Ion Concentration In Solution Research Articles

Determination of Pb(II) ion Adsorption Isotherm Model by Regenerated Spent Bleaching Earth (RSBE)

Waste water from several industries such as paint plant, printing, tin smelting, plastic factory, also fuel leaking from ships and ship welding are the main causes of the presence of Pb(II) ions in the water. Lead is a heavy metal that can adversely affects all organisms in the waters and can accumulate in the food chain, it is harmful to human and animal if exposed to it. Adsorption is one of the technologies for separating dissolved metal ions in liquid that easy handling and very effective. The concentration of heavy metal ions in solution can be reduced by using a adsorbent, such as zeolte, activated charcoal, regenerated spent bleaching earth (RSBE). Spent bleaching earth (SBE) is a disposal from edible of the bleaching unit in oil refinery industries, it can be regenerated to a adsorbent RSBE. The treatment SBE into RSBE, oil of SBE is separated by the solvent extraction method at 72°C for 5 hours with n-hexane as a solvent, followed by washing it with HCl 3%, then physically activated at 470°C for 12 hours. The goal of this study are to increase SBE value and reduce the level of Pb(II) ions in solution with RSBE. Several works done in this study, namely characterization of SBE and RSBE, determination of the absorption capacity of RSBE against Pb (II) ions at equilibrium conditions, and an adsorption isotherm model of Pb (II) ion by RSBE. Results, RSBE has a specific surface area of 165.88 m2/g, a total pore volume of 0.21 cc/g with an average pore diameter of 6.90 nm. Based on these values, RSBE is categorized as a mesoporous adsorbent. The adsorption of Pb (II) ion by RSBE reaches equilibrium after 150 minutes contact time.The adsorption Pb (II) ion by RSBE is follows the Langmuir isotherm adsorption model with a correlation coefficient (R2) value of 0.9935 and a maximum adsorbing capacity value of 4.29 mg Pb (II)/g RSBE.

Preclinical evaluation of acute systemic toxicity of magnesium incorporated poly(lactic-co-glycolic acid) porous scaffolds by three-dimensional printing.

ABSTRACTBiodegradable polymer scaffolds combined with bioactive components which accelerate osteogenesis and angiogenesis have promise for use in clinical bone defect repair. The preclinical acute toxicity evaluation is an essential assay of implantable biomaterials to assess the biosafety for accelerating clinical translation. We have successfully developed magnesium (Mg) particles and beta-tricalcium phosphate (β-TCP) for incorporation into poly(lactic-co-glycolic acid) (PLGA) porous composite scaffolds (PTM) using low-temperature rapid prototyping three-dimensional-printing technology. The PTM scaffolds have been fully evaluated and found to exhibit excellent osteogenic capacity for bone defect repair. The preclinical evaluation of acute systemic toxicities is essential and important for development of porous scaffolds to facilitate their clinical translation. In this study, acute systemic toxicity of the PTM scaffolds was evaluated in mice by intraperitoneal injection of the extract solutions of the scaffolds. PTM composite scaffolds with different Mg and β-TCP content (denoted as PT5M, PT10M, and PT15M) were extracted with different tissue culture media, including normal saline, phosphate-buffered saline , and serum-free minimum essential medium , to create the extract solutions. The evaluation was carried out following the National Standard. The acute toxicity was fully evaluated through the collection of extensive data, including serum/organs ion concentration, fluorescence staining, and in vivo median lethal dose measurement. Mg in major organs (heart, liver, and lung), and Mg ion concentrations in serum of mice, after intraperitoneal injection of the extract solutions, were measured and showed that the extract solutions of PT15M caused significant elevation of serum Mg ion concentrations, which exceeded the safety threshold and led to the death of the mice. In contrast, the extract solutions of PT5M and PT10M scaffolds did not cause the death of the injected mice. The median lethal dose of Mg ions in vivo for mice was determined for the first time in this study to be 110.66 mg/kg, and the safety level of serum magnesium toxicity in mice is 5.4 mM, while the calcium serum safety level is determined as 3.4 mM. The study was approved by the Animal Care and Use Committee of Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences (approval No. SIAT-IRB-170401-YGS-LYX-A0346) on April 5, 2017. All these results showed that the Mg ion concentration of intraperitoneally-injected extract solutions was a determinant of mouse survival, and a high Mg ion concentration (more than 240 mM) was the pivotal factor contributing to the death of the mice, while changes in pH value showed a negligible effect. The comprehensive acute systemic toxicity evaluation for PTM porous composite scaffolds in this study provided a reference to guide the design and optimization of this composite scaffold and the results demonstrated the preclinical safety of the as-fabricated PTM scaffold with appropriate Mg content, strongly supporting the official registration process of the PTM scaffold as a medical device for clinical translation.

Poly(2-Hydroxyethyl methacrylate-co-N,N-dimethylacrylamide)-Coated Quartz Crystal Microbalance Sensor: Membrane Characterization and Proof of Concept.

Application-oriented hydrogel properties can be obtained by modifying the synthesis conditions of the materials. The purpose of this study is to achieve customized properties for sensing applications of hydrogel membranes based on poly(2-hydroxyethyl methacrylate), HEMA and N,N-dimethylacrylamide, DMAa. Copolymer p(HEMA-co-DMAa) hydrogels were prepared by varying the DMAa monomer ratio from 0–100% in 20% increments. Hydrogel membranes were characterized by attenuated infrared spectroscopy. Swelling and sorption were evaluated using cation solutions. Copolymers were also synthesized on the gold surface of quartz crystal microbalances (QCM) as coating membranes. A proof of concept was conducted for approaching the design and development of QCM sensors based on P(DMAa-co-HEMA)-membranes. Results showed that the water and ion adsorption capacity of hydrogel membranes increased with higher DMAa content. Membranes are not selective to a specific location but did show different transport features with each cation. The QCM coated with the selected membrane presented linear relationships between resonance frequency and ions concentration in solution (10–120 ppm). As a consequence, hydrogel membranes obtained are promising for the development of future biosensing devices.

Effect of Detergents on Activity and Magnesium-Dependent Properties of Different Isoforms of Na+,K+-ATPase in the Crude Membrane Fraction of Rat Cerebral Cortex.

We studied the effect of various detergents (Tween-20, Triton X-100, and sodium deoxycholate) on activity and magnesium-dependent properties of Na+,K+-ATPase of the crude membrane fraction of rat cerebral cortex. All studied detergents significantly increased activity of the studied enzyme in a concentration-dependent manner. Sodium deoxycholate provided significantly higher values Na+,K+-ATPase activity (by ≈50%) than Triton X-100 and Tween-20. In the presence of Triton X-100, a changed pattern of the dependence of enzyme activity on the concentration of magnesium ions in the incubation solution was noted. Separate measurement of activities of Na+,K+-ATPase isoforms made it possible to assume that changes in magnesium-dependent properties are due to the predominant effect of Triton X-100 on ouabain-sensitive α2- and α3-isoforms.

Visualization of Ion|Surface Binding and In Situ Evaluation of Surface Interaction Free Energies via Competitive Adsorption Isotherms.

Function and properties at biologic as well as technological interfaces are controlled by a complex and concerted competition of specific and unspecific binding with ions and water in the electrolyte. It is not possible to date to directly estimate by experiment the interfacial binding energies of involved species in a consistent approach, thus limiting our understanding of how interactions in complex (physiologic) media are moderated. Here, we employ a model system utilizing polymers with end grafted amines interacting with a negatively charged mica surface. We measure interaction forces as a function of the molecule density and ion concentration in NaCl solutions. The measured adhesion decreases by about 90%, from 0.01 to 1 M electrolyte concentration. We further demonstrate by molecular resolution imaging how ions increasingly populate the binding surface at elevated concentrations, and are effectively competing with the functional group for a binding site. We demonstrate that a competing Langmuir isotherm model can describe this concentration-dependent competition. Further, based on this model we can quantitatively estimate ion binding energies, as well as binding energy relationships at a complex solid|liquid interface. Our approach enables the extraction of thermodynamic interaction energies and kinetic parameters of ionic species during monolayer level interactions at a solid|liquid interface, which to-date is impossible with other techniques.

D-spacing controllable GO membrane intercalated by sodium tetraborate pentahydrate for dye contamination wastewater treatment

Sodium tetraborate pentahydrate (STB) was intercalated into graphene oxide (GO) nanosheets to form a nanocomposite (STB@GO). Subsequently, it was self-assembled on a substrate membrane to prepare STB@GO nanofiltration membrane. The properties of the STB@GO powder samples and the nanofiltration membrane were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), contact angle (CA), and zeta potential. When the STB concentration was 1.0 g/L in the cross-linking reaction, the membrane was described as the STB2@GO membrane and exhibited a large interlayer space (d-spacing = 1.347 nm), high hydrophilicity (CA = 22.2°), and high negative potential (zeta = −18.0 mV). Meanwhile, the pure water flux of the membrane was significantly increased by 56.60% than that of the GO membrane. In addition, the STB2@GO membrane exhibited a favorable capability for dye rejection,98.52% for Evans blue (EB), 99.26% for Victoria blue B (VB), 91.94% for Alizarin yellow (AY), and 93.21% for Neutral red (NR). Furthermore, the STB2@GO membrane performed better in dye separation under various types and concentrations of dye, pH values, and ions in solution. Thus, this study provides a promising method for preparing laminated GO nanofiltration membranes for dye wastewater treatment.

Mechanical Damage and Chemical Dissolution Kinetic Features of Limestone under Coupled Mechanical-Hydrological-Chemical Effects

To address the mechanical damages of limestone under the coupled mechanical(M)-hydrological(H)-chemical(C) effects, we performed uniaxial compression experiments and dissolution kinetics experiments on limestone in flowing and static solutions for different lengths of time. Through experiments, the peak strengths of the limestone under coupled MHC effects for different time lengths and the major ion concentrations in solutions were obtained. By analyzing the strength damage and chemical dissolution kinetic characteristics, we achieved the strength damage equations and chemical dissolution kinetic equations. Results show that when the solution shifted from the static state to the flowing state, and as its acidity increased, the peak strength loss of the limestone rose as well. The solution mobility had a more significant impact on the peak strength loss than the solution pH value. The limestone dissolution in flowing water was higher than in static water, indicating that solution mobility would promote the limestone dissolution. Among the contributing factors to limestone dissolution, the solution pH value showed the strongest impact, followed by the common-ion effect and then the salt effect. The research result is expected to provide a theoretical basis for maintaining the stability of rocks in geotechnical engineering practice and protection of stone cultural relics.

Release of Mg and Fe From the Octahedral Sheets During the Transformation of Montmorillonite Into Kaolinite

AbstractIsomorphous substitutions of Mg and Fe for Al generally appear in the octahedral sheets of montmorillonite, whereas they are infrequent in kaolinite. Therefore, the release of Mg and Fe from the octahedral sheets probably happens during the transformation of montmorillonite into kaolinite, which could affect the migration of Mg and Fe from clay minerals into surrounding environments. The objective of the current study was to investigate the relationship between Mg and Fe release during the transformation of montmorillonite into kaolinite. The results showed that the d060 value of clay minerals decreased slightly, and the intensities of both the AlMg–OH and AlFe–OH bending vibrations also decreased gradually. In addition, the (Mg+Fe)/Al (major octahedral ions) atomic ratio of kaolinite was lower than that of montmorillonite, especially in identical hydrothermal products. These results indicated that Mg and Fe ions were released progressively from the octahedral sheets during the transformation of montmorillonite into kaolinite. Moreover, the changed relative concentrations of Mg and Fe ions in the supernatant solutions after hydrothermal reactions suggested a random distribution of Mg and/or Fe in the octahedral sheets of the montmorillonite. These results improve understanding of the release relationship between Mg and Fe during clay mineral evolution and of the distribution of these two ions in the octahedral sheets, as well as the chemical composition of clay minerals as an indicator of geological environments.

In vitrodissolution of bioactive glass S53P4 microspheres

AbstractStatic and dynamic in vitro dissolution studies showed large differences for various size‐fractions of non‐porous, flame‐sprayed commercial microspheres (45–500 µm) of bioactive glass S53P4. The smaller the spheres, the more their composition deviated from the nominal glass. The dissolution studies were carried out in simulated body fluid and tris(hydroxymethyl) aminomethane buffer for seven days. The ion concentrations in solutions were analyzed using inductively coupled plasma optical emission spectrometry, and the pH was measured as a function of time. Also, changes in the sphere size distribution and mass losses were determined. The calcium phosphate and the silica‐rich layers at the sphere surfaces were investigated using scanning electron microscopy after several immersion times. The smallest (45–90 µm) spheres appeared almost inert. In contrast, typical silica‐rich and calcium phosphate layers were identified at the largest spheres after three days of static and dynamic dissolutions. During the past years, bioactive glass microspheres have been added to paste‐like injectable bone grafting materials, putties to enhance their molding properties. The obtained results provide a better understanding of the dissolution patterns of bioactive glass microspheres.

Vanadium oxide‐supported copper ferrite nanoparticles: A reusable and highly efficient catalyst for rhodamine B degradation via activation of peroxymonosulfate

AbstractA magnetic vanadium oxide nanoparticles supported on spinel copper ferrite (CuFe2O4–VOx) are prepared, characterized, and examined for the peroxymonosulfate (PMS) activation to degrade Rhodamine B (RhB) in water solution. Interestingly, the results show that despite the inability of mixture of copper ferrite and vanadium oxides nanoparticles to the effective RhB decomposition, the prepared catalyst exhibits an excellent catalytic ability toward RhB oxidation. The influence of vital parameters, such as temperature, PMS concentration, catalyst loading, and initial pH are discussed comprehensively. The kinetic studies demonstrate that the pseudo‐first‐order model is well fitted for RhB degradation in CuFe2O4–VOx/PMS system and the activation energy is estimated at 19.60 kJ mol−1. Furthermore, it is found out that the concentration of leached metal ions in solution is negligible and PMS activation is done mainly on the surface of the catalyst. A probable mechanism of PMS activation over RhB degradation is proposed based on the results of free radical quenching studies and X‐ray photoelectron spectroscopy (XPS) analysis. Radical quenching experiments using various scavengers suggest SO4•−as a main reactive species in the degradation.

Carbonation of Sodium Aluminate/Sodium Carbonate Solutions for Precipitation of Alumina Hydrates—Avoiding Dawsonite Formation

Experimental work has been performed to investigate the precipitation mechanism of aluminum hydroxide phases from sodium aluminate/sodium carbonate pregnant solutions by carbon dioxide gas purging. Such solutions result from leaching calcium aluminate slags with sodium carbonate solutions, in accordance with the Pedersen process, which is an alternative process for alumina production. The concentration of carbonate ions in the pregnant solution is revealed as a key factor in controlling the nature of the precipitating phase. Synthetic aluminate solutions of varying sodium carbonate concentrations, ranging from 20 to 160 g/L, were carbonated, and the resulting precipitating phases were characterized by X-ray diffraction analysis. Based on the results of the previous carbonation tests, a series of experiments were performed in which the duration of carbonation and the aging period of the precipitates varied. For this work, a synthetic aluminate solution containing 20 g/L free Na2CO3 was used. The precipitates were characterized with X-ray diffraction analysis and Fourier-transform infrared spectroscopy.

Chemical Composition and Corrosion Behavior of a-C:H/DLC Film-Coated Titanium Substrate in Simulated PEMFC Environment

The amorphous hydrogenated (a-C:H) film-coated titanium, using different CH4/H2 and deposition times, was prepared by the ion beam deposition (IBD) method, which has the advantage of high adhesion because of the graded interface mixes at the atomic level. The chemical characterizations and corrosion behaviors of a-C:H film were investigated and evaluated by SEM, AFM, Raman spectroscopy, EPMA, TEM and XPS. An a-C:H film-coated titanium was corroded at 0.8 V, 90 °C in a 0.5 mol/L H2SO4 solution for 168 h. The metal ion concentration in the H2SO4 corrosion solution and the potentiodynamic polarization behavior were evaluated. Results indicate that a higher CH4/H2 of 1:0 and a deposition time of 12 h can result in a minimum ID/IG ratio of 0.827, Ra of 5.76 nm, metal ion concentration of 0.34 ppm in the corrosion solution and a corrosion current of 0.23 µA/cm2. The current density in this work meets the DOE’s 2020 target of 1 µA/cm2. Electrical conductivity is inversely proportional to the corrosion resistance. The significant improvement in the corrosion resistance of the a-C:H film was mainly attributed to the increased sp3 element and nanocrystalline TiC phase in the penetration layer. As a result, the a-C:H film-coated titanium at CH4/H2 = 1:0 with improved anti-corrosion behavior creates a great potential for PEMFC bipolar plates.

BIOSORPTION OF Pb(II) AND Cu(II) IONS FROM AQUEOUS SOLUTION USING COFFEE SENNA (Senna occidentalis) LEAVES AS BIOMASS

Conventional reagents for the remediation of heavy metals from wastewaters are expensive. Plant materials are being investigated to serve as alternative. The potential of Senna occidentalis leaves in removing Pb (II) and Cu (II) ions from aqueous solution was investigated using Batch adsorption method. The process was subjected to different experimental conditions such as initial metal concentration, solution pH, contact time, biosorbent dose, temperature and shaking speed. Atomic absorption spectroscopy (AAS) was employed in the determination of metal ion concentrations in solution after agitation, and characterization of plant biomass was done using infrared (IR) and scanning electron microscopy (SEM) analytical techniques. The adsorption process vary with the pH of the reaction medium. The optimum adsorption of Pb (II) and Cu (II) ions was achieved at pH 6 and 4 with percent uptake recorded at 97.70% and 82.32% respectively. At optimum temperatures of 40oC & 60oC for Pb (II) and Cu (II) ions, reaction equilibrium was attained after 120 min and 90 min of contact with 20 mg and 40 mg doses of the biomass respectively. The adsorption data for Pb (II) ion fitted well to Langmuir, Freundlich, Temkin and Dubbinin-Radushkevich isotherms. However, Cu (II) ion adsorption mechanism showed exception to Langmuir adsorption isotherm. The plant material was found to be effective in removing Pb (II) and Cu (II) ions and thus, can serve as a substitute for costly adsorbents in the remediation of Pb (II) and Cu (II) ions from wastewaters.

Efficient exclusion of uranyl ion from aqueous medium by a novel magnetic bio adsorbent (Phyllanthus emblica bark)

The exclusion process of uranyl ion in an aqueous medium is carried out with an adsorption method. The existence of uranyl ion in the environment is a matter of concern due to its toxicity. The biotic factor has been affected badly with the presence of uranyl ion above a permissible limit. In the present study, iron oxide magnetic particles (Fe3O4) were successfully fused with tree bark of Phyllanthus emblica by chemical precipitation, which was characterized by XRD, FTIR, and SEM-EDS study. Moreover, Phyllanthus emblica bark is extremely rich in iron and magnetic adsorbent does not produce any secondary pollutant as compared to other adsorbents. It is a novel as well as green approach towards environment. The amount of the adsorbent (0.3 gm/50 ml) could remove 85.6% of U(VI) in 40 min from a metal ion solution concentration 25 mg/L at room temperature (303 K). The equilibrium adsorption is reported at pH = 7. The adsorption isotherm is defined by Langmuir (r2 = 0.963), while the kinetic interest profile is considered by the kinetics of pseudo second-order (r2 = 0.9988). Estimated thermodynamic parameters are fit for present investigation.

Recovery of lanthanum, praseodymium and samarium by adsorption using magnetic nanoparticles functionalized with a phosphonic group

In this work, the synthesis and application of a promising magnetic adsorbent for the recovery of lanthanum, praseodymium, and samarium was studied. To obtain the magnetic adsorbent, magnetite nanoparticles were functionalized with a phosphonic acid group (PA-MNPs) by an efficient and reproducible method. Based on HR-TEM analysis, PA-MNPs present an average diameter of 6.8 nm, have a spherical shape, and a certain degree of agglomeration at approximately 20 to 40 nm. The nanoparticles' magnetic saturation was found to be approximately 55 emu/g, enough to provoke their complete separation from an aqueous raffinate using a common magnet. The XPS and FTIR analyses provided evidence for a phosphonic acid group on the surface of the magnetite nanoparticles. The effect of the pH and the initial concentration of lanthanide ions in the aqueous feed solution and the adsorbent dose on REE adsorption was studied. Maximum lanthanide ion loading capacities in the range of 20–24 mg lanthanide/g adsorbent were measured close to pH 4 (contact time: 5 min.; mass of adsorbent: 200 mg). The PA-MNPs adsorbent presented high mechanical and chemical stability in aqueous solutions with initial pH between 3 and 7. The more efficient desorption (75–100%) of lanthanide ions from the adsorbent was achieved using H2SO4 0.1 M solution. The feasibility of regenerating and reusing functionalized magnetic nanoparticles in five cycles of adsorption/desorption was verified. Freundlich and Langmuir adsorption isotherms fit the experimental equilibrium data well, which would be indicating that the adsorption process would be ruled by a hybrid model. The results of kinetic experiments were well explained by a pseudosecond-order kinetic model, and a very fast initial adsorption rate was observed.

The elimination of trace arsenic via hollow fiber supported liquid membrane: experiment and mathematical model

This work presents the elimination of arsenic ions from synthetic produced water via hollow fiber supported liquid membrane (HFSLM). Results demonstrate that arsenic ions in synthetic wastewater can be successfully treated to meet the wastewater standard as formulated by the Ministry of Industry and the Ministry of Natural Resources and Environment, Thailand. The discharged limit of arsenic from industrial wastewater must not be greater than 250 ppb. In a single-step operation, arsenic ions are extracted and stripped. Percentages of extraction and stripping proved to be 100% and 98%, respectively. Optimum conditions found proved to be 0.68 M Aliquat 336 dissolved in toluene as the liquid membrane, at pH 12 of feed solution, having a mixture of HCl and thiourea as the synergistic strippant, and flow rates of both feed and strippant solutions of 100 mL/min. A mathematical model, developed to predict the final concentration of arsenic ions in feed and strippant solutions, is seen to fit in well with the experimental results.

ВІРТУАЛЬНИЙ ЛАБОРАТОРНИЙ ПРАКТИКУМ ЯК ЗАСІБ ВИВЧЕННЯ ПРИРОДНИЧИХ ДИСЦИПЛІН

In the article the way of using information technology in the natural education is activated, such as computer modeling of chemical, physical or biological phenomenon processes, introduction into the educational process of the virtual laboratory works. The relevance of the introduction of virtual laboratories in educational practice is due, firstly, to the information challenges of the time, and secondly, the regulatory requirements for the organization of the educational process of general secondary and higher education. It is mentioned that the use of virtual laboratories in the educational process allows students to conduct experiments with equipment and materials that he is able to use due to lack of a real laboratory or its lack of technical content, get practical skills of conducting experiments of integrated natural direction initiating computer models and the process of operation of unique equipment of chemical, physical, biological laboratory, to study dangerous in the real situation processes and phenomena of natural origin, without fear of possible consequences. The article reveals the advantages and disadvantages of using a virtual laboratory workshop during the study of natural sciences. Possibilities of modern virtual laboratories of a natural direction which allow to model objects and processes of the surrounding world and also to organize computer access to the real laboratory equipment. The possibility of realization of a virtual laboratory workshop on chemical disciplines of the natural cycle in the environment of a virtual simulator of the laboratory IrYdiumChemistryLab is shown. This virtual laboratory involves the formulation of specific tasks or the formation of its own strategy for planning the experiment,the resource immediately differs in the ability to intervene in the program and design your own virtual experiment Created on the basis of IrYdiumChemistryLab virtual laboratory works allow to prepare diluent of various concentrations, to calculate and measure concentrations of ions in solutions of strong and weak electrolytes, to titrate, etc. Virtual laboratories must be present in the practice of teaching natural sciences (chemistry, physics, biology). The need to use a virtual laboratory workshop during distance learning is especially relevant.

High performance task-specific ionic liquid in uranium extraction endowed with negatively charged effect

Designing functionalized task-specific ionic liquid is a promising way to alleviate the potential second pollution caused by the usage of tributyl phosphate in PUREX process. In this work, a new anion-functionalized ionic liquid, N,N,N-trimethyltetradecan-1-aminium dibutyl phosphate ([N14111][DBP]), was synthesized and applied in uranium extraction. Thanks to the negatively charged effect, [N14111][DBP] exhibits high efficiency in uranium separation, at optimized condition, the maximum of distribution ratio (concentration of ions in extractant to concentration of ions in aqueous solution) for UO22+ could reach 343.5. What’s more, the selectivity of [N14111][DBP] for UO22+ from transition metal ions was also examined in simulated nuclear industry effluent containing and UO22+ ions were separated and extracted efficiently. The advantage of extraction efficiency and selectivity of [N14111][DBP] compared with DBP highlight the superiority of anion-functionalized extractant.

Anisotropic Growth of Silver Dendrites Regulated by Preferential Adsorption of Nitrate Ions on Crystal Facets

AbstractDendritic structures are widely present in nature, from snowflakes to dendritic cells. However, their formation mechanisms are unclear, which causes long unsolved engineering problems, such as lithium dendrites. Here a strategy to control the growth of dendritic structures by the selective adsorption of ions on crystal facets is reported. Silver particles are synthesized by galvanic replacement reaction and the growth anisotropy of crystals is regulated by changing the concentration of nitrate ions in silver nitrate precursor solution. At a low concentration of nitrate ions, messy branching particles are synthesized while symmetric dendrites are generated at a high concentration of nitrate ions. Molecular dynamics simulation suggests that the selective adsorption of abundant nitrate ions on low‐energy facets promotes the prior growth of the high‐energy facets, resulting in the symmetric dendritic structures. When the potassium nitrate is changed to sodium nitrate, similar phenomena are obtained, confirming the role of selective adsorption of additives in regulating the growth anisotropy of crystals.

Mechanical characteristics and freeze–thaw damage mechanisms of mode-I cracked sandstone from the Three Gorges Reservoir region under different chemical solutions

In consideration of the actual environment of the cold region, a test scheme of freeze–thaw (FT) cycles was adopted to explore the mechanical characteristics of sandstone with mode-I cracks under the three-point bending, tensile, and compressive compression tests. And to explore the chemical and freeze–thaw (FT) damage mechanisms, variations in the ion concentration of solutions and the microstructures of sandstone are observed and analyzed under the FT cycle. Experimental results show that the sandstone has a marked tendency to weaken after repeated FT cycles. The pH and chemical composition of chemical solutions had different effects on the deterioration degree from FT in sandstone. From the combined effects of the chemical corrosion and the FT cycles, the ion concentration that was dissoluted from a chemical solution had a clear, cumulative time periodicity. The surface of the sandstone sample was found to exhibit variable degrees of degradation after the combined effects of chemical solutions and FT cycles, and with an increasing number of FT cycles, the degradation degree in the surface microstructure of the sandstone gradually increased. Meanwhile, the interior of sandstone samples was clearly degraded. Specifically, the size of mineral particles was reduced, their edges and corners gradually disappeared or became smooth, the surface roughness of the mineral was found to decrease, and its structure became loose.