Concentrations Of Metal Cations Research Articles

Modulating the structural and electrical properties of SrFeO3–δ by a-site alkali metal ion doping

The electrical properties of perovskite structured SrFeO3–δ can be modulated by A site doping. The present work focuses on the influence of concentration and ionic radii of alkali metal cation on the structural and electrical properties of Sr1–xAxFeO3–δ (A = Ca, Ba and x = 0, 0.25, 0.50, 0.75). The x-ray diffraction studies confirm the phase change from cubic to orthorhombic with Ca content while orthorhombic to cubic structural translation was observed with Ba concentration. A lattice contraction and expansion were observed for doping depending on the ionic radii of dopant cation. The x-ray photoelectron spectroscopy results indicate the presence of Fe in mixed valence state of +2, +3, +4 state and adsorbed oxygen content was found to be higher upon Ba doping than that of Ca. A maximum conductivity of 1.82 × 10−3 S cm−1 (x = 0.25) and 5.31 × 10−3 S cm−1 (x = 0.5) was observed at 800 °C for Ca and Ba doped samples, respectively, one order higher than the base SrFeO3–δ .Thus, our results emphasise the importance of dopant addition on tailoring the electrode properties for SOFC application.

A Solid-State Electrolyte Facilitates Acidic CO2 Electrolysis without Alkali Metal Cations by Regulating Proton Transport.

Electrochemical CO2 reduction (CO2R) in acidic media provides a pathway to curtail CO2 losses by suppressing the formation of (bi)carbonates. In such systems, a high concentration of alkali metal cations is necessary for mitigating the proton-rich environment and suppressing the competing hydrogen evolution reaction. However, a high cation concentration also promotes salt precipitation within the gas diffusion layer, resulting in poor system durability. Here, we resolve this conundrum by replacing the liquid catholyte with a solid-state proton conductor to regulate H+ transport. This is postulated to allow for a locally alkaline environment at the cathode, enabling selective CO2R even without alkali metal cations. We show that this strategy is effective over a broad range of catalyst systems. For instance, we achieve an 87% CO faradaic efficiency (FE) at 300 mA/cm2 using a composite nanoporous Au and single-atom Ni catalyst, with 0.25 M H2SO4 as the anolyte. Stable operation over 110 h and a high single-pass carbon efficiency of 82.8% were also successfully demonstrated. Importantly, we find that this solid-state system is also particularly effective at converting dilute feedstock (5% CO2) with a CO FE of 47.7%, a factor of 16.4 times higher than a conventional system. Our results introduce a simple yet effective design approach for developing efficient acidic CO2R electrolyzers.

Resources, energy consumption and economic analysis for flame synthesis of ternary cathode materials

Cathode materials account for around one third of the manufacturing cost of lithium-ion battery, which are the major factor preventing the wider applications of power battery packs. Flame synthesis (FS) is a new manufacturing technology of nanostructured materials with few equipment and high efficiency, which potentially can substantially bring down the manufacturing cost of cathode materials. The primary objective of the present study was to quantitatively evaluate the resources, energy consumption and economic feasibility of large-scale production of cathode materials though FS. In the analysis process, the mass flow of reactants and resultants as well as the minimum cathode material selling price (MCSP) of ternary cathode material LiNixCoyMn(1-x-y)O2 (x + y + z = 1) produced by FS were calculated, and compared with that of the conventional hydroxide co-precipitation method. Results show that the production of ternary cathode material through FS can reduce CO2 emissions by ∼60% and water consumption by ∼30%. MCSP of LiNi0.5Co0.2Mn0.3O2 (NCM523), LiNi0.6Co0.2Mn0.2O2 (NCM622), and LiNi0.8Co0.1Mn0.1O2 (NCM811) produced by FS are 224.8 k¥/t, 235.1 k¥/t, 240.0 k¥/t, which respectively are about 2%, 10% and 14% lower than the average selling prices in Chinese market, indicating that FS is economically feasible for producing ternary cathode materials. Particularly, for the production of high-nickel cathode materials, FS has notable potential in simplifying the production process and manufacturing costs. Sensitivity analysis of NCM811 produced by FS shows that when raw material price, fuel and power costs are reduced by 25%, MCSP can be as low as 186.4 k¥/t. When the metal cation concentration of the solution increases to 3.2 mol/L, it enables FS to meet the most rigorous energy consumption limitation standards in China. When the lithium excess is reduced from 10% to 5%, MCSP of NCM811 can be further reduced by 5.6 k¥/t, indicating that lithium loss due to high temperatures in FS is a moderate factor for reducing the manufacturing cost. Finally, this work presents a life cycle assessment (LCA) of NCM materials produced by FS in China. Comparison to the global warming potential (GWP) of the co-precipitation method in the literature indicated that GWP of FS is lower.

БИОХИМИЧЕСКАЯ ХАРАКТЕРИСТИКА ТЕХНИЧЕСКИХ ГИБРИДОВ ВИНОГРАДА СЕЛЕКЦИИ АЗОСВиВ

The aim of the study is to investigate new hybrid grape forms by their main biochemical parameters with the prospect of obtaining new high-tech varieties from them. The paper presents the results of scientific studies of biochemical parameters of new technical hybrid grape forms. These forms were obtained by breeders of the Anapa Zonal Experimental Station of Viticulture and Winemaking, a branch of Federal State Budget Scientific Institution North Caucasian FSC of Horticulture, Viticulture, Wine-making (AZOSViV, a branch of the North Caucasus FSC for Horticulture, Viticulture and Winemaking) and are characterized by late ripening, high productivity, winter hardiness and phylloxera tolerance. Biochemical analysis of the berry must of the studied hybrids was carried out at the institute. Sugars, titratable acids, ammonium compounds, cations and organic acids were studied. The technical grape variety of late ripe-ning Krasnostop Anapsky was used as a control for a comparative analysis of the main biochemical cha-racteristics. A pressing issue for breeders has always been the creation of new sustainable and high-tech grape varieties with their subsequent recommendation for implementation in the production process. The research results showed that the studied hybrids 59-39 and 62-23 annually have stable yields, high sugar accumulation compared to the control variety: 59-39 – 24.2 g / 100 cm3, 62-23 – 24.1, control – 24.0 g/100 cm3. The content of ammonium compounds in hybrid forms is small and comparable to the control. For example, in form 59-39, the content of ammonium compounds is 20 mg/dm3, which is at the level of the control variety. The concentration of metal cations in the juice of berries indicates a high content of these compounds in the soil. The content of potassium in the must is especially high. The studied hybrid forms of grapes have prospects for further study in order to obtain a new variety.

Ion exchange selectivity for protons by sodium ion-form crystalline silicotitanate

ABSTRACT At the Fukushima Daiichi Nuclear Power Station site, crystalline silicotitanate (CST) ion exchangers containing sodium ions (Na+) as exchange ions are used as an adsorbent to remove radioactive cesium (Cs) and strontium (Sr) from groundwater and contaminated water. The ion exchange reactions to remove Cs+ and Sr2+ compete with the reactions with other cations in the water sources. Since the groundwater and contaminated water have low concentrations of metal cations, the influence of competitive ion exchange reactions with protons (H+) is relatively large in the removal of Cs+ and Sr2+ from the water. In this paper, the H+/Na+ ion exchange property of the aqueous solution-CST system was evaluated. Results of batch tests were used to draw the isotherm and Kielland plot for the H+/Na+ ion exchange. The thermodynamic equilibrium constant K and the standard Gibbs energy ΔG 0 of the H+/Na+ ion exchange reaction were evaluated from the Kielland plot. CST exhibited high H+ selectivity in the H+/Na+ ion exchange reaction. The values of K and ΔG 0 were determined to be 7.3 × 104 and − 28 kJ mol−1, respectively. The selectivity of CST for H+ decreased with increasing H+ concentration on the ion exchange sites in CST.

Not only phosphorus: dauciform roots can also influence aboveground biomass through root morphological traits and metal cation concentrations

BackgroundPhosphorus in the soil is mostly too insoluble for plants to utilize, resulting in inhibited aboveground biomass, while Carex can maintain their aboveground biomass through the presence of dauciform roots. However, dauciform roots lead to both morphological and physiological changes in the root system, making their primary mechanism unclear.MethodsA greenhouse experiment was conducted on three Carex species, in which Al-P, Ca-P, Fe-P, and K-P were employed as sole phosphorus sources. The plants were harvested and assessed after 30, 60 and 90 days.Results(1) The density of dauciform roots was positively correlated with root length and specific root length, positively influencing aboveground biomass at all three stages. (2) The aboveground phosphorus concentration showed a negative correlation with both dauciform root density and aboveground biomass in the first two stages, which became positive in the third stage. (3) Aboveground biomass correlated negatively with the aboveground Al concentration, and positively with Ca and Fe concentration (except Al-P). (4) Root morphological traits emerged as critical factors in dauciform roots’ promotion of aboveground biomass accumulation.ConclusionDespite the difference among insoluble phosphorus, dauciform roots have a contributing effect on aboveground growth status over time, mainly by regulating root morphological traits. This study contributes to our understanding of short-term variation in dauciform roots and their regulatory mechanisms that enhance Carex aboveground biomass under low available phosphorus conditions.

Integration of metal organic framework nanoparticles into sodium alginate biopolymer-based three-dimensional membrane capsules for the efficient removal of toxic metal cations from water and real sewage

Sodium alginate (SA) biopolymer has been recognized as an efficient adsorbent material owing to their unique characteristics, including biodegradability, non-toxic nature, and presence of abundant hydrophilic functional groups. Accordingly, in the current research work, UiO-66-OH and UiO-66-(OH)2 metal organic framework (MOF) nanoparticles (NPs) have been integrated into SA biopolymer-based three-dimensional (3-D) membrane capsules (MCs) via a simple and facile approach to remove toxic metal cations (Cu2+ and Cd2+) from water and real sewage. The newly configured capsules were characterized by FTIR, SEM, XRD, EDX and XPS analyses techniques. Exceptional sorption properties of the as-developed capsules were ensured by evaluation of the pertinent operational parameters, i.e., contents of MOF-NPs (1–100 wt%), adsorbent dosage (0.001–0.05 g), content time (0–360 h), pH (1–8), initial concentration of metal cations (5–1000 mg/L) and reaction temperature (298.15–333.15 K) on the eradication of Cu2+ and Cd2+ metal cations. It was found that hydrophilic functional groups (-OH and -COOH) have performed an imperative role in the smooth loading of MOF-NPs into 3-D membrane capsules via intra/inter-molecular hydrogen bonding and van der waals potencies. The maximum monolayer uptake capacities (as calculated by the Langmuir isotherm model) of Cd2+ and Cu2+ by 3-D SGMMCs-OH were 940 and 1150 mg/g, respectively, and by 3-D SGMMCs-(OH)2 were 1375 and 1575 mg/g, respectively, under optimum conditions. The as-developed capsules have demonstrated superior selectivity against targeted metal cations under designated pH and maintained >80 % removal efficiency up to six consecutive treatment cycles. Removal mechanisms of metal cations by the 3-D SGMMCs-OH/(OH)2 was proposed, and electrostatic interaction, ion-exchange, inner-sphere coordination bonds/interactions, and aromatic ligands exchange were observed to be the key removal mechanisms. Notably, FTIR and XPS analysis indicated that hydroxyl groups of Zr-OH and BDC-OH/(OH)2 aromatic linkers played vital roles in Cu2+ and Cd2+ adsorption by participating in inner-sphere coordination interactions and aromatic ligands exchange mechanisms. The as-prepared capsules indicated >70 % removal efficiency of Cu2+ from real electroplating wastewater in the manifestation of other competitive metal ions and pollutants under selected experimental conditions. Thus, it was observed that newly configured 3-D SGMMCs-OH/(OH)2 have offered a valuable discernment into the development of MOFs-based water decontamination 3-D capsules for industrial applications.

An integrated process incorporating pH-controlled biomineralization and sulfate bioreduction to facilitate recovery of schwertmannite and sulfated polysaccharides from acid mine drainage

Acid mine drainage (AMD) poses an environmental challenge to the global mining industry. However, it is also a potential source of iron and sulfate for recovery. In this work, we proposed an integrated process of pH-controlled biomineralization of iron and biological sulfate reduction to facilitate the concurrent purification of AMD and selective recovery of iron and sulfate as valuable products. Compared with the biomineralization controlling pH at 2.8, the modified biomineralization controlling pH at 3.2 improved the iron precipitation efficiency from 9.7 % to 95.3 %, leading to a 53–fold increase in pure-grade schwertmannite Fe8O8(OH)4.08(SO4)1.96 production in AMD. This improvement may be related to the relatively low Gibbs free energy value of the Fe3+ mineralization reaction at pH 3.2. The solution equilibrium calculation using Visual MINTEQ indicated that keeping the system pH at an appropriate level is crucial for the spontaneous and effective biomineralization of Fe to schwertmannite at room temperature. The specific pH required for Fe biomineralization is slightly affected by the content of metal cations (e.g., Al3+, Ca2+, Mg2+, Cu2+, and Mn2+) and oxoanion (AsO33−/AsO43−) in AMD but greatly affected by sulfate content (mM) (pH = 0.149 ln c(SO42−) + 2.551). For the effluent resulting from AMD biomineralization, sulfate reduction at pH 5.0 removed residual Zn2+ (99.9 %), Mn2+ (97 %), Cu2+ (100 %), and sulfate (87.1 %) while recovering sulfated polysaccharides with antiangiogenic bioactivity (as confirmed by the chorioallantoic membrane tests). The pilot-scale continuous flow operation experiments demonstrated that this integrated method has the potential to recover valuable iron/sulfate products from AMD.

NaCl, MgCl2, and AlCl3 Surface Coverages on Fused Silica and Adsorption Free Energies at pH 4 from Nonlinear Optics.

We employ amplitude- and phase-resolved second harmonic generation experiments to probe interactions of fused silica:aqueous interfaces with Al3+, Mg2+, and Na+ cations at pH 4 and as a function of metal cation concentration. We quantify the second-order nonlinear susceptibility and the total interfacial potential in the presence and absence of a 10 mM screening electrolyte to understand the influence of charge screening on cation adsorption. Strong cation:surface interactions are observed in the absence of the screening electrolyte. The total potential is then employed to estimate the total number of absorbed cations cm-2. The contributions to the total potential from the bound and mobile charges were separated using Gouy-Chapman-Stern model estimates. All three cations bind fully reversibly, indicating physisorption as the mode of interaction. Of the isotherm models tested, the Kd adsorption model fits the data with binding constants of 3-30 and ∼300 mol-1 for the low (<0.1 mM) and high (0.1-3 mM) concentration regimes, corresponding to adsorption free energies of -13 to -18 and -24 kJ mol-1 at room temperature, respectively. The maximum surface coverages are around 1013 cations cm-2, matching the number of deprotonated silanol groups on silica at pH 4. Clear signs of decoupled Stern and diffuse layer nonlinear optical responses are observed and found to be cation-specific.

Sensory layers of poly(methyl metacrylate) for capacitive sensors for analysis of the content of heavy metal cations in water

The results of using poly(methyl methacrylate) coatings for the development of the capacitive sensors for analyzing the content of heavy metals in water (using Ni2+ ions as example) are presented. Structural and morphological characteristics of the formed conductive nickel layer and nanostructured poly(methyl methacrylate) films were studied by atomic force microscopy. Based on the analysis of the dependence of the capacitive characteristics of the original sensor on the frequency at different concentrations of Ni2+ ions, the following operating characteristics of the sensor were established: response time – 5 min; operating range of Ni2+ ion concentrations: 1 ‧ 10–3–50 mM; lower detection limit ≈ 0,06 mg/l. It is shown that the formation of a poly(methyl methacrylate) coating on a conductive nickel layer by the spin coating method increases the service life of the sensor to eight cycles while maintaining the level of sensor sensitivity.

Sequential Catalytic Conversion of Methyl Oleate Into Short Chain Alkane and Alkene Compounds

Research on the conversion of methyl oleate (Methyl 9-octadecenoate) into shorter chain alkane compounds through the stages of methyl 9-octadecenoate into 1-octadecanol, 1-octadecanol into 1-octadecene and 1-octadecene into alkane compounds and short chain alkenes with a length of C12 &gt; have been done. The conversion process uses ZSiA and Ni/ZSiA catalysts which are placed in a fixed bed system reactor column and operated at temperatures of 400, 450 and 500 oC. ZSiA catalyst was made by washing natural zeolite with distilled water, soaking with 2 M HCl solution, adding 5% Na2SiO3 w/w, soaking with 2 M NH4Cl solution, calcining at a temperature of 500 oC while flowing nitrogen gas for two hours at a flow rate of 20 milliliters per minute; oxidation during a two-hour oxygen flow rate of 20 milliliters per minute; and impregnation of Ni metal onto the catalyst sample's surface using Ni(NO3)2 6H2O metal 2% w/w. Subsequently, reduction was done for two hours while hydrogen gas was flowing at a rate of 20 mL per minute. The resultant catalyst was subjected to various analyses, including AAS analysis for metal cation content, gravimetric analysis for acidity, NOVA 1000 surface area analyzer for specific surface area, and X-ray diffractometer (XRD, Shimadzu-6000) analysis for crystallinity

Response of wheat (Triticum aestivum L.) and cowpea (Vigna unguiculata L.) to foliar wetting with low pH mine waters containing acid-generating metal cations

Acid mine drainage (AMD) contains metals that have detrimental effects on crop growth if present in excess in plant-available form. The use of untreated AMD from coal mines for crop irrigation on strategically limed soils is considered a potential option for mine water management, especially in remote areas without access to water treatment infrastructure. However, leaf scorching and trace element enrichment of plant tissue are of potential concern, as these waters often contain high concentrations of potentially toxic, acid-generating metals (Al3+, Fe2+ and Mn2+) which may cause foliar damage and hyper-accumulate in plant tissue. The objectives of this trial were to quantify any foliar injury and metal accumulation in wheat (Triticum aestivum L.) and cowpea (Vigna unguiculata L.) vegetative material after foliar wetting with simulated AMD enriched with metal cations, and to ascertain if biomass production will be affected. In this trial, crop water requirements were not met through mine water irrigation, as this was only a foliar wetting investigation. Two pot experiments were set up, with wheat grown in the winter and cowpea in the summer season of 2021. Sulphuric acid was used to lower pH to 2, after the addition of low, intermediate and high concentrations of individual acid-generating metal cations, as well as a combination of all three cations. Areal foliar injury was greatest for cowpea (18.7%) with a combination of Al, Fe and Mn at the highest concentration. The crop was not able to recover at this injury level. No injury was recorded in wheat. Both crops accumulated only limited quantities of the metal cations. Calculated hazard quotient for cattle ranged from 0.022 to 0.53, indicating that such fodder would be safe to consume. It is concluded that there are large differences in crop specie susceptibility to leaf scorching after foliar wetting with acidic metal cation-rich mine waters. It is recommended, therefore, that because large volumes of mine water need to be managed, and centre pivot overhead irrigation is likely to be utilized to this end, that studies to screen more species to select crops tolerant to scorching through foliage wetting with mine water irrigation be conducted. Thereafter, studies to better understand root zone effects of irrigation with such waters need to be conducted on species that can tolerate foliar wetting with these waters.

The elemental profile of ciders made from different varieties of apples

Macro- and microelements are vital components of the nutrient profile of apples and apple juice. Although the mineral composition of apple juices has been well studied, there is a lack of research into the elemental profile of ciders. We aimed to determine the concentrations of macro- and microelements in various samples of ciders. &#x0D; We studied 25 experimental ciders from apple juice of direct extraction (fresh must) and 4 commercial ciders purchased from a retailer in Krasnodar. Mass concentrations of metal cations were determined by high-performance capillary electrophoresis, atomic absorption spectrometry with electrothermal atomization, and atomic emission spectrometry with inductively coupled plasma.&#x0D; The concentrations of macroelements in the ciders from fresh must depending on the variety varied significantly in the following ranges (mg/L): 696–1920 for potassium; 6.7–26.8 for sodium; 4.3–35.5 for calcium; and 10.2–36.8 for magnesium. The commercial ciders had significantly lower concentrations of macroelements. The content of iron ranged from 0.86 to 2.26 mg/L. Among microelements, copper cations were detected in the range from 31.0 to 375 μg/L. The concentrations of toxic elements did not exceed the maximum permissible values in any of the samples, including the commercial ones. Finally, ranges of variation were established in the concentrations of macro- and microelements depending on the varietal characteristics of apples.&#x0D; The pomological varieties of apples used in the study were grown under the same agrotechnical conditions. Therefore, the differences revealed in the elemental profile of the ciders were assumingly due to the genetic characteristics of the respective variety.

Research progress of coincidence Doppler broadening of positron annihilation measurement technology in materials

Positron annihilation technique is an atomic-scale characterization method used to analyze the defects and microstructure of materials, which is extremely sensitive to open volume defects. By examining the annihilation behaviour of positrons and electrons in open volume defects, local electron density and atomic structure information around the annihilation site can be obtained, such as the size and concentration of vacancies, and vacancy clusters. In recent years, positron annihilation spectroscopy has evolved into a superior tool for characterizing features of material compared with conventional methods. The coincident Doppler broadening technique provides unique advantages for examining the local electronic structure and chemical environment (elemental composition) information about defects due to its effectiveness describing high momentum electronic information. The low momentum portion of the quotient spectrum indicates the Doppler shift generated by the annihilation of valence electrons near the vacancy defect. Changes in the peak amplitudes and positions of the characteristic peaks in the high momentum region can reveal elemental information about the positron annihilation point. The physical mechanism of element segregation, the structural features of open volume defects and the interaction between interstitial atoms and vacancy defects are well investigated by using the coincidence Doppler broadening technology. In recent years, based on the development of Doppler broadening technology, the sensitivity of slow positron beam coincidence Doppler broadening technology with adjustable energy has been significantly enhanced at a certain depth. It is notable that slow positron beam techniques can offer surface, defect, and interface microstructural information as a function of material depth. It compensates for the fact that the traditional coincidence Doppler broadening technique can only determine the overall defect information. Positron annihilation technology has been applied to the fields of second phase evolution in irradiated materials, hydrogen/helium effect, and free volume in thin films, as a result of the continuous development of slow positron beam and the improvement of various experimental test methods based on slow positron beam. In this paper, the basic principles of the coincidence Doppler broadening technique are briefly discussed, and the application research progress of the coincidence Doppler broadening technique in various materials is reviewed by combining the reported developments: 1) the evolution behaviour of nanoscale precipitation in alloys; 2) the interaction between lattice vacancies and impurity atoms in semiconductors; 3) the changes of oxygen vacancy and metal cation concentration in oxide material. In addition, coincident Doppler broadening technology has been steadily used to estimate and quantify the sizes, quantities, and distributions of free volume holes in polymers.

Uncovering thermally activated purple-to-blue luminescence in Co-modified MgAl-layered double hydroxide.

Thermally activated blue-to-purple luminescence of Co-modified nano-sandrose MgAl-layered double hydroxides (LDHs) is concentration dependent, occurring only for MgCoAl-LDH with a molar metal cation concentration of 15% Co. Temperature sweep luminescence spectroscopy between 83 K and 298 K shows that the luminescence is strongest at room temperature, increasing with an activation energy of 1 kJ mol-1 between these temperatures. The luminescence occurs in a broad, but fine-structured band below the conduction band (CB) edge at 3.0 eV after excitation at 5.0 eV.

Impact of Li, Na and Zn metal cation concentration in EMIM-TFSI ionic liquids on ion clustering, structure and dynamics.

We use molecular dynamics calculations to investigate the behavior of metal cations (Li, Na and Zn) within ionic liquids (ILs), specifically EMIM-TFSI, and their impact on key properties, particularly focusing on ion-ion correlations and their influence on diffusion and conductivity. The study explores the competition between metal cations and EMIM ions for binding to TFSI and analyzes ion pair dynamics, revealing that metal cation-TFSI pairs exhibit significantly longer lifetimes compared to TFSI-EMIM pairs. This competitive interaction and the increased stability of metal cation-TFSI pairs at higher concentrations leads to reduced ion exchange, resulting in decreased diffusion and conductivity. The observations underscore the importance of ion size and charge in determining their behavior regarding IL dynamics. Overall, this work provides valuable insights for designing ILs with customized properties, particularly in the context of optimizing conductivity and addressing energy storage challenges.

Activity and Selectivity Modulation of CO2 Electroreductions at Au-Water Interfaces Via Tuning Localcation Concentrations

Electrochemical CO2 reduction reaction (CO2RR) is a promising technique for converting the greenhouse gas CO2 into valuable fuels and chemicals in a clean energy society. To understand the underlying electrocatalytic reaction mechanism from the atomic level, researchers are investigating the role of electrolyte ions, particularly alkali metal cations, in various electrocatalytic reactions including CO2RR. Despite this attention, the impact of alkali metal cations is still a topic of debate, and it remains unclear how cations affect the CO2RR and the competing hydrogen evolution reaction (HER).In this study, explicit cations and water solvents were added to Au-water interfacial models to simulate the pathways of CO2RR and HER. Two cations (K+, Li+, and/or H+) were used in the model system to create similarly charged Au surfaces, and the local concentration of alkali metal cations (AM+) was adjusted by replacing AM+ (K+ and Li+) with H+. The first electron transfer step was considered critical in electrocatalytic reductions, so CO2 activation and water dissociation were evaluated for CO2RR and HER, respectively. Ab initio molecular dynamics (AIMD) simulations with the slow-growth sampling approach (SG-AIMD) were used to simulate the corresponding reaction mechanisms, and kinetic barriers were obtained through thermodynamic integrations. With these Au-water-cations interfacial models, a systematic study was conducted to investigate the mechanism of CO2 activation at Au-water-2AM+, Au-water-1AM+, and Au-water-0AM+ interfaces. These results show that a high concentration of metal cations with 2AM+ promotes CO2 activation through short-range electrostatic interactions between cations and key intermediates.Besides CO2 activation, this study also investigated water dissociation during the competing HER. Contrary to the promotion effect observed in CO2RR, local alkali metal cations were found to suppress water dissociation with a high reaction barrier (Figure 1). This can be attributed to the broken connectivity of the hydrogen bond network at Au-water-2AM+ interfaces. The reaction kinetics can be improved by reducing the metal cation concentration. Notably, K+ was found to have a more pronounced promotion effect than Li+ on CO2 activation, while the opposite suppression effect was observed on HER. By tuning the local alkali metal cation concentration, it is anticipated that the overall performance of CO2RR, including both activity and selectivity, can be engineered. Figure 1

The Effects of Magnesium, Zinc and Calcium Ions on Endotoxin-Plasmid DNA Interaction at Various Cation Concentrations, pH Values and Incubation Times

In plasmid DNA (pDNA) production from Gram-negative bacteria, endotoxin has been known as the major contaminant. The separation becomes difficult due to its ability to form a stable complex with pDNA apart from sharing common properties like surface charge, molecular size, temperature, and pH stability. This study focused on the analysis of the zeta potential values of endotoxin, the theoretical number of cations bound per molecule of endotoxin as well as the binding tendency of cations towards endotoxin in the presence of pDNA. These analyses were conducted under various experimental conditions such as types of divalent metal cation, cation concentration, pH and incubation time. The analysis of zeta potential at different cation concentrations and pH values showed that Mg2+ had the most significant effect on endotoxin surface charge. The zeta potential of endotoxin was reduced by a magnitude of 43.55 mV, from −43.53 mV to 0.02 mV in the presence of 2.0 M Mg2+, and a magnitude of 44.12 mV, from −43.53 mV to 0.59 mV at the lowest pH level. However, in the analysis of the theoretical number of cations bound per molecule of endotoxin, Zn2+ showed the highest number (0.6) compared to Ca2+ (0.12) and Mg2+ (0.05). The tendency of Zn2+ to preferentially bind with endotoxins forming a larger aggregated structure was also evident in the DNA gel electrophoresis and transmission electron microscopic analysis. The manuscript highlights the significance of cations in the binding and aggregation of endotoxins, which ultimately improves the recovery of pDNA and affects its subsequent downstream processing.

Assessment of heavy metal distribution, risk, and sourcing in mangrove sediments from three Saudi Arabian Red Sea locations

This work measured the concentration of heavy metal cations (V, Cr, Ni, Cu, Zn, Cd, and Pb) and associated anionic ligands (SOM, carbonate, and silicate) in mangrove sediment samples from the Red Sea of Saudi Arabia to set a biogeochemical baseline within these as yet poorly constrained sensitive ecosystems. Sediments were collected from three regions along the Saudi Arabian coast: Yanbu, Jeddah, and the Farasan Islands. Risk indices and statistical analyses were applied to assess contamination levels and potential sourcing. Results show that Yanbu is at environmental risk as it shows higher concentrations and anthropogenic signatures for most metals (Cr, Cu, Zn, Cd and Pb) compared to the other two regions. Jeddah metal concentrations are similar to the Islands; however, the statistical analyses suggest that a singular anthropogenic source controls heavy metal delivery to its environment.

Facile and green fabrication of algal protein/M(n+) hydrogel through coordination with cations for sustained release of vitamin B6

This study presents a facile method to prepare functional hydrogels based on spirulina algae protein/M(n+) and compares its properties with the conventional heat-induced method. Hence, algae protein isolate was extracted at the isoelectric point (pH 3.1) and hydrogels were synthesized through coordination with various cationic metals (Ca2+, Mg2+, Fe3+, Zn2+, and Cu2+) as a cross-linker. Morphological experiments (SEM) showed that the prepared hydrogels had a porous to dense and integrated structure depending on the type and concentration of metal cations. Fourier transform infrared (FTIR) spectra revealed the interaction of protein functional groups with coordinating metal ions. X-ray diffraction (XRD) patterns showed amorphous structures in algal protein/M(n+) hydrogels. The capacity of water absorption was strongly affected by pH and the type of metal cations and was much higher at pH 7.4 (490–801 %) than at acidic pH (pH 2.1, 212–419 %). The maximum release rate of vitamin B6 (83%) was obtained in Ca2+-hydrogels at pH 7.4 after 8 h. The Peppas-Sahlin model showed the best fit with the release profile of vitamin B6 (0.96–0.99), and it was also determined that the release process was based on Fickian diffusion (n ≤ 0.45) or anomalous transport (0.45 < n < 0.89). In conclusion, the study provided a new perspective on the fabrication of algal protein-based hydrogels, suggesting this matrix could be a novel delivery system for the controlled release of drugs/nutrients.