RESUMO

Ash emission from volcanic eruptions affects the environment, society, and human health. This study shows the total concentration and lung bioaccessible fraction of eight potential toxic metal(loid)s in five Popocatépetl ashfall samples. Mineralogical phases and particle size distribution of the ashfall were analyzed by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) techniques, respectively. The bioaccessibility test of Gamble solution (GS) and Artificial Lysosomal Fluid (ALF) were conducted to simulate extracellular (pH 7) and intracellular (pH 4.5) conditions, respectively. The studied metal(loid)s showed the following total concentration (mg kg-1): 1.98 (As), 0.17 (Cd), 134.09 (Cr), 8.66 (Cu), 697.33 (Mn), 55.35 (Ni), 8.77 (Pb), and 104.10 (Zn). Geochemical indices suggested that some metal(loid)s are slightly enriched compared to the local soil background concentrations. Several mineralogical phases were identified in the collected ashfall deposits, such as plagioclase, pyroxene, and Fe-Ti oxide, among others. According to the risk assessment results, the non-carcinogenic risk related to ashfall exposure returns an HQ > 1 for children. In contrast, the estimation of carcinogenic risk was found to be within the tolerable limit. Metal(loid)s showed low bioaccessibility (< 30%) in GS and ALF, with the highest values found in ALF solution for As (12.18%) and Cu (7.57%). Despite their metal-bioaccessibility, our findings also showed that dominant ash particle size ranged between fine (< 2.5 µm) and extremely fine (< 1 µm), considered highly inhalable fractions. The results obtained in this work indicate that volcanic ashes are bioinsoluble and biodurable, and exhibit low bioaccessibility when in contact with lung human fluids.

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The use of mineral reinforcements in polymer matrix composites has emerged as an alternative for sustainable production, reducing waste and enhancing the physical and mechanical properties of these materials. This study investigated the impact of the melt flow index (MFI) of HDPE and the particle size of two mineral reinforcements, Bahia Beige (BB) and Rio Grande do Norte Limestone (CRN), on the composites. All composites were processed via extrusion, followed by injection, with the addition of 30 wt.% reinforcement. Chemical analyses revealed similar compositions with high CaO content for both minerals, while X-ray diffraction (XRD) identified predominantly calcite, dolomite, and quartz phases. Variations in the MFI, reinforcement type, and particle size showed a minimal influence on composite properties, supported by robust statistical analyses that found no significant differences between groups. Morphological analysis indicated that composites with lower MFI exhibited less porous structures, whereas larger particles of BB and CRN formed clusters, affecting impact resistance, which was attributed to poor interfacial adhesion.

RESUMO

Wood-plastic composites are becoming increasingly recognized for their sustainability and their potential for use in various production processes. Nevertheless, enhancing their mechanical strength continues to be a difficult challenge. The objective of this research was to improve the mechanical strength of wood-plastic composite components manufactured through selective laser sintering (SLS). This was achieved by integrating a sustainable composite material, Prosopis chilensis (PCP), with polyethersulfone (PES) to form a composite referred to as PCPC. This study showcased the effect of various PCP particle sizes on mechanical strengths, dimensional accuracies (DAs), and surface roughness of PCPC parts manufactured using AFS-360 SLS. Single-layer sintering was employed to assess PCPC powder's formability with varying PCP particle sizes, and various tests were conducted to understand the materials' thermal properties and analyze particle dispersion and microstructure. The results demonstrated that PCP particle sizes ≤ 0.125 mm significantly enhanced the mechanical strength, forming quality, and DA compared to other particle sizes and pure PES. Key findings for PCPC parts with PCP ≤ 0.125 mm included a bending strength of 10.78 MPa, a tensile strength of 4.94 MPa, an impact strength of 0.91 kJ/m2, and a density of 1.003 g/cm3. Post-processing further improved these parameters, confirming that optimizing PCP particle size is crucial for enhancing the mechanical properties and overall quality of PCPC parts produced via SLS.

RESUMO

Peanut shells' adsorption performance in caffeine and triclosan removal was studied. Peanut shells were analyzed for their chemical composition, morphology, and surface functional groups. Batch adsorption and fixed-bed column experiments were carried out with solutions containing 30 mg/L of caffeine and triclosan. The parameters examined included peanut shell particle size (120-150, 300-600, and 800-2000 µm), adsorbent dose (0.02-60 g/L), contact time (up to 180 min), bed height (4-8 cm), and hydraulic loading rate (2.0 and 4.0 m3/m2-day). After determining the optimal adsorption conditions, kinetics, isotherm, and breakthrough curve models were applied to analyze the experimental data. Peanut shells showed an irregular surface and consisted mainly of polysaccharides (around 70% lignin, cellulose, and hemicellulose), with a specific surface area of 1.7 m2/g and a pore volume of 0.005 cm3/g. The highest removal efficiencies for caffeine (85.6 ± 1.4%) and triclosan (89.3 ± 1.5%) were achieved using the smallest particles and 10.0 and 0.1 g/L doses over 180 and 45 min, respectively. Triclosan showed easier removal compared to caffeine due to its higher lipophilic character. The pseudo-second-order kinetics model provided the best fit with the experimental data, suggesting a chemisorption process between caffeine/triclosan and the adsorbent. Equilibrium data were well-described by the Sips model, with maximum adsorption capacities of 3.3 mg/g and 289.3 mg/g for caffeine and triclosan, respectively. In fixed-bed column adsorption tests, particle size significantly influenced efficiency and hydraulic behavior, with 120-150 µm particles exhibiting the highest adsorption capacity for caffeine (0.72 mg/g) and triclosan (143.44 mg/g), albeit with clogging issues. The experimental data also showed good agreement with the Bohart-Adams, Thomas, and Yoon-Nelson models. Therefore, the findings of this study highlight not only the effective capability of peanut shells to remove caffeine and triclosan but also their versatility as a promising option for water treatment and sanitation applications in different contexts.

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Nanoscale zero valent iron (nZVI) is globally the main nanomaterial used in contaminated site remediation. This study aims to evaluate the sustainability of using nZVI in the nanoremediation of contaminated sites and to determine the factors that affect the sustainability of the use of nZVI in remediation. Five case studies of nZVI use on a pilot scale were selected. Life cycle analysis tools were used to evaluate environmental, economic, social impacts, and sustainability. The functional unit of the life cycle analyses was 1.00 m3 of remediated soil and groundwater. Case study of Brazil was the least sustainable, while case study of United States was the most sustainable. Only the modification of the functional unit results in variations in the sustainability index. Different factors influence the sustainability of nZVI in remediation, the main factor being the amount of nZVI used in the processes. Finally, this work contributes significantly to the state-of-the-art sustainable use of nZVI in remediation. This is a pioneering study in the detailed and comprehensive assessment of the sustainability of the use of nZVI in remediation. Through the analysis of case studies, it is possible to determine the main factors that influence the sustainability of the nZVI remediation life cycle.

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Two chia mucilages with different viscosities, obtained by extraction conditions optimized in a previous work, were homogenized by high pressure homogenization (HPH). Particle size, molecular weight, zeta potential, FTIR spectrum, rheological properties, water absorption capacity, water holding capacity and iron binding capacity were determined on both mucilages treated and without treatment. Homogenization led to a significant reduction in viscosity respect to chia mucilage controls, which can be related to the decrease in particle size and molecular weight. A high iron binding capacity was obtained for both mucilages. FTIR spectra of both mucilages with iron showed displacements in bands related with stretching of carboxylic uronic acids, suggesting the interaction site with this mineral. This interaction was also verified by particle size determination with a displacement to higher sizes in the presence of iron. Potential zeta showed a significant reduction in the presence of iron. A model to explain the binding between chia mucilage and iron is proposed. HPH appears as an alternative to expand chia mucilage functionality reducing the viscosity of chia mucilage solutions for the offer of a new ingredient also with optimal levels of hydration and iron binding capacity.

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RESUMO

The objective of this study was to evaluate effects of forage inclusion and sources on performance, metabolism, and feeding behavior of dairy calves. Forty-eight Holstein calves were blocked and randomly assigned to 1 of 4 dietary treatments according to sex and BW at 28 d of life to determine the effects of feeding forage sources (ensiled and dry), with different quality on performance, metabolites, and behavior. Treatments consisted of a no-forage coarsely ground starter (CON); or total mixed ration (TMR) containing 7.5% on a dry matter (DM) basis of Tifton hay of either medium quality (MH) or low quality (LH); or 10% on a DM basis of corn silage (CS). During the first 28 d of life, all calves received 3 L of whole milk twice daily, a commercial pelleted starter and no forage, and water ad libitum. After that, the solid diet was changed to the respective dietary treatments. Calves were gradually weaned from 52 to 56 d of age, and followed for 14 d postweaning. Individual solid feed and milk intakes were recorded daily, and BW and metabolic indicators of intermediate metabolism were recorded weekly. Behavior was recorded, and the analysis was conducted on wk 7 (preweaning) and 10 (postweaning). Solid feed intake increased at wk 7 and 8 when MH, LH, and CS were included in TMR; the same results were observed postweaning. The diets did not affect the average daily gain and BW, but the feed efficiency increased with the CON diet. The ß-hydroxybutyrate concentration was greater in calves receiving TMR-containing forage than CON diet. Furthermore, calves supplemented with forage had a greater rumination time. In conclusion, all forage sources included in the TMR showed feed intake and behavior benefits, reinforcing the need for fiber from forage in pre- and postweaning diets.

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The particle size distribution (PSD) in emulsion polymerization (EP) has been modeled in the past using either the pseudo bulk (PB) or the 0-1/0-1-2 approaches. There is some controversy on the proper type of model to be used to simulate the experimental PSDs, which are apparently broader than the theoretical ones. Additionally, the numerical technique employed to solve the model equations, involving hyperbolic partial differential equations (PDEs) with moving and possibly steep fronts, has to be precise and robust, which is not a trivial matter. A deterministic kinetic model for the PSD evolution of ab initio EP of vinyl monomers was developed to investigate these issues. The model considers three phases, micellar nucleation, and particles that can contain n≥0 radicals. Finite volume (FV) and weighted-residual methods are used to solve the system of PDEs and compared; their limitations are also identified. The model was validated by comparing predictions with data of monomer conversion and PSD for the batch emulsion homopolymerization of styrene (Sty) and methyl methacrylate (MMA) using sodium dodecyl sulfate (SDS)/potassium persulfate (KPS) at 60 °C, as well as the copolymerization of Sty-MMA (50/50; mol/mol) at 50 and 60 °C. It is concluded that the PB model has a structural problem when attempting to adequately represent PSDs with steep fronts, so its use is discouraged. On the other hand, there is no generalized evidence of the need to add a stochastic term to enhance the PSD prediction of EP deterministic models.

RESUMO

Nanoscale particles described by Mie resonance in the UV-vis-NIR region are in high demand for optical applications. Controlling the shape and size of these particles is essential, as it results in the ability to control the wavelength of the Mie resonance peak. In this work, we study the extensive scattering properties of gadolinium niobate particles with complex bar- and cube-like shapes in the UV-vis-NIR region. We perform our experimental analysis by characterizing the morphology and extinction spectra, and our theoretical study by implementing a Mie scattering model for a distribution of spherical particles. We can accurately model the size distribution and extinction spectra of complex shaped particles and isolate the contribution of aggregates to the extinction spectra. We can separate the contributions of dipoles, quadrupoles, and octupoles to the Mie resonances for their respective electric and magnetic parts. Our results show that we can tune the broad Mie resonance peak in the extinction spectra by the nanoscale properties of our system. This behavior can aid in the design of lasing and luminescence-enhanced systems. These dielectric gadolinium niobate submicron particles are excellent candidates for light manipulation on the nanoscale.

RESUMO

The particle size (PS) of reconstituted corn (REC) can affect the grinding rate and starch digestibility in dairy cows. We evaluated the effect of the PS of REC ensiled for 40 days on the pasture dry matter intake (DMI), lactation performance, total tract digestibility, and ruminal fermentation of grazing dairy cows. The treatments were coarse REC (CO, 1694 µm), fine REC (FI, 1364 µm), or finely ground (GC, 366 µm) flint corn (68% vitreousness) at 29.6 ± 1.4% of diet DM (mean ± SD). Eighteen dairy cows (mean milk yield 21.3 kg/d) were split into three groups by production level and were assigned within each group to a sequence of treatments in 3 × 3 Latin squares of 21-day periods. Cows were individually fed a constant amount of whole-plant corn silage 3 ×/d (2.7 kg DM/d) and corn treatments and soybean meal according to their group. There was no significant interaction between treatment and the production level. Cows fed FI had a lower DMI (16.7 vs. 18.1 kg/d) than those fed GC, and both did not differ from CO (17.7 kg/d). There was no treatment effect on milk yield (mean: 19.2 kg/d). Cows fed CO had the lowest total tract digestibility of starch (86.3 vs. 92.3% of intake) and the highest fecal starch concentration (7.0 vs. 4.0% of DM). The NDF digestibility was lower for GC-fed cows than CO- and FI-fed cows. Plasma glucose was higher in cows fed FI and CO (75.0 mg/dL) than those fed GC (70.8 mg/dL). Ruminal volatile fatty acids and the pH did not differ. Fine grinding of REC increased the feed efficiency relative to CO and GC. Coarse grinding of REC ensiled for 40 days reduced the total tract starch digestibility relative to FI and GC.