High Solute Concentrations Research Articles

Small Amphiphile-Based Coacervation.

Coacervation plays an important role in the molecular assembly towards soft materials with a diversity of function (e. g., underwater adhesives of mussels and membraneless organelles). Coacervation is observed when one homogenous solution spontaneously separates into two immiscible liquid phases of low and high solute concentration, also known as liquid-liquid phase separation (LLPS), which enables spatiotemporally local concentration of specific molecules. LLPS is a common physical phenomenon in aqueous solutions of polyelectrolytes, surfactants and biomolecules, which has been extensively explored for applications in the fields of environmental remediation, cosmetic formulation, protein purification, extractive fermentation and pharmaceutical microencapsulation. This review summarizes the development of LLPS with low molecular weight amphiphiles to construct simple and complex coacervates using conventional surfactants and novel amphiphiles such as azobenzene-derivatives and peptides. We also highlight the applications of these amphiphile coacervates in the extraction of biomolecules, construction of protocell models and drug delivery.

Toward efficient broad-spectrum UV absorption of carbon dots: Facile preparation, performance characterization and its application as UV absorbers

UV absorbers are sustainable substances that inhibit the ultraviolet (UV) radiative degradation of polymers. In previous reports, the as-prepared carbon dots (CDs) possess only an absorption band at UVA (320–400 nm). To achieve broad-spectrum UV absorption (200–400 nm), increasing the concentration of the CDs solution becomes common. However, a high concentration solution seriously affects the light transmittance due to its heavy yellow color. Furthermore, the promising organic UV absorbers cannot achieve broad-spectrum UV absorption. In this work, we initially synthesized three-component water-soluble carbon dots (OP–CDs), which delivers an excellent UV absorption (98 % UVA and 100 % UVB at the concentration of 1.7 × 10−2 mg/mL; 99 % transmittance in visible light). Moreover, OP–CDs exhibit outstanding stability at high temperatures and different pH. With the corporation of OP–CDs and polyvinyl alcohol (PVA), a high-performance UV-shielding film was formed, leading to enhanced broad-spectrum UV shielding performance and improved mechanical properties, resistance of photocatalytic activity and anti-UV aging ability compared with pure PVA film. Notably, the PVA film remains high transparency with the addition of OP–CDs. The study suggests that the corporation of OP–CDs and polymers is effective in anti-UV degradation.

A Review on Current Nanofiber Technologies: Electrospinning, Centrifugal Spinning, and Electro‐Centrifugal Spinning

AbstractNanofiber‐based products are widely used in the fields of public health, air/water filtration, energy storage, etc. The demand for nonwoven products is rapidly increasing especially after COVID‐19 pandemic. Electrospinning is the most popular technology to produce nanofiber‐based products from various kinds of materials in bench and commercial scales. While centrifugal spinning and electro‐centrifugal spinning are considered to be the other two well‐known technologies to fabricate nanofibers. However, their developments are restricted mainly due to the unnormalized spinning devices and spinning principles. High solution concentration and high production efficiency are the two main strengths of centrifugal spinning, but beaded fibers can be formed easily due to air perturbation or device vibration. Electro‐centrifugal spinning is formed by introducing a high voltage electrostatic field into the centrifugal spinning system, which suppresses the formation of beaded fibers and results in producing elegant nanofibers. It is believed that electrospinning can be replaced by electro‐centrifugal spinning in some specific application areas. This article gives an overview on the existing devices and the crucial processing parameters of these nanofiber technologies, also constructive suggestions are proposed to facilitate the development of centrifugal and electro‐centrifugal spinning.

ANOVA of Cerium Chloride on Morphology and Metamorphosis Development in Tadpoles of C. melanogaster

In this experiment, the effects of 0.004 mg·L-1, 0.02 mg·L-1, 0.1 mg·L-1, and 0.5 mg·L-1 cerium chloride solutions on the growth and metamorphosis development of the tadpoles of the black spotted frog were investigated. The experimental results showed that cerium chloride solution at 0.5 mg·L-1significantly reduced the survival rate of tadpoles, which was 6.67% at 168h (7d) in the 0.5 mg·L-1 treatment compared with 93.3% in the blank control (lake water). The growth condition (body weight) at 168h (7d) (0.56 g) was different from that of the blank control (lake water) tadpoles (The growth (mass) of tadpoles at 0.5 mg·L-1 slowed down significantly in early development compared to the blank control (lake water) tadpoles (0.67g ± 0.05g); at the same time, we noticed that the tadpoles at 0.5 mg·L-1 concentration were in a dormant state of growth, and the mass was not significantly different compared to the beginning of the experiment. The metamorphosis time of tadpoles in the high concentration of cerium chloride salt solution (31 ± 5 days) was greater than that of the blank control tadpoles (26 ± 3 days). Tadpoles at concentrations of 0.02 mg·L-1, 0.1 mg·L-1, and 0.5 mg·L-1 were significantly heavier than the blank control tadpoles at metamorphosis. The results of this experiment indicated that moderate concentration levels of cerium chloride (0.004 mg·L-1, 0.02 mg·L-1) could significantly accelerate the growth and promote the metamorphosis development of the tadpoles of C. melanogaster.

Alkali lignin as a pH response bifunctional material with both adsorption and flocculation for wastewater treatment

Abstract Alkali lignin (AL) has attracted great attention as a material for treating dye wastewater due to its low cost and environmental friendliness. However, the unique structure and aggregation characteristics of AL regarding the dye wastewater removal mechanism have not been systematically revealed. Here, the removal process of typical cationic dye contaminants (methylene blue, MB) from dye wastewater by AL at different pH was explored and the unique synergistic effect mechanism of adsorption and flocculation was revealed. With increasing pH, the removal rate initially increased and then decrease. With increasing MB concentration, the optimal pH value corresponding to the maximum adsorption rate increased regularly. Zeta potential and Fourier transform infrared spectroscopy (FTIR) showed that electrostatic and π–π interactions and hydrogen bonding consisted push-pull balance under the influence of pH. In addition, scanning electron microscopy (SEM), ultraviolet and visible spectrum (UV) and particle size analysis showed that the aggregate structure and synergistic mechanism changed with the solution pH and concentration. In the low concentration solution, adsorption dominated. While in the high concentration solution, flocculation dominated. The removal mechanism consisted of the synergy of adsorption and flocculation laying the foundation for the efficient and environmentally friendly treatment of dye wastewater by AL.

Effective treatment of high-concentration SDBS solution by developing a novel integrated technology of foam separation and photocatalysis

With the rapid increasing drainage of industrial sewage, the problems arising from sewage containing high-concentration surfactant become more urgent. In order to purify the high-concentration surfactant solution, a novel integrated technology of foam separation and TiO2 photocatalysis was developed. An anionic surfactant of sodium dodecyl benzene sulfonate (SDBS) was used as the model surfactant and its initial concentration in the simulated solution was 0.5 g/L. First, foam separation had been performed to primitively reduce SDBS concentration in the simulated solution. Based on the results of independent factor test, a five-level-three-factor central composite design (CCD) based on response surface design (RSM) was used to predict the optimal experimental conditions. Under above conditions, the enriching proportion and removing percentage of SDBS were 4.69 ± 0.14 and 84.85 ± 0.71 %, respectively. The surface tension and foam stability of the residual solution after foam separation had been measured using pulling ring method and bubbling method, respectively. The residual solution after foam separation possessed a higher surface tension and weaker foam stability compared with those of freshly prepared SDBS solution. Extrinsic fluorescence spectra using pyrene showed that interfacial adsorption had led to the generation of hydrophilic SDBS micelles. In order to perform TiO2 photocatalysis, the adsorption capacity of SDBS on TiO2 nanoparticles had been studied. The adsorption of SDBS on TiO2 nanoparticles obeyed Pseudo-second-order dynamics model and Freundlich isotherm model. Based on the unique optical property and particle entrainment capacity of foam, a coupling operation of foam separation and TiO2 photocatalysis was proposed to degrade SDBS in the residual solution. The suitable operating conditions were identified and the maximum degradation percentage of SDBS reached 94.86 ± 1.06 %. The total SDBS removing percentage of developed technology was 99.38 ± 0.10 %. Total organic carbon (TOC) concentrations of SDBS solution before and after treatment were measured using combustion oxidation coupled nondispersive infrared absorption method. Finally, the economic analysis was carried out to assess the cost effectiveness of the integrated technology of foam separation and TiO2 photocatalysis.

Sequential treatment of simulated textile wastewater using zero-valent aluminum under alkaline conditions and biodegradation

The azo dye reactive yellow 145 (RY145) is inherently recalcitrant due to the presence of azo, ethyl sulfone and monochlorotriazine groups. This study explored removal of RY145 using zero valent aluminum (ZVAl) treatment under alkaline conditions followed by aerobic degradation using the bacterial strains Pseudomonas aeruginosa (RS1) and Thiosphaera pantotropha. During pretreatment using 1 g L−1 ZVAl at pH 11, 59% decolorization was observed after 30 min for 50 mg L−1 dye. However, even after carbon source supplementation, the supernatant could not support microbial activity due to the high aluminum concentration in solution at pH 11. After pH adjustment to neutral and Al(OH)3 precipitation, complete decolorization occurred and subsequently microbial degradation of the intermediates could be achieved. ZVAl pretreatment followed by biological treatment could cause an overall TOC reduction of 65% within 96 h. Sorption of dye on the precipitate only contributed to 13% dye removal. The bacterial cultures could utilize nitrogen from the dye intermediates formed after alkaline ZVAl treatment. The sequential treatment also reduced the concentration of total amines and phytotoxicity to Vigna radiata seeds. When a simulated textile wastewater containing 200 mg L−1 of RY145 was subjected to this sequential treatment, complete dye decolorization and 99.2% overall TOC reduction was observed in 30.5 h. The other compounds present in the synthetic wastewater facilitated decolorization as well as mineralization of the dye.

Microstructural Characteristics of 3Y-TZP Ceramics and Their Effects on the Flexural Strength

This work evaluates the effects of grain growth and tetragonality of the t-ZrO2 phase on the mechanical properties of 3Y-TZP ceramics. Samples were sintered at 1475 °C for 2 h, and at 1600 °C for 2, 12, or 24 h. After sintering, the tetragonal ZrO2 polytypes t and t′ were observed under all sintering conditions, while a residual content of monoclinic ZrO2 was detected in samples sintered at 1600 °C for 24 h. The average grain size was found to vary from 0.65 ± 0.10 to 2.20 ± 0.35 μm. Moreover, zirconia ceramics sintered at 1475 °C for 2 h exhibit higher flexural strength (1210 ± 85 MPa), while samples sintered at 1600 °C for 24 h exhibit the lowest flexural strength (910 ± 90 MPa). These results were related to the progressive formation of Y3+-rich grains (t′-ZrO2) due to the grain boundary segregation-induced phase (GBSIPT) mechanism. Due to the high stabilizer concentration in the solid solution, these grains present lower tetragonality, being highly stable at room temperature. Consequently, the observed strength reduction of samples sintered at 1600 °C for 24 h is related to the presence of the t′-ZrO2 phase, which is less prompt to the phase transformation toughening process, limiting shielding zones’ effectiveness at the crack tip.

Modeling on the phase equilibrium of gas hydrate in electrolytes containing system

The phase equilibrium of gas hydrate is fundamental for flow assurance, energy exploitation, and hydrate concerning technique. In this study, the electrolyte NRTL equation coupled with the two-step hydrate model of Chen and Guo was successfully applied to predict the phase equilibrium of gas hydrate in the presence of single and binary mixed electrolytes. The predicted results were in good agreement with the available experimental data over a wide range of electrolyte concentrations when taking into account the contributions of long-range and short-range interactions in saline solution. Validated with 943 hydrate experimental data of pure gas and gas mixture formed in single and mixed electrolytes, the average absolute deviations in pressure are 5.42 % and 4.71 %, respectively. More importantly, it is further investigated that the proposed model shows a better performance for the high-concentration saline solution with concentration up to the near-saturation, with an average deviation of 0.59 K for methane hydrate. Therefore, the proposed model in this work is significant for comprehending gas hydrate phase behavior in saline solution, and provides better guidance for hydrate exploitation and industrial applications.

Efficient dual-ions hybrid capacitive system for superior deionization with enhanced kinetics match

Capacitive deionization (CDI) is regarded as a promising water purification technology to tackle the global water crisis challenges. However, CDI technology is limited by the low capacity of harvesting more ions from highly concentrated feed water. This can be solved by coupling appropriate cathode with anode materials to enhance kinetics and capacities. In this study, a dual-ion hybrid capacitive deionization (HCDI) system was designed and constructed to enhance the charge efficiency and desalination capacity. The system consists of a BiOCl redox electrode and a capacitive electrode made of graphene-based MnO2 nanorods composite (MnGA). The BiOCl redox electrode was used to capture chloride ions and the MnGA capacitive electrode was employed to form an electric double layer for trapping sodium ions during discharging processes. It was found that a better capacitive electrode could realize the full potential of the counter redox electrode in the HCDI system. Consequently, the assembled dual-ion MnGA||BiOCl HCDI system showed enhanced kinetics characteristics in high-concentration NaCl solution with desalination capacity reaching 69.18 mg/g and charge efficiency of up to 75.21%. The satisfying kinetic match between anode and cathode has achieved optimized charge balance, which maximized the electrochemical performance of the HCDI system. This HCDI system was able to improve utilization efficiency, enhance desalination capacity, and achieve good stability at a low cost. Hence, it is promising for future practical deionization applications.

Solid solution softening and hardening in binary BCC alloys

Solute-dislocation interaction energies are calculated using Density Functional Theory and the 2-D lattice Greens function approach for Al, Ti, Cr, Fe, Zr, Nb, Mo, Ru, Hf, Ta, W, Re solutes in BCC Nb, Ta, Mo, and W. The predictions are then used in an extension of the Rao-Suzuki model to analyze the experimentally observed solid solution strengthening and softening in Nb-X, Fe-X, Ta-X, Mo-X and W-X crystals, X= Mo, W, Ta, Si or Re. DFT predictions for the solute dislocation interaction energies for Fe-Si, taken from the literature are also analyzed. The original Rao-Suzuki model considers kink migration controlled mobility of screw dislocations in body-centered cubic (BCC) structures and is valid for high solute concentrations (>5 at%) as well as above a critical temperature. Here, we extend the Rao-Suzuki model to include kink-pair nucleation statistics in the presence of solutes which is expected to be the rate limiting process at low temperatures (<0.2Tmelt). Such an extension should be valid up to low concentration of solutes as well as fairly low temperatures. The key parameters required for the model are solute – ½[111] screw dislocation interaction energies in pure Nb, Ta, Mo or W. These parameters were derived in this paper using first principles calculations. Using the calculated interaction energies, the model satisfactorily reproduces experimentally observed solution strengthening data in Nb-Mo, Nb-W, Nb-Re crystals at temperatures from 77 to 600K, for solute concentrations in the range 8.5 to 19 at% for Mo, 6 to 15 at.% for W and 5 to 9 at.% for Re. Similar agreement is found for strengthening/softening data for Ta-W, Ta-Re, Ta-Nb, Fe-Si, Mo-Re and W-Re crystals in the temperature range 77 – 600K. We also explore sensitivity of these predictions to the variation in the solute-dislocation energies. In Ta-W, a 10% variation (±0.015 eV) produces a modest change in solution hardening, which is within experimental error. The refined Rao-Suzuki model can be used in designing high strength, multi-component BCC alloys for high temperature applications.

Application of Reverse Electrodialysis Power for Oxygen Generation in Undersea Diving

With continued growth of marine exploration and underwater missions, there is a need to design new diving technologies. Currently, dive time is limited by scuba tank weight and volume. The use of an electrolysis system, powered by a battery, for driving chemical reactions could be introduced to produce a steady supply of oxygen during dives. However, batteries have a limited capacity, are heavy, and are detrimental to the environment when disposed. Developing an electrochemical technology that utilizes resources abundantly available to a diver (salt water) to drive the oxygen evolution reaction would expand the duration and sustainability of ocean dives. Reverse electrodialysis (RED) is a multi-membrane system that aims to convert salinity gradient energy into electrical energy. Redox mediators are typically used to convert ionic mixing into electricity at electrodes placed adjacent to a stack of membranes. However, replacing redox mediators with water splitting electrodes can enable the sustainable production of fuel (H2) and/or oxygen (O2). We aim to examine if a RED oxygen generation system could meet oxygen requirements for scuba diving. Evolving oxygen from water would enable the development of artificial gills, allowing for an inexhaustible supply of oxygen thus displacing the need to carry oxygen tanks. Here we propose a system where instead of an air tank, a diver carries a RED cell, a 2 L volume of dilute solution, and a cylinder of other compressed gases for breathing (Fig. 1a). A RED cell is comprised of a stack of alternating anion and cation exchange membranes separated by channels of high and low concentration solutions (HC and LC) (Fig. 1b). A stack is made up of repeating units, which consist of a pair of selective membranes and a pair of solution channels, between the anode and cathode chambers. Salt ions in solution migrate due to the concentration gradient and two redox based electrodes convert this ionic flux into electric flux. We show here that the oxygen evolution activation overpotentials are a significant fraction of internal resistance (77%) in a RED system with a small number of cell pairs (N=5). However, this resistance is nearly negligible (3.2%) as the number of cell pairs increases (N=500). We further compare the RED systems to four different battery-electrolysis systems (Li-ion, Ni-MH, Ni-Cd, and lead acid) to contextualize the performance of the RED oxygen generation system with competing technologies. For large (N=100+) systems and long (10 hr) dives, RED is comparable in size to a battery-electrolysis system. With 500 membrane pairs, a RED powered diving system is 10.8 L and weighs 29 kg. Typical 12 L scuba tanks weigh 16 kg, and the size of a Li-ion battery powered electrolysis system for a 1 hour dive is, 2.2 L and 3.5 kg (19.2 L and 32.6 kg for a 10 hour dive).Figure 1. (a) Configuration of a RED cell for scuba divers using the surrounding seawater, a fixed dilute volume, and a fixed volume of additional gases for breathing carried by the diver. (b) Schematic of RED cell. Oxygen and hydrogen are produced at the anode and cathode by redox reactions. Figure 1

Human embryonic stem cells cultured on hydrogels grafted with extracellular matrix protein-derived peptides with polyethylene glycol joint nanosegments.

Human pluripotent stem cells (hPSCs) can be proliferated on completely synthetic materials under xeno-free cultivation conditions using biomaterials grafted with extracellular matrix protein (ECM)-derived peptides. However, cell culture biomaterials grafted with ECM-derived peptides must be prepared using a high concentration of peptide reaction solution (e.g. 1000μg/ml), whereas the ECM concentration of the ECM-coated surface for hPSC culture is typically 5μg/ml. We designed a polyethylene glycol (PEG) joint nanosegment (linker) to be used between base cell culture biomaterials and bioactive ECM-derived peptides to enhance the probability of contact between ECM-derived peptides and cell binding receptors of hPSCs. Vitronectin-derived peptides with glycine joint nanosegments (GCGG) were conjugated onto poly (vinyl alcohol-co-itaconic acid) hydrogels via PEG joint nanosegments, and human embryonic stem cells (hESCs) were cultivated on these hydrogels. hESCs could successfully be cultivated on hydrogels while maintaining their pluripotency and differentiation potential to differentiate into cells that are induced from three germ layers in vitro and in vivo, where only a 50μg/ml ECM-derived peptide concentration was used when the PEG joint nanosegments were introduced into peptides that were grafted onto hydrogel surfaces. The joint nanosegments between bioactive peptides and base cell culture biomaterials were found to contribute to efficient hESC attachment and proliferation.

Mechanical, electrical properties and microstructures of combinatorial Ni-Mo-W alloy films

Nickel-molybdenum-tungsten (Ni-Mo-W) alloys have been suggested for applications of advanced micro-electro-mechanical systems (MEMS) in extreme environments due to their high strength, good electrical conductivity, and excellent thermal stability. In this work, we have carried out combinatorial experiments to reveal composition-dependent phase formation, physical properties, and thermal stability of Ni-Mo-W alloy films. Combinatorial synthesis through a magnetron sputtering process fabricated thin films with a composition range of Ni 56–92 Mo 6–38 W 0.5–7.5 . Structural analysis for the as-deposited combinatorial film revealed that a nanotwinned and strongly textured nano-columnar fcc structure was formed in the Ni-rich compositions, while solute content greater than 30% resulted in the formation of metallic glasses. The specimen exhibited very high hardness (8.8–12.5 GPa) and moderate electrical resistivity (85–135 μΩ ∙ cm), and both the properties were found to increase with solute concentration. Annealing of the combinatorial film at 600 ℃ for 1 h revealed that nanotwinned structure is thermally stable for high Ni concentrations. Metallic glasses with high solute concentration also exhibited high thermal stability and were not crystallized after annealing. Alloys with intermediate solute content experienced the transformation from the amorphous to fcc nanocrystalline phase with nanotwins. The annealed combinatorial film maintained high hardness and moderate electrical resistivity after annealing. • Composition-dependent phase formation and physical properties of Ni 56–92 Mo 6–38 W 0.5–7.5 alloy films were investigated. • A nanotwinned (NT) and nano-columnar fcc structure was formed in the Ni-rich compositions. • The solute content greater than 30% resulted in the formation of metallic glasses. • The specimen exhibited high hardness (8.8–12.5 GPa) and moderate electrical resistivity (85–135 μΩ · cm). • The NT structure with high Ni content and metallic glasses with high solute concentration were thermally stable.

Research on the Ammonia Removal from Synthetic Wastewater by Electrodialysis and Electrodeionization

In this work, the technical capabilities of lab-scale electrodialysis (ED) and the electrodeionization (EDI) processes on removing ammonia from synthetic wastewater were investigated. The overall performance of ED and EDI process in the removal of ammonia from high ammonia concentration synthetic wastewater was assessed by applied electric potential, feed concentration, and energy consumption. Under the conditions of working electric potential, ED showed that ammonia concentration could be reduced from 1,000 to 309 mg/L with a best removal efficiency of 69.1%, EDI showed that the ammonia concentration could be reduced from 1,000 to 120.9 mg/L with a best removal efficiency of 87.91%, the energy consumption of ED and EDI were in the range of 1.7–12.96 Wh/L and 6.2–149.2 Wh/L, respectively. Under the conditions of feed concentration, ED and EDI obtained a best removal efficiency of 57.93% and 98.5%, respectively, the energy consumption was in the range of 9.36–53.55 Wh/L and 62.7–218.1 Wh/L, respectively, excessive applied electric potential and concentration will lower current efficiency and increase energy consumption. The ammonia removal efficiency of EDI was found to be higher than ED, but the current efficiency of EDI was lower than ED, and the stack current of EDI increased quickly under constant voltage when the feed concentration was over 1,000 mg/L. The results showed that EDI was suitable for low concentration solution treatment, whereas ED was suitable for high concentration solution treatment. As a novel technology of groundwater contamination treatment, the process was proved to be feasible and provided foundation for further research.

Study on Droplet Impact and Spreading and Deposition Behavior of Harvest Aids on Cotton Leaves.

The deposition and spreading of pesticide droplets on the surface of plants is a severe challenge to precise pesticide application, which directly affects the pesticide utilization rate and efficacy. Cotton harvest aids are widely used in machine-picked cotton but the effect of formulation and concentration on the droplet behavior and defoliation effect of cotton defoliants is not clear. To clarify the influence of formulation and concentration on the droplet behavior of cotton defoliants, four formulations (suspension concentrate (SC), water dispersible granule (WG), oil dispersion (OD), and wettable powder (WP)) of cotton defoliants were used to prepare different concentrations of harvest aid solutions, according to the spraying volume. The physicochemical properties, droplet impact, and spreading and deposition behavior were studied. The results indicated that the four kinds of harvest aids have good physicochemical properties and can be wet and spread on cotton leaves. The surface tension of the high-concentration harvest aid solution (the spraying volume was less than 1.2 L/667 m2) was increased, which increased the contact angle and reduced the adhesion tension, adhesion work, and the spreading area. Once the harvest aid solution systems impacted the cotton leaves, it could spread to the maximum in a short time (10 ms). The field experiment showed that the droplet spectrum of harvest aids changed slightly, the coefficient of variation (CV) did not exceed 50%, and the defoliation rate was better when the spraying volume was 1.5 L/667 m2. The correlation and principal component analysis showed that the spraying volume (concentration) and coverage were negatively correlated with the defoliation rate, while the viscosity, diffusion factor, and spreading rate were positively correlated with the defoliation rate. Overall, the use of appropriate spraying volume application in cotton fields can improve the performance of spray, increase the effective deposition and wetting spread of defoliants on cotton leaves, further reduce the dosage of defoliants, and improve pesticide utilization. These results can provide a theoretical basis for the scientific preparation and spraying of cotton harvest aid solutions.

THE INFLUENCE OF THE PRECURSOR COMPOSITION ON THE PECULIARITIES OF THE BARIUM TITANATE FORMATION

In the process of obtaining barium titanate by the Pechini method, a connection between the conditions of complexes precipitation and the nature of their thermal decomposition was established. X-ray phase analysis of thermally decomposed precursors showed that the formation of a single-phase system based on barium titanate can be achieved in the range of Ba/Ti ratio 0.96-1.01 at high reagent concentration and low solution pH during the precursor deposition process. On the basis of thermogravimetric analysis, a possible mechanism of precursor decomposition and its composition is assumed. It is shown that the number of hydroxide groups in the structure affects the crystallization mechanism, total mass loss, and the amount of water adsorbed on the surface. In particular, samples obtained at low solution pH have a minimal amount of hydroxyl groups and decompose according to a typical four-step mechanism of thermal decomposition of barium titanyl oxalate. Other samples contain hydro and carbo groups, which leads to an increase in the final decomposition temperature above 770 °C and a multistage decomposition process due to the difference in the activation energy of the nucleation of different phases. This, in turn, may determine the dominance of the nucleation process over the growth and nucleation of smaller crystallites, compared to the product of pure oxalate decomposition. On the one hand, the high content of chloride ions at the lowest pH promotes the crystallization of the product and the formation of additional nucleation centers from the phase of amorphous titanium dioxide. On the other hand, the formation of smaller crystallites occurs due to the absence of significant particle collisions in conditions of low concentration of the solution. On the basis of thermogravimetric analysis, it is shown that at high concentration, barium titanyl oxalate decomposes mainly by the mechanism of formation of intermediate oxycarbonates, and not barium carbonate and titanium dioxide. Thus, the optimization of the precursor precipitation parameters and the study of the barium titanate formation mechanism allow for better regulation of the composition and crystallite size of the final product.

Mango enriched with sucrose and isomaltulose (Palatinose®) by osmotic dehydration: Effect of temperature and solute concentration through the application of multilevel statistical models

Osmotic dehydration (OD) is useful for the enrichment of mangos with interesting solutes. Isomaltulose has healthier properties than sucrose and its use is still scarce in OD processes. The OD of mangos with isomaltulose and sucrose was evaluated, and the effect of solute concentrations (25%, 30%, 35%) and temperatures (25, 35, 45°C) was estimated by multilevel statistical analysis in order to find the best conditions for a greater water loss (WL) and solid gain (SG). In sucrose OD, the highest concentration (35%) had the greatest effect than the temperature for WL and SG. For isomaltulose OD, the concentration provided greater WL and SG, but the effect of temperature was slightly more expressive for SG than WL. The maximum working conditions (35% of isomaltulose or sucrose and 45°C) promoted greater WL and SG for both carbohydrates, and with the OD it was possible to enrich mango with isomaltulose by taking advantage of the osmotic gradient, getting an osmodehydrated product with low glycemic and isulinemic indexes. Novelty impact statement Through the osmotic dehydration, it is possible to enrich mango samples with isomaltulose due to its healthy attributes. Instead, a traditional statistical analysis, the multilevel statistical modeling was applied, which was suitable for evidence that the highest solute concentration and temperature conditions promoted the greatest water loss and solid gain, favoring the enrichment process.

Composite-polymer modified bentonite enhances anti-seepage and barrier performance under high-concentration heavy-metal solution

Modified bentonite (MB) was prepared with acrylic acid and sodium carboxymethyl cellulose as monomers, which was characterized with carboxyl and hydroxyl groups on a coverage film. The adsorption capacities for Cd2+ and Pb2+ were increased to 222.41 mg/g and 397.17 mg/g, respectively, indicating that Cd2+ was less competitive than Pb2+. Multiple adsorption kinetics and isotherms indicated that the Cd2+ adsorption by MB was dominated by ion exchange, while Pb2+ adsorption was a combination of physical adsorption and ion exchange. The positron annihilation lifetime (PAL) further indicated that the adsorption of both Cd2+ and Pb2+occurred in the interlayer micropores of MB. Regarding to the chemical compatibility of MB, its free swelling index (FSI) and the hydraulic conductivity reached 85 mL/2 g and 5.87 × 10−11 m/s in deionized water, respectively. In high-concentration Cd2+ and Pb2+ solutions, MB maintained a lower permeability in the Cd2+ solution. The mechanism can be speculated that appropriate adsorption capacity of Cd2+ by MB results in higher content of trapped polymers as polymer blockage in MB, which contributed to maintain impermeability under high-concentration heavy-metal solution.

Glucose Determination by a Single 1535 nm Pulsed Photoacoustic Technique: A Multiple Calibration for the External Factors.

Photoacoustic spectroscopy has been proved to be a potential method for noninvasive blood glucose detection. We used 1535 nm pulsed laser to excite photoacoustic signal in glucose solution and then explored the influence of different glucose concentration on photoacoustic signal to analyze the sensitivity of photoacoustic signal to glucose at this wavelength. We designed a simple photoacoustic cell structure, which used a focused ultrasonic transducer to receive signals, so as to reduce signal attenuation. In terms of the results, we have found that for high-concentration glucose solutions, the results have strong linearity and discrimination, and when the concentration is close to the human body level, the signal difference is not so obvious. Therefore, we explore the external factors affecting the photoacoustic signal in detail and propose a calibration method. Through calibration, the signal generated by the low-concentration glucose solution also has a good linearity.