Solution Research Articles

Mechanism of polyaspartic acid as acid-base regulation depressant in reverse flotation separation of molybdenite and talc

The separation of talc and molybdenite through flotation has become a significant issue. The current inorganic and organic depressants demonstrate inadequate selectivity and limited efficacy in both positive flotation and reverse flotation of molybdenite. In this study, the utilization of the highly efficient green agent polyaspartic acid (PASP) as a molybdenite depressant was explored to investigate its pH-dependent acid-base depression mechanism. In the case of pH 4.0, molybdenite exhibited effective depression, talc was floated, PASP was desorbed at pH 10.0, and molybdenite was activated. In this study, the impact of electrostatic force on the adsorption process of PASP and examined the mechanism of PASP on molybdenite surface were studied by means of micro-flotation experiments, zeta potential measurements, analysis of solution chemistry, Fourier Transform Infrared Spectrometer (FT-IR) analysis, Ultraviolet–visible spectroscopy (UV–Vis) study, and X-ray photoelectron spectroscopy (XPS) detections. PASP produced chemisorption through the coordination of O or N atoms lone pair electrons with Mo2+ on the molybdenite surface. In this process, electrostatic repulsion determines whether the mineral can come into contact with PASP.

Aqueous solution chemistry in silico and the role of data-driven approaches

Aqueous solution chemistry <i>in silico</i> and the role of data-driven approaches

Enhancing casein micelle dissociation in diluted skim milk systems using combined processing techniques

The present work aims to evaluate the dissociation of casein micelles in diluted skim milk (SM) systems after undergoing solvent- or emulsifying salt-based dissociation coupled with ultra-high-pressure homogenization (UHPH). Specifically, part I evaluated dilute SM solutions combined with varying ethanol concentrations (0%-60%) at varying temperatures (5-65°C) in combination with UHPH (100-300 MPa), and part II evaluated dilute SM solutions combined with varying concentrations (0-100 mM) of either sodium hexametaphosphate (SHMP) or sodium citrate (SC) in combination with UHPH (100-300 MPa). In part I, high concentrations of ethanol (40%-60% vol/vol) at elevated temperatures (45-65°C) achieved extensive dissociation of casein micelles, especially in combination with UHPH at ≥200 MPa, as shown by a reduction in sample absorbance and in casein particle size compared with the control (dilute SM, 65°C) under optimum conditions (dilute SM, 60% ethanol, 65°C, ≥200 MPa). In part II, the level of casein micelle dissociation using emulsifying salts (ES) was dependent on the ES type and concentration. Considerable casein micelle dissociation in dilute SM systems was achieved with SHMP concentrations ≥1 mM and SC concentrations ≥10 mM, resulting in decreased sample absorbance, bimodal casein size distributions, and increased hydrophobicity (∼2-fold increase in intrinsic fluorescence) compared with the control (dilute SM). This dissociation was further enhanced with UHPH (≥200 MPa). These results indicate that both solvent- and ES-based casein dissociation techniques can be optimized when used in combination with UHPH. Together, these processing techniques can be used to extensively dissociate casein micelles with the potential to use these altered systems for value-added applications such as functional ingredients or encapsulation agents.

Utilizing integrated neutron diffraction and elastoplastic self-consistent crystal plasticity model to quantitatively assess the strengthening mechanism in Al–12.5Ce and Al–12.5Ce–0.4Mg alloys

An integrated in-situ neutron diffraction and elastic plastic self-consistent crystal plasticity (EPSC-CP) modeling scheme is performed on a binary Al–12Ce alloy and a ternary Al–12Ce–0.4Mg alloys. Using this scheme, the constitutive parameters, i.e. elastic constants and slip system parameters of individual phases can be calibrated which can be used in microstructure-based CP models to predict materials performance. From this study, it is shown that the elastic constants of Al11Ce3 intermetallics calculated from density function theory calculation in the literature are rather accurate. When applied to the EPSC-CP model, the lattice strains of both the binary and ternary alloys are correctly predicted as compared with experiments, and large lattice strain differences between Al (100) plane and Al11Ce3 (010) plane are demonstrated. The slip system parameters calibrated by the scheme shows that the addition of 0.4 wt% Mg in the alloy has little influence on the critical resolved shear stress of initial dislocation glide in the Al matrix which caused plastic yield in the material. This can be explained by the very dilute Mg solute content in the Al solid solution, causing large spacing of Al–Mg lattice misfit sites and little impact on resistance of dislocation glide at initial yield. The 0.4 wt% Mg addition, on the other hand, has a large influence on the hardening term in the slip system parameters, indicating those Al–Mg misfit sites do help dislocation accumulation during the deformation. The impact of dilute Mg addition on the Al slip system parameters is also reflected in the flow behavior of the ternary alloy: little impact on the yield stress, but a large impact on working hardening and tensile strength of the materials which is consistent with the literature.

Impact of thermodynamics and kinetics on the carbon capture performance of the amine-based CO2 capture system

Solvent-based CO2 capture is a commonly employed post-combustion technique in processes involving absorber-stripper columns. This study focused on computer simulations with equilibrium- and rate-based modeling of CO2 capture using the amine solvents 2-amino-2-methyl-1-propanol (AMP), diethanolamine (DEA), and methyl diethanolamine (MDEA) and thermodynamic methods involving electrolyte NRTL models. The objective of this study was to understand the impacts of rate-based modeling, the type of amine, and thermodynamic methods on carbon capture. Within this study, the amine-based CO2 capture process from coal-power plant flue gas was studied using Aspen Plus modeling. Simulations were also conducted to determine the impact of thermodynamics and kinetics on the CO2 capture performance of the system. The results were analyzed on the basis of captured CO2 according to the solvents and models. The equilibrium approach was mostly invalid because of the oversimplified ideal stage assumptions through the column. The lowest carbon capture capacity was obtained with MDEA, while DEA yielded the best results. A sensitivity analysis with rate-based modeling showed the significant impact of the inlet CO2 composition. The amine-based CO2 capture process simulation included solution chemistry, electrolyte thermodynamics, rigorous transport property modeling, reaction kinetics, and rate-based multistage simulation, which could be applicable to different solvent systems.

Effect of Iron(III) ions on rutile flotation: Surface properties and adsorption mechanism

Various studies have shown that the presence of metal ions in the slurry can significantly impact flotation. However, it was still uncertain how iron, a typical metal ion, affected rutile flotation. Micro-flotation experiments, x-ray photoelectron spectroscopy, icp-oes, solution chemistry calculation, zeta potential and contact angle test were used to explore the effect of iron ions on the surface properties and floatability of rutile in this investigation. Micro-flotation results showed that iron ions not only substantially increased the rutile flotation recovery from 42.27 % to 75.69 % at pH = 4, but also converted the optimal pH of flotation from a point (pH = 4) to a platform (pH = 4–8). Solution chemistry calculations indicated that iron ions could form complexes with hydroxyl to produce FeOH2+, which reacted with benzohydroxamic acid (BHA) to create [Fe(C7H6NO2)2]+ at pH=4–7. The analysis conducted through X-ray photoelectron spectroscopy, coupled with the results obtained from contact angle measurements, revealed that the complex [Fe(C7H6NO2)2]+ had the capability to engage with Ti-OH groups, improving the hydrophobicity of rutile surface. Zeta potential analysis results further illustrated that Fe3+/BHA complexes reinforce the adsorption of BHA and iron ions onto rutile surface by the formation of [Fe(C7H6NO2)2]+. In addition, the O1s peak fitting results and ICP-OES analysis results proved that at the same pH, 60 mg/L was the optimal concentration for iron ion activation, which may be limited by Saturated adsorption capacity of [Fe(C7H6NO2)2]+.

Effects of chemical solution on the deformation and strength characteristics of expansive soil

Effects of chemical solution on the deformation and strength characteristics of expansive soil

Simple chemical solution deposition of Al2O3 dielectric layers for low-cost fabrication of transparent electronic devices

Simple chemical solution deposition of Al2O3 dielectric layers for low-cost fabrication of transparent electronic devices

INTERACTION OF L-CARNOSINE WITH NICOTINIC AND ISONICOTINIC ACIDS IN AQUEOUS SOLUTIONS AT 298.15 K

Understanding the mechanism of interaction of drugs with proteins has drawn attention of numerous researchers. The thermodynamic investigations of liquid-phase systems containing peptide and drug make it possible to determine the nature and driving forces of the interaction between them. In this work, we present results of interaction study of peptide L-carnosine (Car), as model of polypeptide chains in protein, with isonicotinic and nicotinic acids, as the drug models, in aqueous solution using calorimetric method. Calorimetric measurements of the enthalpy of L-carnosine dissolution in water and aqueous solutions with two isomers of pyridine carboxylic acid additives were performed on an ampoule-type isoperibolic dissolution calorimeter at 298.15 K. The error of measuring single heat effects was below 0.2%. The relative combined uncertainty in the measurements of the enthalpies of dissolution was not more than 0.7%. Based on the obtained experimental data and the using the HEAT computer program, the thermodynamic parameters (lgKc, ΔcG, ΔcH, ΔcS) of the complex formation between the reagents were calculated. A comparison of the affinity of peptide to interaction with nicotinic acid and isonicotinic acid was carried out. It is shown that the interaction of L-carnosine with isonicotinic acid leads to the formation of a more stable complex than with nicotinic acid. This fact may be mainly explained by the changing of ionic state of the reagents in solution and the predominance of the zwitterionic forms of isonicotinic acid in compared with nicotinic acid. The data obtained reveal the presence of molecular complexes between Car and isomers of pyridine carboxylic acid with 1:2 stoichiometry in aqueous solutions. The complexes of Car with the isonicotinic acid are mainly enthalpically stabilized, while those of Car with nicotinic acid are stabilized by both enthalpic and entropic contributions to the free Gibbs energy. The main interactions in complexes stabilization are believed to be electrostatic forces and hydrogen bonds formation between peptide and pyridine monocarboxylic acids. For citation: Tyunina E.Yu., Mezhevoi I.N., Barannikov V.P. Interaction of L-carnosine with nicotinic and isonicotinic acids in aqueous solutions at 298.15 K. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 7. P. 48-54. DOI: 10.6060/ivkkt.20246707.7010.

Assessment of Water Quality of Tighra Reservoir using Weighted Arithmetic Water Quality Index (WA-WQI)

Water is a natural resource used for drinking, agriculture, and industry. Being a vital source of life for living beings, its quality needs to be assessed regularly and the environmental health of water resources should be maintained accordingly. This study assessed the water quality of Tighra reservoir, which is the primary source of water supply in Gwalior, M.P. For this task, the water sampling was carried out during Jun-Sep, 2023. Total 32 samples were collected to cover pre &amp; post monsoon and monsoon season. Subsequently, the water quality parameters such as pH, Turbidity, Acidity, Alkalinity, Chloride, Hardness, Total solids (TS), Total dissolved solids (TDS), Total suspended solids (TSS), Dissolved solid (DS), Iron (Fe), MPN were determined to assess weighted arithmetic water quality index (WA-WQI). Consequently, the WQI ranges from 15.91 to 121.76 respectively. Furthermore, poor water quality was observed at SS7 followed by SS6, and SS5. However, good quality of water was observed at SS1 followed by SS2, SS3, and SS8. The seasonal distribution of WQI reveals that June (19.38-121.75) with SS7 and SS6 have poor water quality, July (16.74-66.87) with SS5, SS6, and SS7 have poor water quality, August (38.08-79.28) with SS4, SS5, SS6, and SS7 have poor water quality, September (15.91-101.11) with SS4, SS5, SS6, and SS7 have poor water quality. The aforementioned findings will surely help to local authorities to take suitable action for the upgradation water quality of Tighra reservoir.

Comparison of viscoelastic flows in two- and three-dimensional serpentine channels.

Polymer solutions in the dilute regime play a significant role in industrial applications. Due to the intricate rheological properties of these highly viscoelastic fluids, especially in complex flow geometries, a thorough numerical analysis of their flow dynamics is imperative. In this research, we present a numerical investigation of purely elastic instability occurring in two- and three-dimensional serpentine channels under conditions where fluid inertia is negligible and across a broad spectrum of polymer relaxation times. Our findings reveal a strong qualitative agreement between the existing experimental results obtained from dilute solutions of flexible polymers in microfluidic devices and the numerical simulations conducted in two and three dimensions using the Oldroyd-B model. Spatial flow observations and statistical analysis of temporal flow features indicate that this purely elastic turbulent flow exhibits nonhomogeneous, non-Gaussian, and anisotropic characteristics across all scales. Additionally, our comparison of two- and three-dimensional simulations demonstrates that the elastic instability is primarily driven by the curvature of the streamlines induced by the flow geometry, rather than the weak secondary flow in the azimuthal direction. Therefore, our two-dimensional numerical simulations successfully replicate, at least qualitatively, the features observed in three-dimensional experiments. Furthermore, spectral analysis suggests that, in comparison to elastic turbulence in the dilute regime, the range of scales for the excited fluctuations is narrower.

Elastoplastic properties of ion exchangers based on cross-linked polyelectrolytes

In this paper, we dilatometrically studied the elastoplastic properties of spherical grains of industrial weakly acidic and strongly acidic ion-exchanger in experiments with constant uniaxial compression and a subsequent unload at room temperature, depending on the ionic form and concentration of the electrolyte solution. It was found that the ionic form of polyacrylate and polymethacrylate cross-linked with triethylene glycol dimethacrylate and divinylbenzene, respectively, and the concentration of the external solution affects their elastoplastic properties. In dilute solutions of sodium chloride and calcium chloride, the gels exhibited elastic properties with close relative amplitudes of deformation. The amplitude of deformation of the grain of polymethacrylate crosslinked with divinylbenzene, in the Ni form, in a dilute nickel chloride solution was significantly lower than that of the Ca form, with significant plastic deformation. With an increasing concentration of the external solution of calcium and nickel chlorides under mechanical load on the grain of polymethacrylate cross-linked with divinylbenzene, the total deformation of the granule and the magnitude of elastic deformation decreased, while the residual (plastic) deformations increased. In concentrated solutions of CaCl2 and NiCl2, such an ion-exchanger became an inelastic rigid material. Even under increased mechanical load, the magnitude of its elastic compressive deformation was very small. The K-form of a swollen in water strongly acidic polystyrene cation-exchanger with grafted sulpho groups cross-linked with divinylbenzene is also characterized by elastic deformations, i.e. the polymer is in a highly elastic state. However, the polystyrene matrix is more rigid compared to polyacrylic and polymethacrylic cation-exchangers in the alkali metal ion form, so the amplitude of deformation is significantly smaller. For such a cation-exchanger in Ca- and Ni- forms, elastic deformations prevail even in concentrated solutions.

Osteopontin stabilization and collagen containment slows amorphous calcium phosphate transformation during human aortic valve leaflet calcification

Calcification of aortic valve leaflets is a growing mortality threat for the 18 million human lives claimed globally each year by heart disease. Extensive research has focused on the cellular and molecular pathophysiology associated with calcification, yet the detailed composition, structure, distribution and etiological history of mineral deposition remains unknown. Here transdisciplinary geology, biology and medicine (GeoBioMed) approaches prove that leaflet calcification is driven by amorphous calcium phosphate (ACP), ACP at the threshold of transformation toward hydroxyapatite (HAP) and cholesterol biomineralization. A paragenetic sequence of events is observed that includes: (1) original formation of unaltered leaflet tissues: (2) individual and coalescing 100’s nm- to 1 μm-scale ACP spherules and cholesterol crystals biomineralizing collagen fibers and smooth muscle cell myofilaments; (3) osteopontin coatings that stabilize ACP and collagen containment of nodules preventing exposure to the solution chemistry and water content of pumping blood, which combine to slow transformation to HAP; (4) mm-scale nodule growth via ACP spherule coalescence, diagenetic incorporation of altered collagen and aggregation with other ACP nodules; and (5) leaflet diastole and systole flexure causing nodules to twist, fold their encasing collagen fibers and increase stiffness. These in vivo mechanisms combine to slow leaflet calcification and establish previously unexplored hypotheses for testing novel drug therapies and clinical interventions as viable alternatives to current reliance on surgical/percutaneous valve implants.

The complex effect of dissolved organic carbon on desorption of per- and poly-fluoroalkyl substances from soil under alkaline conditions

Per- and poly-fluoroalkyl substances (PFASs) are contaminants of emerging concern, yet the understanding of factors that control their leaching and release from contaminated soils remains limited. This study aimed to investigate the impact of dissolved organic carbon (DOC) on the release of PFASs—specifically, perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), and perfluorooctanoic acid (PFOA)from soils contaminated by aqueous film forming foam (AFFF). Batch aqueous leaching experiments were conducted on AFFF-contaminated soils under alkaline solution conditions (pH 9.5, 10.5, and 12) as it enhances leaching of both PFAS and DOC. Leaching of PFOS was significantly increased under alkaline conditions. Although the leaching of PFAS generally increased with pH, PFOS appeared to be more retained under the very alkaline pH conditions used in this study. At the same solution pH, leaching of PFOS and DOC was less in Ca(OH)2 than in NaOH. The retention of PFOS under these conditions may be attributable to the shielding of the negative charge of the soil components and colloids (e.g., DOC and clay minerals) in the leachates and/or the screening of negative charges on head groups of PFOS due to the high concentration of divalent cations. Solution chemistry affected desorption of PFOS more than PFHxS and PFOA. The study highlights that the influence of DOC on PFAS leaching and transport can be very complex, and depends on leachate chemistry (e.g., pH and cation type), PFAS chemistry, the magnitude of PFAS contamination and factors that influence the solid:liquid partitioning of organic carbon in soil.

A comprehensive investigation of the process and atmospheric coupling corrosion on corroded and mechanical properties of the SPA-H weathering steel

Weathering steel has recently become popular in engineering due to its corrosion resistance, but its mechanical characteristics must alter during double corrosion, process chemical solution corrosion (CSC), and atmospheric corrosion (AC). However, no studies have been published on the coupling effect of process and atmospheric corrosion. The durability and safety of weathering steel structures can be challenging to assess. As a result, we used SPA-H weathering steel as the object, ran process corrosion and double corrosion simulations (process corrosion plus atmospheric corrosion simulation), and created three corrosion conditions: non-corrosion, single-side corrosion, and double-side corrosion. CSC was the corrosion process. Following CSC, the second (120, 360, 720, and 1200 hour) Copper-Accelerated Acetic Acid-Salt Spray Testing (CASS) was performed to simulate atmospheric corrosion. A correlation analysis was conducted using the grey correlation method between indoor and atmospheric corrosion. After corrosion testing, these specimens were subjected to White Light Interferometry (WLI) and tensile coupon tests (TCT) to evaluate the corrosion characteristics and the deterioration of material mechanical properties. Finally, linear fitting was used to produce the calculation formula between the mechanical properties and the mass loss ratio of single-side and double-side corrosion.

Study on the effect of wet scrubbing technique on emissions in a dual fuel engine operating with diesel and hydrogen.

Reducing emissions from internal combustion (IC) engines is a crucial goal, encompassing nitrogen oxide (NO), hydrocarbon (HC), carbon monoxide (CO), and smoke. To enhance both performance and emissions, contemporary IC engines have turned to alternative gases such as hydrogen (H2) and exhaust after-treatment systems. A promising method to effectively decrease exhaust emissions entails the application of the scrubber technique as an exhaust gas after-treatment. This study's objective is to explore two avenues for curtailing exhaust emissions. The first involves substituting traditional fuels in IC engines with hydrogen gas (H2) at a flow rate of 6 LPM. The second entails integrating a liquid chemical solution into the scrubber technique. Notably, the utilization of KMnO4 solutions exhibits an appreciable reduction in NO and CO emissions compared to solutions containing NaOH. The experimental process included two aspects: investigating hydrogen fuel (H2) as an alternative fuel for IC engines and incorporating a scrubber technique using both KMnO4 and NaOH solutions. These experiments were conducted using a single-cylinder engine with a power output of 5.2 kW, cooled by water. The engine underwent tests under various load conditions, spanning from minimal to maximal loads. The findings revealed that employing KMnO4 solutions within the scrubber technique led to reductions of 25% and 40% in NO and CO emissions, respectively, in contrast to the utilization of NaOH solutions. Similarly, introduction hydrogen gas also has a significant effect on emission reduction.

The Streptococcus phage protein paratox is an intrinsically disordered protein.

The bacteriophage protein paratox (Prx) blocks quorum sensing in its streptococcal host by directly binding the signal receptor and transcription factor ComR. This reduces the ability of Streptococcus to uptake environmental DNA and protects phage DNA from damage by recombination. Past work characterizing the Prx:ComR molecular interaction revealed that paratox adopts a well-ordered globular fold when bound to ComR. However, solution-state biophysical measurements suggested that Prx may be conformationally dynamic. To address this discrepancy, we investigated the stability and dynamic properties of Prx in solution using circular dichroism, nuclear magnetic resonance, and several fluorescence-based protein folding assays. Our work shows that under dilute buffer conditions Prx is intrinsically disordered. We also show that the addition of kosmotropic salts or protein stabilizing osmolytes induces Prx folding. However, the solute stabilized fold is different from the conformation Prx adopts when it is bound to ComR. Furthermore, we have characterized Prx folding thermodynamics and folding kinetics through steady-state fluorescence and stopped flow kinetic measurements. Our results show that Prx is a highly dynamic protein in dilute solution, folding and refolding within the 10 ms timescale. Overall, our results demonstrate that the streptococcal phage protein Prx is an intrinsically disordered protein in a two-state equilibrium with a solute-stabilized folded form. Furthermore, the solute-stabilized fold is likely the predominant form of Prx in a solute-crowded bacterial cell. Finally, our work suggests that Prx binds and inhibits ComR, and thus quorum sensing in Streptococcus, by a combination of conformational selection and induced-fit binding mechanisms.

Hydrophobic CHA-ZIFs with a junctional trap between cha and d6r cages for adsorption of 2,3-butanediol in aqueous solution

Hydrophobic CHA-ZIFs with a junctional trap between cha and d6r cages for adsorption of 2,3-butanediol in aqueous solution

Nanobubble transport in porous media: Towards agro- and environmental applications

Nanobubbles have been increasingly used in various applications involving porous media, such as groundwater remediation and irrigation. However, the fundamental scientific knowledge regarding the interactions between nanobubbles and the media is still limited. The interactions can be repulsive, attractive, or inert, and can involve reversible or irreversible attachment as well as destructive mechanisms. Specifically, the stability and mobility of nanobubbles in porous media is expected to be dependent on the dynamic conditions and the physicochemical properties of the porous media, solutions, and nanobubbles themselves. In this study, we investigated how changes in solution chemistry (pH, ionic strength, and valence) and media characteristics (size and wettability) affect the size and concentration of nanobubbles under dynamic conditions using column experiments. Quartz crystal microbalance with dissipation monitoring provided a deeper understanding of irreversible and elastic nanobubbles’ interactions with silica-coated surfaces. Our findings suggest that nanobubbles are less mobile in solutions of higher ionic strength and valence, acidic pH and smaller porous media sizes, while the wettability of porous media has a negligible influence on the retention of nanobubbles. Overall, our findings provide insights into the underlying mechanisms of nanobubble interactions and suggest potential strategies to optimize their delivery in various applications.

Rapid assessment of vanilla (Vanilla planifolia) quality parameters using portable near-infrared spectroscopy combined with random forest

The determination of moisture and vanillin content significantly influences the quality of vanilla. Currently, conventional chemical methods employed for assessing these parameters are time-consuming, involve complex sample preparation, are expensive, and environmentally unfriendly due to the use of chemical solutions. Portable Near-Infrared (NIR) spectroscopy emerges as a promising alternative, characterized by smaller dimensions and lower costs. This study investigates the performance of two portable NIR spectrometers with distinct wavelengths at 740–1070 nm and 1350–2550 nm, in conjunction with Random Forest (RF) and Partial Least Square (PLS) regression, and preprocessing techniques including min-max normalization, 1st derivative, standard normal variate (SNV), multiplicative scatter correction (MSC), 1st derivative + SNV, and 1st derivative + MSC for predicting moisture and vanillin content. At the wavelength range of 1350–2550 nm, RF coupled with 1st derivative produced the best moisture content prediction model with an R2 of 0.971, and RF paired with 1st derivative+SNV yielded the best vanillin content prediction with an R2 of 0.983. This work highlights that the integration of portable NIR and RF allows for rapid and non-destructive detection of moisture and vanillin content. This methodology provides a novel regression method for predicting vanilla qualities.