Alkali Source Research Articles

Morphology-controllable synthesis of CuCo2O4 arrays on Ni foam as advanced electrodes for supercapacitors

The rational design of novel electrode materials with controllable morphologies plays a vital role in fabricating high-performance supercapacitors. In this work, a variety of CuCo2O4 arrays with different components (nanoneedle, nanosheet and nanorod) on nickel foam have been synthesized through facile hydrothermal routes. The key roles of NH4F and the alkali sources in the formation of different CuCo2O4 arrays have been discussed. As a three-electrode cell, the Ni supported CuCo2O4 nanoneedle arrays exhibit a specific capacitance of 1227.8 F g−1 at 5 mA cm−2 and capacitance retention of 95.4% after 1000 cycles, suggesting the potential application for supercapacitors. Furthermore, an asymmetric supercapacitor is fabricated with CuCo2O4 nanoneedle arrays (the anode) and activated carbon (AC) electrode (the cathode), which achieves a high energy density (31.2 W h kg−1) and excellent cycling stability (102% after 4000 cycles). Such remarkable performance is ascribed to the favorable porous structure of CuCo2O4 nanoneedle arrays which can offer abundant channels for ion diffusion and numerous active spots for reversible redox reactions. It is hoped that our work could provide inspirations for the morphology-controllable fabrications of electrode materials.

2D nanoporous Ni(OH)2 film as an electrode material for high-performance energy storage devices.

A two-dimensional (2D) nanoporous Ni(OH)2 film was successfully developed from triethanolamine (TEA) as the alkali source and soft template using a scalable hydrothermal technique. The nanostructured Ni(OH)2 film was flexible and translucent, and could be directly compressed on a current collector. Owing to the uniform well-defined morphology and stable structure, the Ni(OH)2 film binder-free electrode displayed a high specific capacity, exceptional rate capability, and admirable cycle life. The specific capacitance was 453.6 mA h g−1 (1633 F g−1) at 0.5 A g−1. The assembled Ni(OH)2//activated carbon (AC) asymmetric supercapacitor (ASC) device had an energy density of 58.7 W h kg−1 at a power density of 400 W kg−1. These prominent electrochemical properties of Ni(OH)2 were attributed to the high electrical conductivity, high surface area, and unique porous architecture. Free tailoring, binder-free, and direct pressing were the most significant achievements of the Ni(OH)2 film in the development of high-performance energy storage devices.

One-step solvothermal synthesis of Fe3O4@Carbon composites and their application in removing of Cr (VI) and Congo red

Fe3O4 @C nano-adsorption was prepared by a simple one-step solvothermal synthesis method using Fe (NO3)3 、cyclodextrin as raw materials, meanwhile urea as an alkali source. The obtained samples were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, and Brunauer-Emmett-Teller. The adsorption behavior of the Fe3O4@C toward Cr (VI) and Congo red was also studied. The core-shell structure Fe3O4@C exhibited large specific surface area of 112.91 m2 g−1. The prepared Fe3O4@C samples demonstrated typical ferromagnetic behavior and high removal capacity in removing the toxic Cr (VI) ions and organic pollutant CR from wastewater, together with facile magnetic separability and good recyclability. Equilibrium adsorption performance was conducted by using the Langmuir and Freundlich model and Freundlich model could simulate the adsorption process of Congo red and Cr (VI) better. The maximum adsorption capacity of Cr (VI) and Congo red was 33.35 mg g−1 and 262.72 mg g−1 by calculation.

Alkali chalcogenido ortho manganates(II) A 6MnQ 4 (A=Rb, Cs; Q=S, Se, Te)

Abstract The six isotypic alkali ortho chalcogenido manganates A 6[MnII Q 4] (A=Rb, Cs; Q=S, Se, Te) were synthesized – in most cases in pure phase – from stoichiometric mixtures of the manganese monochalcogenides MnQ, the elemental chalcogens and Rb2S/Cs2S2 (sulfido salts) or the pure alkali elements (selenido and tellurido salts) as alkali sources at maximum temperatures between 650 and 800°C. Their hexagonal crystal structures were refined by means of X-ray single crystal data (space group P63 mc, Na6ZnO4-type structure, Z=2; A/Q: Rb/S: a=1019.34(2), c=792.560(10) pm, R1=0.0166; Rb/Se: a=1055.74(2), c=821.14(2) pm, R1=0.0275; Rb/Te: a=1126.68(2), c=860.54(2) pm, R1=0.0152; Cs/S: a=1056.68(2), c=831.22(2) pm, R1=0.0168; Cs/Se: a=1096.04(3), c=858.13(2) pm, R1=0.0194; and Cs/Te: a=1167.72(3), c=896.95(2) pm, R1=0.0140). The chiral structures contain isolated C 3 symmetric, but very close to ideal tetrahedral, ortho manganate(II) anions [MnII Q 4]6− with Mn–Q distances of 248.7–250.7 (Q=S), 260.7–263.0 (Q=Se) and 280.0–282.4 pm (Q=Te). The chalcogenide ions form a hexagonal closed packing with slightly puckered 36 nets, in which the A(2) cations occupy 3/4 of the octahedral interstices, whereas Mn takes 1/8 and A(1) 3/8 of the tetrahedral voids. Magnetic measurements on the three Cs compounds showed Curie-Weiss behavior down to a temperature of 1.9 K, with magnetic moments significantly reduced with respect to the expected spin-only value of a d 5 ion. The electronic band structures of the four salts (Na/Rb)6Mn(S/Te)4, which were calculated within the GGA+U approach, allow a comparison of the chemical bonding characteristics and the magnetic properties within the alkali cation and the chalcogenido ligand series.

Thorough conversion of CO2 through two-step accelerated mineral carbonation in the MgCl2-CaCl2-H2O system

Abstract This study describes a two-step accelerated mineral carbonation technology at moderate temperatures and atmospheric pressure by choosing the “problematic ions for seawater utilization” as mineralizers in the simplified seawater-MgCl2-CaCl2-H2O system, that is, Ca2+ as the first mineralizer and Mg2+ in the residual solution as the second. Not only can carbonate ions generated from the absorption and ionization of CO2 be fixed by Ca2+ through the first carbonation process with the added alkali source, MgO, but HCO3− in the residual solution can also be mineralized by Mg2+ through the second carbonation process. Meanwhile, pure CaCO3 and MgCO3·3H2O, which have the possible benefit of reuse, can be obtained as by-products. Then, more variables were set to optimize the technical conditions to enhance the decalcification rate and carbon sequestration ratio, reduce the reaction time during the first mineralization and attempt to realize the combination of HCO3− and Mg2+ by adding NaOH to produce MgCO3·3H2O as another by-product in a moderate environment during the second mineralization.

The Reaction Kinetics of Gaseous Alkali Capture by Kaolin in Syngas Atmosphere

AbstractAlumosilicate minerals are suitable sorbents at high temperatures for removing alkalis in syngas. Thermogravimetric investigations of these sorbents usually focus on the reaction mechanisms. Herein, a crucible arrangement is described that allows evaporation of the alkali source and sorption of gaseous alkali components in one temperature zone. With this experimental setup, kinetic investigations of alkali sorption are possible in a conventional thermobalance. Experiments were performed with sodium chloride as the alkali source and kaolin as the getter material. The reaction rate increased with alkali concentration and showed an exponential dependence on temperature. Thus, the Arrhenius model approach and power law model were selected for mathematical description.

Magnetic effervescent tablets containing ionic liquids as a non-conventional extraction and dispersive agent for determination of pyrethroids in milk

Conventional magnetic effervescent tablet has many drawbacks, such as not practicable for field processing, rapid moisture absorption, and poor tablet storage characteristics. Herein, we developed a novel magnetic effervescent tablet containing ionic liquid microextraction (MET-ILM) for determination of pyrethroids in dairy milk. It contains only Na2CO3 as an alkali source (no acidic source) in the Fe3O4 magnetic tablet; the CO2-forming reaction is initiated in the acidic solution containing the analytes, and thus the prepared tablet can be stored for long time periods without deterioration. The combined action of extractant and sorbent vastly increase the extraction efficiency. The optimized procedure consisted of an effervescent tablet, 2:1 HCl:Na2CO3, and 60 μL [C6MIM]PF6 as extraction solvent. The LODs for five pyrethroids were 0.024–0.075 μg kg−1 with recoveries of 78.3–101.8%. The RSDs were <4.8% and <6.3% for intra- and inter-day precisions. Overall, the method is very feasible for use in the field.

Converting waste coal fly ash into effective adsorbent for the removal of ammonia nitrogen in water

Converting coal fly ash waste into an adsorbent for the removal of ammonia nitrogen is an effective approach. Chemically treated highly porous converted coal fly ash was prepared through hydrothermal synthesis with hydroxide acting as an alkali source for ammonia nitrogen removal from wastewater. The highly porous converted coal fly ash was characterized by scanning electronic microscopy, Fourier transform infrared spectrometry, X-ray powder diffraction, Brunauer–Emmett–Teller analysis, and the results showed that the specific surface area of the highly porous converted coal fly ash had increased significantly from the original 0.15–270 m2 g−1. The adsorption isotherms fitted satisfactorily to the Langmuir model, which indicated the adsorption by the chemically treated highly porous converted coal fly ash as a monolayer coverage. The maximum ammonium nitrogen uptake capacity of converted coal fly ash was 139 mg g−1. Kinetics data were fitted to the pseudo-second-order equation, suggesting that chemisorption, i.e., the process of ion exchange, was the rate determining step.

Preparation of hierarchical β-Ni(OH)2 nanostructures and adsorption characterization of methyl orange dye

The β-Ni(OH)2 nanostructures have been prepared by hydrothermal with ammonia as alkali source. The morphology of β-Ni(OH)2 evolves from hexagon sheets to flower-like hierarchical structure built up from the nanosheets as increasing the amount of ammonia. Hierarchical β-Ni(OH)2 nanostructures have strong adsorption effect on methyl orange dyes. The adsorption mechanism of β-Ni(OH)2 has been investigated, which could be expressed by pseudo-second order kinetic model with best match.

Nitrogen/sulfur co-doped graphene networks uniformly coupled N-Fe2O3 nanoparticles achieving enhanced supercapacitor performance

Nitrogen/sulfur dual-doped graphene with uniformly coupled N doped Fe2O3 (N-Fe2O3/NSG) composite has been successfully synthesized via an easily one-step green method, in which ammonium thiocyanate (NH4SCN) is applied as nitrogen source and sulfur source without adding other alkali sources or dispersants. Surprisingly, N atom is doped into Fe2O3 while being doped into graphene in hydrothermal process. XPS reveals that the N atom percentage in N-Fe2O3/NSG is 2.75% higher than that in NSG (1.69%) at the same condition, indicating that N is successfully doped into Fe2O3. To the best of our knowledge, the N-Fe2O3/NSG composite is applied to supercapacitor electrode material for the first time and the superior electrochemical properties has been proved. In 6.0 M KOH electrolyte, N-Fe2O3/NSG electrode exhibit large specific capacitance (1567 F g−1 at 1 A g−1) and a high rate capability (864 F g−1 even at 10 A g−1). Particularly, the specific capacitance remains at 91.3% of the initial value after 5000 cycles under the current density of 5 A g−1. This pronounced supercapacitor performance is attributed to the incorporation of N and S into the graphene network to introduce more defects in the graphene lattice structure, activating the associated C atoms and effectively reducing the activation energy required for oxidation-reduction reactions of graphene surface and also the increased active point of Fe2O3 due to nitrogen doping.

Extraction of Ramie Fiber in Alkali Hydrogen Peroxide System Supported by Controlled-release Alkali Source.

This protocol demonstrates a method for ramie fiber extraction by scouring raw ramie in an alkali hydrogen peroxide system supported by a controlled-release alkali source. The fiber extracted from ramie is a type of textile material of great importance. In previous studies, ramie fiber was extracted in an alkali hydrogen peroxide system supported only by sodium hydroxide.However, due to the strong alkalinity of sodium hydroxide, the oxidation reaction speed of hydrogen peroxide was difficult to control and thus resulted in great damage to the treated fiber. In this protocol, a controlled-release alkali source, which is composed of sodium hydroxide and magnesium hydroxide, is used to provide an alkali condition and buffer the pH value of the alkali hydrogen peroxidesystem. The substitution rate of magnesium hydroxide can adjust the pH value of the hydrogen peroxide system and has great influence on the fiber properties. The pH value and oxidation-reduction potential (ORP) value, which represents the oxidation ability of alkali hydrogen peroxide system, were monitored using a pH meter and ORP meter, respectively. The residual hydrogen peroxide content in the alkali hydrogen peroxide system during the extraction process and the chemical oxygen demand (COD) value of wastewater after fiber extraction are tested by KMnO4 titration method. The yield of fiber is measured using a precision electronic balance, and residual gums of fiber are tested by a chemical analysis method. The polymerization degree (PD value) of fiber is tested by an intrinsic viscosity method using the Ubbelohde viscometer. The tensile property of fiber, including tenacity, elongation, and rupture, is measured using a fiber strength instrument. Fourier transform infrared spectroscopy and X-ray diffraction are used to characterize the functional groups and crystal property of fiber. This protocol proves that the controlled-release alkali source can improve the properties of the fiber extracted in an alkali hydrogen peroxide system.

Extraction of Ramie Fiber in Alkali Hydrogen Peroxide System Supported by Controlled-release Alkali Source

This protocol demonstrates a method for ramie fiber extraction by scouring raw ramie in an alkali hydrogen peroxide system supported by a controlled-release alkali source. The fiber extracted from ramie is a type of textile material of great importance. In previous studies, ramie fiber was extracted in an alkali hydrogen peroxide system supported only by sodium hydroxide.However, due to the strong alkalinity of sodium hydroxide, the oxidation reaction speed of hydrogen peroxide was difficult to control and thus resulted in great damage to the treated fiber. In this protocol, a controlled-release alkali source, which is composed of sodium hydroxide and magnesium hydroxide, is used to provide an alkali condition and buffer the pH value of the alkali hydrogen peroxidesystem. The substitution rate of magnesium hydroxide can adjust the pH value of the hydrogen peroxide system and has great influence on the fiber properties. The pH value and oxidation-reduction potential (ORP) value, which represents the oxidation ability of alkali hydrogen peroxide system, were monitored using a pH meter and ORP meter, respectively. The residual hydrogen peroxide content in the alkali hydrogen peroxide system during the extraction process and the chemical oxygen demand (COD) value of wastewater after fiber extraction are tested by KMnO4 titration method. The yield of fiber is measured using a precision electronic balance, and residual gums of fiber are tested by a chemical analysis method. The polymerization degree (PD value) of fiber is tested by an intrinsic viscosity method using the Ubbelohde viscometer. The tensile property of fiber, including tenacity, elongation, and rupture, is measured using a fiber strength instrument. Fourier transform infrared spectroscopy and X-ray diffraction are used to characterize the functional groups and crystal property of fiber. This protocol proves that the controlled-release alkali source can improve the properties of the fiber extracted in an alkali hydrogen peroxide system.

MASERASI ALKALI DARI BATANG PISANG (Musa paradisiaca) MENGGUNAKAN PELARUT AQUADEST

The purpose of this research is to determine the time of alkali absorption from banana stem in semibatch and batch. In this study maceration maseration is a leaching process used to obtain the time required for solvent to absorb alkali in banana stem ash. While the batch system maseration is a leaching process used to obtain the time required for the solvent to reach saturation point (stop absorbing). Data collection techniques in this research are: sample preparation and drying of banana stem, banana stalking process banana stem, brazing ash process of banana stem in semibatch and batch, and determination of alkaline content by titration method. From result of research can be concluded that banana stem potentially serve as source of alkali because potassium (K2O) and sodium (Na2O) content in banana ash sticks respectively 36,19% and 13,99%. Water content and yield of banana ash sticks were 78.6% and 17.7%, respectively. The time for the semibatch system is obtained in 72 hours, while for the batch system was obtained in 12 days. Normalities of alkali extracts in semibatch and batch maceration still increased. Where in the ratio of banana stem ash/solvent is 1 gram / 25 ml; 2 gram / 25 ml; 3 gram / 25 ml; and 4 gram / 25 ml respectively had a normality value that still increased from 0.219 N to 0.567 N; 0.407 N to 0.891 N; 0.578 N to 1,315 N; and 0.819 N to 1,345 N. The highest permeated alkali yield was obtained ratio (banana stem ash/ solvent) 1 gram / 25 ml of 52.37%.

Recovery of reactive MgO from reject brine via the addition of NaOH

Reject brine, generated as a waste at the end of the desalination process, presents a useful source for the extraction of valuable resources. This study investigated the recovery of reactive MgO from reject brine obtained from a local desalination plant. This was enabled via the reaction of Mg2+ present within reject brine with an alkali source (NaOH), which led to the precipitation of Mg(OH)2, along with a small amount of CaCO3. The determination of the optimum NaOH/Mg2+ ratio led to the production of the highest amount of yield. The synthesized Mg(OH)2 was further calcined under a range of temperatures (500–700°C) and durations (2−12h) to produce reactive MgO. A detailed characterization of MgO obtained under these conditions was presented in terms of its reactivity, specific surface area (SSA), composition and microstructure. While an increase in the calcination temperature and duration decreased the reactivity and SSA of MgO, samples calcined at 500°C for 2h revealed the highest reactivity, which was reflected by their SSA of 51.4m2/g.

Incidence of Alkali Release in Concrete Dams. Evaluation of Alkalis Releasable by Feldspars

Alkali release from aggregates can constitute a source of alkalis in concrete exposed to wet environments for long periods of time. Feldspars are one of the minerals that can release alkalis to the concrete with time. The formation of reaction products in the interface with the paste due to the alkali release from sodium and potassium feldspars has been observed in a concrete with granite aggregates. This has been observed after more than 25 years of exposure. It is necessary to evaluate the amount of alkalis releasable to define the formulation of concrete before manufacturing. Different test methods have been used to evaluate the potential alkali release from the granite extracted from the same quarry as that used in the dam. The test solutions have different composition and concentration, and different temperatures were used. Finally, the results of potential extraction are evaluated to determine the most realistic with respect to the field behavior.

Technology and Provenance Analysis of Glass Fragments from an Ottoman Bathhouse (Hamam) in Kyparissia, Peloponnese, Greece

ABSTRACTThis study focuses on the analysis of a post-medieval assemblage of glass vessels and tableware, recovered from an Ottoman bathhouse in Kyparissia, SW Peloponnese, Greece. The chemical composition of the samples was estimated using SEM/EDS, whereas minor and trace elements were identified by qualitative XRF analysis. Raman spectroscopy was applied in order to examine the connectivity of the silicate glass matrix in more detail. The acquired data indicate significant chemical variations among the samples, especially in regards to the alkali source and the decolourant used. Moreover, one high-lead glass has also been identified. The provenance analysis, which was based on the statistical treatment of the resulted and published analytical data, indicated that the different glass types originated both from the eastern regions of the Ottoman Empire and from glassmaking centres in central and northern Europe. The determination of technology and provenance of the assemblage provided with valuable new information regarding the production and trading network of glass in mainland Greece during the Ottoman rule.

Inclusion of geopolymers derivate from fly ash and pumice in reinforced concrete

This paper presents results of a research project related to the development of alkali-activated geopolymers, synthesized from alumina-silicate minerals (fly ash and pumice) which are added to concrete. Alkali sources used in geopolymer synthesis were sodium hydroxide and sodium silicate solution. New materials were structurally characterized by Infra-Red spectroscopy (IR) and X-Ray Diffraction (XRD). Concretes obtained after geopolymers addition as Portland cement substitutes at 10%, 20% and 30%, were mechanically analysed by compression resistance at 7, 14, 28 and 90 drying days. Results were referred to standard (concrete of Portland cement) allows to know cementitious characteristics of geopolymers are lower than those for standard, but it keeps growing at longer drying time than Portland cement. By Electrochemical Impedance Spectroscopy (EIS) it is found that this new material shows high electrical resistance and have been proved as a protection agent against corrosion in reinforced concrete exhibiting anticorrosive properties higher than those showed by the conventional concrete mixture.

Preparation of lamellar-stacked TS-1 and its catalytic performance for the ammoximation of butanone with H2O2

A SiO2 particle was prepared with different alkali sources, and then lamellar-stacked TS-1 catalysts were hydrothermally synthesized using the SiO2 particle as a silica source. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectra, nitrogen adsorption–desorption and UV–vis absorption spectra were used to characterize the TS-1 catalysts. The effect of the alkali source during the preparation of the SiO2 particle on the textural properties and catalytic performance of the TS-1 catalyst was thoroughly investigated. The TS-1 catalyst that was prepared with a SiO2 particle using tetrapropylammonium hydroxide (TPAOH) as an alkali source (TS-1-TPAOH) possessed more meso- and macro-pores and a higher framework Ti content than the catalyst that was prepared with a SiO2 particle using NH3·H2O as an alkali source (TS-1-NH3·H2O). As a result, the TS-1-TPAOH catalyst had a better catalytic performance for butanone ammoximation with H2O2 than conventional TS-1 and TS-1-NH3·H2O catalysts. Furthermore, the influences of reaction conditions, including reaction temperature, reaction time, the amount of catalyst and the molar ratio between H2O2 and butyl ketone oxime on the catalytic performance of the TS-1-TPAOH catalyst were evaluated. The unique structure of the lamellar-stacked TS-1 catalyst can effectively avoid the diffusing of large reactant molecules into zeolite channels and has potential applications in other oxidation reactions.

Evaluation of a low‐cost magnesium product for phosphorus recovery by struvite crystallization

AbstractBackgroundThe development of a cost‐effective process of struvite crystallization requires the selection of appropriate sources of alkali and magnesium. In this study, the effectiveness of two industrial grade products, MgO and Mg(OH)2, as magnesium and alkali sources to recover phosphorus as struvite were investigated and compared in a first set of experiments. Subsequently, the use of industrial Mg(OH)2 was compared in two different struvite crystallization systems, an upflow fluidized bed reactor (FBR) and a continuous stirred tank reactor (CSTR) coupled to a settler tank.ResultsAt the same operational conditions, the consumption of MgO was higher than Mg(OH)2 consumption. Moreover, industrial Mg(OH)2 consumption for FBR and the CSTR operation was 1.6 and 1.1 1 mol Mg added mol‐1 P precipitated, respectively. This difference was caused by the high mixing intensity and the higher contact time between the Mg(OH)2 slurry and the influent in the CSTR, favouring the conversion.ConclusionsBoth industrial grade magnesium products are promising options for struvite crystallization. However, Mg(OH)2 was more effective than the starting material, MgO, to recover phosphorus. Struvite crystallization by adding an industrial grade Mg(OH)2 could be economically viable with regard to alternative physico‐chemical P removal processes using metal salts, increasing the attractiveness of this P recovery process. © 2017 Society of Chemical Industry

Surfactant-Free Solvothermal Synthesis of 3D Flowerlike Iron Alkoxide (Fe-EG) Micro/Nanostructures: Structure, Formation Mechanism, and Fenton Oxidation of Azo Dyes

A three-dimensional (3D) flowerlike iron alkoxide (Fe-EG) micro/nanostructure has been fabricated for the first time via a facile surfactant-free solvothermal method using CH3COONa·3H2O as the alkali source and systematically characterized. The green-colored 3D flowerlike Fe-EG micro/nanostructure is a polymeric ferrous glycolate with the chemical formula [Fe2(OCH2CH2O)2(HOCH2CH2OH)2]n. Upon quasi-in situ monitoring of the morphology and composition of the samples collected at various reaction times, a coordination/ligand substitution/reduction/polymerization mechanism for Fe-EG is tentatively proposed. The Fe-EG micro/nanostructure exhibited ∼99.7% Acid Orange 7 (AO7) degradation efficiency in 40 min with H2O2 as the oxidant at pH0 = 6.0. It is believed that the high dispersion of a large amount of Fe3+ on the surface of in situ-formed 3D flowerlike amorphous FeOOH with a large surface area and rich porous structure by the moderate interfacial hydrolysis process of Fe-EG benefits the adsorption of dye mo...