Search Results (370)

Polysaccharides and phenols are commonly co-localized in various plant-derived foods, including highland barley (Hordeum vulgare L. var. nudum Hook. f.). The interactions between these compounds can influence multiple characteristics of food products, including their physicochemical properties and functional performance, such as bioavailability, stability, and digestibility, which may support promising application of the phenol and polysaccharide complex in health food industry. In this study, two complexes with potential existence in highland barley, such as β-glucan-ferulic acid (GF) and β-glucan-quercetin (GQ), were prepared using the equilibrium dialysis method in vitro. FTIR and SEM results showed that ferulic acid and quercetin formed complexes with β-glucan separately, with covalent and non-covalent bonds and a dense morphological structure. The pH value, reaction temperature, and concentration of phosphate buffer solution (PBS) were confirmed to have an impact on the formation and yield of the complex. Through the test of the response surface, it was found that the optimum conditions for GF and (GQ) preparations were a pH of 6.5 (6), a PBS buffer concentration of 0.08 mol/L (0.3 mol/L), and a temperature of 8 °C (20 °C). Through in vitro assays, GF and GQ were found to possess good antioxidant activity, with a greater scavenging effect of DPPH, ABTS, and hydroxyl radical than the individual phenolic acids and glucans, as well as their physical mixtures. Taking GF as an example, the DPPH radical scavenging capacity ranked as GF (71.74%) > ferulic acid (49.50%) > PGF (44.43%) > β-glucan (43.84%). Similar trends were observed for ABTS radical scavenging (GF: 54.56%; ferulic acid: 44.37%; PGF: 44.95%; β-glucan: 36.42%) and hydroxyl radical elimination (GF: 39.16%; ferulic acid: 33.06%; PGF: 35.51%; β-glucan: 35.47%). In conclusion, the convenient preparation method and excellent antioxidant effect of the phenol–polysaccharide complexes from highland barley provide new opportunities for industrial-scale production, development, and design of healthy food based on these complexes. Full article

Experimental and theoretical studies were applied to investigate the adsorption properties of testagen (KEDG) peptide on copper surfaces in sodium chloride solution and, implicitly, its inhibition efficiency (IE) on metal corrosion. The tetrapeptide synthesized from the amino acids lysine (Lys), glutamic acid (Glu), aspartic acid (Asp), and glycine (Gly), named as H-Lys-Glu-Asp-Gly-OH, achieved an inhibition efficiency of around 86% calculated from electrochemical measurements, making KEDG a promising new copper corrosion inhibitor. The experimental data were best fitted to the Freundlich adsorption isotherm. The standard free energy of adsorption ($\mathsf{\Delta }{\mathrm{G}}_{\mathrm{a}\mathrm{d}\mathrm{s}}^{\mathrm{o}}$) reached the value of −30.86 kJ mol⁻¹, which revealed a mixed action mechanism of tetrapeptide, namely, chemical and physical spontaneous adsorption. The copper surface characterization was performed using optical microscopy and SEM/EDS analysis. In the KEDG presence, post-corrosion, SEM images showed a network surface morphology including microdeposits with an acicular appearance, and EDS analysis highlighted an upper surface layer consisting of KEDG, sodium chloride, and copper corrosion compounds. The computational study based on DFT and Monte Carlo simulation confirmed the experimental results and concluded that the spontaneous adsorption equilibrium establishment was the consequence of the contribution of noncovalent (electrostatic, van der Waals) interactions and covalent bonds. Full article

Separating azeotropes is an important, difficult, and expensive task, in particular for the 2-propanol–water mixture. The literature on the problem is rich in modeling studies but often lacking even the simplest experimental confirmation. In this paper, extractive distillation, liquid–liquid equilibrium-based extraction, and salting-out were experimentally tested for the desired separation. Among the four tested extractive distillation entrainers, none was able—in the investigated experimental setup—to push the system over the azeotropic composition threshold. Four novel hydrophobic deep eutectic extraction media were tested for the desired separation, and those based on menthol or thymol with decanoic acid were found most promising. Among 16 tested salting-out agents, 5 of them produced two-liquid phases, and only 4 hydrophilic inorganic salts promoted 2-propanol separation, with sodium carbonate being the most promising candidate. The purity of the products was tested with FTIR and ¹H-NMR. The experimental findings were compared with COSMO-RS model predictions, with moderate success. Full article

Rare earth metals (REMs) are vital for high-tech industries, but their extraction from secondary sources is challenging due to environmental and technical constraints. This study investigates the ion-exchange extraction of light REMs (neodymium, praseodymium, and samarium) from sulfuric and phosphoric acid solutions, modeling industrial leachates from apatite concentrates and phosphogypsum. The study considers the use of anion- and cation-exchange resins with different functional groups for efficient and environmentally safe REM separation. Experimental sorption isotherms were obtained under static conditions at 298 K and analyzed using a thermodynamic model based on the linearization of the mass action equation. Equilibrium constants and Gibbs energy were calculated, which reveals the spontaneity of the processes. Cation-exchange resins demonstrated high selectivity towards individual REMs, while anion-exchange resins were suitable for group extraction. Infrared spectral analysis confirmed the presence of sulfate and phosphate complexes in the resin matrix, clarifying the ion-exchange mechanisms. Thermal effect measurements indicated exothermic sorption on anion-exchange resins with negative entropy and endothermic sorption on cation-exchange resins with positive entropy. The findings highlight the potential of ion-exchange resins for selective and sustainable REM recovery, offering a safer alternative to liquid extraction and enabling the valorization of industrial wastes like phosphogypsum for resource recovery. Full article

The deterioration of freshwater ecosystems in anthropogenic wetlands is intensified due to phosphorus inputs from fertilizers applied in agricultural areas. In addition, managing the excess green waste generated in these ecosystems increases the complexity of the problem. To move towards a sustainable society based on the circular economy, the use of controlled combustion of green waste to obtain bioenergy—followed by the application of the resulting ash for phosphorus removal from freshwater bodies via adsorption processes—should be considered. Furthermore, those ashes could be used as natural fertilizers and incorporated into the cultivated fields. This paper presents a deep study of the adsorption of phosphorus ions using ashes from the main green waste produced in wetlands. Various experiments were conducted to determine the effects of different variables in the removal process. A double kinetic model was necessary to explain the presence of two different removal processes. The Langmuir model described the equilibrium isotherm data of both adsorbents through an endothermic process. Acidic pH in the initial solutions was preferred because it promotes phosphorus removal by calcium dissolution. The alkalinity did not have a substantial effect on the adsorbent capacity. Calcium was the element that had a more significant influence on the overall process. Finally, a removal study using blended materials was performed. A combined model was proposed and validated based on the original isotherm models for the pure materials. Full article

Propylene production through the CO₂-assisted oxidative dehydrogenation of propane (CO₂-ODP) is an effective route able to address the ever-increasing demand for propylene and simultaneously utilize CO₂. In this study, a series of alumina-supported gallium oxide catalysts of variable Ga₂O₃ loading was synthesized, characterized, and evaluated with respect to their activity for the CO₂-ODP reaction. It was found that both the catalysts’ physicochemical characteristics and performance were strongly affected by the amount of Ga₂O₃ dispersed on Al₂O₃. Surface basicity was maximized for the sample containing 20 wt.% Ga₂O₃, whereas surface acidity was monotonically increased with increasing Ga₂O₃ loading. A volcano-type correlation was found between catalytic performance and acid/base properties, according to which propane conversion and propylene yield exhibited optimum values for intermediate surface basicity and acidity, which both correspond to the sample containing 30 wt.% Ga₂O₃. The dispersion of a suitable amount of Ga₂O₃ on the Al₂O₃ surface not only enhances the conversion of propane to propylene but also suppresses the formation of side products (C₂H₄, CH₄, and C₂H₆) at temperatures of practical interest. The 30%Ga₂O₃-Al₂O₃ catalyst exhibited very good stability at 550 °C, where byproduct formation and carbon deposition were limited. Mechanistic studies indicated that the reaction proceeds through a two-step oxidative route with the participation of CO₂ in the abstraction of H₂, originating from propane dehydrogenation, through the reverse water–gas reaction (RWGS) reaction, shifting the thermodynamic equilibrium towards propylene generation. Full article

Small heat shock proteins (sHsps) are ubiquitous low-molecular-weight chaperones that prevent protein aggregation under cellular stress conditions. In the absence of stress, they assemble into large oligomers. In response to stress, such as elevated temperatures, they undergo conformational changes that expose hydrophobic surfaces, allowing them to interact with denatured proteins. At heat shock temperatures in bacteria, large sHsp oligomers disassemble into smaller oligomeric forms. Methanogens are a diverse group of microorganisms, ranging from thermophilic to psychrophilic and halophilic species. Accordingly, their sHsps exhibit markedly different temperature dependencies based on their optimal growth temperatures. In this study, we characterized sHsps from both hyperthermophilic and mesophilic methanogens to investigate the mechanisms underlying their temperature-dependent behavior. Using analytical ultracentrifugation, we observed the dissociation of sHsps from a mesophilic methanogen into dimers. The dissociation equilibrium of these oligomers was found to be dependent not only on temperature but also on protein concentration. Furthermore, by generating various mutants, we identified the specific amino acid residues responsible for the temperature dependency observed. The C-terminal region containing the IXI/V motif and the α-crystallin domain were found to be the primary determinants of oligomer stability and its temperature dependence. Full article

Investigating viable processes for the use of lignocellulosic biomass in clean fuels and high-value-added chemical products is essential for sustainable development. Large amounts of lignin are available every year as by-products of the paper and biorefinery industries, causing a series of problems, particularly environmental ones. Its structure and composition make lignin compatible with the concept of sustainability, since it can be used to produce new chemical products with high added value. As such, this study aims to extract lignin from green coconut fiber (LIG), with the subsequent impregnation of a sodium-octanoate-based surfactant (LIG-SUR), and determine its applicability as an adsorbent for removing copper ions from synthetic waste. To this end, the green coconut fiber lignocellulosic biomass was initially subjected to alkaline pre-treatment with 2% (w/v) sodium hydroxide in an autoclave. Next, the surface of the lignin was modified by impregnating it with sodium octanoate, synthesized from the reaction of octanoic acid and NaOH. The physical and chemical traits of the lignin were studied before and after surfactant impregnation, as well as after copper ion adsorption. The lignin was analyzed by X-ray fluorescence (XRF), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The adsorption tests were carried out using lignin pre-treated with surfactant in a batch system, where the effects of pH and adsorbent concentration were investigated. XRF and SEM analyses confirmed surfactant impregnation, with Na₂O partially replaced by CuO after Cu²⁺ adsorption. FTIR analysis revealed shifts in O–H, C–H, C=O, and C=C bands, indicating electrostatic interactions with lignin. Adsorption kinetics followed the pseudo-second-order model, suggesting chemisorption, with equilibrium reached in approximately 10 and 60 min for LIG-SUR and LIG, respectively. The Langmuir model best described the isotherm data, indicating monolayer adsorption. LIG-SUR removed 91.57% of Cu²⁺ and reached a maximum capacity of 30.7 mg·g⁻¹ at 25 °C and a pH of 6. The results of this research showed that pre-treatment with NaOH, followed by impregnation with surfactant, significantly increased the adsorption capacity of copper ions in solution. This technique is a viable and sustainable alternative to the traditional adsorbents used to treat liquid waste. In addition, by using green coconut fiber lignin more efficiently, the research contributes to adding value to this material and strengthening practices in line with the circular economy and environmental preservation. Full article

Chloride ions in zinc refining accelerate equipment corrosion and anode and cathode losses, increase lead content, and reduce zinc quality. Therefore, the removal of chloride ions has become a research priority. The existing copper slag dechlorination process has problems such as the solid film barrier leading to impeded mass transfer, product wrapping triggering active site coverage, and incomplete reactions due to insufficient reaction-driving force, leading to low utilization of copper slag, poor dechlorination efficiency, and long reaction times. To address these issues, a new method of deep dechlorination based on the reduction of Cu²⁺ by liquid-phase mass transfer is proposed in this paper. The process utilizes ascorbic acid as a reducing agent, establishes a homogeneous aqueous phase reaction system, breaks through the solid membrane barrier, and avoids the encapsulation of the product layer, achieving efficient dechlorination. The enol structure of ascorbic acid promotes rapid dechlorination through proton-coupled electron transfer (PCET). Thermodynamic calculations show that compared to the current copper slag dechlorination process, this method increases the reaction-driving force by 18.6%, reduces the Gibbs free energy (ΔG^θ) by 59.3%, and increases the equilibrium constant by 6.7 × 10⁹ times, making the reaction more complete and achieving a higher degree of purification. The experimental results show that under optimized conditions, the chloride ion concentration in the solution decreases from 1 g/L to 0.0917 g/L within 20 min, with a removal rate of 90.8%. The main precipitate is CuCl. This process provides a more efficient solution to the chloride ion contamination problem in the hydrometallurgical zinc refining process. Full article

Melt crystallization is a promising separation technique that produces ultra-high-purity products while consuming less energy and generating lower CO₂ emissions than conventional methods. However, accurately modeling melt crystallization is challenging due to significant non-idealities and complex phase equilibria in multicomponent systems. This study develops and evaluates two neural network-based surrogate models for acrylic acid melt crystallization: a stand-alone (black-box) model and a thermodynamically guided (hybrid) model. The hybrid model incorporates UNIQUAC-based solid–liquid equilibrium constraints into the learning process. This framework combines first-principles thermodynamic knowledge—particularly activity coefficient calculations and mass balance equations—with multi-output regression to predict key process variables. Both models are rigorously tested for interpolation and extrapolation, with the hybrid approach demonstrating superior accuracy even under operating conditions significantly outside the training domain. Further analysis reveals the critical importance of accurate solid–liquid equilibrium (SLE) data for thermodynamic parameterization. A final case study illustrates how the hybrid approach can quickly explore feasible operating regions while adhering to strict product purity targets. These findings confirm that integrating mechanistic constraints into neural networks significantly enhances predictive accuracy, especially when processes deviate from nominal conditions, providing a practical framework for designing and optimizing industrial-scale melt crystallization processes. Full article

In this research, a nanoscale magnetic biosorbent was synthesized by incorporating magnetic nanoparticles (Fe₃O₄ NPs) into a natural carbon framework derived from black cumin (BC) seeds. The prepared Fe₃O₄/BC was utilized as a low-cost, eco-friendly, and reusable nanobiosorbent for the removal of organic (e.g., methylene blue (MB) dye) pollutants from synthetic solutions. The results indicated that Fe₃O₄/BC had extensive surface oxygenous functional groups with a high affinity for MB dye capture at different concentrations such as 10–60 mg L⁻¹. The optimization results suggested the removal of ~99% of methylene blue from its initial concentration (i.e., 10 mg L⁻¹) using 2.0 g L⁻¹ of Fe₃O₄/BC at pH = 7, temperature = 27 °C, and contact time = 120 min, with equilibrium adsorption capacity = 5.0 mg g⁻¹ and partition coefficient = ~57.0 L g⁻¹. The equilibrium adsorption efficacy at the highest initial concentration (i.e., 60.0 mg L⁻¹) was found to be 29.0 mg g⁻¹. The adsorption isotherm was well explained by the Freundlich model for MB. The renderability of this magnetic bioadsorbent by acid treatments showed a ~66% decline in removal efficiency (%) (~99% to ~33%; ~5.0 to ~1.7 mg g⁻¹) for MB after six repetitive cycles of adsorption and desorption. The current Fe₃O₄/BC gives a better partition coefficient than previously reported acid-washed BC seeds and other BC-seed-based nanobioadsorbents, Hence, a synthesized Fe₃O₄/BC nanobiosorbent demonstrates potential for use in treating water contaminated with organic pollutants. Full article

In this study, chitosan (Chi) functionalized with the amino acid serine (Ser) was synthesized for the adsorption-based recovery of Pt(IV) from aqueous solutions. To identify the active functional groups of the amino acid and the support material, the synthesized adsorbent was characterized using SEM, FT-IR, and EDX analyses, and its point of zero charge (pH_PZC) was determined. Static and dynamic adsorption studies were conducted to optimize process parameters. Under static conditions, equilibrium studies established the maximum Pt(IV) concentration that could be adsorbed onto Chi–Ser, as well as its maximum adsorption capacity. At pH > 4, with an S-L ratio of 0.1 g:25 mL Pt(IV) solution, a contact time of 90 min, and a temperature of 298 K, the maximum adsorption capacity reached 7.23 mg/g. The adsorption process was best described by the Sips isotherm. The Taguchi method was employed to optimize static adsorption conditions. The Clark equation most accurately modeled the adsorption process under dynamic conditions. Additionally, multiple adsorption–desorption cycles evaluated the adsorbent’s reusability. Full article

In this work, the effects of dodecylamine storage state on the adsorption behavior of calcium sulfate dihydrate and silica were systematically investigated by using Raman detection, solution equilibrium calculation, and calculation based on density functional theory. The results show that the selective adsorption behavior of dodecylamine with calcium sulfate dihydrate and silica is closely related to its occurrence state. The adsorption of dodecylamine in the ionic state with calcium sulfate dihydrate and silica is dominated by the strong electrostatic adsorption between the H-O atoms under acidic conditions, while that of dodecylamine in the molecular state is dominated by the weak electrostatic adsorption between the Ca-N or Si-N atoms under alkaline conditions. Finally, by comparing the distribution coefficients and adsorption energies of the ionic/molecular states of dodecylamine with the change in pH, the reason why dodecylamine adsorbs calcium sulfate dihydrate more readily under acidic conditions was explained at the atomic level. Full article

Most novel active pharmaceutical ingredients have low water solubility; therefore, solubility-enhancing methods are applied. The aim of the present investigation is to study the impact of nine commonly used pharmaceutical excipients (fillers, surfactants, cyclodextrins, polymers) on solubility, permeability and their relationship. This is crucial for ensuring optimal bioavailability. Carbamazepine, naproxen and pimobendan were chosen as model compounds due to their different acid–base properties. Equilibrium solubility was measured by the traditional shake flask method. Effective permeability was determined by the PAMPA model. Measurements of ionizable compounds were carried out at three pH values. The pH-dependent change in the investigated parameters is maintained even in the presence of excipients. Fillers resulted in a slight or no effect, while the impact of other excipients showed a significant concentration dependence. The impact of excipients was influenced by the structure and ionization state of the molecules. The dominance of the ionized form moderates the impact of excipients. The changes in solubility were more pronounced than in the case of permeability. By examining the effect of the ionization state and interactions with excipients, this work supports the development of formulations that enhance solubility with minimal impacts on permeability. Additionally, it can serve as good basis for preformulation studies and design optimization. Full article

Soil plays a critical role as a natural barrier in mitigating the infiltration of industrial-derived phosphate pollution into groundwater, with its phosphate retention capacity governed mainly by its mineralogical composition. In this study, three soil samples were collected from the Huangmailing phosphate mine area, and the minerals responsible for phosphate retention were identified through batch adsorption experiments, chemical extraction, and spectroscopy analyses. The distribution of phosphate retention within soil samples was further quantified using a geochemical model. The results indicate that the adsorption capacity of soils to phosphate ranges from 0.193 to 0.217 mg/g. Adsorption equilibrium was reached at 750 min, conforming to the intra-particle diffusion kinetic model. Elevated temperatures facilitate phosphate adsorption. Under acidic and neutral conditions, approximately 80–90% of the phosphate is adsorbed onto iron oxides, primarily through inner-sphere surface complexation, thus unaffected by ionic strength. Under alkaline conditions, the retention mechanism was dominated by the release of exchangeable Ca²⁺ from vermiculite and biotite, as well as the precipitation of hydroxyapatite. Notably, the critical pH at which the retention mechanism shifts decreased with increasing content of layered silicate minerals and the concentration of cations in the solution. Our study underscores the distinct roles of effective minerals in phosphate retention under different pH conditions and highlights the significance of exchangeable Ca²⁺ in layered silicate minerals under alkaline conditions. Based on these findings, it is recommended that sites with favorable mineralogical characteristics tailored to the pH of phosphate-containing wastewater be prioritized for phosphorus chemical industries. This study also assesses the cost-effectiveness of adding vermiculite to soil in industrial and agricultural applications. The findings can provide a scientific basis for preventing groundwater phosphorus pollution in critical areas. Full article