Hydroxide Systems Research Articles

A Review of Thermochemical Energy Storage Systems for District Heating in the UK

Thermochemical energy storage (TCES) presents a promising method for energy storage due to its high storage density and capacity for long-term storage. A combination of TCES and district heating networks exhibits an appealing alternative to natural gas boilers, particularly through the utilisation of industrial waste heat to achieve the UK government’s target of Net Zero by 2050. The most pivotal aspects of TCES design are the selected materials, reactor configuration, and heat transfer efficiency. Among the array of potential reactors, the fluidised bed emerges as a novel solution due to its ability to bypass traditional design limitations; the fluidised nature of these reactors provides high heat transfer coefficients, improved mixing and uniformity, and greater fluid-particle contact. This research endeavours to assess the enhancement of thermochemical fluidised bed systems through material characterisation and development techniques, alongside the optimisation of heat transfer. The analysis underscores the appeal of calcium and magnesium hydroxides for TCES, particularly when providing a buffer between medium-grade waste heat supply and district heat demand. Enhancement techniques such as doping and nanomaterial/composite coating are also explored, which are found to improve agglomeration, flowability, and operating conditions of the hydroxide systems. Furthermore, the optimisation of heat transfer prompted an evaluation of heat exchanger configurations and heat transfer fluids. Helical coil heat exchangers are predominantly favoured over alternative configurations, while various heat transfer fluids are considered advantageous depending on TCES material selection. In particular, water and synthetic liquids are compared according to their thermal efficiencies and performances at elevated operating temperatures.

Doping effects on magnesium hydroxide: Enhancing dehydration and hydration performance for thermochemical energy storage applications

Thermochemical energy storage (TCES) holds significant promise owing to its remarkable energy storage density and extended storage capabilities. One of the most extensively studied systems in TCES involves the reversible hydration/dehydration reaction of magnesium hydroxide (Mg(OH)2) to magnesium oxide (MgO). This system suffers from several challenges such as the dehydration temperature of 360 °C, which is considered higher for some applications, low kinetics, and conversion fraction, in addition to the conversion decay after cycles. Nonetheless, it is essential to recognize that each material within thermochemical systems has distinct operational requirements, including temperature and pressure conditions, making them suitable for specific applications. Consequently, the development of materials is a pivotal factor in expanding the effectiveness of sustainable technologies. This research addresses challenges associated with the reversible reaction by partially substituting Mg with transition metal elements like Zn, Ni, Mn, Co, and Cu, leading to the development of new materials Mg1-xMx(OH)2 with x = 0.05. The results indicate successful synthesis of hydroxide systems through coprecipitation. Morphological analysis reveals that material morphology plays a significant role in the performance of thermochemical systems. Additionally, the developed materials demonstrate a reduction in dehydration temperature, reaching 295 °C with cobalt doping. There is also an increase in the conversion reaction, with a 10 % improvement in energy density recorded for the material doped with 5 % Zn. Lastly, the developed materials exhibit good cyclability performance for up to 6 cycles.

Nitrate Reactivity in Iron (Oxy)hydroxide Systems: Effect of pH, Iron Redox State, and Phosphate

Nitrate Reactivity in Iron (Oxy)hydroxide Systems: Effect of pH, Iron Redox State, and Phosphate

Role of Chitosan Hydrogels in Clinical Dentistry.

Biopolymers are organic polymers that can be treated into intricate designs with porous characteristics that mimic essential biologic components. Due to their superior biosafety, biodegradability, biocompatibility, etc., they have been utilized immensely in biomedical engineering, regeneration, and drug delivery. To obtain the greatest number of results, a literature search was undertaken in scientific search engines utilizing keywords. Chitosan is used in a variety of medical sectors, with the goal of emphasizing its applications and benefits in the clinical dental industry. Chitosan can be dissolved in liquid form and combined with other substances to create a variety of products, including fibers, hydrogels, membranes, microspheres, resins, sponges, pastes, tablets, and micro granules. Chitosan has been studied in a variety of dental applications. Chitosan is used in the prevention of caries and wear, in pulpotomy to accelerate osteogenesis in guided tissue regeneration due to its hemostatic property, and primarily to benefit from its antimicrobial activity by adding it to materials, such as glass ionomer cement, calcium hydroxide, and adhesive systems. With its antibacterial activity and biocompatibility, chitosan is leading the pack as a promising ingredient in the production of dental materials. The current review provides an update on the background, fundamentals, and wide range of uses of chitosan and its gels in dental science.

CO2 electroreduction to multicarbon products from carbonate capture liquid

CO2 electroreduction to multicarbon products from carbonate capture liquid

Solubility and thermodynamic properties of sodium theophylline salt in aqueous sodium hydroxide solution at different temperatures

The solubility data of sodium theophylline salt in the water and aqueous sodium hydroxide systems with molarities of 0.00, 0.01, 0.10, 0.20, 0.49, and 0.96 mol kg−1 at temperatures ranging from 283.15 to 368.15 K are determined via the equilibrium method. The experimental results show that the solubility of sodium theophylline increases on increasing the temperature at the same concentration of NaOH solution and decreases with an increase in the NaOH concentration at the same temperature. These results correlate well with the polynomial empirical equation, the modified Apelblat equation, and the λh equation. At the same time, it is found that the modified Apelblat equation gives better correlation results than the polynomial empirical and the λh equations. The results show that the three models correlate well with the solubility data of sodium theophylline. The modified Van’t Hoff equation is used to estimate the thermodynamic properties including the dissolution enthalpy, the dissolution entropy, and the Gibbs free energy change of sodium theophylline when dissolved in aqueous NaOH solution at different concentrations. The solubility data and correlation results obtained from the experiments can provide basic data for the cooling crystallization, separation, and purification of sodium theophylline and are expected to be of great significance for the research and development of sodium theophylline and for caffeine production.

Surfactant Intercalation in Li-Al-Based Binary and Ternary Layered Double Hydroxides by the Microwave-Assisted Rapid Ion-Exchange Process and Its Application in Iodine Adsorption

Recognizing the extreme speeds of reactions with microwaves, anionic forms of surfactants (sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS)) have been intercalated successfully by ion-exchange reactions in binary Li-Al and ternary Li-M-Al (M = Mg, Co, Ni, Cu, and Zn) layered double hydroxide (LDH) systems with the aid of microwaves. The samples have been characterized extensively. The basal spacings of 28.2 and 30.4 Å have been estimated for Li-Al-DS and Li-Al-DBS LDH samples, respectively, suggesting a perpendicular arrangement of DS− and DBS− anions in the interlayer space. The characteristic vibration bands of both LDH and the surfactant (DS− and DBS−) in the FTIR spectra confirmed the binding mode of surfactant molecules within the interlayers. DS−-intercalated Li-Al LDH showed lower thermal stability than the DBS−-intercalated sample. The nitrate-intercalated Li-M-Al (M = Mg, Co, Ni, Cu, and Zn) LDHs were ion-exchanged with SDS and SDBS to yield DS−-and DBS−-intercalated systems. The expanded basal spacings and a change in crystallite morphology confirmed the vertical intercalation of DS− and DBS− in Li-M-Al LDHs. ICP-AES and elemental analyses determined the metal contents and the surfactant content. FTIR spectra of intercalated samples confirmed the surfactant’s presence in the interlayer. The presence of Co, Ni, and Cu in Li-M-Al LDHs has been confirmed from UV-visible spectra. The Li-Al-DBS sample adsorbed iodine efficiently from methanol solutions, and the Langmuir model could explain the adsorption data in a better way. The adsorption followed pseudo-second-order kinetics.

Unveiling Chemically Robust Bimetallic Squarate‐Based Metal–Organic Frameworks for Electrocatalytic Oxygen Evolution Reaction

AbstractHere, this work reports an innovative strategy for the synthesis of chemically robust metal–organic frameworks (MOFs), and applies them as catalysts for the electrocatalytic oxygen evolution reaction (OER). A bimetallic squarate‐based MOF (Sq‐MOF) with a zbr topology serves as an excellent platform for electrocatalytic OER owing to its open porous structure, high affinity toward water, and presence of catalytically active 1D metal hydroxide strips. By regulating the Ni2+ content in a bimetallic squarate MOF system, the electrochemical structural stability toward OER can be improved. The screening of various metal ratios demonstrates that Ni3Fe1 and Ni2Fe1 Sq‐zbr‐MOFs show the best performance for electrocatalytic OER in terms of catalytic activity and structural stability. Ni2Fe1 Sq‐zbr‐MOF shows a low overpotential of 230 mV (at 10 mA cm−2) and a small Tafel slope of 37.7 mV dec−1, with an excellent long‐term electrochemical stability for the OER. Remarkably, these overpotential values of Ni2Fe1 Sq‐zbr‐MOF are comparable with those of the best‐performing layered double hydroxide (LDH) systems and outperforms the commercially available noble‐metal‐based RuO2 catalyst for OER under identical operational conditions.

Evaluation of Mechanical Performance of Compacted Magnesium Hydroxide after Carbonation Curing

In this study, the potential to directly use magnesium hydroxide as an alternative binder was investigated. A compaction molding technique was employed, where magnesium hydroxide powder was mixed with water at relatively low water-to-binder ratios, compacted in a mold, then subjected to accelerated CO2 curing at room temperature to form a carbonate binder. The influence of water-to-binder ratio and compaction pressure on the mechanical and microstructural properties of compacted magnesium hydroxide systems under accelerated CO2 curing was evaluated. Results showed that compaction pressure and water-to-binder ratio have a significant effect on CO2 uptake and strength development. An optimum compaction level was found to be 3 MPa in this study, where compressive strengths of 33.5±4.0 and 70.8±4.1 MPa were reached after 2 and 5 days of CO2 curing. Results highlight the potential to tailor the mechanical properties of magnesium hydroxide systems through processing, and to reach strengths comparable to those of magnesium oxide systems but with the advantage of skipping the calcination step and reducing water demand.

In situ monitoring of cellulose etherification in solution: probing the impact of solvent composition on the synthesis of 3-allyloxy-2-hydroxypropyl-cellulose in aqueous hydroxide systems

Cellulose etherification can be affected by tuning the solvent composition as indicated by monitoring the reaction using in situ IR spectroscopy and rheology measurements together with NMR characterisation.

Nickel isotope fractionation during precipitation of Ni secondary minerals and synchrotron-based analysis of the precipitates

The determination of fractionation factors associated with important biogeochemical processes controlling Ni availability in the environment is necessary to confidently use Ni isotope signatures as tracers in environmental studies. In this paper we present experimental results on Ni isotope fractionation during the precipitation of Ni secondary minerals (Ni hydroxide, Ni hydroxycarbonate and Ni sulfide minerals) that can control Ni fate and mobility in settings where high dissolved Ni(II) concentrations may pose a serious threat to the environment. Results show a preferential partition of lighter isotopes into the solid phase with associated fractionation factors ε of −0.40‰ ± 0.04‰, −0.50‰ ± 0.02‰, and −0.73‰ ± 0.08‰ relative to the hydroxide, carbonate and sulfide systems, respectively. Early kinetically induced isotope fractionation, followed by possible re-equilibration with the reacting solutions was suggested for the three investigated systems. Distortions of Ni-O bonds in the octahedra constituting the structures of Ni hydroxide and hydroxycarbonate minerals could have also contributed to the isotopic fractionation measured in these systems. In contrast, for Ni sulfide system, the magnitude of Ni isotope fractionation seemed to be determined by water and sulfide ligands exchange in solution prior to mineral nucleation. Although there is insufficient evidence to determine whether complete equilibrium occurred in the three studied systems, the fractionation factors reported in this study can provide useful indicators of Ni isotope fractionation associated with fast precipitation of secondary minerals involved in the sequestration of Ni from contaminated environments. These findings also contribute to the characterization of Ni isotope systematics which is still in the early stages of development.

Single and Binary Fe- and Al-hydroxides Affect Potential Phosphorus Mobilization and Transfer from Pools of Different Availability

Phosphorus (P) fixation is a global problem for soil fertility and negatively impacts agricultural productivity. This study characterizes P desorption of already fixed P by using KCl, KNO3, histidine, and malic acid as inorganic and organic compounds, which are quite common in soil. Goethite, gibbsite, and ferrihydrite, as well as hydroxide mixtures with varying Fe- and Al-ratio were selected as model substances of crystalline and amorphous Fe- and Al-hydroxides. Especially two- and multi-component hydroxide systems are common in soils, but they have barely been included in desorption studies. Goethite showed the highest desorption in the range from 70.4 to 81.0%, followed by gibbsite with values in the range from 50.7 to 42.6%. Ferrihydrite had distinctive lower desorption in the range from 11.8 to 1.9%. Within the group of the amorphous Fe-Al-hydroxide mixtures, P desorption was lowest at the balanced mixture ratio for 1 Fe: 1 Al, increased either with increasing Fe or Al amount. Precipitation and steric effects were concluded to be important influencing factors. More P was released by crystalline Fe-hydroxides, and Al-hydroxides of varying crystallinity, but desorption using histidine and malic acid did not substantially influence P desorption compared to inorganic constituents.

Hydrogen absorption/desorption properties of light metal hydroxide systems

Hydrogen absorption/desorption properties of light metal hydroxide systems

Influence of dolomite on the properties and microstructure of alkali-activated slag with and without pulverized fly ash

In this work, dolomite or a combination of dolomite and pulverized fly ash is to substitute up to 40% of blast-furnace slag in sodium hydroxide and sodium carbonate-activated slag systems. The influence of dolomite incorporation on the strength development, flowability, setting time, pore structure, hydrated phase assemblage, and microstructure of alkali-activated slag (AAS) are studied. The results show that dolomite incorporation up to 20% or up to 40% when fly ash is present, has little detrimental effects on the compressive strength of AAS pastes. Dolomite works mainly as an inert filler in AAS systems, leading to an increased reaction of slag at early stages due to filler effect. Different from its chemical role on ordinary portland cement (OPC) systems with enhanced hydrotalcite formation, the dolomite does not substantially affect the chemistry of reacted products in AAS systems at room temperature.

Preparation of two-color photoluminescence emission based on azo dye-layered double hydroxide systems and controlling photoluminescence properties of Allura Red AC

The purpose of the present study was to synthesize types of organic–inorganic hybrid photofunctional materials and also to control their photoluminescence properties. Furthermore, we reported synthesis of a nanohybrid with two-color blue/violet and two-color red/yellow photoluminescence (PL) using the photofunctional anion (Allura Red AC) and Mg–Al-layered double hydroxide (LDH) nanosheets as the basic building blocks. The detailed chemical structure of the obtained composites was characterized by X-ray diffraction and infrared spectra (FT-IR). The results confirmed that Allura Red AC was successfully intercalated into the interlayer space of LDHs and the Allura Red AC–Mg3Al-LDH and Allura Red AC–Zn3Al-LDH hybrids were obtained with interesting photoemission properties. The PL analysis and diffuse reflectance spectroscopy (DRS) were used to study the photophysical properties. Allura Red AC–LDH systems exhibited a blue shift photo emission compared with the pristine Allura Red AC sample. Furthermore, Allura Red AC–Mg3Al-LDH exhibited superior photoluminous efficiency with a dual-color emission, while Allura Red AC and Allura Red AC–Zn3Al-LDH were one-color systems. Decreased band gap energy of Allura Red AC–LDH which is lower than that of Allura Red AC caused improved conductivity properties. Moreover, it was found from the DRS results that Allura Red AC–LDH could be regarded as the adsorbent electromagnetic wave and as a cover to protect materials against the electromagnetic waves. Therefore, this work provided a facile way for fabricating nanohybrids with two-color PL and controlling photoluminescent properties of the nanohybrids which had potential applications in the area of photoluminescent materials.

Role of aqueous extract of celery (Apium graveolens L.) seeds against the corrosion of aluminium/sodium hydroxide systems

In this study, hydrogen evolution (HE) and weight loss (WL) measurements were applied to evaluate the role of an aqueous extract of celery (Apium graveolens L.) seeds (AECS), in inhibiting the corrosion of aluminium/sodium hydroxide systems. It was found that corrosion rates obtained from the measurements increase with increasing the alkali concentration giving reaction order about 0.68. The addition of increasing amounts of AECS inhibits the corrosion rate of Al in 0.25M and maximum inhibition efficiency of 93.33% was obtained at 1.50gL−1. While at certain concentration of inhibitor (0.50gL−1) the inhibition efficiency increases with increasing alkali concentration up to 0.25M, after which it started to decrease. The inhibitor mechanism was discussed on the basis of its adsorption on Al surface from 0.25M NaOH. Langmuir and Dubinin–Radushkevich isotherms are the models that best fit the adsorption data. While FTIR spectroscopy confirmed the adsorption of inhibitor species on the Al surface. The thermodynamic parameters were determined and discussed.

Synergistic effect of combined dimethyl methylphosphonate with aluminum hydroxide or ammonium polyphosphate retardant systems on the flame retardancy and thermal properties of unsaturated polyester resin

ABSTRACTA series of flame-retardant unsaturated polyester resin (UPR) were prepared by the addition of dimethyl methylphosphonate (DMMP) with various amounts of aluminum hydroxide (ATH) or ammonium polyphosphate (APP) as the flame retardants. The combustion resistance effects of ATH/DMMP and APP/DMMP systems were evaluated by limiting oxygen index test and vertical burning test (UL-94). The thermal properties of UPR were investigated by thermogravimetric analysis. The structure of char was observed by scanning electron microscopy. DMMP incorporated with ATH or APP improved the flame retardancy and thermal properties of UPR. However, the fire-retardant mechanism of these two systems were different: The ATH/DMMP system provided synergistic effect in charring property of the UPR, produced great amount of residual char, and thus revealed the excellent flame retardancy. The APP/DMMP system further improved the flame retardancy of the UPR due to the change in the residual char structure rather than the increase in the production of char.

Recent Advances in the Synthesis, Characterization and Application of Zn+-containing Heterogeneous Catalysts.

Monovalent Zn+ (3d104s1) systems possess a special electronic structure that can be exploited in heterogeneous catalysis and photocatalysis, though it remains challenge to synthesize Zn+‐containing materials. By careful design, Zn+‐related species can be synthesized in zeolite and layered double hydroxide systems, which in turn exhibit excellent catalytic potential in methane, CO and CO2 activation. Furthermore, by utilizing advanced characterization tools, including electron spin resonance, X‐ray absorption fine structure and density functional theory calculations, the formation mechanism of the Zn+ species and their structure‐performance relationships can be understood. Such advanced characterization tools guide the rational design of high‐performance Zn+‐containing catalysts for efficient energy conversion.

Desorption of cesium from the surface of montmorillonite-humic acids and montmorillonite-iron hydroxide systems

The paper has investigated the impact of the nature and concentration of desorbing reagents NH4Cl, (NH4)2Ox, NH4H2Cit, (NH4)2HCit and FeCl3 on washing of cesium ions from model clayey montmorillonite humic acids and montmorillonite iron (III) hydroxide systems. By their desorbing abili ty 0.1 M solutions of ammonium salts are arranged in the series: NH4Cl < NH4H2Cit < (NH4)2Ox < (NH4)2HCit. Also rather effective are 0.01 M solutions of FeCl3 in which along with autodesorption by ions Fe3+, FeOH2+ and Fe(OH)2+ the desorption process also involves H+ (pH 2.3) ions.

Alkali-metal ion coordination in uranyl(VI) poly-peroxide complexes in solution. Part 1: the Li⁺, Na⁺ and K⁺--peroxide-hydroxide systems.

The alkali metal ions Li(+), Na(+) and K(+) have a profound influence on the stoichiometry of the complexes formed in uranyl(VI)-peroxide-hydroxide systems, presumably as a result of a templating effect, resulting in the formation of two complexes, M[(UO2)(O2)(OH)]2(-) where the uranyl units are linked by one peroxide bridge, μ-η(2)-η(2), with the second peroxide coordinated "end-on", η(2), to one of the uranyl groups, and M[(UO2)(O2)(OH)]4(3-), with a four-membered ring of uranyl ions linked by μ-η(2)-η(2) peroxide bridges. The stoichiometry and equilibrium constants for the reactions: M(+) + 2UO2(2+) + 2HO2(-) + 2H2O → M[(UO2)(O2)(OH)]2(-) + 4H(+) (1) and M(+) + 4UO2(2+) + 4HO2(-) + 4H2O → M[(UO2)(O2)(OH)]4(3-) + 8H(+) (2) have been measured at 25 °C in 0.10 M (tetramethyl ammonium/M(+))NO3 ionic media using reaction calorimetry. Both reactions are strongly enthalpy driven with large negative entropies of reaction; the observation that ΔH(2) ≈ 2ΔH(1) suggests that the enthalpy of reaction is approximately the same when peroxide is added in bridging and "end-on" positions. The thermodynamic driving force in the reactions is the formation of strong peroxide bridges and the role of M(+) cations is to provide a pathway with a low activation barrier between the reactants and in this way "guide" them to form peroxide bridged complexes; they play a similar role as in the synthesis of crown-ethers. Quantum chemical (QC) methods were used to determine the structure of the complexes, and to demonstrate how the size of the M(+)-ions affects their coordination geometry. There are several isomers of Na[(UO2)(O2)(OH)]2(-) and QC energy calculations show that the ones with a peroxide bridge are substantially more stable than the ones with hydroxide bridges. There are isomers with different coordination sites for Na(+) and the one with coordination to the peroxide bridge and two uranyl oxygen atoms is the most stable one.