Molar Potassium Research Articles

An Aluminum Anode with Superior Discharge Characteristics Prepared via Grain Refinement

AbstractAs Electric Vehicles became more important in the field of energy, the disadvantages of lithium‐ion batteries became apparent. This led to an increased interest in metal‐air batteries, particularly aluminum‐air batteries, as alternatives to lithium‐ion batteries. However, aluminum‐air batteries also have their own deficiencies, with one of the main areas of research being the improvement of anode characteristics. Improving anode characteristics is a crucial area of research in this field. Aluminum alloys have traditionally been used to overcome obstacles in creating batteries with favorable electrochemical properties. However, recent studies suggest that reducing the grain size of aluminum anodes can have positive effects. In this study, we investigated the electrochemical behavior of three aluminum alloys that were grain‐refined by Al‐5Ti‐1B and compared the results to a commonly used aluminum alloy as an anode in aluminum‐air batteries. We chose Al−Ti alloys with variable amounts of titanium (0.01, 0.05, and 0.1 wt.%) for evaluation. We selected a 4 molar potassium hydroxide solution as the test electrolyte due to the merits of alkaline electrolytes. Our study found that the alloy with 0.05 wt.% of titanium is the best anode choice. This anode has promising discharge characteristics at high current density (50 mA/cm2) and is an appropriate choice for electric vehicles.

Manganese cobalt sulfide/molybdenum disulfide nanowire heterojunction as an excellent bifunctional catalyst for electrochemical water splitting

Heterointerface engineering enhances catalytic active centers and charge transfer capabilities to increase oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) kinetics. In this study, a novel heterostructure of manganese cobalt sulfide-molybdenum disulfide on nickel foam (MnCo2S4-MoS2/NF) was synthesized via a two-step hydrothermal process. The nanowire-shaped MnCo2S4-MoS2 on NF displayed accelerated charge transfer ability and multiple integrated active sites. When tested in one molar (1 M) potassium hydroxide (KOH) electrolyte, it furnished low overpotentials of 105 and 171 mV for the HER and 220 and 300 mV for the OER at the current densities of 20 and 50 mA cm−2, respectively. An electrolyzer based on MnCo2S4-MoS2/NF required low operating potentials of 1.41 and 1.49 V to yield the current densities of 10 and 20 mA cm−2, respectively, surpassing commercial and previously reported catalysts. Density functional theory (DFT) analysis revealed that the MnCo2S4-MoS2 heterostructure possesses the optimal adsorption free energies for the reactants, an extended electroactive surface area, good charge transfer ability, and reasonable density of electronic states close to the Fermi level, all of which contribute to the high activity of catalyst. Thus, heterointerface engineering is a promising strategy for creating efficient catalysts for overall water splitting.

Purification and characterization of glutaminase from Iraqi fruit of ‎ Capsicum annuum

L-glutaminase has recently attracted much attention due to its medicinal and industrial potential. It's an antileukemic drug with flavor-enhancing properties when used in fermented foods manufacturing. The enzyme purification was determined by ammonium sulfate precipitation, Ion exchange chromatography and gel filtration chromatography with estimating glutaminase activity and characterization of purified glutaminase in several parameters such as substrate concentration and reaction time pH, and temperature influence in this study. As a result, glutaminase is purified in three steps: ammonium sulfate precipitation with 30% saturation, DEAE-Cellulose and Sephacryl S-200. The specific activity increased to 85 U/mg protein with 4 folds of purification and 18% enzyme recovery. When glutaminase was incubated in the presence of 150 millimolar glutamine at thirty-five centigrade for thirty minutes, the enzyme reached its maximal activity of 1.8 u/ml, in the presence of a 0.05 Molar potassium phosphate buffer solution, at pH 8. Keywords: Capsicum annum, glutaminase, enzyme activity, glutaminase purification

Communication—Fe/FeNi3 Embedded in Nitrogen-Doped Carbon Nanotubes as Bifunctional Oxygen Electrocatalysts

Both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial for metal-air batteries. Achieving a single phase that offers both functionalities is of practical relevance. Here, we report a facile method to couple Fe-Nx moieties and FeNi3 nanoparticles, and embed these in nitrogen-doped carbon nanotubes (Fe/FeNi3@NC). The Fe/FeNi3@NC catalyst demonstrates excellent bifunctional performance in 0.10 molar potassium hydroxide. We observe a half-wave potential of 0.83 V for ORR, and a potential of 1.58 V at a current density of 10 mA cm−2 for OER. The oxygen electrode fabricated using Fe/FeNi3@NC exhibits a peak power density of 143 mW cm−2 for rechargeable Zn-air battery. Over a ∼9 h duration test, the material is also shown to be as stable as the commercial Pt/C + IrO2 in operating conditions.

Effect of Alkaline Pre-Treatment on Cassava Pulp for Optimum Biogas Production

(Being produced in vast quantity as one of by-product from cassava starch processing chains, cassava pulp has great potential for energy recovery by harnessing biogas through anaerobic digestion (AD). This study aims to enhance biogas production by comparative investigation in batch mode digestion. 5%TS w/v of cassava pulp mixed with mill effluent were pre-treated with 10 molar potassium hydroxide (KOH), sodium hydroxide (NaOH), and calcium hydroxide (Ca(OH)2) solution for 6 hours contact time. Effects of different alkaline pre-treatment on cassava substrate were assessed in total dissolved solid (TDS), soluble chemical oxygen demand (SCOD), Volatile Fatty Acids to Alkalinity ratio (VFA/TA), and reducing sugars. Daily accumulated biogas yield was taken as final indicator of the effect of different pre-treatment. KOH pre-treatment in pH 11 resulted highest dissolved solid 13.07 mg/L, and improved soluble chemical oxygen demand (SCOD) formation up to 75.61% (480,000 mg/L) than control substrate. The experiment revealed peak biogas production by KOH pre-treated substrate was found at day 6 after digestion executed, and achieved 546 ml. The finding proves out of different pre-treatment method applicable to cassava pulp, KOH pre-treatment could realistically increase biogas yield for cassava mills. Biogas production increased up to 101%, 92%, and 70% using KOH, Ca(OH)2 and NaOH respectively. However, when future provision to the technology for AD system and design is concerned, the choice of highly reactive alkali could lead to complication in the system.

Two chromatographic methods for the quantitative determination of some pesticides applied for cucumber pests in Egypt

AbstractTwo novel sensitive and accurate thin‐layer chromatography and high‐performance liquid chromatography methods were used for monitoring the residues of four pesticides: mandipropamid, metalaxyl, thiophenate methyl and carbendazim, which are widely used to eliminate cucumber pests in Egypt. The first method is a thin‐layer chromatography method, using silica gel plates as a stationary phase and hexane/methanol/acetone/glacial acetic acid (7.5:2:0.5:0.1, v/v) as a developing system. The second method is high‐performance liquid chromatography using isocratic elution and a mobile phase consisting of acetonitrile/0.02 molar potassium dihydrogen phosphate buffer (25:75, v/v) at a flow rate of 1 mL min−1 with UV detection at 225 nm. All the obtained results were evaluated regarding the agricultural committee of Egypt and showed acceptable pesticides residues.

Effect of Porosity and Pore Size on Microstructures and Mechanical Properties of Metakaolin Blended with Ca(OH)<sub>2</sub> and PLA as Porous Geopolymers

Geopolymer is generally made of pozzolanic materials and alkali activators such as sodium alkali or potassium alkali. It can be solidified at ambient temperature to be developed as construction materials. Polylactic acid (PLA) was chosen to create pores in order for porous geopolymers. In this research, the porous geopolymer was developed either to reduce the weight of materials or to be utilized as thermal insulation materials. It was performed by metakaolin (MK), calcium hydroxide (Ca(OH)2), 10 molar potassium hydroxide (10M KOH) and potassium silicate (K2SiO3) for geopolymer pastes. These geopolymer pastes were mixed with 40 wt%, 50 wt% and 60 wt% of PLA and fired at 550°C for 6 h., therefore, pores inside geopolymer structure were found. Consequently, those geopolymers were characterized the mechanical properties e.g. compressive and flexural strength by Universal Testing Machine (UTM), microstructures by Scanning Electron Microscope (SEM), chemical compositions as functional groups by Fourier Infrared Spectroscope (FTIR). Furthermore, the pore size, bulk density, apparent porosity and thermal conductivity coefficient of geopolymers were analyzed. The results presented that the quantity of PLA affected the compressive strength and porosity of geopolymers. In conclusion, our porous geopolymer with 40 wt% PLA gave the highest strength.

Performance of zinc air batteries with added $$\hbox {K}_{2}\hbox {CO}_{3}$$ K 2 CO 3 in the alkaline electrolyte

Intentionally adding potassium carbonate to the high molar alkaline electrolyte is one possibility to mitigate the negative impact of carbonation in zinc air batteries (ZABs) that were investigated in this novel study. In this work, an experimental analysis of the electrochemical performance of ZABs with added potassium carbonate in potassium hydroxide electrolyte was conducted. The experiments included polarization curve measurements, electrochemical impedance spectroscopy measurements, and constant current discharge with an in-house battery set-up. In addition, ionic conductivity was measured for mixtures of potassium hydroxide and potassium carbonate solutions. The results implied that up to 50 mol% of added potassium carbonate in the electrolyte had a weaker influence on the cell performance than a decreased amount of hydroxide ions in the electrolyte from 21.9 to 1.8 mol%. However, discharge measurements showed that the cell potential and the maximum state-of-discharge are decreased for the operation with 50.00 mol% of added potassium carbonate. The conductivity measurements revealed that solutions with 9 \(\hbox {mol} {\mathrm{\,l}}^{-1}\, \hbox {K}^+\) and added potassium carbonate possessed similar ionic conductivity, when compared to the standard 6 M KOH electrolyte. All in all, the analysis showed that it was acceptable to add potassium carbonate to the high molar potassium hydroxide electrolyte, while still obtaining stable cell potential under the premise to increase the practical energy density and the long-term stability of zinc air batteries. The here presented findings might help to establish the zinc air battery as next generation type battery.

Combination of driselase and lysing enzyme in one molar potassium chloride is effective for the production of protoplasts from germinated conidia of Fusarium verticillioides

Various cell wall degrading enzymes and the protoplasting media were evaluated for the production of protoplast in Fusarium verticillioides. Among the various enzymes tested, driselase at 12.5mg/ml in 1M KCl protoplasting medium produced the maximum number of protoplast. Next to driselase, lysing enzyme at 10mg/ml in 1.2M MgSO4 protoplasting medium was found to be the second best enzyme for the production of protoplast. More interestingly, the combined use of driselase @ 12.5mg/ml and lysing enzyme @ 10mg/ml in 1M KCl exhibited the additive effect on protoplast formation. Germinated conidia of F. verticillioides are the most susceptible fungal material for protoplast production. The use of sucrose at 1.2M in the regeneration medium supported the maximum regeneration of protoplast. From the present study, we recommend driselase (12.5mg/ml) and lysing enzyme (10mg/ml) in 1M KCl protoplasting medium and germinated conidia of F. verticillioides for the maximum production of protoplasts and 1.2M sucrose is the best osmoticum for the regeneration of protoplasts.

Building a better Mousetrap I: Using Design of Experiments with unconfounded ions to discover superior media for growth and lipid production by Chlorella sp. EN1234

An unconfounded Scheffe Mix approach was used to probe important ions and their interactions in supporting biomass and lipid production by Chlorella sp. EN1234. Six major cations and anions; NH4+, NO3−, Na+, K+ PO4− and Cl− were examined. Piepel plots and RSM analysis showed that in a number of cases, the major media anions PO4− and Cl− negatively influence final cell densities, and that maximal cell density is obtained with nitrate over ammonium, with an optimal effect when mixed with equal molar potassium. As well, although it is commonly assumed that lipid content increases in nitrogen deficient media, here little correlation between nitrogen content and total lipid content was found with mixtures that supported high lipid productivity. Thus these mixtures define the composition space within which further R&D might produce the best trade-off between total biomass production and high cellular lipid content.

Potassium Starvation in Yeast: Mechanisms of Homeostasis Revealed by Mathematical Modeling

The intrinsic ability of cells to adapt to a wide range of environmental conditions is a fundamental process required for survival. Potassium is the most abundant cation in living cells and is required for essential cellular processes, including the regulation of cell volume, pH and protein synthesis. Yeast cells can grow from low micromolar to molar potassium concentrations and utilize sophisticated control mechanisms to keep the internal potassium concentration in a viable range. We developed a mathematical model for Saccharomyces cerevisiae to explore the complex interplay between biophysical forces and molecular regulation facilitating potassium homeostasis. By using a novel inference method (“the reverse tracking algorithm”) we predicted and then verified experimentally that the main regulators under conditions of potassium starvation are proton fluxes responding to changes of potassium concentrations. In contrast to the prevailing view, we show that regulation of the main potassium transport systems (Trk1,2 and Nha1) in the plasma membrane is not sufficient to achieve homeostasis.

A Validated Stability-Indicating Liquid Chromatographic Method for Determination of Degradation Impurities and Diastereomers in Voriconazole Tablets

A reversed-phase gradient liquid chromatographic method has been developed for the quantitative determination of Voriconazole, along with its degradation and diastereomeric impurities in tablet dosage form. Chromatographic separation has been achieved on an Inertsil ODS 3V, 150 × 4.6 mm, 5 μm column. The mobile phase consisting of solvent A 0.05 molar (M) potassium dihydrogen phosphate (pH 2.5 buffer) and solvent B (mixture of acetonitrile and methanol in the ratio 90:10 (v/v)), was delivered at a flow rate of 1.2 mL min−1 with the detection wavelength at 256 nm. Resolution of Voriconazole and all five potential impurities was achieved at greater than 2.0 for all pairs of compounds. The drug was subjected to stress conditions such as oxidative, acid and base hydrolysis, and thermal and photolytic degradation. Voriconazole was found to degrade significantly under base hydrolysis stress conditions compared to acid hydrolysis stress conditions. The degradation products were well-resolved from the main peak and its impurities, thus proving the stability-indicating power of the method. The stressed samples were assayed against a reference standard and the mass balance was found to be close to 99.0%. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision, and robustness.

Assessing Potential Reactivity of Aggregates in Presence of Potassium Acetate Deicer

The standard ASTM C1260 and ASTM C1293 test methods focus on identifying aggregate reactivity in the presence of alkali hydroxides. The sensitivity of these test methods to assess aggregate reactivity in the presence of deicing chemicals is unknown. Preliminary efforts to develop a test method to identify aggregate reactivity in the presence of deicing chemicals yielded a mortar bar test (EB-70 test) based on soaking the mortar bars containing the suspect aggregates in a 6.4 molar potassium acetate (6.4 M KAc) deicer solution, instead of a 1 normal sodium hydroxide (1 N NaOH) solution, as in the standard ASTM C1260 test. The EB-70 test method was effective in identifying highly reactive aggregates but erratic in assessing moderate, slowly reactive aggregates. Deficiencies in that method were attributed to the lack of a precise understanding of the mechanisms involved in high pH jump observed on interaction of KAc with alkali hydroxides and calcium hydroxide. The knowledge gained in recent studies in understanding the mechanism has provided a sound basis for making some modifications to the EB-70 test method. A revised EB-70 test method is presented: it uses a 1 N NaOH and 3 M KAc deicer as its soak solution. Evidence from testing 31 different aggregates with a range of aggregate mineralogy and reactivity indicated that the revised method was effective in characterizing a range of aggregate reactivity in the presence of deicing chemicals. Limited studies were conducted to evaluate a low-lime fly ash (Class F) in mitigating mortar bar expansions in the EB-70 test method. A low-lime fly ash was effective in controlling mortar bar expansion in the revised EB-70 test method.

Nitrogen-Doped Carbon Nanotube Arrays with High Electrocatalytic Activity for Oxygen Reduction

The large-scale practical application of fuel cells will be difficult to realize if the expensive platinum-based electrocatalysts for oxygen reduction reactions (ORRs) cannot be replaced by other efficient, low-cost, and stable electrodes. Here, we report that vertically aligned nitrogen-containing carbon nanotubes (VA-NCNTs) can act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction in alkaline fuel cells. In air-saturated 0.1 molar potassium hydroxide, we observed a steady-state output potential of -80 millivolts and a current density of 4.1 milliamps per square centimeter at -0.22 volts, compared with -85 millivolts and 1.1 milliamps per square centimeter at -0.20 volts for a platinum-carbon electrode. The incorporation of electron-accepting nitrogen atoms in the conjugated nanotube carbon plane appears to impart a relatively high positive charge density on adjacent carbon atoms. This effect, coupled with aligning the NCNTs, provides a four-electron pathway for the ORR on VA-NCNTs with a superb performance.

The Relationship Between KCl Infusion and Changes of ECG, Electrolytes of Plasma and K Content of Donkey's Red Blood Cells

Sudden marked increases in the serum potassium concentration, up to 8 to 9 meq L(-1), are the result of transcellular movement of potassium and are associated with profound electrocardiographic abnormalities and fluid shifts. Electrocardiographic changes associated with hyperkalemia have been described in the cat, the dog, the horse and are well documented in man. Since there is no research about the effects of hyperkalemia on electrocardiogram of donkey, the purpose of this study was to induce the experimentally hyperkalemia in donkey and studying the relationship between KCl infusion and changes of ECG, electrolytes of plasma and K content of donkey's red blood cells. This research was carried out in seven clinically healthy female donkeys, injected with 0.35 molar potassium chloride solutions to jugular vein. Results indicated that potassium content of RBC at 30, 45, 60, 75 and 90 min, blood potassium level at 30, 45, 60, 75 and 90 min, blood calcium at 60, 75, 90 and 105, increased significantly and blood magnesium decreased significantly at 135 min. Electrocardiographic changes were first degree A-V block, wandering pacemaker, inversion of negative to positive T-wave, flattening of the P-wave, ventricular premature beat, sinus arrest, bradycardia and sinus tachycardia.

Evaluation of Soil Extractants in Terms of Growth

There is a strong criticism against usage of buffered ammonium acetate as an extractant for the determination of exchangeable elements in acid soils dominated by low‐activity clays. There are several reports regarding the use and misuse of diethylene triamine penta acetic acid as a universal extractant for iron, manganese, copper, and zinc, etc., in acid soils. Similarly there were several attempts to develop extractants to suit different soils. Rubber growing soils are classified as Ultisols and are acidic in reaction dominated by low‐active clays. In this study, two systems of extraction of soil nutrients in rubber growing soils were compared. Soil samples from 14 different soils were extracted with neutral normal ammonium acetate for bases viz. calcium, magnesium, potassium, and sodium; one molar potassium chloride for aluminum and diethylene triamine penta acetic acid for manganese (System I), and 0.1 molar barium chloride (System II) to extract all the above in a single step. It was seen that barium chloride extracted more of exchangeable elements when compared to ammonium acetate. Paired t‐test indicated that the difference between System I and II was significant with regard to bases and manganese. Plant growth expressed as volume was regressed on the soil properties measured in both the systems. The regression equation indicated that organic carbon, phosphorus, bases, aluminum and manganese measured using barium chloride contributed significantly to the variability in growth with an R2 of 0.979, and the regression analysis was significant. None of the soil properties measured in System II showed any significant effect on growth. Considering the facts it is suggested to adopt barium chloride extraction, which is a simple single‐step procedure that extracts all elements that contribute to the cation exchange capacity at field pH unlike ammonium acetate that is buffered at pH 7.

Enzymatic synthesis of [formula omitted] on the preparative scale

The problems inherent in the enzymatic and chemical synthesis of S- adenosyl- l-methionine (SAM) led us to develop an efficient, simple method for the synthesis of large amounts of labeled SAM. Previously, we reported that the problem of product inhibition of E. coli SAM synthetase encoded by the metK gene was successfully overcome in the presence of sodium p-toluenesulfonate ( pTsONa). This research has now been expanded to demonstrate that product inhibition of this enzyme can also be overcome by adding a high concentration of β-mercaptoethanol (βME), acetonitrile, or urea. In addition, a recombinant strain of E. coli has been constructed that expresses the yeast SAM synthetase encoded by the sam2 gene. The yeast enzyme does not have the problem of product inhibition seen with the E. coli enzyme. Complete conversion of 10 mM methionine to SAM was achieved in incubations with either the recombinant yeast enzyme and 1 molar potassium ion or the E. coli enzyme in the presence of additives such as βME, acetonitrile, urea, or pTsONa. The recombinant yeast SAM synthetase was used to generate SAM in situ for use in the multi-enzymatic synthesis of precorrin 2.

Determination of the concentration of higher alcohols with enzyme coupled flow-injection analysis in model systems

The activities of native and immobilized alcohol oxidases (AOD) originating from Pichia pastoris, Hansenula sp., Candida boidinii and Peniophora gigantea were compared with regard to the oxidation of various higher alcohols. Except Candida boidinii, the immobilized enzymes were applied in a flow-injection analysis system and investigated as a function of the various operation variables. During the oxidation O 2 is consumed which concentration was measured with an amperometric detector. At the same time H 2O 2 is produced, the concentration of which is used for the oxidation of a redox indicator (ABTS) catalysed by peroxidase and measured with a photometer. The amperometric method is simpler and more economical, but less sensitive. The photometric method consumes the dissolved redox indicator and peroxidase, but is highly sensitive especially for higher alcohols. The concentrations of n-propanol, n-butanol and n-pentanol can be measured with satisfactory sensitivity with immobilized alcohol oxidases originating from Pichia pastoris and Peniophera gigantea in a one molar potassium phosphate buffer (pH 7.5). The concentrations of isopropanol, octanol, dodecanol and benzylalcohol can be measured only when larger than 1 g l −1.

Olivine dissolution at 25°C: Effects of pH, CO 2, and organic acids

The dissolution rates of Fo 100 and Fo 91 in aqueous solutions in the pH range 2–12.4 at 25°C have been measured using fluidized bed and batch reactors. Rates depend upon the pH, the partial pressure of CO 2, and the presence of organic ligands. At low P CO 2 (≤10 −4.5 atm) with no organic ligands present, the rate of olivine dissolution, R, is given by R ( mol cm −2 s −1 ) = 9.07 × 10 −12a H + 0.54 + 5.25 × 10 −15 + 2.33 × 10 −17a H + −0.31 , where a H + is the activity of H + in solution. However in basic solutions, when the partial pressure of CO 2 is equal to atmospheric levels ( P CO 2 = 10 −3.5 atm), olivine dissolution rates are nearly pH independent throughout the pH range 6–12 and are about equal to the minimum rate of dissolution under CO 2 purged conditions. At pH 11 the presence of atmospheric levels of CO 2 reduces the dissolution rate by over an order of magnitude (to 10 −14.1 mol cm −2 s −1). Apparently, positive charge on the olivine surface can be neutralized by increasing P CO 2 . In contrast, experiments conducted in the acidic and near neutral pH ranges indicate that organic ligands chelate surface Mg causing an increase in the olivine dissolution rate when present. Organic ligand effects are greatest in the near neutral pH domain. For example, at pH 4 dissolution rates are increased by 0.75 log units (to 10 −12.25 mol cm −2 s −1) in solutions of 10 −3 molar ascorbic acid or 0.05 molar potassium acid phthalate over rates measured in organic free solutions. The chelation effect becomes less important as pH decreases. Rates at pH 2 in the presence of these organic ligands are indistinguishable from those measured without organics.

Errors in the measurement of extractable soil inorganic nitrogen caused by impurities in the extracting solution

Abstract The potassium salts used as extracting solutions to determine soil inorganic nitrogen contain nitrogen impurities which could introduce a small error into the analysis. Ammonium nitrogen can be removed from the extracting solutions by raising the pH of the solution to pH 11.0 by the addition of 1 Molar potassium hydroxide and then boiling and stirring for a period of 15 minutes to expel all the ammonia. The pH can be readjusted to 6.0 with an appropriate dilute acid depending on the potassium salt being purified. As there is no simple method for the removal of nitrate it is suggested that the potassium salts are tested and a batch with a low level of nitrate selected for use where soil nitrate levels are expected to be low.