing, ABC transporters, and the two-component system and could promote the intercellular communications and the microbial growth and proliferation and maintain the stability of the community structure. Therefore, the degradation rate of DBP and DEHP in purple soils depended on their initial content and their own properties. Actinobacteria played an important role in the PAEs degradation, and Pandoraea played a major part in promoting PAEs degradation and regulating the stability of the structure and function of degrading bacterial communities.

Validation of a Novel Neurologic Assessment Test for Healthcare Staff.

BACKGROUND: To measure the effectiveness of an educational intervention, it is essential to develop high-quality, validated tools to assess a change in knowledge or skills after an intervention. An identified gap within the field of neurology is the lack of a universal test to examine knowledge of neurological assessment. METHODS: This instrument development study was designed to determine whether neuroscience knowledge as demonstrated in a Neurologic Assessment Test (NAT) was normally distributed across healthcare professionals who treat patients with neurologic illness. The variables of time, knowledge, accuracy, and confidence were individually explored and analyzed in SAS. RESULTS: The mean (standard deviation) time spent by 135 participants to complete the NAT was 12.9 (3.2) minutes. The mean knowledge score was 39.5 (18.2), mean accuracy was 46.0 (15.7), and mean confidence was 84.4 (24.4). Despite comparatively small standard deviations, Shapiro-Wilk scores indicate that the time spent, knowledge, accuracy, and confidence are nonnormally distributed ( P < .0001). The Cronbach α was 0.7816 considering all 3 measures (knowledge, accuracy, and confidence); this improved to an α of 0.8943 when only knowledge and accuracy were included in the model. The amount of time spent was positively associated with higher accuracy ( r2 = 0.04, P < .05), higher knowledge was positively associated with higher accuracy ( r2 = 0.6543, P < .0001), and higher knowledge was positively associated with higher confidence ( r2 = 0.4348, P < .0001). CONCLUSION: The scores for knowledge, confidence, and accuracy each had a slightly skewed distribution around a point estimate with a standard deviation smaller than the mean. This suggests initial content validity in the NAT. There is adequate initial construct validity to support using the NAT as an outcome measure for projects that measure change in knowledge. Although improvements can be made, the NAT does have adequate construct and content validity for initial use.

Vitamin D3 Bioaccessibility from Supplements and Foods-Gastric pH Effect Using a Static In Vitro Gastrointestinal Model.

Vitamin D3 deficiency is a global phenomenon, which can be managed with supplementation and food fortification. However, vitamin D3 bioaccessibility may depend on factors such as matrix composition and interactions throughout the gastrointestinal (GI) tract. This research focused on the effect of different matrices on vitamin D3 content during digestion, as well as the effect of pH on its bioaccessibility. The INFOGEST protocol was employed to simulate digestion. Three different types of commercial supplements, two foods naturally rich in vitamin D3, and three fortified foods were investigated. High-Performance Liquid Chromatography was used to determine the initial vitamin D3 content in the supplements and foods, as well as after each digestion stage. The results indicate that the foods exhibited higher bioaccessibility indices compared to the supplements and a higher percentage retention at the end of the gastric phase. The pH study revealed a positive correlation between an increased gastric pH and the corresponding content of vitamin D3. Interestingly, exposing the matrix to a low pH during the gastric phase resulted in an increased intestinal content of D3. Vitamin D3 is more bioaccessible from foods than supplements, and its bioaccessibility is susceptible to changes in gastric pH. Fasting conditions (i.e., gastric pH = 1) enhance the vitamin's bioaccessibility.

Changes in the Soil Organic Carbon of Grasslands in the High Andes of Peru after Their Conversion to Croplands and Their Environmental Controls

The high-Andean grasslands of Peru provide a wide range of goods and services, not only locally, but also regionally and globally. However, land-use change and global warming are threatening these ecosystems, of which soil organic carbon (SOC) is a key element affecting their sustainability. In this study, we have analyzed the variation of SOC stocks to a depth of 20 cm in 16 paired cropland and grassland sites located in the Sullccapallcca stream micro-watershed (elevation &gt; 3600 m.a.s.l., Ayacucho, Peru). We have also analyzed the environmental controls on the SOC stocks and their variation with land-use change. We found that the studied high-Andean grasslands store high SOC contents (247 Tn SOC ha−1), whose spatial variability was partially explained by the slope of the terrain (r2 = 0.26, p &lt; 0.05). Despite the higher NDVI, the conversion of these grasslands into croplands decreased the SOC stock by 39 Tn SOC ha−1 on average, a decrease that was more pronounced when the initial SOC content of the grassland was higher (r2 = 0.60, p &lt; 0.05). This study provides the first evidence of the effects of land-use change on the SOC in the region, although the mechanisms involved still need to be investigated.

Zinc-protoporphyrin formation in nitrite-free Parma Ham and its relationship with intrinsic parameters and red color profile of processed hams

A total of 134 fresh hams, assayed for Ferrochelatase (FeCH) activity and ultimate pH (pH48), were processed in compliance with the procedures established for PDO Parma ham and finally, analyzed for salt, moisture, Zinc Protoporphyrin IX (ZnPP), heme, iron and zinc contents, and proteolysis index (PI). The variation in ZnPP content was related to the intrinsic parameters of fresh and matured hams by a Partial Least Square Regression model. The most favorable factors on the formation of ZnPP were total iron content (representative of the initial hemoprotein content), and FeCH activity, demonstrating the main role played by these raw matter-specific predictors in the long matured dry-cured hams. To a lesser extent, zinc content and pH48 were involved with a positive and negative role, respectively. Salt content and PI of matured hams showed an inhibitory and a favorable influence, respectively, toward the ZnPP formation. Principal Component Analysis showed the associations between the sensory red color profile and the physicochemical traits of matured hams. The red color intensity increased in agreement with the red-violet and red-pink hues scores. The formation of a high amount of ZnPP was associated with the increased perception of the red-violet shade, with a lower lightness (L*) and Hue angle (h°). Moisture increase contributed to the shift in color perception to red-pink, while marked progress in PI strengthened the perception of the red-brown shade. ZnPP and final heme favored the red color of matured hams, although a high concentration of these pigments increased in particular the red-violet perception.

Biodrying of municipal solid waste-correlations between moisture content, organic content, and end of the biodrying process time.

Biodrying refers to the decomposition of organic municipal solid waste (MSW) under aerobic conditions. This process usually lasts 14days and requires large amounts of air to be injected into the waste matrix. The efficiency of the biodrying process depends on several geotechnical parameters, including initial moisture content, initial organic content, bulk density, dry density, solid particle density, and porosity. To examine the potential influence of these parameters on the biodrying process, we analyzed 13 biodried MSW samples. The results revealed a strong positive linear relationship between the initial moisture content and the mass loss percentage. In the first three days of the biodrying process, the waste mass rapidly decreased; afterwards, the daily mass loss occurred at a less rapid, more constant rate. The established average mass removal ratio between the volatile solids and water was 1:6.38 with a standard deviation of 1.06. Dry and solid particle densities were preserved in all 13 experiments; thus, the corresponding void ratio remained unchanged. This finding suggests that the settlement and degradation of MSW that occur during the biodrying process did not significantly influence the airflow rate.

Experimental study on the evolution process of hydrate deposition, blockage and decomposition in reducing pipeline

BackgroundIn the process of deep-water oil and gas extraction, due to the special structure of the reducing pipeline, the flow field of the pipeline changes here, making it easier for hydrates to form and accumulate at reduced-diameter zone and increasing the risk of pipeline blockage. MethodsAiming at the problem of hydrate deposition and blockage in reducing pipeline, an experimental study was carried out through the self-designed and reduced-diameter transparent flow loop to investigate the hydrate deposition and blockage and decomposition evolution of hydrate at reduced-diameter zone under different conditions of flow velocities and initial cyclopentane volume contents. Significant FindingsThe study found that the flow field formed at reduced-diameter zone was the main reason affecting the distribution of hydrate particles, and the flow velocity and the initial hydrate volume fraction were the main controlling factors affecting the blockage in reducing pipeline. The flow velocity of 1.6 m/s was determined as the safe boundary for cyclopentane hydrate in reducing pipeline. Based on the experimental results, the mechanism of cyclopentane hydrate deposition and blockage in reducing pipeline was revealed, and targeted prevention and control methods for hydrate blockage at reduced-diameter zone were proposed. It is of great significance to ensure the safe flow of hydrate in reducing pipeline.

The effect of emulgel preparation on the stability of Kojic acid in the topical anti-hyperpigmentation products.

The emulgel, a novel drug delivery system, merges emulsion and gel, offering advantages like enhanced stability, precise control over drug release kinetics, and increased drug absorption compared to emulsions alone. Kojic acid (KA) demonstrates potent inhibition of the tyrosinase enzyme, a crucial player in the melanin synthesis pathway. The main objective of this experimental study is to formulate KA within an emulgel framework and assess its stability under various environmental conditions. One percent of KA emulgel and 1% simple gel, serving as the control product, were supplemented with varying concentrations of sodium metabisulfite (SMBS) for its antioxidant properties. The formulations were segregated into four groups and subjected to diverse maintenance and stress conditions over a three-month period. Monthly evaluations of physicochemical alterations were conducted, initially employing digital photography, followed by the extraction of KA and subsequent quantification of its concentration through high performance liquid chromatography (HPLC). The best formulations for retaining KA among the prepared ones were the 0.25% SMBS KA emulgel and the 0.1% SMBS KA simple gel, capable of retaining 86% and 76% of the initial KA content under stress conditions, respectively (p < 0.0001). Regarding to this study, ideal storage condition for KA emulgel and simple gel is in the refrigerator temperatures. Moreover, optimal SMBS concentrations for stability enhancement are 0.25% for emulgel and 0.1% for the simple gel. A significant statistical difference was observed between refrigerated emulgel and simple gel in the retention of KA in the presence of optimum concentration of antioxidants (p < 0.0001).

Carbon Farming practices assessment: Modelling spatial changes of Soil Organic Carbon in Flanders, Belgium

Carbon sequestration in soils is a strategy to mitigate climate change and promote sustainable soil management. Since the European Union (EU) stimulates the reduction of greenhouse gases (GHG) from the atmosphere, the necessity to explore innovative approaches to sequester carbon in agricultural landscapes is becoming urgent. Carbon Farming (CF) has emerged as a promising program to mitigate climate change in agriculture but there is still a lack of agreement on which tools can be used to calculate Soil Organic Carbon (SOC) dynamics in this context. Using the RothC model a spatial analysis of SOC in the agricultural parcels of Flanders, Belgium was performed. Two among the various CF practices were simulated: a use of cover crops (CC) and the most common crop rotations adopted in the area, enriched with the use of cover crops. The performances of the model were evaluated and compared to other studies in areas with similar climate and environments. The selected CF practices can mitigate the carbon emissions from agricultural soils up to 60 % of the current projections. The most sensitive variables in the RothC model that affect the final total SOC, and thus determining the model outcome, are the Business As Usual (BAU) carbon inputs and the initial carbon content. For these variables the Pearson Correlation Coefficient with the change in SOC reached values of −0.78 and −0.50 respectively. To achieve net carbon sequestration in the agricultural soils of Flanders, Belgium, more effective solutions need to be evaluated. Furthermore, a larger amount and accessibility of data are required to reach better modelling performances.

Porous and Dense Alginate/Chitosan Composite Films Loaded with Simvastatin for Dressing Applications

Alginate is a biocompatible polysaccharide matrix used for bioactive dressings with inherent healing properties. Most alginate dressings are produced as single-layer dressings. This study explores the potential of bilayer membranes to modulate drug release and enhance antimicrobial properties. We used alginate and chitosan loaded with simvastatin, an anti-inflammatory drug. One membrane comprised dense layers of both alginate and chitosan, while the other featured a dense alginate upper layer and a porous chitosan lower layer. The current study introduces a new approach in which a bilayer membrane is modeled instead of creating a polymeric blend between alginate and chitosan. The upper layer of the membrane contains only alginate loaded with simvastatin, while the bottom layer contains only chitosan. Another innovation is the study of the use of a porous lower layer of chitosan. Therefore, the association of these polymers in a bilayer and porous membrane gives advanced therapeutic dressings (with anti-inflammatory and antimicrobial properties intrinsic to the membrane) that are more efficient in the healing of complex wounds. Comprehensive characterization encompassed physicochemical, thermal, morphological, and mechanical properties. Microbiological tests were conducted using chitosan extract, and cytotoxicity evaluations were performed on fibroblast and keratinocyte cells. The results showed interlayer adhesion due to ionic interactions between alginate and chitosan surfaces. The drying process influenced the morphological and physicochemical features of the membranes. Simvastatin release profiles demonstrated sustained release over an extended period (approximately 60%–70% of the drug after 96 h). Storage assessments revealed that after six months, the membranes maintained around 98% of the initial simvastatin content. The antimicrobial activity test underscored the bacteriostatic efficacy of the chitosan porous layer, making it well-suited for infected wounds. Cell viability tests confirmed the non-cytotoxic nature of the films, highlighting their promising characteristics for treating diverse skin lesion types.

Unveiling the origins of galactic bars: insights from barred and unbarred galaxies

ABSTRACT A significant fraction of local galaxies exhibit stellar bars, non-axisymmetric structures composed of stars, gas, and dust. Identifying key differences between the properties of barred and unbarred galaxies can uncover clues about the conditions for triggering bar formation. We explore the early stages of bar formation in a small sample of disc barred galaxies extracted from the TNG50 cosmological simulation, and compare their properties to those of unbarred galaxies. According to our results, the most important difference between barred and unbarred galaxies is that the former have systematically higher fractions of stellar to dark matter mass in their inner regions, from very early stages and prior to the formation of the bars. They harbour high initial gas content, fostering increased star formation rates and leading to a central mass concentration that grows faster over time compared to unbarred galaxies. Examining the evolution of the halo spin within $10\, \mathrm{ckpc}$ reveals that barred galaxies have higher angular momentum transfer from the disc to the halo. Curiously, both barred and unbarred galaxies share similar initial low values of the halo spin, consistent with those proposed in the literature for bar formation. Furthermore, we evaluate existing stability criteria to capture the complexity of the process, and investigate the effects of mergers, flybys, and environment as possible drivers of bar formation. We find no clear link between mergers and disc instabilities resulting in the formation of bars, even though some of the simulated barred galaxies might have been influenced by these events.

Mechanical behavior of Ni[formula omitted]Ti[formula omitted] shape memory alloys with void defects

Superelasticity of NixTi100−x B2 shape memory alloys (SMAs) with different atomic compositions and void defects are investigated using molecular dynamics simulations. In the first part of this study, the effect of species content on the martensitic transformation is explored, with x ranging from 48% to 52%. All samples displayed similar behavior under compression, where transformation from B2 to B19’ was observed. On the other hand, under tension, both Ni48Ti52 and Ni50Ti50 displayed single-step transformation from B2 to L10, while the Ni-rich sample exhibited a simultaneous double-step transformation from B2 to B19’ to L10. The mechanical performance of the samples with voids under compression was also explored. The void surface was found to act as a barrier, hindering the phase transformation to B19’ structure and its elastic response, ultimately reducing the maximum stress prior to fracture. Statistical methods established connections between various properties and offered mathematical models to correlate the initial setup variables Ni content and void radius, with properties derived from deformation tests. Consequently, this study provides both an atomic description of the deformation behavior of NiTi SMAs and a statistical framework for establishing the relationships between materials properties.

Distribution characteristics and migration pathways of metals during hydrothermal liquefaction of municipal sewage sludge in the presence of various catalysts

A series of hydrothermal liquefaction (HTL) experiments with two different samples of municipal sewage sludge (MSS) were conducted at 350 °C for 30 min residence time in a high pressure batch reactor. The main aim of the study was to explore the distribution and migration pathways of a broad range of metals and metalloids in the HTL products (bio-oil, char and aqueous phase) obtained in the presence of various homogeneous and heterogeneous catalysts (Na2CO3, Li2CO3, K2CO3, Ba(OH)2, Fe2O3, CeO2, NiMo/MoO3, MoS2, Ni/NiO, SnO2, FeS). The elements under study included 16 environmentally significant metals and metalloids (As, B, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se, Sn, Zn and Hg). The study showed that the quantitative migration of the tested metals and metalloids to the particular HTL products, relative to their initial content in the raw sludge, is different for the individual elements. Most metals exhibited a particularly strong affinity to the solid fraction (biochar). In the obtained HTL bio-oils, all tested elements were identified, except of Cd. It was also found that B and As have high affinity to the aqueous phase. A direct effect of catalysts on the contents of some elements in the products was also proved by the study, e.g. increased concentration of Cr in the biochar when Fe2O3 was used as a process catalyst. Due to the wide scope of the tested elements and broad range of catalyst used, the results obtained represent a unique and comprehensive set of environmental data compared to similar HTL studies previously conducted for MSS.

Leaching of catalyst platinum from cured silicone elastomers: A preliminary study for comparing reagents

Addition curing systems involve two-part silicones which require the mixture of a silicone polymer with a catalyst to initiate the cure. Platinum is the most commonly used metal catalyst for addition curing of silicones by hydrosilylation which involves the crosslinking by the addition reaction of silicon hydride species to unsaturated bonds, mainly CC, but also CO or CN double bonds. After crosslinking of the polymers, the platinum catalyst cannot be recovered but remains in the silicone materials throughout the entire product life. In the end, platinum is disposed of together with the silicones and is thus lost to the value chain. The overall objective of this work was to develop a recycling process for the recovery of platinum from addition-cured silicone elastomers. In the first step, this was achieved by efficient digestion methods and by optimizing the leaching processes for exemplary commercial silicone elastomer products. Two different silicone materials were investigated, both of which were crosslinked with a platinum catalyst. The initial Pt content in the tested samples was 12.6 ± 0.2 mg/kg for a commercial silicone impression material and 6.3 ± 0.5 mg/kg for a silicone baking mold, measured by graphite furnace atomic absorption spectrometry (GF-AAS). Samples were first frozen with liquid nitrogen to improve brittleness and then crushed with a simple food processor to obtain a silicone granule. Various acid mixtures, mainly based on sulfuric acid, were investigated as digestion methods in order to extract platinum from the silicone network. These had different effects on the dissolution behavior of silicone samples and the amount of platinum extracted in each case. The amount of platinum leached from the filtrate of the digested samples in each case was measured by ICP-OES to evaluate the efficiency of different leaching mixtures. In addition, the dissolved platinum species present in the solutions was identified by UV/VIS as tetrachloridoplatinate(II) complex. The best platinum leaching results so far were obtained with two methods, both of which used a leaching mixture based on sulfuric acid and hexamethyldisiloxane (M2). In the presence of hydrochloric acid, 9.6 ± 1.6 mg platinum/kg was leached from the silicone impression material and 4.2 ± 0.8 mg platinum/kg from the silicone baking mold. With the additional use of aqua regia instead of hydrochloric acid, 10.4 ± 2.8 mg platinum/kg was extracted from the silicone impression material and 4.8 ± 1.0 mg platinum/kg was extracted from the silicone baking mold. These methods were replicated with n = 3. Using statistical evaluation methods (F-test, t-test, and confidence interval), no significant difference was found between these two best methods. Recovery of platinum(0) from leach mixtures has not yet been achieved due to high dilution and very low platinum concentration in samples and will be part of another study.

Upgrading of Pyrolytic Char Generated from Waste Tyre Pyrolysis for Solid Tyre Industry

In Sri Lanka, accumulation of tons of low-quality pyrolytic char (PT-char) in pyrolysis plants is a significant issue in waste tyre management. Finding a solution to upgrade low-quality PT-char is urgent in Sri Lankan context as it initiates a method of finding a solution to the disposal issue of PT-char. As a result, the current study introduces an efficient and cost-effective routine for upgrading low grade PT-char into value-added products which is not being successful before. The upgrading method entails carefully regulating size reduction of the low-grade PT-char (particle size&lt;50 μm) and following optimization of acid-base demineralization parameters. After the size reduction of PT–char, demineralization procedure was introduced using low char: acid/base ratios (1:2), diluted acids and bases (2 M HCl and 2 M NaOH), low temperatures (30 0C-60 0C), and short reaction times (30-60 minutes). Purity and surface characteristics of upgraded char were investigated using XRD, elemental analysis, SEM, and TGA. Based on a CHN analysis, 67% (w/w) of initial carbon content of crude C-PT char was increased up to 91% (w/w) by washing it twice with 2 M HCl and once with 2 M NaOH (2 M H2+2 M S) while reducing ash content from 17.65% (w/w) to 3.59% (w/w). Significance removal of metals such as Zn (1.14% w/w) , Fe (0.34% w/w), Mg (0.25% w/w) and Ca (2.71% w/w) from C-PT char were observed after treating with 2 M H2+2M S (Zn 0.36%w/w , Fe 0.06%w/w, Mg 0.01%w/w and Ca 0.01% w/w). Removal of Zn from C-PT char further confirmed by XRD and surface modification was confirmed by SEM images. Additionally, the rheological and physico-mechanical properties of the upgraded char incorporated solid tyre base compounds were evaluated and compared with commercial grades of carbon black; N 330, and N 660. It was observed that tensile strength, tear strength, hardness and compression properties of purified PT-char incorporated rubber compounds were not significantly different and exhibit resemble properties to the samples prepared using commercial carbon black grades. Overall, it can be confirmed that upgraded PT char has a significant potential to be used as an economical alternative for reinforcement filler in solid tyre industry and upgrading procedure is efficient and economically viable than the conventional methods. &#x0D; Keywords: Pyrolytic char, Demineralization, Purification, Modification

Distinctions of the Emergence of Convective Flows at the “Diffusion–Convections” Boundary in Isothermal Ternary Gas Mixtures with Carbon Dioxide

This study discusses the influence of the composition of a ternary gas mixture on the possibility of occurrence of convective instability under isothermal conditions due to the difference in the diffusion abilities of the components. A numerical study was carried out to study the change in “diffusion–concentration gravitational convection” modes in an isothermal three-component gas mixture He + CO2 − N2. The mixing process in the system under study was modeled at different initial carbon dioxide contents. To carry out a numerical experiment, a mathematical algorithm based on the D2Q9 model of lattice Boltzmann equations was used for modeling the flow of gases. We show that the model presented in the paper allows one to study the occurrence of convective structures at different heavy component contents (carbon dioxide). It has been established that in the system under study, the instability of the mechanical equilibrium occurs when the content of carbon dioxide in the mixture is more than 0.3 mole fractions. The characteristic times for the onset of convective instability and the subsequent creation of structural formations, the values of which depend on the initial content of carbon dioxide in the mixture, have been determined. Distributions of concentration, pressure and kinetic energy that allow one to specify the types of mixing and explain the occurrence of convection for a situation where, at the initial moment of time, the density of the gas mixture in the upper part of the diffusion channel is less than in the lower one, were obtained.