Molar Ratio In Solution Research Articles

Design Parameters for Ionic Liquid–Molecular Solvent Blend Electrolytes to Enable Stable Li Metal Cycling Within Li–O2 Batteries

AbstractEffective utilization of Li‐metal electrodes is vital for maximizing the specific energy of lithium–oxygen (Li–O2) batteries. Many conventional electrolytes that support Li–O2 cathode processes (e.g., dimethyl sulfoxide, DMSO) are incompatible with Li‐metal. Here, a wide range of ternary solutions based on solvent, salt, and ionic liquid (IL) are explored to understand how formulations may be tailored to enhance stability and performance of DMSO at Li‐metal electrodes. The optimized formulations therein facilitate stable Li plating/stripping performances, Columbic efficiencies >94%, and improved performance in Li–O2 full cells. Characterization of Li surfaces reveals the suppression of dendritic deposition and corrosion and the modulation of decomposition reactions at the interface within optimized formulations. These observations are correlated with spectroscopic characterization and simulation of local solvation environments, indicating the persistent importance of DMSO–Li+‐cation interactions. Therein, stabilization remains dependent on important molar ratios in solution and the 4:1 solvent‐salt ratio, corresponding to ideal coordination spheres in these systems, is revealed as critical for these ternary formulations. Importantly, introducing this stable, non‐volatile IL has negligible disrupting effects on the critical stabilizing interactions between Li+ and DMSO and, thus, may be carefully introduced to tailor other key electrolyte properties for Li–O2 cells.

An investigation into potential pathways for nickel and cobalt loss during impurity removal from synthetic nickel laterite pressure acid leach solutions via partial neutralisation

The primary pathways by which nickel (Ni) and cobalt (Co) loss could occur from acidic sulfate solution during partial neutralisation of synthetic nickel laterite pressure acid leach solutions (to pH 4 at 85 °C) was investigated. Knowledge of the avenues by which Ni and Co loss occurs will enable minimisation of valuable metal losses through optimisation of the partial neutralisation process. Precipitation of Ni and Co as their hydroxides did not appear to be a pathway by which metal loss occurred during partial neutralisation. Additionally, co-precipitation of Ni and Co with either Fe(III) or Al was not found to be a significant route for valuable metal loss. Adsorption onto freshly precipitated hydrous oxides of Al and Fe(III), as well as haematite, a major component of nickel laterite pressure leach discharge solids, appeared to be the primary route by which Ni and Co loss occurs during partial neutralisation. There was a preference for Co to adsorb onto haematite and ferric iron precipitates whilst Ni preferentially adsorbed onto Al precipitates. The molar ratio of Al to Fe(III) in the synthetic feed liquor was found to be a key variable controlling Ni and Co loss during partial neutralisation. Final Ni losses initially increased with increasing Al/Fe molar ratio in the feed, being at their highest in the absence of Fe(III) (10.7% Ni loss), and when the Al/Fe molar ratio in solution was unity (11.9% Ni loss), then decreased significantly when the Al/Fe ratio in the feed liquor was greater than or equal to 2 (2% Ni loss). Cobalt losses generally decreased with increasing Al/Fe ratio in solution except for in the presence of haematite where Co losses were 3.30%, confirming that Co adsorption onto haematite is a significant route by which loss of this valuable metal occurs during partial neutralisation.

Complex of lysozyme and Myramistin: formation and adsorption at the water–xylene interface

Lysozyme and Myramistin are able to associate when their molar ratio in solution reaches 1: 1. Lysozyme preserves its secondary structure in the complex, whose surface activity at the water–p-xylene interface represents a model for the drug interaction with cellular membrane.

Effect of the Titanium Isopropoxide:Acetylacetone Molar Ratio on the Photocatalytic Activity of TiO2 Thin Films.

TiO2 thin films with different titanium isopropoxide (TTIP):acetylacetone (AcacH) molar ratios in solution were prepared by the chemical spray pyrolysis method. The TTIP:AcacH molar ratio in spray solution varied from 1:3 to 1:20. TiO2 films were deposited onto the glass substrates at 350 °C and heat-treated at 500 °C. The morphology, structure, surface chemical composition, and photocatalytic activity of the obtained TiO2 films were investigated. TiO2 films showed a transparency of ca 80% in the visible spectral region and a band gap of ca 3.4 eV irrespective of the TTIP:AcacH molar ratio in the spray solution. TiO2 films consist of the anatase crystalline phase with a mean crystallite size in the range of 30–40 nm. Self-cleaning properties of the films were estimated using the stearic acid (SA) test. A thin layer of 8.8-mM SA solution was spin-coated onto the TiO2 film. The degradation rate of SA as a function of irradiation time was monitored by Fourier-transform infrared spectroscopy (FTIR). An increase in the TTIP:AcacH molar ratio from 1:4 to 1:8 resulted in a ten-fold increase in the photodegradation reaction rate constant (from 0.02 to the 0.2 min−1) under ultraviolet light and in a four-fold increase under visible light.

Ion distribution in analcime-leucite mineral and Na+-K+ mixed solution

Abstract Ion exchange behavior of analcime-leucite mineral was discussed in this work. Leucite was firstly prepared from analcime in 3.0 mol/L K2CO3 solution, and a liner relationship was fitted between temperature and ion exchange extent. Na+ and K+ distribution in analcime-leucite mineral and Na+-K+ mixed solutions were investigated by varying the K/(K + Na) molar ratio in solution from 0 to 1.0. It turned out that the mutual conversion between analcime and leucite can be realized depending on solution composition, but analcime had a wide stable range of K/(K + Na) ratio in the solutions, indicating Na+ was more accessible into the analcime-leucite framework. Present results also made it necessary to reevaluate the K+ extraction and harmful metal ion immobilization ability of analcime-leucite mineral under the influence of Na+.

“Precipitation on Nanoparticles”: Attractive Intermolecular Interactions Stabilize Specific Ligand Ratios on the Surfaces of Nanoparticles

AbstractConfining organic molecules to the surfaces of inorganic nanoparticles can induce intermolecular interactions between them, which can affect the composition of the mixed self‐assembled monolayers obtained by co‐adsorption from solution of two different molecules. Two thiolated ligands (a dialkylviologen and a zwitterionic sulfobetaine) that can interact with each other electrostatically were coadsorbed onto gold nanoparticles. The nanoparticles favor a narrow range of ratios of these two molecules that is largely independent of the molar ratio in solution. Changing the solution molar ratio of the two ligands by a factor of 5 000 affects the on‐nanoparticle ratio of these ligands by only threefold. This behavior is reminiscent of the formation of insoluble inorganic salts (such as AgCl), which similarly compensate positive and negative charges upon crystallizing. Our results pave the way towards developing well‐defined hybrid organic–inorganic nanostructures.

Effect of Zn:S molar ratio in solution on the properties of ZnS thin films and the formation of ZnS nanorods by spray pyrolysis

The ZnS layers morphology, structure, composition, and optical properties were investigated with respect to the precursors (zinc chloride and thiocarbamide, Zn:S) molar ratio in spray solution (1:1, 1:2, and 1:3) and growth temperatures in the range of 400–600 °C. Scanning electron microscopy (SEM), X‐ray diffraction (XRD), energy dispersive X‐ray analysis (EDX), UV–VIS, and PL spectroscopy were applied to characterize the ZnS layers. Layers obtained at temperatures up to 450 °C are not well crystallized and contain residues originated from undecomposed precursors. ZnS films become crystalline at Ts = 500 °C. Layers grown from 1:1 solution at 550 °C are mixture of ZnS and ZnO phases, whereas at 600 °C layers of ZnO were obtained. Films produced from 1:2 solution at 500–600 °C are of ZnS with a wurtzite structure and Eg of 3.66 eV, but contain traces of ZnO phase when grown at 550 or 600 °C. Appearance of ZnO phase in the films grown from 1:1 and 1:2 solutions is explained by the results of the studies on the formation and decomposition of dichlorobis(thiocarbamide)zinc(II) complex as an intermediate compound formed in the solution of zinc chloride and thiocarbamide. Spraying the solutions with Zn:S = 1:3, which contain more thiocarbamide than required for the complex formation, results in single‐phase ZnS layers with wurtzite structure at growth temperatures up to 600 °C. Moreover, ZnS layers obtained from 1:3 solution at 550 °C and higher are composed of highly c‐axis oriented ZnS nanorod‐like crystals with diameter of ca. 80 nm and length of ca. 300 nm.

Effect of [Al] and [In] molar ratio in solutions on the growth and microstructure of electrodeposition Cu(In,Al)Se2 films

In this paper, the cyclic voltammetric studies were used to realize the element's reduction potential and chemical reaction mechanism for presuming the formation routes of quaternary Cu(In,Al)Se2 crystals. Thereafter, the prior adjustment of deposited potential from −0.6V to −1.0V can be identified a suitable potential as co-electrodeposition. The material characteristics of Cu(In,Al)Se2 films are dominated by the percentage of aluminum content. Thus, the influence of aluminum and indium concentrations in solutions on the percentage composition, surface morphology, structural and crystal properties, and optical energy band gap of Cu(In,Al)Se2 films were investigated. Energy dispersive X-ray spectroscopy (EDS) indicated that the ratio of Al to (Al+In) in Cu(In,Al)Se2 films varied from 0.21 to 0.42 when adjusting aluminum and indium concentrations in solutions. Scanning electron microscopy (SEM) shows that the surface morphology changed from round-like structures into cauliflower-like structures and became rough when the aluminum concentration increased and indium concentration decreased in solutions. X-ray diffraction (XRD) patterns revealed three preferred growth orientations along the (112), (204/220), and (116/312) planes for all species. The (αhυ)2 versus hυ plots (UV–Visible) shows that the optical energy band gap of the Cu(In,Al)Se2 films can be successfully controlled from 1.17eV to 1.48eV by adjusting the aluminum and indium concentrations. Furthermore, the shift of the (112) peak in the XRD patterns and variation of optical band gap are evidence that the incorporation of aluminum atoms into the crystallitic CuInSe2 forms Cu(In,Al)Se2 crystals.

Synergistic effects in mixtures of two identically charged ionic surfactants with different critical micelle concentrations

Expressions for the critical micelle concentration (cmc) and activity coefficients as functions of surfactant composition in mixtures of two identically charged monovalent ionic surfactants are derived from the nonlinear Poisson–Boltzmann (PB) theory. For the special case of no added salt, the simple expression cmcα = xcmcα1 + (1 − x)cmcα2 is deduced, where the exponential parameter α > 1 depends on the number of ionic species in a surfactant molecule as well as the curvature of the self-assembled interface. Theoretical predictions are compared with cmc values obtained with some different experimental techniques for mixtures of the two cationic surfactants didodecyldimethylammonium bromide (DDAB) and dodecyltrimethylammonium bromide (DTAB) in water and in the absence of added salt. It is demonstrated that the PB theory generates significantly better agreement with experimental data than predicted by ideal behaviour or the regular mixture theory. We find that maximum synergistic effects occur at a DDAB mole fraction in solution y = 0.005. According to the PB theory, this very low value of y corresponds to a mole fraction of DDAB in the self-assembled interfacial aggregates equal to x = 0.995. Moreover, our calculations of the surfactant composition in the self-assembled interfacial aggregates above cmc demonstrate that the transition from small micelles to large bilayer aggregates is found to consistently occur at a mole fraction of DDAB equal to about x = 0.41–0.42, irrespective of the surfactant molar ratio in solution. Experimental observations strongly support the fact that concentrations of free surfactant, as well as the surfactant composition in the self-assembled interfacial aggregates, may be accurately calculated from the non-linear Poison–Boltzmann theory. On the other hand, a micelle-to-bilayer transition induced by changes in surfactant mole fraction in the self-assembled interfacial aggregates is consistent with neither ideal surfactant behaviour nor synergistic behaviour according to the regular mixture theory.

Spontaneous precipitation of calcium silicate hydrate in aqueous solutions

AbstractCalcium silicate hydrates (C‐S‐H) are very important not only for their contribution to the development of cement and concrete properties but also for use as fillers and in silicate glasses. In the present work, the thermodynamics and the kinetics of the spontaneous precipitation of C‐S‐H from aqueous solutions were investigated over the pH range 10‐12 at 25 °C. The thermodynamic driving force was calculated taking into consideration all equilibria involved in the supersaturated solutions. In the range of the solution supersaturation values examined the precipitation occurred spontaneously, with the exception of the series of experiments done at pH 12.0, where induction times preceded the appearance of the precipitate. The rates were measured at constant pH as a function of the solution supersaturation and were found to depend strongly on the solution supersaturation, pH and on the total calcium to total silicate molar ratio in solution. Fit of the kinetics results in a power law relating rates of precipitation with respect to C‐S‐H precipitated, suggested a surface diffusion controlled mechanism for the formation of C‐S‐H. The precipitated solids did not show significant morphological differences at different pH values. From the induction times preceding the spontaneous precipitation at pH 12.0, a value of 30 mJm‐2 was calculated for the surface energy of C‐S‐H. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Phosphate removal from water using lithium intercalated gibbsite

In this study, lithium intercalated gibbsite (LIG) was investigated for its effectiveness at removing phosphate from water and the mechanisms involved. LIG was prepared through intercalating LiCl into gibbsite giving a structure of [LiAl 2(OH) 6] + layers with interlayer Cl − and water. The results of batch adsorption experiments showed that the adsorption isotherms at various pHs exhibited an L-shape and could be fitted well using the Langmuir model. The Langmuir adsorption maximum was determined to be 3.0 mmol g −1 at pH 4.5 and decreased with increasing pH. The adsorption of phosphate was mainly through the displacement of the interlayer Cl − ions in LIG. In conjunction with the anion exchange reaction, the formation of surface complexes or precipitates could also readily occur at lower pH. The adsorption decreased with increasing pH due to decreased H 2PO 4 −/HPO 4 2− molar ratio in solution and positive charges on the edge faces of LIG. Anion exchange is a fast reaction and can be completed within minutes; on the contrary, surface complexation is a slow process and requires days to reach equilibrium. At lower pH, the amount of adsorbed phosphate decreased significantly as the ionic strength was increased from 0.01 to 0.1 M. The adsorption at higher pH showed high selectivity toward divalent HPO 4 2− ions with an increase in ionic strength having no considerable effect on the phosphate adsorption. These results suggest that LIG may be an effective scavenger for removal of phosphate from water.

Effect of inorganic anions on the morphology and structure of magnesium calcite.

Calcium carbonate was precipitated from calcium hydroxide and carbonic acid solutions at 25 degrees C, with and without addition of different magnesium (MgSO(4), Mg(NO(3))(2) and MgCl(2)) and sodium salts (Na(2)SO(4), NaNO(3) and NaCl) of identical anions, in order to study the mode of incorporation of magnesium and inorganic anions and their effect on the morphology of calcite crystals over a range of initial reactant concentrations and limited c(i)(Mg(2+))/c(i)(Ca(2+)) molar ratios. The morphology, crystal size distribution, composition, structure, and specific surface area of the precipitated crystals, as well as the mode of cation and anion incorporation into the calcite crystal lattice, were studied by a combination of optical and scanning electron microscopy (SEM), electronic counting, a multiple BET method, thermogravimetry, FT-IR spectroscopy, X-ray diffraction (XRD), and electron paramagnetic resonance (EPR) spectroscopy. In the systems of high initial relative supersaturation, precipitation of an amorphous precursor phase preceded the formation of calcite, whereas in those of lower supersaturation calcite was the first and only polymorphic modification of calcium carbonate that appeared in the system. The magnesium content in calcite increased with the magnesium concentration in solution and was correlated with the type of magnesium salt used. Mg incorporation caused the formation of crystals elongated along the calcite c axis and, in some cases, the appearance of new [011] faces. Polycrystalline aggregates were formed when the c(i)(Mg(2+))/c(i)(Ca(2+)) molar ratios in solution were increased. Addition of sulfate ions, alone, caused formation of spherical calcite polycrystalline aggregates.

Responses of Quaking Aspen Seedlings to Solution Calcium and Aluminum

Quaking aspen (Populus tremuloides Michx.) seedlings were grown in nutrient solutions to study their responses to various levels of calcium (Ca) and aluminum (Al) in four experiments. In solutions with 100 to 2500 µM Al, seedlings had visible symptoms of Al toxicity and/or Al‐induced deficiencies of Ca or phosphorus (P). The symptoms became more prominent with increasing solution Al, and less prominent with increasing solution Ca. Elongation of shoots and roots declined significantly with increasing solution Al, and usually increased with increasing solution Ca. Therefore, elongation of shoots and roots was closely related to ratio of solution Ca/Al. The molar ratio of solution Ca/Al associated with 90% of maximum elongation was 0.23 for shoots and 1.86 for roots. The levels of solution magnesium (Mg) and NH4 did not significantly affect the response of aspen to solution Ca/Al ratio. Concentrations of leaf Ca, nitrogen (N), and Mg as well as root Ca, potassium (K) and Mg decreased as solution Al increased, whereas leaf Ca, N, and P and root Ca and K usually increased with increasing solution Ca. Adding Al into solutions increased leaf and root Al. Shoot elongation was positively and closely related to the root Ca/Al ratio, while root elongation was positively and closely related to root Ca. In addition, aspen growth was significantly related to tissue N and K. These relationships indicate that Ca deficiency was a primary, but probably not the sole cause of growth reduction in solutions with high Al.

Comparison of modified montmorillonite adsorbents: Part I: preparation, characterization and phenol adsorption

This study concerns with the development of modified montmorillonites as adsorbents for water treatment. Polymeric aluminium and iron intercalated forms of montmorillonites have been prepared in the absence and presence of an alkylammonium cationic surfactant (Hexdecyl-trimethyl-ammonium bromide, HDTMA). Montmorillonites intercalated with polymeric Al, Fe, Fe/Al (2:1 Fe to Al ratio in solution), possess large N 2 Brunauer–Emmett–Teller (BET) surface areas. XRD data also shows trace amounts of illite and plagioclase within the clay materials. Montmorillonites intercalated with HDTMA, polymeric Fe/HDTMA, polymeric Al/HDTMA and polymeric Fe/Al/HDTMA (1:1 metal to surfactant molar ratio in solution) undergo some losses of N 2 BET surface areas. Preliminary adsorption studies on phenol have shown that polymeric Al/HDTMA- and HDTMA-only-modified montmorillonites possess a good affinity for phenol, whereas the polymeric Al/Fe modified- and starting montmorillonites have little affinity for phenol adsorption.

Bromide as a Tracer for Nitrate‐N Uptake in Alfalfa Herbage

AbstractThe 15N isotope is a reliable way to measure nitrate‐N (NO‐3‐N) uptake in N2‐fixing legumes, but is too expensive for plant breeding programs. Our goal is to develop an affordable method of selecting alfalfa (Medicago sativa L.) for NO‐3‐N uptake under field conditions. In this research, we tested whether the anion bromide (Br‐), which is used to trace NO‐3‐N movement in soils and is inexpensive to analyze, reflects NO‐3‐N uptake in alfalfa. ‘Webfoot’ (1994 and 1995), ‘Agate’ (1995), and ‘Ineffective Agate’ (1995) alfalfa were established in pots in the greenhouse. After removing herbage, daily additions of solutions containing Br‐ and 15N‐labeled NO‐3‐N were made to the pots. Uptake of Br‐ and N derived from NO‐3‐N was determined in herbage regrowth sampled after 15, 25, and 35 d and the molar ratio of NO‐3‐N‐derived N:Br‐ was calculated. In both years, when a constant molar ratio in solution was provided at variable tracer concentrations, NO‐3‐N uptake and Br‐ uptake both increased with increasing applied tracer concentration, but ratios in herbage were not constant for treatment, germplasm, or days of regrowth. These results imply that selection must be carried out under well‐controlled tracer supply and crop management. At a constant NO‐3‐N concentration, but increasing solution Br‐ concentration, NO‐3‐N uptake remained constant and Br‐ uptake increased. Molar ratios of NO‐3‐N‐derived N:Br‐ in herbage directly reflected applied solution ratios in a soil‐sand mixture (1994), but were less responsive in sand (1995) above molar ratios of 100:1 in solution. Individual plant analysis showed close agreement in Br‐ and NO‐3‐N uptake among plants in all germplasms across a wide range of tracer supply, and indicated that selection for NO‐3‐N uptake using Br‐ uptake would result in minimal error. We conclude that Br‐ is a promising alternative tracer for use in selecting alfalfa for NO‐3‐N uptake.

Chemical precipitation of cesium from waste solutions with iron(II)hexacyanocobaltate(III) and triphenylcyanoborate

Abstract Two chemical processes involving precipitation of cesium from waste solutions with iron(II)hexacyanocobaltate(III) and triphenylcyanoborate have been conducted. Various parameters have been investigated such as pH, molar ratio of Fe2+/Co(CN) 6 3− , molar ratio of triphenylcyanoborate to cesium and the nature of the simulated wastes. High percentage of cesium removal from different waste solutions has been achieved by using iron(II)hexacyanocobaltate(III). Precipitation of cesium with triphenylcyanoborate depends mainly on the concentration of triphenylcyanoborate and cesium as well as the molar ratio in solution. Triphenylcyanoborate can be used as a selective precipitant for cesium in both acidic and alkaline solution of pH not more than 10.

Effect of Precipitating Conditions on the Formation of Calcium−HEDP Precipitates

Phosphonates are water treatment chemicals that are effectively utilized in many industrial processes as dispersants, bleaching agents, or scale and corrosion inhibitors. In many of these applications, the phosphonates are able to react with divalent cations such as calcium to form stable divalent cation−phosphonate precipitates. The focus of this paper is to define the conditions under which distinct calcium−phosphonate precipitates will form and to study how each of these precipitate's unique chemical and physical properties govern the release of phosphonate from porous media. The phosphonate used in this study was (1-hydroxyethylidene)-1,1-diphosphonic acid (HEDP). By variation of the pH and calcium/HEDP molar ratio in solution, two distinct precipitates were formed: (1) a soluble, fibrous 1:1 calcium/HEDP precipitate; and (2) a less soluble, spherical 2:1 calcium/HEDP precipitate. Critical pH values that define the conditions under which each distinct precipitate forms were identified. Below the firs...

Effect of Monosilicic Acid on Hydrolytic Reactions of Aluminum

AbstractThe mechanisms and products of hydrolytic reactions of Al ions as influenced by Si(OH)4 were studied under the experimental parameters of degere of hydrolysis of Al (OH/Al molar ratios,) Si/Al molar ratios, Al concentrations of 1.39 × 10‐3M and 1.39 × 10‐4M, and time.As the degree of hydrolysis of Al increased, the amounts of Si along with Al initially precipitated and removed from the solution phase by ultrafiltration consistently increased. The coprecipitation data, infrared evidence, and stoichiometric considerations of Si(OH)4 removal and proton release strongly indicate that the predominant coprecipitation of Si(OH)4 with hydroxy‐Al ions is the condensation reaction involving the hydroxyl groups in hydroxy‐Al ions. At the OH/Al molar ratios of 1 and 2 and in the absence of Si(OH)4, precipitation of Al continued with aging; whereas at the Si/Al molar ratios of 0.5 and 1, the reaction products were metastable, and there was formation of a significant portion of nonextractable Al which was not removed by ultrafiltration.In the absence of Si(OH)4, the product was crystalline Al(OH)3 even at the OH/Al molar ratio of 1. Materials amorphous to X‐ray and electron diffraction were the only products at Si/Al molar ratios of 0.5 and 1, OH/Al molar ratios of 2 and 3, and both initial Al concentrations even after prolonged aging. Decreasing degree of hydrolysis of Al resulted in a distinct decrease in particle size for crystalline products, and in a decrease in the extent of aggregation for amorphous products. The thermal stability and Si/Al ratio of the reaction products were influenced by the Si/Al molar ratio of solution and the period of aging. The presence of Si(OH)4 in solutions also resulted in a decreased Cl inclusion in the reaction products.The results clearly show that the presence of Si(OH)4 affects the hydrolytic reactions of Al at all degrees of hydrolysis of Al. This knowledge is of basic significance for a further understanding of pedogenic processes, and the fate of certain nutrients and environmental pollutants.