Concentrated Solutions Research Articles

Comparative analysis of multi-effect evaporators in an ammonium acetate concentration process for L-methionine production

The process of treating an acetic acid aqueous solution generated during L-methionine production with ammonia and recovering a highly concentrated ammonium acetate aqueous solution using a multi-effect evaporator process was studied. The electrolyte non-random two-liquid model was applied to calculate the activity in the electrolyte solution, and the Hayden-O’Connell model was used to consider the dimerization reaction of acetic acid in the vapor phase. The dissociation equilibrium constant of acetic acid was modeled based on experimental values, and all other thermodynamic property models and parameters were used as implemented in the Aspen Plus software. Economic evaluation was carried out with various sensitivity tests, considering the loss of acetic acid and ammonia, as well as the steam cost. Evaporator operation was found to be more economical when the molar ratio of acetic acid to ammonia was equal, feed concentration was high, feed flow rate was low, and evaporator temperature was low. These results were confirmed in actual plant operations, with significant correlations between the feed flow rate and evaporator temperature. Our findings have significant implications for the development of sustainable and economical L-methionine production methods that enable the recycling of ammonium acetate.

Preparation of Graphene Oxide (GO) incorporated-Polyvinylidene Fluoride (PVDF) Nanofiltration Membrane with Alkaline Post-Treatment for Textile Wastewater Treatment

The purpose of this research is to study the potential of polyvinylidene fluoride (PVDF) polymer incorporated with graphene oxide (GO), following with the alkaline etching post-treatment process for dye waste water treatment. Its anti-oxidation properties of PVDF, have led to its choice as a host polymer due to its high thermal stability, great organic selectivity, and excellent chemical and mechanical resistance. In addition, the post-treatment with a NaOH solutions of varied concentration ranging from 0 M to 0.2 M for 30 minutes was conducted in alter the morphology of the fabricated membrane with the aim to increase the perm-selectivity of the membranes. Besides, the fabricated membranes were further characterized in terms of the chemical and physical properties using Fourier-Transform Infrared Spectroscopy (FTIR), Contact Angle (CA), Ultraviolet Visible spectroscopy (UV-Vis), Atomic Microscopy (AFM) and Scanning Electron Microscopy (SEM). The experimental results showed that the post-treatment has decreased the membrane flux of dye wastewater. Based on the obtained result, as the concentration of NaOH solution increased, the permeability increased. While the overall dye rejection of the membrane remained of above 90 %.

An oxidation flow reactor for simulating and accelerating secondary aerosol formation in aerosol liquid water and cloud droplets

Abstract. Liquid water in cloud droplets and aqueous aerosols serves as an important reaction medium for the formation of secondary aerosol through aqueous-phase reactions (aqSA). Large uncertainties remain in estimates of the production and chemical evolution of aqSA in the dilute solutions found in cloud droplets and the concentrated solutions found in aerosol liquid water, which is partly due to the lack of available measurement tools and techniques. A new oxidation flow reactor (OFR), the Accelerated Production and Processing of Aerosols (APPA) reactor, was developed to measure secondary aerosol formed through gas- and aqueous-phase reactions, both for laboratory gas mixtures containing one or more precursors and for ambient air. For simulating in-cloud processes, ∼ 3.3 µm diameter droplets formed on monodisperse seed particles are introduced into the top of the reactor, and the relative humidity (RH) inside it is controlled to 100 %. Similar measurements made with the RH in the reactor < 100 % provide contrasts for aerosol formation with no liquid water and with varying amounts of aerosol liquid water. The reactor was characterized through a series of experiments and used to form secondary aerosol from known concentrations of an organic precursor and from ambient air. The residence time distributions of both gases and particles are narrow relative to other OFRs and lack the tails at long residence time expected with laminar flow. Initial cloud processing experiments focused on the well-studied oxidation of dissolved SO2 by O3, with the observed growth of seed particles resulting from the added sulfuric acid agreeing well with estimates based on the relevant set of aqueous-phase reactions. The OH exposure (OHexp) for low RH, high RH, and in-cloud conditions was determined experimentally from the loss of SO2 and benzene and simulated from the KinSim chemical kinetics solver with inputs of the measured 254 nm UV intensity profile through the reactor and loss of O3 due to photolysis. The aerosol yield for toluene at high OHexp ranged from 21.4 % at low RH with dry seed particles present in the reactor to 78.1 % with cloud droplets present. Measurement of the composition of the secondary aerosol formed from ambient air using an aerosol mass spectrometer showed that the oxygen-to-carbon ratio (O : C) of the organic component increased with increasing RH (and liquid water content).

Why Single-Chain Nanoparticles from Weak Polyelectrolytes Can Be Synthesized at Large Scale in Concentrated Solution?

Here, the unresolved question of why single-chain nanoparticles (SCNPs) prepared from a weak polyelectrolyte (PE) precursor can be synthesized on a large is addresses, unlike SCNPs obtained from an equivalent neutral (nonamphiphilic) polymer precursor. The combination of the standard elastic single-chain nanoparticles (ESN) model -developed for neutral chains- with the classical scaling theory of PE solutions provides the key. Essentially, the long-range repulsion between electrostatic blobs in a weak PE precursor restricts the cross-linking process during SCNPs formation to the interior of each blob. Consequently, the maximum concentration at which PE-SCNPs can be prepared without interchain cross-linking is not determined by the full size of the PE precursor but, instead, by the smaller size of its electrostatic blobs. Therefore, PE-SCNPs can be synthesized up to a critical concentration where electrostatic blobs from different chains touch each other. This concentration can be 30 times higher than that for non-PE polymer precursors. Upon progressive dilution, the size of PE-SCNPs synthesized in concentrated solution increases until it reaches the bigger size of PE-SCNPs prepared under highly diluted conditions. PE-SCNPs do not adopt a globular conformation either in concentrated or in diluted solution. It shows that the main model predictions agree with experimental results.

Application of Cyrene solvent for the fabrication of polymethyl methacrylate, polyethyl methacrylate and composite films containing hydroxyapatite and diamonds

AbstractCyrene is a new biodegradable solvent, which represents a green alternative to many traditional toxic solvents for advanced polymers. Therefore, this investigation is motivated by interest in applications of Cyrene for polymer processing. The feasibility of solubilization of polymethyl methacrylate (PMMA) and polyethyl methacrylate (PEMA) in Cyrene is demonstrated. The ability to form relatively concentrated solutions of the high molecular mass polymers is an important factor for the formation of PMMA and PEMA films by a dip coating method. It was found that the polymer coatings provide corrosion protection of stainless steel in 30 g L−1 NaCl solutions. Another important finding is that the use of Cyrene facilitates the fabrication of stable suspensions of hydroxyapatite (HAp), microdiamond, and nanodiamond particles. Therefore, the problems of the dispersant selection for dispersion of chemically inert diamond and development of biocompatible dispersants are avoided using Cyrene. For the fabrication of composite films, HAp nanorods with reduced particle size are obtained using rutin as a chelating capping agent. Composite films containing HAp, microdiamond and nanodiamond in the PMMA or PEMA matrix are obtained. The composite films are promising for biomedical applications. It was found that the film morphology, composition and microstructure are influenced by the solvent–particle–polymer interactions and processing conditions.

An unenhanced 3D-FLAIR sequence using long repetition time and constant flip angle to image endolymphatic hydrops.

To evaluate a three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) sequence using a long repetition time (TR) and constant flip angle (CFA) in differentiating between perilymph and endolymph in a phantom study, and unenhanced endolymphatic hydrops (EH) imaging in a patient study. Three solutions in similar ion and protein concentrations with endolymph, perilymph, and cerebrospinal fluid were prepared for variable flip angle (VFA) 3D-FLAIR (TR 10,000 ms) and CFA (120°) 3D-FLAIR using different TR (10,000, 16,000, and 20,000 ms). Fifty-two patients with probable or definite Meniere's disease received unenhanced CFA (120°) 3D-FLAIR using a long TR (20,000 ms) and 4-h-delay enhanced CFA (120°) 3D-FLAIR (TR 16,000 ms). Image quality, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of them were compared. Agreement in the evaluation of the EH degree between them was analyzed. In the phantom study, CNRs between perilymphatic and endolymphatic samples of VFA 3D-FLAIR (TR 10,000 ms) and CFA 3D-FLAIR (TR 10,000, 16,000, and 20,000 ms) were 6.66 ± 1.30, 17.90 ± 2.76, 23.87 ± 3.09, and 28.22 ± 3.15 (p < 0.001). In patient study, average score (3.65 ± 0.48 vs. 4.19 ± 0.40), SNR (34.56 ± 9.80 vs. 51.40 ± 11.27), and CNR (30.66 ± 10.55 vs. 45.08 ± 12.27) of unenhanced 3D-FLAIR were lower than enhanced 3D-FLAIR (p < 0.001). Evaluations of the two sequences showed excellent agreement in the cochlear and vestibule (Kappa value: 0.898 and 0.909). The CFA 3D-FLAIR sequence using a long TR could be used in unenhanced EH imaging with high accuracy. Unenhanced imaging of endolymphatic hydrops is valuable in the diagnosis and follow-up of patients, especially those who cannot receive contrast-enhanced MRI. Ion and protein concentration differences can be utilized in differentiating endolymph and perilymph on MRI. Endolymphatic and perilymphatic samples could be differentiated in vitro on this 3D-FLAIR sequence. This unenhanced 3D-FLAIR sequence is in excellent agreement with the enhanced constant flip angle 3D-FLAIR sequence.

Nature of serpentinite interactions with low-concentration sulfuric acid solutions

Abstract The nature of serpentinite interaction with low-concentration sulfuric acid solutions is studied. Using IR-Fourier spectroscopy, X-ray, and serpentinite leaching with sulfuric acid solutions containing 10–60% of stoichiometrically required amount (SRA) of H2SO4 (taken relative to the molar magnesium content in serpentinite), it is shown that the appearance and influence of silica on the course of serpentinite dissolution is detected at concentrations of 30–40% of SRA of H2SO4. On the basis of the obtained results, this article points out the technological, economic, and ecological advantages of use of sulfuric acid solutions of low concentrations in the process of acid processing with the aim of producing magnesium salts.

АЛЛЕЛОПАТИЧЕСКАЯ АКТИВНОСТЬ ТРЕХРЕБЕРНИКА НЕПАХУЧЕГО (TRIPLEUROSPERMUM INODORUM (L.) SCH. BIP.)

The purpose of reseach was to study the allelopathic activity of T. inodorum in laboratory conditions against seeds and seedlings of watercress (Lepidium sativum L.). Objectives: to identify the effect of aqueous extracts of different concentrations of the dry aerial part of T. inodorum on the dynamics of germination and the initial growth of test plant seedlings; to compare the allelopathic effects of T. inodorum identified by two biotesting methods. We used classical methods for determining the allelopathic activity of plants by biotesting on seeds and seedlings of higher plants. The preparation of a concentrated (1 : 25) aqueous extract was carried out using the hot extraction method (4 g of the above-ground part of the three-rib was poured into 100 ml of boiling water and infused for 1 hour). By successively diluting the initial extract, solutions of lower concentrations were obtained (1: 50, 1: 100 and 1: 200). The results obtained indicate a high allelopathic activity of aqueous extracts of the dry aerial part of T. inodorum, which is expressed in a decrease in seed germination and inhibition of seedling growth. With an increase in the concentration of aqueous extracts of three-ribs, the sizes of the root and hypocotyl naturally decrease. Moreover, the most sensitive organ of the test plant is the root, the size of which at the weakest concentration (1: 200) decreases by almost 2 times, while the size of the hypocotyl decreases slightly. A more clear concentration dose-effect relationship was shown by the results of biotesting for root elongation. As the concentration of extracts increases, the size of watercress roots gradually decreases, and the toxicity index of aqueous extracts increases from 21.4 to 86.6 %.

Closer Approach towards the Preparation of Cellulose and Microcrystalline Cellulose from Corn Husks

AbstractIn this work, cellulose was effectively produced from corn husks by a simple and eco‐friendly method. Major influencing variables for cellulose extraction were examined, and the highest yield of lignin and hemicellulose cleavage was achieved after corn husks were treated in 12.5 wt % NaOH solution at solid/liquid ratio (S/L) of 1:10 g mL−1, 70 °C for 90 min. Subsequent bleaching conducted in 10 wt % H2O2 solution at 80 °C for 90 min produced cellulose with a lightness value (L*) of ∼87, chromaticity indexes a* = −1.85, b* = 2.94 with high purity, 90.86 %, and crystallinity, 64.94 %. Fourier transform infrared, scanning electron microscopy, and x‐ray diffraction analysis showed a clear transition in morphology, structure modification, and crystallinity consistent with the alteration of the chemical composition from raw material to delignified residue and the bleached one. To synthesize microcrystalline cellulose (MCC), the hydrolysis was investigated in H2SO4 solutions of different concentrations and durations via monitoring particle size distribution by laser diffraction spectroscopy. At the most efficient conditions (30 wt % H2SO4, 18 h, 45 °C, 1:10 S/L ratio), the obtained MCC reached an average particle size of 42.68 µm, crystallinity degree of 61.6 %, and cellulose purity of 92.5 %. Meanwhile, similar parameters with 4 N HCl solution produced MCC with the same purity but higher crystallinity (65.6 %), higher mean size, 67.62 µm, and higher aspect ratio. SEM images showed that 4 N HCl caused less detrimental and erosive action, and less fragmentation on cellulose microfibrils compared to 30 wt % H2SO4. The study's outcome supports the feasibility of corn husks to produce cellulose and MCC for further applications.

Influence of silica on the crystallization of sodium hydroaluminate

To extract aluminium from highly concentrated aluminate solutions of alumina-containing raw materials, decomposition is performed through the crystallization of sodium hydroaluminate. This paper presents the results of a study on the stability of aluminate solutions. To calculate the probable yield of Al2O3 in the solid phase, it is necessary to determine the crystallization rate of sodium hydroaluminate according to the composition of the initial solutions and the conditions of the process. The influences of SiO2 content on the decomposition of aluminate solutions with Na2Ok concentrations of 540 g/dm3 and 590 g/dm3 with and without inoculum were studied. In addition, the influence of silica on the appearance of precipitating crystals of sodium hydroaluminate was considered. A sharp increase in the stability of the aluminate solutions at rest in the presence of silica was observed. Different crystallization conditions for sodium hydroaluminate have been investigated. Silica slows the crystallization process of sodium hydroaluminate, affecting both the nucleation and crystal growth rates. The effect of SiO₂ on the rate of decomposition is similar to the reduction in the degree of supersaturation.

Investigating Key Volatile Compound Diffusion in Cocoa Beans during Yeast Fermentation-like Incubation.

An experimental setup was devised to investigate the permeability of cocoa bean seed coat and pulp to key volatile compounds during fermentation. Four labeled compounds (ethyl acetate-d3, ethyl octanoate-d15, 2-phenylethanol-d5, linalool-d5) and 2 unlabeled (beta-damascenone, delta-decalactone) were chosen for the investigation. The beans (cotyledons), depulped beans, or pulped beans were immersed separately in a concentrated solution of these volatile compounds at 36 or 46 °C for durations ranging from 3 to 120 h. The imbibed beans were dissected, and the cotyledons were analyzed by SPME-GC/MS. The diffusion of volatile compounds from the external solution to the seed was categorized into three groups: (1) not diffusible (ethyl octanoate-d15); (2) semidiffusible (ethyl acetate); and (3) totally diffusible (2-phenylethanol-d5, linalool-d5, beta-damascenone, delta-decalactone). The impact of the yeast on volatile compound diffusion was also investigated by immerging the pulped beans into the same concentrated solution with a yeast starter. Results highlighted the positive role of yeast in the diffusion of volatile compounds. The starter positively contributed to volatile compound diffusion after a transition phase occurring at approximately 48 h of fermentation, enriching the cocoa beans with key aromatic volatile compounds.

Mathematical analysis of non-linear boundary-value problems in reaction-diffusion model of chitosan-alginate microsphere using homotopy perturbation and Akbari-Ganji methods

This article describes the non-linear reaction-diffusion model, which depicts the behaviour of hydrogen peroxide production and glucose oxidation in the chitosan-alginate microsphere. Analytical solutions of glucose, oxygen, gluconic acid and hydrogen peroxide concentrations in planar coordinates under steady-state circumstances are obtained for all reaction-diffusion parameters. The non-linear boundary value problem's approximate analytical expressions are obtained using asymptotic techniques based on the homotopy perturbation and Akbari-Ganji method. The exact and commonly used MATLAB program provided a numerical simulation. It is demonstrated that the resulting analytical expressions strongly agree with the numerical outcomes reported in the literature. Furthermore, determining hydrogen peroxide flux and pH profiles within the microspheres are also discussed. The theoretical findings make it possible to forecast and enhance the efficiency of enzyme kinetics.

Extreme dependence of dynamics on concentration in highly crowded polyelectrolyte solutions.

Charge-carrying species, such as polyelectrolytes, are vital to natural and synthetic processes that rely on their dynamic behavior. Through single-particle tracking techniques, the diffusivity of individual polyelectrolyte chains and overall system viscosity are determined for concentrated polylysine solutions. These studies show scaling dependences of D ~ c-6.1 and η ~ c7.2, much stronger than theoretical predictions, drawing the applicability of power law fits into question. Similar trends are observed in concentrated solutions prepared at various pH and counterion conditions. These hindered system dynamics appear universal to polyelectrolyte systems and are attributed to the large effective excluded volumes of polyelectrolyte chains inducing glassy dynamics. The framework of the Vrentas-Duda free-volume theory is used to compare polyelectrolyte and neutral systems. Supported by this theory, excluding counterion mass from total polymer mass results in all environmental conditions collapsing onto a common trendline. These results are applicable to crowded biological systems, such as intracellular environments where protein mobility is strongly inhibited.

Hybrid super absorbent resin based on waste slag modified zeolite: A potential component adopted to agricultural water retention

The hybrid super absorbent resin (SAR), Poly(acrylicacid-co-acrylamide-co-2-acrylamido-2-methyl-1-propane sulfonic acid) based on zeolite synthesized from solid waste slag (P(AA-co-AM-co-AMPS)/zeolite) was synthesized. The chemical and structural characteristics of the materials were examined through FTIR, XRD, and SEM studies. In the presence of zeolite, the flat surface of the composite transformed into interconnected porous structure. The deionized water equilibrium swelling capacity of the hybridized SAR (835.79 g/g) was higher than that of the pure SAR (524.53 g/g). As much as 40 % of the water was released from the fully swollen hybrid SAR when it was centrifuged. P(AA-co-AM-co-AMPS)/zeolite had a swelling loss rate just of 27.64 % after five swelling/drying cycles. In addition, it still had good absorption in ionic salt solutions of different concentrations and good water retention at different temperatures. This confirmed that the hybridized SAR had excellent water holding capacity and salt solution adsorption. The FTIR and XRD results showed that the excellent performance of the hybridized SAR may originate from the interconnection of the zeolite and the pure SAR. The P(AA-co-AM-co-AMPS)/zeolite may be utilized as an agricultural water retaining agent.

Synthesis and photocatalytic activity of zinc-doped copper sulfide with porous nanotubes structures

Zinc-doped copper sulfide (Zn-doped CuS) particles were synthesized by a hydrothermal method in EG (EG) solutions of different concentrations. The results showed that the concentration of EG could regulate the structural morphology of Zn-doped CuS, and the Zn-doped CuS formed in pure EG had a porous nanotubular structure, and its photocatalytic degradation efficiency of methylene blue was as high as 96 % under visible light with good stability. SEM and TEM imaging confirmed that the diameter of the Zn-doped CuS with porous nanotubular structure was 100 nm, and the wall thickness was 30 nm. This study presents a strategy to enhance the photocatalytic activity and performance of CuS for environmental applications through EG concentration and zinc doping.

Morse index of concentrated solutions for the nonlinear Schrödinger equation with a very degenerate potential

Morse index of concentrated solutions for the nonlinear Schrödinger equation with a very degenerate potential

Cadmium Removal by Adsorption on Biochars Derived from Wood Industry and Craft Beer Production Wastes

Cadmium pollution is a serious environmental issue that has an impact on both the ecosystem and human health. As a result, its removal from water is essential. Agro-industrial wastes are suggested as a sustainable adsorbent option, as they are among the most readily available renewable sources worldwide. Biochar is a carbonized biomass that has been shown to be a viable and novel adsorbent. This article compares the results of cadmium adsorption on biochars derived from wood industry and craft beer production wastes. Biochars were characterized before and after adsorption. Batch adsorption results of 0.18 mmol/L Cd(II) concentration solutions indicated adsorption percentages (A%) of 99.7% and 92.2% for sawdust biochar and barley biochar, respectively. For this cadmium concentration, the sawdust biochar presented an adsorption capacity (qm) of 0.0172 mmol/L, while the barley biochar presented a value of 0.0159 mmol/L. The influence of initial Cd(II) concentration on single and multimetal solutions was studied, and a decrease in Cd(II) adsorption on sawdust biochar was observed in the presence of Ni(II) and Zn(II). The Freundlich isotherm model was found to be the best fit to the data for Cd(II) adsorption isotherms on both biochars. According to the results of this article, sawdust biochar has the best performance as an adsorbent and can be safely disposed of in building bricks at the end of its useful life.

Chaotropic Ions Mediated Polymer Gelation for Thermal Management.

Energy and environmental issues have increasingly garnered significant attention for sustainable development. Flexible and shape-stable phase change materials display great potential in regulation of environmental temperature for energy saving and human comfort. Here, inspired by the water absorption behavior of salt-tolerant animals and plants in salinity environment and the Hofmeister theory, highly stable phase change salogels (PCSGs) are fabricated through in situ polymerization of hydrophilic monomers in molten salt hydrates, which can serve multiple functions including thermal management patches, smart windows, and ice blocking coatings. The gelation principles of the polymer in high ion concentration solution are explored through the density functional theory simulation and verified the feasibility of four types of salt hydrates. The high concentration chaotropic ions strongly interacted with polymer chains and promoted the gelation at low polymer concentrations which derive highly-stable and ultra-moisturizing PCSGs with high latent heat (> 200 J g-1). The synergistic adhesion and transparency switching abilities accompanied with phase transition enable their smart thermal management. The study resolves the melting leakage and thermal cycling stability of salt hydrates, and open an avenue to fabricate flexible PCM of low cost, high latent heat, and long-term durability for energy-saving, ice-blocking, and thermal management.

Thermodynamic description of U(IV) solubility and hydrolysis in chloride systems: Pitzer activity model for the system U4+–Na+–Mg2+–Ca2+–H+–Cl––OH––H2O(l)

This study presents updated chemical, thermodynamic, and activity models for the system U4+–Na+–Mg2+–Ca2+–H+–Cl––OH––H2O(l) derived using the Pitzer formalism and a strict ion interaction approach. The models build on comprehensive solubility datasets in dilute to concentrated NaCl, MgCl2, and CaCl2 solutions. The Nuclear Energy Agency-Thermochemical Database (NEA-TDB) selection of solubility and hydrolysis constants in the reference state were taken as anchoring point, and were extended further with the solid nanocrystalline phase UO2∙H2O(ncr) and the ternary complex Ca4[U(OH)8]4+. The former was identified in long-term solubility experiments at ambient conditions, whereas the latter has been selected in analogy to Th(IV), Np(IV), and Pu(IV) considering experimental evidences available for these An(IV) in alkaline, concentrated CaCl2 solutions. These models represent an improved tool for the calculation of U(IV) solubility and aqueous speciation in a variety of geochemical conditions including concentrated brine systems relevant in salt-based repositories for nuclear waste disposal.

Simplified Universal Equations for Ionic Conductivity and Transference Number

Nernst-Einstein equation can provide a reasonable estimate of the ionic conductivity of dilute solutions. For concentrated solutions, alternate methods such as Green–Kubo relations and Einstein relations are more suitable to account for ion-ion interactions. Such computations can be expensive for multicomponent systems. Simplified mathematical expressions like the Nernst-Einstein equation do not exist for concentrated multicomponent mixtures. Newman’s treatment of multicomponent concentrated solutions yields a conductivity relation in terms of species concentration and Onsager phenomenological coefficients. However, the estimation of these phenomenological coefficients is not straightforward. Here, mathematical formulations that relate the phenomenological coefficients with the friction coefficients are developed, leading to simplified, ready-to-use expressions of conductivity and transference numbers that can be used for a wide range of ionic mixtures. This approach involves spectral decomposition of the matrix of Onsager phenomenological coefficients. The general analytical expressions for conductivity and transference number are simplified for binary electrolytes, and numerical solutions are provided for ternary and quaternary mixtures with ion dissociation.