Saturated NaCl Research Articles

Metal-free nitrogen-doped porous carbons derived from pomelo peel treated by hypersaline environments for oxygen reduction reaction

Metal-free nitrogen-doped carbon materials with advanced porous structure are considered as one of the most promising next-generation non-platinum catalysts for the oxygen reduction reaction (ORR) applied to fuel cells and metal-air batteries. In this work, we develop nitrogen-doped porous carbons based on pyrolysis of pomelo peel by chemical treatment under hypersaline environments containing saturated NaCl, ZnCl2 and FeCl3. The obtained carbon exhibits outstanding ORR activity with a half-wave potential (0.86V vs RHE) and the kinetics current (10.40 mA·cm−2), which are much higher than those obtained from the Pt/C (0.83V, 5.22 mA·cm−2 respectively). Also, the carbon displays superior stability and methanol tolerance to the Pt/C. The significantly improved performance of the synthesized carbon can be attributed to a synergy of enlarged pore volume, increased pyridinic nitrogen doping level and decreased stacking defects of graphite layers in the carbon, caused by the unique hypersaline treatment on the pomelo peel. Moreover, the effect of the hypersaline treatment on the formation of the advanced porous nitrogen-doped carbons is discussed here. The proposed synthetic strategy may offer a facile and efficient route to prepare cost-effective carbon materials derived from other biomasses for the current energy storage and conversion fields.

Reusable, salt-tolerant and superhydrophilic cellulose hydrogel-coated mesh for efficient gravity-driven oil/water separation

Oil/water separation has been realized by various materials with special wettability, but most of them require complex instrumentation or involve toxic orcorrosive chemicals which may cause potential high cost and environmental concerns. In this work, a superhydrophilic and underwater superoleophobic cellulose hydrogel-coated mesh was fabricated through a simple and green process with the raw materials being low in cost and environmentally benign. The resulting mesh could separate different oil/water mixtures with a separation efficiency higher than 98.9% and a permeate flux up to 12,885 L m−2 h−1 solely driven by gravity. Importantly, this mesh still maintained a separation efficiency >98.2% even after 60 cycles of separation, suggesting its excellent stability for a long term application. Impressively, the mesh also exhibited great anti-salt properties. It was capable to separate saturated NaCl aqueous solutions from their oil (hexane) mixtures with a high separation efficiency. And even immersed in saturated NaCl for 12 h or subjected to sonication treatment, the mesh did not show any worsening in separation properties. These distinct advantages together with the high potential for scale-up production make the mesh very promising toward cost-effective oil/water separation in real-world practice.

Additive Induced Formation of Ultrathin Sodium Chloride Needle Crystals.

A multitude of ultrathin crystal needles are formed during the evaporation of saturated aqueous NaCl solution droplets in the presence of amide containing additives. The needles are as small as 300 nm wide and 100–1000 μm in length. Heating experiments, X-ray diffraction, and energy dispersive X-ray spectroscopy showed that the needles are cubic sodium chloride crystals with the needle length direction pointing toward [100]. This shape, not expected for the 43̅m point group symmetry of NaCl, has been explained using a model, based on tip formation by initial morphological instability followed by time dependent adsorption of additive molecules blocking the growth of the needle side faces. The latter also suppresses side branch formation, which normally occurs for dendrite growth.

TESTE DE ENVELHECIMENTO ACELERADO PARA AVALIAR O POTENCIAL FISIOLÓGICO DE SEMENTES DE CANUDO-DE-PITO

Objetivou-se neste trabalho avaliar o potencial fisiológico de sementes de Mabea fistulifera Mart. após variados períodos de exposição ao envelhecimento acelerado. O experimento foi realizado utilizando o teste de envelhecimento acelerado no método tradicional e com o uso de solução saturada de NaCl sob temperaturas de 41, 43 e 45ºC em períodos de exposição de 0, 24, 48, 72 e 96 h, arranjado em esquema fatorial 2 x 3 x 5 (soluções x temperaturas de envelhecimento x tempos de exposição) em um delineamento experimental inteiramente casualizado (DIC) com quatro repetições. Foram avaliados o teor de água das sementes, a porcentagem de germinação, o índice de velocidade de germinação, o tempo médio de germinação e a frequência relativa de germinação. O teste de envelhecimento acelerado reduziu o vigor das sementes de canudo-de-pito, sendo que, quando aplicado pelo método tradicional por 24 horas em temperatura de 43ºC e em solução saturada de NaCl por 72 horas na mesma temperatura, este teste se mostrou adequado para a avaliação do potencial fisiológico destas sementes.

Qualidade de sementes de alface avaliada pelo teste de envelhecimento acelerado

Accelerated aging as a vigor test has been one of the most used, and its application suits many crops. The aim of this research was to analyze the applicability of the accelerated aging test in the vigor of lettuce seeds (Lactuca sativa) by its correlation with other tests for the expeditious evaluation of the physiological quality of the horticultural seeds. Six lots of lettuce seeds were used. The first count of germination, standard germination, electrical conductivity, accelerated aging, controlled deterioration, and seedling's field emergence was performed. The design was completely randomized, with four replications. The use of the accelerated aging test at 41°C per 24 h period using saturated NaCl solution is indicated for the evaluation of lettuce seed vigor.

Polyimide–polyurea copolymer coating with outstanding corrosion inhibition properties

ABSTRACTA novel class of copolymers containing polyimide and polyurea blocks with unique physical properties and capable of providing effective protection to aluminum alloy 2024‐T3 substrate against corrosion has been prepared. The structure and properties of polyurea‐b‐polyimide (PUI) copolymers were controlled by varying the co‐monomer concentration. The PUI block copolymer can reorganize into a supra‐molecular structure by forming intra‐ and inter‐hydrogen bonding interactions between adjacent copolymer chains, resulting in a dense and compact structure capable of protecting the imide ring from hydrolysis when exposed to a corrosive environment. Apart from minimized surface hydrolysis, the establishment of compacted morphology also leads to a drastically improved barrier property and reduced diffusivity. The corrosion rate and polarization resistances of PUI‐coated aluminum alloys were measured by using direct current polarization technique. Increasing polyurea concentration resulted in a remarkable decrease in diffussivity and surface energy, consistent with the measured remarkable increase in the coatings durability and corrosion performance. Corrosion inhibition tests were carried out for more than 30 weeks in a saturated NaCl solution containing 3.5 wt % of salt. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45861.

Utilización de técnicas petrográficas para evaluar los efectos inducidos del NaCl, condiciones climáticas extremas y el paso del tráfico en las superficies de las carreteras españolas

The asphalt surface layer is the most exposed to weather and traffic conditions on roads, especially those subjected to winter maintenance. Therefore, a deep knowledge of the mechanisms which can damage this layer is necessary to improve its design, construction and long-term use. With this purpose, two types of asphalt mixtures used on roads from NW Spain were subjected to durability tests (freezing-thaw and thermal-stress) with a saturated NaCl solution. After the durability tests, a wheel tracking test was performed on the samples, and the resultant material was analyzed by optical polarized light and fluorescence microscopy. This analysis showed that the binder-aggregate low adhesion was the main responsible of the asphalt mixture damage. This damage was concentrated in the aggregates because the binder acted as an impermeable wall. Consequently, the NaCl solution penetrated and degraded the aggregates quickly and strongly.

A Flow Cytometry Protocol to Estimate DNA Content in the Yellowtail Tetra Astyanax altiparanae.

The production of triploid yellowtail tetra Astyanax altiparanae is a key factor to obtain permanently sterile individuals by chromosome set manipulation. Flow cytometric analysis is the main tool for confirmation of the resultant triploids individuals, but very few protocols are specific for A. altiparanae species. The current study has developed a protocol to estimate DNA content in this species. Furthermore, a protocol for long-term storage of dorsal fins used for flow cytometry analysis was established. The combination of five solutions with three detergents (Nonidet P-40 Substitute, Tween 20, and Triton X-100) at 0.1, 0.2, and 0.4% concentration was evaluated. Using the best solution from this first experiment, the addition of trypsin (0.125, 0.25, and 0.5%) and sucrose (74 mM) and the effects of increased concentrations of the detergents at 0.6 and 1.2% concentration were also evaluated. After adjustment of the protocol for flow cytometry, preservation of somatic tissue or isolated nuclei was also evaluated by freezing (at −20°C) and fixation in saturated NaCl solution, acetic methanol (1:3), ethanol, and formalin at 10% for 30 or 60 days of storage at 25°C. Flow cytometry analysis in yellowtail tetra species was optimized using the following conditions: lysis solution: 9.53 mM MgCl2.7H20; 47.67 mM KCl; 15 mM Tris; 74 mM sucrose, 0.6% Triton X-100, pH 8.0; staining solution: Dulbecco's PBS with DAPI 1 μg mL−1; preservation procedure: somatic cells (dorsal fin samples) frozen at −20°C. Using this protocol, samples may be stored up to 60 days with good accuracy for flow cytometry analysis.

Metal-Rich Coating Development for Fracture Mitigation in Al-Mg Alloys

The AA5xxx-series is a lightweight family of aluminum alloys utilized in marine vehicles [1]. Specifically, AA5456-H116 is solid solution strengthened by a supersaturation of the Al matrix with 5 wt. % Mg. However, mildly elevated temperatures can lead to precipitation of the highly anodic β phase (Al3Mg2) on the grain boundaries. This process is termed sensitization and is often quantified by the ASTM G-67 Nitric Acid Mass Loss Test (NAMLT)). In saline environments β dissolution can lead to severe intergranular stress corrosion cracking (IG-SCC). This behavior is governed by a coupled anodic dissolution process (of the β phase and under certain conditions the (α) Al matrix), which by the hydrolytic acidification mechanism catalyzes formation of an aggressive, locally acidified crack tip chemistry. Occluded acidification enables crack tip hydrogen (H) production everywhere the Al matrix discharges protons. This newly evolved H ingresses into the fracture process zone, thereby enabling embrittlement of the inter-β phase ligaments and increasing the likelihood for grain boundary decohesion. Such H effects enable crack propagation between discrete β phase particles by a hydrogen-assisted mechanism to drive crack growth though IG-SCC [2]. Mild cathodic polarization (to avoid β and α breakdown) has been shown to effectively eliminate IG-SCC in highly sensitized AA5083-H131 (NAMLT ≤40 mg/cm2) tested in 0.6 M NaCl [2]. The aim of the current study is to evaluate the efficacy of this mitigation strategy under more aggressive conditions; specifically, for AA5456-H116 (which has a higher bulk Mg content), at a higher NAMLT level (65 mg/cm2), as well as more aggressive solution chemistries that more accurately simulate marine splash and spray as well as alternate immersion service conditions. This assessment will be conducted first using potentiostatic control with an infinite cathode, followed by utilization of pure sacrificial anode materials as well as by newly discovered chemical inhibition mechanisms which inform development of metal-rich coatings for IG-SCC mitigation. IG-SCC is found to be mitigated in highly sensitized AA5456-H116 alloy by bulk solution electrochemical potential (Ebulk) control in a variety of environments using potentiostatic control, galvanic coupling at cathodic potential, and by added protective ion content. Specifically, fracture mechanics testing quantified the da/dt vs. K behavior in full immersion environments of 0.6 M NaCl (pH 5.6), saturated (5.45 M) NaCl (pH 6.2), 2 M MgCl2 (pH 3.4), and saturated (5 M) MgCl2 (pH 2.4). For each environment, testing at Ebulk from -0.8 VSCE to -1.1 VSCE resulted in at least a 2 order of magnitude decrease in IG-SCC growth rates as compared to IG-SCC severity at OCP (-0.8 VSCE­­­) [3]. The degree of mitigation was traced to the breakdown potentials for both the Al-matrix (Epit (α)) and the β (Epit (β)) in the bulk environment. Significantly, these results suggest local pitting of the Al matrix proximate to the crack tip more prominently catalyzes metal ion hydrolysis to enable additional hydrogen ingress and embrittlement [3]. Cathodic polarization established at the crack tip reduces pitting, which in turn slows hydrogen evolution. Zinc- and magnesium-rich coatings are potential candidates to inhibit Al matrix breakdown and mitigate IG-SCC. Therefore, the protective ability of magnesium and zinc on AA5456-H116 was assessed in galvanic coupling conditions. The magnitude of this potential depended on sacrificial anode pigment characteristics and exposure time, and both potential-based and chemical effects on the overall galvanic protection were evident. Therefore, the effect of solution ion content was tested by adding Zn2+ or Mg2+ions to dilute and saturated NaCl bulk fracture testing solutions. Ion protective ability depends on several factors. Moreover, several Mg, Zn, and Al primers demonstrated efficacy in supplying the necessary galvanic couple potential, which may protect against IG-SCC through galvanic couple and chemical effects. Overall, mitigation of IG-SCC in highly sensitized AA5456-H116 in aggressive full immersion environments suggests that electrochemical potential based protection is a viable strategy with opportunity for use in alternate immersion environments. These findings are pertinent to inform the development of coating systems that aim to protect marine structures via metal-based pigments by sacrificial anode-based cathodic protection. Acknowledgments This research was financially supported by the Office of Naval Research with Dr. Airan Perez as the Scientific Officer.

Assessment of the influence of Concrete Modification in the Water Uptake/Evaporation Kinetics by Electrochemical Impedance Spectroscopy

Corrosion of reinforcing steel in concrete is a worldwide problem. An important factor affecting such process is the concrete composition and, especially the presence of additives. In fact, the kinetics of water absorption and water evaporation are affected both by the environment conditions and by the nature of the additives. This is important for powdered additives, which can partially occlude the porous structure, changing porosity and permeability of concrete too.Reinforced concrete samples were modified by adding spent fluid cracking catalyst powders (SFCC) and an environment friendly commercial inhibitor. The samples were submitted to consecutive cycles of 15day of immersion (in saturated NaCl electrolyte) followed by 15day of drying. Samples were regularly monitored by electrochemical Impedance Spectroscopy (EIS). The results revealed that the additives interfere with the water adsorption/evaporation kinetics in concrete, a process resulting from the joint effect of diffusion and capillary processes. These interferences occur due to three combined mechanisms: two related to pore blocking and pozzolanic activity, which are the result of structural changes in concrete and affect the diffusion processes/mechanism; the third one is the capillary mechanism, which is strongly dependent from the chemical nature of the additives, but can also be influenced by structure modifications. This mechanism can increase, reduce or eliminate the capillary processes.

Erratum to: Mitigation of Intergranular Stress Corrosion Cracking in Al–Mg by Electrochemical Potential Control

Intergranular stress corrosion cracking in the Al–Mg alloy AA5456-H116 is suppressed via cathodic polarization in 0.6 M NaCl, saturated (5.45 M) NaCl, 2 M MgCl2, and saturated (5 M) MgCl2. Three zones of intergranular stress corrosion cracking (IG-SCC) susceptibility correlate with pitting potentials of unsensitized AA5456-H116 and pure β phase (Al3Mg2) in each solution. These critical potentials reasonably describe the influence of α Al matrix and β phase dissolution rates on IG-SCC severity. Complete inhibition occurred at applied potentials of −1.0 V and −1.1 V versus saturated calomel electrode (V SCE) in 0.6 M NaCl. Whereas only partial mitigation of IG-SCC was achieved at −0.9 V SCE in 0.6 M NaCl and at −0.9, −1.0, and −1.1 V SCE in the more aggressive environments. Correlation of pitting potentials in bulk environments with IG-SCC behavior suggests an effect of bulk environment [Cl−] and pH on the stabilized crack tip chemistry.

Efficient carbon-supported Ag–MFe2O4 (M = Co, Mn) core–shell catalysts for oxygen reduction reactions in alkaline media

Nanoparticles with core–shell or hollow interiors have immense potential for catalysis. Herein, Ag@MxFe3−xO4 (M = Co, Mn) core–shell nanoparticles were firstly synthesized through a seed-mediated method. These particles were then loaded onto carbon catalyst supports to form Ag@MxFe3−xO4/C. Then, hollow-MxFe3−xO4/C was prepared with the diffusion of Ag from Ag@MxFe3−xO4/C in saturated NaCl solution at room temperature. As a result, Ag@MnFe2O4/C demonstrates better oxygen reduction reaction (ORR) activity than Ag@CoFe2O4/C and other Ag@MnxFe3−xO4/C with various Mn/Fe ratios. Moreover, Ag@MFe2O4/C shows superior ORR catalytic activities over hollow-MFe2O4/C, which can be due to electronic coupling between Ag core and MFe2O4 shell. Furthermore, Ag@MnFe2O4/C catalysts demonstrate high durability for the ORR in alkaline media and insensitivity to methanol. These findings will provide helpful guidance for design and fabrication of carbon-supported core–shell catalysts for ORR in the future.

Envelhecimento acelerado e ocorrência de fungos para avaliação do potencial fisiológico de sementes de arroz

The accelerated aging test is one of the most widespread for the vigor of the seeds of various cultivated species, being able to provide information with a high degree of consistency. However, the performance of the artificially aged seeds can be influenced negatively by the presence of fungi. Thus, the present work aimed to study the accelerated aging test at different salt concentrations to determine the physiological and health potential of rice cultivars. Were used seeds of rice cultivars Irga 409, Irga 424 and Epagri 144. The accelerated aging test was conducted in three stages: traditional test with water; test using saturated NaCl solution (SS) and supersaturated NaCl solution (SSS), during periods of 24, 48, 72 and 96 hours at 42 °C. After, we evaluated the degree of moisture, germination and seed health. The deleterious effects of accelerated aging test were attenuated with the increase of salt concentrations. The accelerated aging test in saturated solution (SS) for 48 h and super saturated solution (SSS) at 48, 72 and 96 hours allows classifying rice cultivars at different levels of force. Seeds contaminated by fungal agents had a positive response in germination when treated with saline solutions

Preparation and application of PANI/N-doped porous carbon under the protection of ZnO for supercapacitor electrode

The N-doped porous carbon (C) with excellent porous structure was preparfig. 4ed and it was derived from a new kind of carbon precursor (porous PANI which was synthesized in saturated NaCl solution). The structure of the N-doped porous carbon (C) was protected during carbonization by a new method (with ZnO coated on the surface of carbon precursor by sol–gel method). Moreover, the novel N-doped porous carbon (C) was used to fabricate compounds (as materials for supercapacitor) together with PANI. Morphology, structural characteristics, electrochemical properties of porous carbon (C), PANI/N-doped porous carbon (CP) and other materials appeared by scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) ,Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, cyclic voltammetry (CV) and galvanostatic charge and discharge (GCD). The N-doped porous carbon kept the excellent morphology and structure of the porous PANI synthesized in saturated NaCl solution and CP5 (PANI/N-doped porous carbon whose mass ratio of aniline and C is 5:1) has a specific capacity of 455 F/g at 1 A/g and cycle performance 83% retention of the initial value at 10 A/g after 800 cycles. The exceptional electrochemical performance indicates that the composite CP5 has good prospects in application of electrode materials for supercapacitor.

Selection of the best barrier solutions for liquid displacement gas collecting metre to prevent gas solubility in microbial electrolysis cells

Microbial electrolysis cells (MECs) are a novel technology aiming at producing hydrogen from biomass or wastewater. The collection and preservation of the gas generated in the MECs is the first and most important operation in gas measuring techniques. There are several techniques for the quantitative evaluation of gas production in MECs, such as Owen method, respirometre, and gas bag methods. However, the costs associated with these methods could make MEC technology scale-up expensive and impractical. This work describes evaluation of commonly used biogas measurement techniques and analyses potential errors associated with liquid displacement gas measurement. Inaccuracy mainly due to CO2, and CH4 dilution in displaceable liquids was evaluated by testing solubility of CO2 in 12 different barrier solutions. 95% saturated NaCl (pH 0.5) solution exhibited lower CO2 solubility among the tested solutions. These results indicate that gas production in MECs can be accurately tested using an inexpensive, simple gas metre.

Selection of the best barrier solutions for liquid displacement gas collecting meter to prevent gas solubility in microbial electrolysis cells (MECs)

Microbial electrolysis cells (MECs) are a novel technology aiming at producing hydrogen from biomass or wastewater. The collection and preservation of the gas generated in the MECs is the first and most important operation in gas measuring techniques. There are several techniques for the quantitative evaluation of gas production in MECs, such as Owen method, respirometre, and gas bag methods. However, the costs associated with these methods could make MEC technology scale-up expensive and impractical. This work describes evaluation of commonly used biogas measurement techniques and analyses potential errors associated with liquid displacement gas measurement. Inaccuracy mainly due to CO2, and CH4 dilution in displaceable liquids was evaluated by testing solubility of CO2 in 12 different barrier solutions. 95% saturated NaCl (pH 0.5) solution exhibited lower CO2 solubility among the tested solutions. These results indicate that gas production in MECs can be accurately tested using an inexpensive, simple gas metre.

Bulk properties and hydration numbers of components of water–salt, water–urea, and water–urea–salt systems

With an increase in the concentration of additives, the hydration numbers of compounds decrease. Thus, in a saturated 54.6% solution, urea loses approximately 3/4 of the initial amount of water, forming an aquacomplex of the composition (NH2)2CO∙H2O. In a supersaturated 44% solution, the sodium chloride aquacomplex is dehydrated by 2/3, and in a supersaturated 67% solution, sodium sulfate is dehydrated by 5/6. The density of these solutions is 1.354÷1.360 g/cm3 (44% NaCl) and 1.800÷1.849 g/cm3 (67% Na2SO4). In a saturated urea solution, NaNO3, NaCl, and Na2SO4 complexes lose 53÷55% of hydration water. It is shown that the interactions in the binary water–urea system somewhat increase the hydration number of the salts (structural hydration). The hydration water density, a structurally important characteristic, increases in the series of solutions of urea, NaNO3, NaCl, and Na2SO4. In the same series of additives, the excess volume of binary water–urea and water–salt systems becomes more negative.

Distribution and quantity of microplastic on sandy beaches along the northern coast of Taiwan

Plastic pollution is now ubiquitous in the world's oceans, and studies have shown macroplastic and microplastic pollution of beaches in several East Asian countries. However, to our knowledge, no study of microplastic pollution has been conducted in Taiwan yet. Therefore, we collected sand samples from four beaches along the northern coast of Taiwan in 2015 and extracted microplastic particles using a saturated NaCl solution. Microplastic particles were identified using synchrotron-based FTIR spectroscopy. We recovered 4 to 532 particles from eight 0.0125m3 samples, with a total of 1097 particles weighing 0.771g. A negative trend between the size of the particles and their numbers was documented. We thus established that microplastic pollution was ubiquitous along Taiwan's northern coast. Future research should more comprehensively sample beaches around the entirety of Taiwan's coast, and special emphasis should be placed on identifying different sources and movements of microplastic.

Efficient solar-to-chemical conversion with chlorine photoanode

The photoelectrochemical water splitting is an artificial photosynthetic approach that could provide a sustainable supply of clean energy, however, the sluggish kinetics of the oxygen evolution reaction (OER) has been a bottleneck to the solar-to-chemical conversion. Here we report an implementation of 8% efficient photoanode based on the photoelectrolysis of saturated NaCl solution. Replacing the OER with the chlorine evolution reaction (CER) has transformed both the thermodynamic basis and the kinetic process of the photoelectrolysis, more chemical energy can be produced with much less driving force. The RuO2/TiO2/n-Si photoanode exhibits a high rate of photoelectrochemical conversion (35mA/cm2 at equilibrium potential), which steadily and exclusively produces Cl2 without detectable O2.

Antisolvent crystallization of NaCl using the minute-bubble technique – Effects of different antisolvent types

To develop a crystallization technique that enables the control of the crystal size distribution, antisolvent crystallization of sodium chloride (NaCl) under a continuous supply of N2 minute-bubbles was performed. The effects of the additive volume ratio of ethanol (EtOH) on the molar yield and size distribution of the NaCl crystals and the effects of the antisolvent type on crystallization phenomena of NaCl were examined. The initial concentration of NaCl in the saturated solution was set at 5.54mol/l, and EtOH was added as an antisolvent to the saturated NaCl solution, where the added volume ratio of EtOH was in the range of 5 to 50vol% (as EtOH/NaCl system). As a comparison, the antisolvent crystallization phenomenon of NaCl in a MeOH/NaCl system was also investigated. N2 minute-bubbles with an average bubble size of 40µm were continuously supplied to the NaCl supersaturated solution using a self-supporting bubble generator, and NaCl was crystallized. Consequently, the production enhancement and crystal size minimization of NaCl were caused by the residence of minute-bubbles because of the acceleration of nucleation and the inhibition of crystal coalescence. Moreover, the results indicated that the enhancement effect of NaCl crystal production and the minimizing effect of average crystal size depended on the additive volume and the type of alcohol as antisolvent.