Hydroxide In Aqueous Solution Research Articles

POROUS FLY ASH-BASED GEOPOLYMER USABLE AS AN UNCONVENTIONAL CONSTRUCTION MATERIAL

Geopolymer foam with thermal insulation properties was made by foaming the alumino-silicate mixture composed of fly ash and clay brick waste activated with alkaline activator (water glass and sodium hydroxide in aqueous solution). Other mixture components were expanded perlite as siliceous additive, usual fine aggregate (quartz sand), and less frequently used surfactant (olive oil). The main characteristics of the geopolymer foam were: low density, low thermal conductivity, and relatively high compressive strength. The residual materials contributed to low costs and the complete replacement of ordinary cement led to the significant reduction of CO2 emissions.

Chemical Bath Deposition of α-GaOOH with Tunable Morphology on Silicon Using the pH Adjustment

The growth of GaOOH by chemical bath deposition has received great attention over the past years as a first step to form Ga2O3 with the α- or β-phases by combining a wet chemical route with thermal annealing in air. By using gallium nitrate and sodium hydroxide in aqueous solution, we show that the structural morphology of GaOOH deposits is thoroughly tunable in terms of both dimensions, density, and nature by varying the initial pH value from acidic to basic conditions. In the low-pH region associated with a low supersaturation level and where Ga3+ ions represent the dominant Ga(III) species, GaOOH microrods with a low aspect ratio and low density prevail. In the intermediate-pH region associated with a high supersaturation level and where GaOH2+ ions represent the dominant Ga(III) species, GaOOH prismatic nanorods with a high aspect ratio and high density are preferentially formed. In the high-pH region where Ga(OH)4- complexes are predominantly formed, the growth of partially crystallized GaOOH thin films with a typical thickness of about 1 μm proceeds. These findings show the correlation between the characteristics of the chemical bath and the resulting structural morphology of GaOOH deposits. They further open great perspectives to grow GaOOH and hence Ga2O3-based materials on silicon with a dedicated structural morphology using chemical bath deposition for engineering devices in the fields of gas sensing, solar-blind UV-C photodetection, and power electronics.

Bn2DT3A, a Chelator for 68Ga Positron Emission Tomography: Hydroxide Coordination Increases Biological Stability of [68Ga][Ga(Bn2DT3A)(OH)

The chelator Bn2DT3A was used to produce a novel 68Ga complex for positron emission tomography (PET). Unusually, this system is stabilized by a coordinated hydroxide in aqueous solutions above pH 5, which confers sufficient stability for it to be used for PET. Bn2DT3A complexes Ga3+ in a hexadentate manner, forming a mer-mer complex with log K([Ga(Bn2DT3A)]) = 18.25. Above pH 5, the hydroxide ion coordinates the Ga3+ ion following dissociation of a coordinated amine. Bn2DT3A radiolabeling displayed a pH-dependent speciation, with [68Ga][Ga(Bn2DT3A)(OH)]- being formed above pH 5 and efficiently radiolabeled at pH 7.4. Surprisingly, [68Ga][Ga(Bn2DT3A)(OH)]- was found to show an increased stability in vitro (for over 2 h in fetal bovine serum) compared to [68Ga][Ga(Bn2DT3A)]. The biodistribution of [68Ga][Ga(Bn2DT3A)(OH)]- in healthy rats showed rapid clearance and excretion via the kidneys, with no uptake seen in the lungs or bones.

Tailoring the electrode surface structure by cathodic corrosion in alkali metal hydroxide solution: Nanostructuring and faceting of Au

Nanostructured metals are vital materials in several (electro)chemical applications. Despite the substantial progress in this field, still many limitations are associated with traditional synthetic procedures, including the availability of stable nanoparticles on appropriate supports by avoiding migration and aggregation. On that front, cathodic corrosion has emerged as a powerful technique to tailor the surface structure of metal surfaces on the nanoscale. Cathodic corrosion crucially depends on the electrode potential, the nature and the concentration of cations, as well as the electrode material. Controlling these parameters is essential for applying cathodic corrosion in materials design. In this short review, we discuss the most critical parameters controlling cathodic corrosion and highlight the importance of the nature and the concentration of alkali metal hydroxides in aqueous solution.

Lactate adsorption by layered double hydroxides in aqueous solution and cell culture medium

When cells proliferate in a culture medium, metabolites such as lactic acid gradually accumulate and eventually hinder cell growth. Herein, we considered various layered double hydroxides (LDH) and layered double oxides (LDO) for the selective removal of lactate in aqueous solution and a culture medium by anion exchange. NO3•Mg-Al LDH showed high lactate adsorption, low adsorption of glucose (a nutrient in culture medium), appropriate pH stability, and low cytotoxicity within a limited contact time. In contrast, NO3•Ni-Al LDH, NO3•Ca-Al LDH, Mg-Al LDO, and Cl•Mg-Al LDH had a lower performance than NO3•Mg-Al LDH. To further improve the performance, the anion of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES, a common pH buffer in culture media) was tested as the intercalated anion in Mg-Al LDH. HEPES•Mg-Al LDH (Mg/Al = 2) was found to be the most promising adsorbent for culture medium regeneration because its adsorption behavior was similar to that of NO3•Mg-Al LDH, while it had a much lower cytotoxicity. The traditional methods for regenerating a culture medium by removing accumulated lactate to increase the cell density in large-scale cell culture and lower the costs, including electrolysis, cell modification, and modification of the culture medium’s composition, are complicated to operate and expensive. The adsorption method using HEPES•Mg-Al LDH presented in this study, instead, can be easily operated and has low costs. Thus, it is expected to be applied in actual cases for regenerating culture media.

Retraction of "Cyclodextrin Metal-Organic Frameworks: From the Research Laboratory to the Marketplace".

ConspectusCyclodextrin-based metal-organic frameworks (CD-MOFs), derived from γ-cyclodextrin (γ-CD) and potassium ions, constitute a new class of porous, renewable, and edible MOFs that can be synthesized wholly from naturally occurring starting materials on a large scale. γ-CD is a C8 symmetrical cyclic oligosaccharide, composed of eight asymmetric α-1,4-linked d-glucopyranosyl residues, which possesses a bucket-shaped cavity with an inner diameter of ∼1 nm and a depth of ∼0.8 nm. Upon combining 1 equiv of γ-CD with 8 equiv of potassium hydroxide in aqueous solution, followed by vapor-diffusion of MeOH (or EtOH) into the solution during several days, CD-MOF-1 is obtained as cubic crystals. It was discovered serendipitously in 2010 as the first CD-MOF with a cubic cell of space group I432 and unit cell dimensions of approximately 31 × 31 × 31 Å3. Other CD-MOFs, namely, CD-MOF-2 and CD-MOF-3, can be obtained, respectively, wherein potassium is replaced with rubidium and cesium ions. CD-MOFs comprise infinite body-centered frameworks of (γ-CD)6 cubic units linked by alkali metal cations with spherical pores which reside at the center of the cubes interconnected by both cylindrical and triangular channels.During the past decade, CD-MOFs have emerged as a new class of multifunctional materials based on a porous framework with an extended structure displaying robust crystallinity, permanent porosity, and biocompatibility. The family of CD-MOFs has been enlarged by a growing collection of metal nodes involving alkali metal cations (Li+, Na+, K+, Rb+, Cs+) and γ-CD as well as its derivatives. As a result of the ability of their porous extended frameworks to absorb guest molecules, including gases, drug molecules, metal-based nanoclusters, and nanoparticles, CD-MOFs have potential applications in areas as disparate as adsorption and separation, sensing, template syntheses of metal-based nanoparticles and gels, electrical memory, drug delivery, and catalyst stabilization.In this Account, we tell the story of CD-MOFs, a scientific discovery that was made in our research laboratory at the Northwestern University, and the subsequent commercialization of CD-MOF technology on the part of a spinoff company, which developed a line of successful skin care products. This Account includes representative synthetic methods for the preparation of CD-MOFs, along with a brief overview of their structural features and a general summary of their state-of-the-art applications. The examples, however, are only illustrative, and a significant body of additional findings is emanating from our own laboratory and others, especially in the development of new synthetic strategies, tuning the framework stabilities, and exploring the guest-inclusion properties of CD-MOFs. We refer readers to communications, papers, and reviews on CD-MOFs and to references therein. We also put on record how CD-MOFs have been rebranded as organic molecular vessels (OMVs), a smart, functional, environmentally friendly delivery platform for commercial skin care applications. We hope that, in the telling and retelling of the story of CD-MOFs, this Account may encourage the commercialization of discoveries that have been made in other research laboratories.

Equilibrium and Kinetic Simulation of Groundwater Deironing and Demanganation

Chemical equilibria of iron and manganese aqueous species were analyzed at various Eh–pH and aqueous CO2 concentration. Thermodynamic and equilibrium-kinetic simulations were conducted for the oxidations of iron and manganese aqueous species with reference to groundwater demanganation and deironing, using the most probable rate constants of congruent dissolution reactions of iron and manganese carbonates, rate constants of homogeneous iron oxidation, and surface catalytic oxidation of manganese on suspension of iron hydroxide in aqueous solution. A kinetic–thermodynamic model is suggested for iron and manganese oxidation in groundwater under the effect of dissolved oxygen. The numerical simulations show that deironing is relatively effective, whereas the dissolved manganese(II) concentration increases because of slower manganese oxidation and the dissolution of manganese-bearing siderite. Hence, effective groundwater demanganation is possible if the host rocks contain no manganese-bearing siderite.

Removal of two anionic reactive textile dyes by adsorption into MgAl-layered double hydroxide in aqueous solutions.

Textile dyes pose a significant challenge for water pollution due to the poor degradability of their complex aromatic structures (e.g., RR-120 and RBB-150). In order to minimize the harmful effects of RR-120 and RBB-150, the capacity of MgAl-layered double hydroxide for removing of these contaminants was studied herein. Batch adsorption experiments were conducted to investigate the effect of various operating parameters, such as solution pH, contact time, dye concentration, and temperature in order to provide optimal conditions for removal. Structural and morphological analyses were used to highlight the assembly and/or interaction LDH-dye. The state of equilibrium of RR-120 and RBB-150 adsorption was pH- and temperature-dependent and followed the pseudo-second-order rate model. Also, the equilibrium adsorption data of both dyes were found to adopt the Langmuir type isotherm model, which assumes a monolayer arrangement in LDH-dye. Furthermore, the effects of four major coexisting and competing mono- and divalent interlayer anions, such as NO3-, Cl-, CO32-, and SO42-, on the uptakes of RR-120 and RBB-150 were studied and the results showed that NO3- anions had insignificant effect on the uptakes of RR-120 and RBB-150 by MgAl. An equivalent study on the presence of both dyes in competitive trial adsorption/desorption from binary aqueous solution was investigated. And finally, the reuse operation of recovered material after dye adsorption was tested in up to 5 cycles of recyclability.

Fabricated of Cu Doped ZnO Nanoparticles for Solar Cell Application

Copper with different concentrations doped with zinc oxide nanoparticles were prepared from a mixture of zinc acetate and copper acetate with sodium hydroxide in aqueous solution. The structure of the prepared samples was done by X-ray diffraction, atomic force microscopy (AFM) and UV-VIS absorption spectrophotometer. Debye-Scherer formula was used to calculate the size of the prepared samples. The band gap of the nanoparticle ZnO was determined by using UV-VIS optical spectroscopy.

Fabricated of Cu Doped ZnO Nanoparticles for Solar Cell Application

Copper with different concentrations doped with zinc oxide nanoparticles were prepared from a mixture of zinc acetate and copper acetate with sodium hydroxide in aqueous solution. The structure of the prepared samples was done by X-ray diffraction, atomic force microscopy (AFM) and UV-VIS absorption spectrophotometer. Debye-Scherer formula was used to calculate the size of the prepared samples. The band gap of the nanoparticle ZnO was determined by using UV-VIS optical spectroscopy.

Stabilization of spherical nanoparticles of iron(III) hydroxides in aqueous solution by wormlike micelles

HypothesisThe low Ksp value of Fe(OH)3 (3 × 10−38 at 298 K) explain the immediate coagulation when the pH of a solution of Fe(III) is adjusted to 7. However, stable dispersions of Fe(OH)3 can be formed when the pH is adjusted to 7 in the presence of wormlike micelles formed by cetyltrimethylammonium bromide and sodium salicylate. The formation of a structure containing Fe(OH)3 nanoparticles decorating wormlike micelles is responsible for the high stability of the dispersions. ExperimentsFe(OH)3 nanoparticles were obtained by increasing the pH of solutions of cetyltrimethylammonium bromide and Fe(III), previously complexed with salicylate at pH 3. The interaction between nanoparticles and the chains of wormlike micelles was investigated by DLS, SAXS, TEM and Cryo-TEM. FindingsDLS revealed higher scattering contrast and slower diffusion for wormlike micelles in the presence of nanoparticles. These results were interpreted as the decoration of the chains of wormlike micelles by nanoparticles of Fe(OH)3. A pearl-necklace model was successfully used to adjust SAXS curves, revealing nanoparticles with ∼3 nm of diameter, spaced ∼2 nm apart along the string. This result agrees with TEM and Cryo-TEM images. The formed structure prevents the coagulation of nanoparticles, assuring high stability to the dispersion.

Crystal structure of sodium di-hydrogen arsenate.

Single crystals of the title compound, Na(H2AsO4), were obtained by partial neutralization of arsenic acid with sodium hydroxide in aqueous solution. The crystal structure of Na(H2AsO4) is isotypic with the phosphate analogue and the asymmetric unit consists of two sodium cations and two tetra-hedral H2AsO4- anions. Each of the sodium cations is surrounded by six O atoms of five H2AsO4- groups, defining distorted octa-hedral coordination spheres. In the extended structure, the sodium cations and di-hydrogen arsenate anions are arranged in the form of layers lying parallel to (010). Strong hydrogen bonds [range of O⋯O distances 2.500 (3)-2.643 (3) Å] between adjacent H2AsO4- anions are observed within and perpendicular to the layers. The isotypic structure of Na(H2PO4) is comparatively discussed.

Control of morphology and optical properties of PbS nanostructured thin films by deposition parameters: study of mechanism

ABSTRACTPbS thin films were grown on glass substrates by chemical bath deposition (CBD) using lead nitrate, thiourea and sodium hydroxide in aqueous solutions at three different temperatures (22, 36 and 50 °C). The microstructure and morphology evolution of the films were investigated using X-ray diffraction, scanning electron microscopy and atomic force microscopy. Optical properties were studied using UV–Vis–IR spectroscopy. The results indicate that temperature plays an important role in controlling the morphology and optical properties of nanostructured PbS thin films through changing deposition mechanism. The active deposition mechanism changed from cluster to ion-by-ion mechanism with an increase in deposition temperature from 22 to 50 °C, and consequently, film properties such as morphology, optical absorption and preferred orientation changed completely.

Advantages of aeration in arsenic removal and arsenite oxidation by structural Fe(II) hydroxides in aqueous solution

Structural Fe(II) Hydroxide (SFH) was used to remove As(III) and As(V) from aerated synthetic wastewater with initially 30mg/L As at neutral pH values. Batch experiments were performed to investigate the influence of O2, pH and coexisting HPO42⿿ on As removal by 0.5g (Fe)/L SFH. The results suggested that removal efficiency for As(III) and As(V) were ⿼60% and ⿼50% under anoxic conditions at initial pH 7.0 and 9.0, respectively. However, the efficiency increased to over 90% for both As(III) and As(V) under oxic conditions. The in situ mineral transformation of SFH to newly formed Fe(II/III) and FeOOH was responsible for the robust removal. As(III) removal was nearly unaffected by HPO42⿿ (1.0mM), while obviously inhibition was observed in the case of As(V). The microstructure of fresh and reacted SFH was characterized by FTIR and XPS and these results indicate that As was removed via inner-sphere complexation and precipitation. XPS studies showed that As(III) was converted to As(V) after 2h of reaction in the pH range of 7.0⿿9.0, which is attributable to enhanced formation of Fe(IV) by the Fenton reaction during mineral transformation. In practice, results of this study suggest that aeration is advantageous to significantly enhancement of As(III) oxidation and removal with highly reactive SFH.

Degradation of Direct Black 38 dye catalyzed by lab prepared nickel hydroxide in aqueous medium

<div> <p>This study is focused on degradation of Direct Black dye, a common azo dye, catalyzed by nickel hydroxide in aqueous solution. Nickel sulfatehexahydrate, sodium hydroxide and sodium hypochlorite were used for synthesis of nickel hydroxide catalyst. The catalytic performance of nickel hydroxide for oxidative degradation of Direct Black dye was examined in terms of discrete parameters like effect of temperature, concentration of dye, stirring speed, time of reaction etc. Curve Expert software was used for kinetics analysis of batch experimental data. Degradation reaction was taking place according to Langmuir-Hinshelwood mechanism. According to this mechanism the reactants react in adsorbed form at the surface of nickel hydroxide catalyst. </p> </div> <p> </p>

Hydroxide Solvation and Transport in Anion Exchange Membranes.

Understanding hydroxide solvation and transport in anion exchange membranes (AEMs) can provide important insight into the design principles of these new membranes. To accurately model hydroxide solvation and transport, we developed a new multiscale reactive molecular dynamics model for hydroxide in aqueous solution, which was then subsequently modified for an AEM material. With this model, we investigated the hydroxide solvation structure and transport mechanism in the membrane. We found that a relatively even separation of the rigid side chains produces a continuous overlapping region for hydroxide transport that is made up of the first hydration shell of the tethered cationic groups. Our results show that hydroxide has a significant preference for this overlapping region, transporting through it and between the AEM side chains with substantial contributions from both vehicular (standard diffusion) and Grotthuss (proton hopping) mechanisms. Comparison of the AEM with common proton exchange membranes (PEMs) showed that the excess charge is less delocalized in the AEM than the PEMs, which is correlated with a higher free energy barrier for proton transfer reactions. The vehicular mechanism also contributes considerably more than the Grotthuss mechanism for hydroxide transport in the AEM, while our previous studies of PEM systems showed a larger contribution from the Grotthuss mechanism than the vehicular mechanism for proton transport. The activation energy barrier for hydroxide diffusion in the AEM is greater than that for proton diffusion in PEMs, implying a more significant enhancement of ion transport in the AEM at elevated temperatures.

Hydrothermal Synthesis and Structural Characterization of Orthorhombic LiMnO<sub>2</sub> with Low Stacking Faults

LiMnO2 are synthesized by hydrothermal technique by using Mn(CH3COO)2.4H2O and MnO2 with the same mole ratio which are dissolved in aqueous solution with different concentration LiOH. Structural characterization based on X-ray diffraction and Raman spectroscopy reveals that LiMnO2 is in a well-order orthorhombic structure with lower stacking faults compared to the LiMnO2 prepared by other techniques. Experimental results show that the concentration of lithium hydroxide in aqueous solution affect the quality of LiMnO2.

Crystal structure, spectroscopic and thermal properties of the coordination compounds M(1,3-diethyl-2-thiobarbiturate) M = Rb+, Cs+, Tl+ and NH4+

Four new compounds of 1,3-diethyl-2-thiobarbituric acid (C8H11N2O2S, Hdetba) with Rb+, Cs+, Tl+ and NH4+ ions were prepared by Hdetba neutralization with the metal carbonates or ammonium hydroxide in aqueous solution. The colorless crystals have been investigated using X-ray diffraction techniques, differential scanning calorimetry, thermogravimetry and infrared spectroscopy. The coordination compounds of MDetba with M=Rb, Cs and Tl crystallize in the orthorhombic space group P212121, but compound NH4Detba crystallizes in the triclinic space group P1¯. The MDetba structures were compared at the molecular and supramolecular levels. The Detba− ion in the NH4+ compound forms conformer (A) with two diethyl groups on one side of the ion ring, whereas the Detba− ion in the Rb(I), Cs(I) and Tl(I) compounds forms conformer (B) with two diethyl groups on different sides of the ring. The results of IR spectroscopy and thermal analysis are consistent with the X-ray data.

Oxidative degradation of Methyl Orange catalyzed by lab prepared nickel hydroxide in aqueous medium

This study is focused on oxidative degradation of Methyl Orange, a common azo dye, catalyzed by nickel hydroxide in aqueous solution at 303, 313, 323, and 333 K. Sodium hypochlorite, sodium hydroxide, and nickel sulfate hexahydrate in distilled water were used as starting material for preparation of nickel hydroxide. Pyrex glass batch reactor was used to study the effect of various conditions such as temperature, concentration, agitation, and catalyst dose on catalytic degradation of Methyl Orange in aqueous medium. About 80% Methyl Orange was degraded in 120 min. Experimental data were subjected to kinetic analysis using CurveExpert software. Degradation reaction was taking place according to Langmuir–Hinshelwood mechanism. According to this mechanism, the reactants adsorb at the surface of catalyst in first step followed by reaction between adsorbed reactants in second step. Adsorption of Methyl Orange on surface of catalyst followed Langmuir adsorption isotherm. Apparent activation energy, true activation energy, and heat of adsorption were determined as 13.2, 32.7 and –23.5 kJ mol−1, respectively.

Theoretical investigation on the mechanism and dynamics of oxo exchange of neptunyl(VI) hydroxide in aqueous solution.

Four types of reaction mechanisms for the oxo ligand exchange of monomeric and dimeric neptunyl(VI) hydroxide in aqueous solution were explored computationally using density functional theory (DFT) and ab initio classical molecular dynamics. The obtained results were compared with previous studies on the oxo exchange of uranyl hydroxide, as well as with experiments. It is found that the stable T-shaped [NpO3(OH)3](3-) intermediate is a key species for oxo exchange in the proton transfer in mononuclear Path I and binuclear Path IV, similar to the case of uranyl(VI) hydroxide. Path I is thought to be the preferred oxo exchange mechanism for neptunyl(VI) hydroxide in our calculations, due to the lower activation energy (22.7 and 13.1 kcal mol(-1) for ΔG(‡) and ΔH(‡), respectively) of the overall reaction. Path II via a cis-neptunyl structure assisted by a water molecule might be a competitive channel against Path I with a mononuclear mechanism, owing to a rapid dynamical process occurring in Path II. In Path IV with the binuclear mechanism, oxo exchange is accomplished via the interaction between [NpO2(OH)4](2-) and T-shaped [NpO3(OH)3](3-) with a low activation energy for the rate-determining step, however, the overall energy required to fulfill the reaction is slightly higher than that in mononuclear Path I, suggesting a possible binuclear process in the higher energy region. The chemical bonding evolution along the reaction pathways was discussed by using topological methodologies of the electron localization function (ELF).