MgO Precursor Research Articles

Enhanced CO2 capture and stability of MgO modified with alkali metal nitrates and carbonates at moderate temperature

AbstractBACKGROUNDMagnesium oxide (MgO) is favored for solid‐state carbon dioxide (CO2) capture due to its high theoretical adsorption capacity, abundant reserves, low cost, and environmental friendliness. However, its practical application in industry is hindered by low CO2 adsorption capacity under moderate operating conditions. In this work, MgO was modified by a deposition method using LiNO3, NaNO3, KNO3, Na2CO3 and K2CO3 as additives.RESULTSThe study determines optimal ratios within the [(Li, Na, K)x − (Na, K)]y/MgO system, specifically identifying x = 0.5 and y = 0.15 as most effective. At 275 °C under pure CO2 conditions, the adsorption capacity peaks at 0.631 g CO2 g−1 adsorbent. Effective regeneration of the adsorbent occurs at 400 °C under 100% N2 for 15 min. Under Integrated Gasification Combined Cycle (IGCC) conditions, the adsorption capacity stabilizes at 0.462 g g−1 after 20 cycles, representing a 25% decrease from initial capacity.CONCLUSIONExperimental findings demonstrate that the inclusion of alkali metal salts in MgO precursors enhances the adsorbent's microstructure, thereby improving its CO2 capture efficiency and bolstering cycling stability. This research enhances our understanding of the factors influencing CO2 adsorption and cyclic stability in alkali metal salt‐promoted MgO, providing valuable insights for further refinement in the formulation and synthesis protocols of MgO‐based CO2 adsorbents. © 2024 Society of Chemical Industry (SCI).

Elucidating the function of MgO precursors on the adsorptive removal and recovery of water phosphorus

Phosphorus (P) recovery with MgO-based adsorbents (MBA) is an effective method for water management and eutrophication prevention. However, the function of MgO precursors on the adsorptive removal and recovery of water P has not yet been sufficiently studied. Therefore, five distinct precursors, namely MgCl2·6H2O, Mg(NO3)2·6H2O, Mg(CH3COO)2·4H2O, Mg(OH)2, and Mg5(OH)2(CO3)4·xH2O, were employed to synthesize MgOs, resulting in the formation of corresponding calcination products identified as CH-MgO, NI-MgO, AC-MgO, HY-MgO, and BC-MgO, respectively. The surface morphology, Brunauer-Emmett-Teller specific surface area (SBET), total pore volume (TPV) and average pore size (APS) of the MgOs were impacted by their precursors, which affected their ability for P recovery. The flower-like BC-MgO showed the highest adsorption capacity (mg P/g) for P (426.2), followed by AC-MgO (398.1), CH-MgO (329.5), HY-MgO (296.6), and then NI-MgO (274.9). BC-MgO recovered 56.2 % of total P (TP) and 61.7 % orthophosphate (ortho-P) from livestock wastewater, and 56.3 % TP and 95.9 % ortho-P from sewage treatment effluent. P adsorption was pH dependent and positively correlated with the adsorbents SBET and TPV. Surface complexation and deposition, ligand exchange, and electrostatic attraction were the main processes involved in P adsorptive capture and its recovery. The leaching of Mg2+ into water was negligible from all studied MgOs, particularly BC-MgO and AC-MgO. The recovered P from the P-loaded BC-MgO enhanced seed germination and root growth and thus might be used in soil as an alternative P fertilizer. Based on those findings we can conclude that BC-MgO showed high potential applications for the removal and recovery of P from wastewater under wide range of water pH and therefore can be used for remediation of P-rich water. Those results are meaningful for MBA engineering application, preventing water eutrophication, producing alternative P fertilizers, and achieving sustainable development goals in future.

Efficient Rhodamine B dye uptake onto MgZrO3@g-C3N4 nanostructures: Fabrication and adsorption mechanism

Pristine graphitic carbon nitride (g-C3N4) was synthesized by calcination of urea under elevated temperature. A blend of g-C3N4 nanosheets and nanosized ZrO2 and MgO precursors were used to prepare MgZrO3@g-C3N4 hybrid nanocomposite (MZCN) then it was assessed for the adsorption of Rhodamine B (RhB) dye from aqueous solution. The X-ray diffraction analysis revealed the development of the monoclinic ZrO2, cubic MgO, and hexagonal graphitic carbon nitride phases. The energy diffraction X-rays (EDX), photoelectron electron, and Fourier transformed infrared (FT-IR) spectroscopy analyses collectively validated the formation of the presumed composite. An improved porosity with a surface area 35.86 m2.g−1 and pore volume 0.087 cm3.g−1 were determined by N2 adsorption setup. The adsorption kinetics fitted well with the pseudo-first-order model (R2 > 0.99), which designated an adsorption process influenced by physisorption. The kinetics models investigations revealed a film diffusion control of the adsorption process. The adsorption equilibrium matched perfectly with the Langmuir isotherm model (R2 > 0.99) marking a maximum adsorption capacity of 370.8 mg g−1, demonstrating outstanding monolayer adsorption process. In addition, the Freundlich constant (n = 1.76) value is falling in the range 1–10 suggested a favorable adsorption of RhB onto the composite surface. The mechanistic enquiry suggested van der Waal, hydrogen bonds and π–π electron–donor interactions between the electron-rich RhB and the functional groups in the adsorbent’s molecule. This work stipulates that MgZrO3@g-C3N4 holds promise as efficient adsorbent for organic dyes from contaminated wastewater.

The influence of chemical composition and preparation procedure on CO2 capture performance of NaNO3 /MgO-based sorbents

MgO based sorbents modified by 5–50 mol.% NaNO3 have been prepared by various methods and investigated in detail. It has been showed that optimal synthesis method is incipient wetness impregnation of MgO precursor with sodium nitrate water solution. The highest sorption capacity of 6.5 mmol CO2 g–1 sorb after 1 hour of sorption from the gas mixture with 50 vol.% CO2 at 320 °C was achieved using the MgO modified by 10 mol.% NaNO3. Sorption capacity for MgO modified by 10 mol.% NaNO3 during 10 consecutive sorption-desorption cycles is approximately 4.5–5.5 mmol CO2 g–1 sorb. The duration of the sorption stage is 30 min, the CO2 content in the feed gas is 50 vol.% and sorption-regeneration temperature is 300–350 °C respectively. It has been showed that increasing the sorption pressure to 10 bar allows reducing sorption temperature from 320 °C to 220–260 °C. The sorption capacity is reached up to 4.0 mmol CO2 g–1 sorb at 25 vol.% CO2 that is twice higher than that at 1 bar. It has been demonstrated that steam and hydrogen treatment before sorption doesn’t lead to a significant change in the sorption properties and phase composition of NaNO3 modified MgO-based sorbent.

A Hands-on Guide to the Synthesis of High-Purity and High-Surface-Area Magnesium Oxide

In this study, magnesium nitrate, chloride or sulphate were used in the synthesis of Mg(OH)2, the precursor of MgO. It was found that the counter ion strongly influences the purity of the Mg(OH)2, as well as the specific surface area of the obtained MgO. The latter is also strongly influenced by the calcination temperature. The choice of the precipitating agent can lead to the introduction of K+ or Na+ ions and hence NH3 (aq) is the best choice. A multistep precipitation procedure of Mg(OH)2 was proposed to lower the concentration of typical impurities (Fe, Ni and Mn) found in commercial p.a. purity Mg(NO3)2. The effect of the number of portions of water used for washing of Mg(OH)2 on the purity of the final product has also been investigated in detail. The stages of formation of grains of Mg(OH)2 and their subsequent thermal decomposition was described together with determination of the introduction of new impurities into the material. Large scale (1500 g) preparation of Mg(OH)2 with an improved purity was performed and described. Therefore, this study explains what measures should be taken to obtain pure magnesia catalysts and is a valuable resource for catalytic research in which magnesia is used.

HierarchicalMgAl‐layered double hydroxide growth on porousMgOtemplate for pollution removal

AbstractDifferent from alumina, magnesium oxide is seldom used in the synthesis of layered double hydroxide. In this work, MgAl layered double hydroxide with hierarchical structure was synthesized by using porous MgO as precursor via a facile in situ reaction at room temperature. And no chemical reagents are needed to provide an alkaline environment that allows precipitation to form during the synthesis process. Crystal structure, morphology, functional group, and surface features of the porous MgO precursor, the synthesized layered double hydroxide and its calcined product were characterized by X‐ray diffraction, Fourier transform infrared techniques. The results demonstrate that the synthesized layered double hydroxide is a pure phase and composed of nanosheets. Moreover, the synthesized layered double hydroxide inherits the morphology of the porous MgO precursor and forms a hierarchical structure. This structure has a large specific surface area (249 m2 g−1) to increase the adsorption properties. Adsorption experimental results show that the maximum adsorption capacities of Congo red and Cr(VI) ions over the synthesized layered double hydroxide were 847.5 and 103.7 mg g−1, respectively. The adsorption process follows the Langmuir and pseudo‐second equation. Both adsorption processes were found to be spontaneous and endothermic.

Development and Characterization on the Isothermal Kinetics of Mg(OH)2-sol Synthesized by Chemical Method

ABSTRACT The thermal decomposition of magnesium hydroxide is key to the preparation of high-quality magnesia-based refractories. As we all know, Mg(OH)2 is the precursor of MgO, so the calcination of Mg(OH)2 has attracted widespread attention. The dehydration process of Mg(OH)2-sol was studied by isothermal thermogravimetric kinetics, and the phase transition process and the variation of the microscopic morphology were mainly characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results showed that the Doyle approximation function and Gorbatchev approximation function were used to calculate the activation energy of the dehydration reaction of Mg(OH)2 to be 69.35 kJ·mol−1 and 65.81 kJ·mol−1, respectively. The sintering temperature was higher than 350°C, and the phase composition and microstructure analysis of the combination indicated that the plate-like structure of Mg(OH)2 had been completely transformed into the cubic structure of MgO.

A new magnetic composite with potential application in boron adsorption: Development, characterization, and removal tests

In this work, a new magnetic composite, with good performance in the adsorption of boron from aqueous solutions, is proposed. The composite was prepared from CoFe2O4 and MgO precursors, which were produced by the sol-gel method using orange juice residues. X-ray diffraction, scanning electron microscopy, infrared spectroscopy, 57Fe Mössbauer spectroscopy, and magnetization measurements have indicated that the ferrimagnetic CoFe2O4 nanocrystalline phase is immersed in the MgO matrix. The magnetic composite was applied to boron compounds removal from synthetic effluents (with boron concentrations up to 20 mg L−1), showing up to 92% removal capacity. After the boron adsorption process on the MgO surface, X-ray diffraction, scanning electron microscopy, and infrared spectroscopy results have shown the formation of crystalline Mg(OH)2 (with needle-like structures), and 57Fe Mössbauer spectroscopy has indicated that the fraction of Fe+3 ions in the nanograin surfaces was changed in comparison with the pristine adsorbents. Three possible boron adsorption mechanisms are suggested: adsorption at the Mg(OH)2 crystallite surface, adsorption through the formation of Fe–O–B bonds, and adsorption by an amorphous Mg(OH)2 gel. The pseudo-first order model was successfully used to fit the kinetic adsorption curves, whereas the Freundlich model has described the isotherms, thus indicating a heterogeneous distribution of adsorption heat and affinities. The composite was found to adsorb about 6% more boron than pure MgO and can be recoverable with a permanent magnet.

Facile fabrication of magnesium peroxide with different morphologies via the isomorphic transformation of magnesium oxide for Fenton-like degradation of methylene blue

Magnesium peroxide (MgO2) has been widely used in the field of environmental remediation including organics degradation and bacterial inactivation, due to its good stability, environmental friendliness and high active oxygen content. In this work, MgO2 rod, cube and flower were synthesized firstly by the reaction of isomorphic MgO and H2O2, and used as Fenton-like oxidants for methylene blue (MB) degradation. The structure and morphology of as-prepared products were characterized by XRD, SEM and TEM techniques. It was found that the synthesized MgO2 retained the original morphologies of MgO precursors. The MgO precursors firstly interacted with H2O to produce hydrated MgO intermediate (MgOH+), which was further oxidized into MgO2 by H2O2. The flower-like MgO could be completely converted into MgO2 phase in a relatively short time, due to the porous structure assembled by thin nanosheets. Besides, the MgO precursors also served as self-templates for in-situ growth of MgO2, allowing the MgO2 products to maintain the morphological characteristics of MgO precursors. The results of degradation experiments showed that MgO2 rod exhibited better performance for MB degradation than MgO2 cube and flower, owing to its unique structure and high active oxygen content.

Formation of anorthite containing cordierite materials through reaction sintering kaolin, MgO and CaO precursors

The effect of CaO on cordierite formation from kaolin-MgO-CaO powder mixtures, milled for 5 h and reaction sintered for 2 h in the temperature range 900-1400?C, was investigated. Phases formed in the developed materials were characterized by x-ray powder diffraction method (XRD) and Raman spectroscopy. Non-isothermal differential thermal analysis (DTA) and thermogravimetric (TG) experiments were performed from room temperature to 1400?C, at heating rates from 20 to 40?C/min. Activation energies were determined using Kissinger method. It was found that sintering the stoichiometric kaolin-magnesia mixture led to the nucleation and growth of monolithic cordierite; while cordierite along with anorthite were present in the other two samples where 4 or 8 wt% of CaO was added. The increase in CaO decreased cordierite formation temperature and increased the activation energy, which ranged from 445 to 619 kJ/mol for ?-cordierite and from 604 to 1335 kJ/mol for ?-cordierite.

Chemical Interaction Between MgO Support and Iron Catalyst

In this paper the chemical interaction between catalyst and support has been studied to understand the observed different growth rate of CNTs in our previous paper. Both pure MgO and Mg(NO3)2 . 6H2O as sources of the MgO catalyst support and Fe2(SO4)3 · xH2O as the source of the Fe catalyst, were employed. A Fe catalyst supported on MgO has been synthesized using the wet impregnation method followed by calcination. To compare the catalyst grain size and its distribution, the sample were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and BET specific surface area (SSA) measurement and X-ray photoelectron spectroscopy (XPS). XPS technique have utilized complementary to demonstrate the existence of chemical interaction between MgO support and Fe catalyst. Results revealed that the type of precursor used to prepare the support has a significant influence on the morphology of the support and the associated distribution of the Fe catalysts. The highest yield of MgFe2O4 phase was obtained using a pure MgO precursor which after calcination results in a homogenous distribution of nano-sized Fe particles over the support surface

Highly Porous Polymer-Derived Bioceramics Based on a Complex Hardystonite Solid Solution.

Highly porous bioceramics, based on a complex hardystonite solid solution, were developed from silicone resins and micro-sized oxide fillers fired in air at 950 °C. Besides CaO, SrO, MgO, and ZnO precursors, and the commercial embedded silicone resins, calcium borate was essential in providing the liquid phase upon firing and favouring the formation of an unprecedented hardystonite solid solution, corresponding to the formula (Ca0.70Sr0.30)2(Zn0.72Mg0.15Si0.13) (Si0.85B0.15)2O7. Silicone-filler mixtures could be used in the form of thick pastes for direct ink writing of reticulated scaffolds or for direct foaming. The latter shaping option benefited from the use of hydrated calcium borate, which underwent dehydration, with water vapour release, at a low temperature (420 °C). Both scaffolds and foams confirmed the already-obtained phase assemblage, after firing, and exhibited remarkable strength-to-density ratios. Finally, preliminary cell tests excluded any cytotoxicity that could be derived from the formation of a boro-silicate glassy phase.

Recycle of cotton waste by hard templating with magnesium acetate as MgO precursor.

As one of the hard-templating methods, MgO-templating was employed to recycle cotton to produce activated carbon with magnesium acetate as MgO precursor. Results showed that cotton carbonized while magnesium acetate decomposed to nanoscale MgO particles based on thermogravimetric and X-ray diffraction analysis. Carbonized residuals of cotton were able to replicate the MgO morphology thus creating pores. The size of MgO varied with impregnation ratio, treatment temperature, and time. Overall, the optimum conditions were MgO/cotton impregnation ratio 0.25, temperature 800 °C, and treatment time 60 min. Cotton-based activated carbon thus produced manifested surface area and total pore volume of 1139 m2/g and 0.85 cm3/g respectively. Both micropores and mesopores were detected based on iodine, methylene blue adsorption values, and N2 adsorption-desorption studies.

The nature of MgO precursor decomposition and pore-forming in hard-templating of porous carbon derived from cotton

As one of the hard templating method for making porous materials, MgO templating was under intensive investigation for its various advantages. In this research, MgO templating was employed to reuse textile waste cotton. The main purpose was to compare the pyrolysis behaviors of four MgO-precursors (magenesium acetate, magnesium chloride, magnesium citrate and MgO particles) for their effectiveness as templating agents. Thermogravimetric and X-ray diffraction analysis showed that precursors decomposed stepwise or disintegrate to form nano-size MgO particles. At the same time, carbonized cotton was able to replicate the morphology of MgO particles to create porous structures. The effects of precursor and treatment temperature on the morphology of MgO, pore structures and surface chemistry were investigated. Results proved that by manipulating templating conditions, cotton waste was able to produce activated carbon of various properties.

Morphological control of inverted MgO-SiO2 composite catalysts for efficient conversion of ethanol to 1,3-butadiene

In this work, three novel MgO-SiO2 composite catalysts with inverted structure have been synthesized via a facile and scalable strategy by means of the incipient wetness impregnation of the silica sol onto MgO precursors with different morphologies, and evaluated for the one-step conversion of ethanol to 1,3-butadiene. The prepared flower-like MgO-SiO2 composite catalysts exhibited highly enhanced catalytic activity than those catalysts synthesized from MgO precursors with nanodisks and nanosheets morphologies. Characterization results based on XRD, FT-IR, UV–vis, BET, CO2-TPD, NH3-TPD, ethanol-TPD, and 29Si MAS NMR revealed that unique layered flower-like architectures may facilitate the formation of interfacial Mg-O-Si chemical bond in binary MgO-SiO2 composite catalysts which are mainly responsible for the superior activity. This study presents a new strategy to design and develop the catalyst for efficient conversion of bio-ethanol to 1,3-butadiene by morphological control of MgO-SiO2 bifunctional catalysts.

New compound Mg3In4V6O24 and its physicochemical characteristic

A new compound of the formula Mg3In4V6O24 belonging to the family M3A4V6O24 [where M = metal(II), A = metal(III)] was obtained by the solid-state reaction method. The compound was synthesized by heating in air a mixture of Mg3(VO4)2 and InVO4 or MgV2O6 and In2O3 or In2O3 and V2O5, with a precursor of MgO. The new compound was characterized by XRD, SEM, IR, UV–Vis and DTA–TG methods. Mg3In4V6O24 was shown to crystallize in the triclinic system. Its unit cell parameters were calculated. The new compound is stable in air up to 1000 °C and is a semiconductor (Eg ~ 3.3 eV).

Highly Porous Sr/Mg‐Doped Hardystonite Bioceramics from Preceramic Polymers and Reactive Fillers: Direct Foaming and Direct Ink Writing

Novel hardystonite‐based bioceramics are obtained by thermal treatment, in air, of silicone resins and reactive fillers. Using commercial silicones embedding SrO and MgO precursors, in addition to CaO and ZnO precursors, a quite complex solid solution (Ca1.4Sr0.6Zn0.85Mg0.15Si2O7) can be achieved, at 1100 °C, instead of pure hardystonite (Ca2ZnSi2O7), with improvements in biocompatibility and bioactivity. Highly porous foams are obtained by gas evolution at the early stage of heat treatment (at 300–350 °C), from the dehydration of active filler present in hydrated form (Mg(OH)2). Additionally, direct ink writing of silicone‐based pastes is used for the manufacturing of scaffolds with non‐stochastic pore architecture. In the latter case, strong scaffolds (with compressive strength exceeding ≈12 MPa) are obtained by adding fine glass powders as an additional filler. This addition enhances the viscous flow upon firing, but do not compromise the phase evolution, owing to the exact match in the composition between glass and silicone/filler mixture.

Tailoring and exploring the basicity of magnesium oxide nanostructures in ionic liquids for Claisen-Schmidt condensation reaction

Solid basic catalysts are extremely useful for green catalytic processes because of their high activity, easy separation, and minimal corrosion. Herein, we report the development and effect of the basicity of five various MgO nanostructures developed by microwave (MW) irradiation in different ionic liquids (ILs) on the Claisen-Schmidt Condensation Reaction. The growth of the shape-controlled MgO nanostructures in the presence of the synergetic effect of the ILs with the MW irradiation developed various basic sites on the surface of the MgO nanocrystals. Due to the synergetic effect (formation of hydrogen bonding and π-π interactions between the ILs and the MgO precursor in the presence of MW irradiation) produced active basic sites in the final nanostructure. The TPD & XPS results show that the synergetic effect strongly altered the percentages of high, low, and moderate basic sites of the catalysts. To determine their catalytic activity based on the obtained different basicity in the MgO nanostructures, prepared all nano structures were tested in the reaction. The altered basicity of the MgO catalysts strongly affected on reaction results and demonstrated better activity than pure MgO. Particularly, hexagonal MgO nanostructures with exposed crystal facets (110) and (111) having high surface area and basicity showed an outstanding activity. In addition, effect or reaction parameters such as temperature, catalyst amount, solvent effect, and reaction time were determine and obtained optimized reaction condition for outstanding results. To determine the diversity of prepared MgO nanostructures, various substituted chalcones were prepared in optimized reaction condition in good to efficient yield. Recyclability of prepared catalyst was also determined up-to 6 cycles and physicochemical changes before and after recyclability test was determined. The proper correlation of obtained basicity & basic sites with the catalytic activity was established with this protocol.

Preparation of rod‐like MgO by simple precipitation method for CO2 capture at ambient temperature

AbstractRod‐like MgO was prepared by the simple precipitation method and subsequently evaluated for CO2 capture efficiency under ambient‐temperature adsorption and intermediate‐temperature regeneration. The MgO precursor was analyzed by thermogravimetric analysis (TGA) and X‐ray power diffraction (XRD), it was decomposed completely at 500°C to form MgO. The as‐synthesized MgO samples were characterized by XRD, BET and FE‐SEM. The MgO samples were comprised of grains with an approximate length of 4‐6 μm and diameter of 0.5 μm. The BET surface area of MgO was 330.5 m2/g, which was much higher than that of commercial MgO (CM‐MgO, 103.2 m2/g). The CO2 uptake on MgO samples were evaluated by TGA. As‐synthesized MgO had the high CO2 sorption capacity compared to CM‐MgO. The effect of temperature on CO2 sorption capacity was also investigated. In addition, the stability of sample was evaluated by cyclic experiment.

Factors Governing MgO(111) Faceting in the Thermal Decomposition of Oxide Precursors

The preparation of metal oxide particles, such as MgO, NiO, and ZnO, exposing polar facets via the decomposition of suitable precursors in air, molten salts, ionic liquids, or other media has been reported; however, the main driving force(s) and factors that determine their morphology have largely remained elusive. For instance, the adsorption of ions within a molten medium on a growing oxide surface has been proposed to stabilize MgO{111} facets by the so-called molten salt route (MSR). In this article, we examine the thermal decomposition of MgO precursors to assess the influence of precursor decomposition pathways, including the physical state of the reaction intermediates and the possibility of dissolution–recrystallization processes in the formation of octahedral MgO particles. We found that solid-to-solid conversions and recrystallizations in molten nitrates or chlorides are usually incapable of producing well-defined MgO{111} facets, indicating that ion adsorption on MgO may not be the main morphol...