A study of thermally activated Mg-Fe layered double hydroxides as potential environmental catalysts

Layered double hydroxides (LDHs) and mixed oxides derived after thermal decomposition of LDH with different Mg-Fe content were investigated. These materials were chosen because of the possibility to tailor their various properties, such as ion-exchange capability, redox and acid-base properties and surface area. Layered double hydroxides, [Mg1-x Fex (OH)2](CO3)x/2 ? m H2O, (where x presents the content of trivalent ions, x = M(III)/[M(II) + M(III)]) were synthesized, using low supersaturation precipitation method. The influence of different Mg/Fe ratio on the structure and surface properties of LDH and derived mixed oxides was investigated in correlation to catalytic properties in chosen test reaction (Fischer-Tropsch synthesis). It was determined that the presence of active sites in the mixed oxides is influenced by structural properties of the initial LDH and by the presence of additional Fe phases. Furthermore, the synthesis outside the optimal range for the synthesis of single phase LDHs leads to the formation of metastable, multiphase systems with specific characteristics and active sites.

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Mg-Fe-mixed oxides derived from layered double hydroxides: A study of the surface properties

Journal of the Serbian Chemical Society ◽

10.2298/jsc110429149h ◽

2011 ◽

Vol 76 (12) ◽

pp. 1661-1671 ◽

Cited By ~ 12

Author(s):

Milica Hadnadjev-Kostic ◽

Tatjana Vulic ◽

Radmila Marinkovic-Neducin ◽

Aleksandar Nikolic ◽

Branislav Jovic

Keyword(s):

Surface Properties ◽

Layered Double Hydroxides ◽

Active Sites ◽

Mixed Oxides ◽

Lower Surface ◽

Multiphase System ◽

Fischer Tropsch ◽

Acid And Base ◽

Phase Range ◽

Double Hydroxides

The influence of surface properties on the selectivity of the synthesized catalysts was studied, considering that their selectivity towards particular hydrocarbons is crucial for their overall activity in the chosen Fischer- -Tropsch reaction. Magnesium- and iron-containing layered double hydroxides (LDH), with the general formula: [Mg1-xFex(OH)2](CO3)x/2?mH2O, x = = n(Fe)/(n(Mg)+n(Fe)), synthesized with different Mg/Fe ratio and their thermally derived mixed oxides were investigated. Magnesium was chosen because of its basic properties, whereas iron was selected due to its well-known high Fischer-Tropsch activity, redox properties and the ability to form specific active sites in the layered LDH structure required for catalytic application. The thermally less stable multiphase system (synthesized outside the optimal single LDH phase range with additional Fe-phase), having a lower content of surface acid and base active sites, a lower surface area and smaller fraction of smaller mesopores, showed higher selectivity in the Fischer-Tropsch reaction. The results of this study imply that the metastability of derived multiphase oxides structure has a greater influence on the formation of specific catalyst surface sites than other investigated surface properties.

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Investigation of layered double hydroxides type ZnMgAl-carbonate and derivates.

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314088998 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C1100-C1100

Author(s):

Weberton do Carmo ◽

Gustavo de Carvalho ◽

Juliana da Silva ◽

Luciano Chagas ◽

Alexandre Leitão ◽

...

Keyword(s):

Layered Double Hydroxides ◽

Mixed Oxides ◽

Inorganic Materials ◽

Precipitation Method ◽

Trivalent Cation ◽

Catalyst Precursor ◽

Step Size ◽

Co Precipitation ◽

Double Hydroxides ◽

Urea Method

Layered double hydroxides (LDHs) or hydrotalite-like compounds belong to a class of synthetic two-dimensional inorganic materials with lamellar structures, where the hydroxyl-hydrated compounds are formed by chemical substitution of divalent ion of the brucite-like octahedral layers by trivalent ions [1]. The LDH are represented by the general formula, Figure a , where M2+, M3+ are divalent and trivalent cation and Am- is interlayer anion responsible by charge balancing, the range of divalent and trivalent ions (x) varies normally between 0.17 a 0.33. According Montanari and co-works [2] compounds type ZnAl-hydrotalcites (ZnAl-HT) have relevant industrial interest; however the scientific literature concerning this material as catalysts or catalyst precursor is scarce. Based on this fact, in the present communication we will present a studied on how the variation in percentage of Zinc in a ZnMgAl-HT catalyst precursor can influence the formation of mixed oxides after calcination. The ZnMgAl-HTs, Figure b , y=5, 10,15,20,25,50,75 and 100% were prepared by co-precipitation and urea method. Mg-Zn/Al mixed oxides were prepared from calcinations of hydrotalcites precursors at 5000C for 4 hours. The material synthesized were characterized by X-ray powder diffraction, the measurements were carried out in Bruker D8 DaVinci diffractometer, equipped with CuKα radiation , LynxEye linear Position Sensitive Detector, Ni-filter. Data was collect between 8 and 800in 2θ with step size of 0.020and the count time of 0.05 per step. Soller slit 2.50of divergence and 0.2 mm primary slit were used. For the ZnMgAl-HT samples the measurements were performed at different temperatures, range 25-12000C, heating rate 50C/min. It was observed differences among XRD patterns for y greater than 25% of Zn in urea method at 5000C, and for co-precipitation method just for the substitution at 50 and 75% of Zn. These results suggested that the increase in Zn percentage change the structure of calcinated samples.

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Layered Double Hydroxides (LDHs) Type Materials Used in Water Treatment

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.660.273 ◽

2015 ◽

Vol 660 ◽

pp. 273-278 ◽

Cited By ~ 1

Author(s):

Simona Nichitus ◽

Gabriela Calin ◽

Alexandra Burlui ◽

Carmen Stadoleanu ◽

Vasile Burlui

Keyword(s):

Water Treatment ◽

Layered Double Hydroxides ◽

Mixed Oxides ◽

Waste Water Treatment ◽

Sol Gel ◽

Synthesis Method ◽

Cost Effective ◽

Thermally Activated ◽

Materials Used ◽

Double Hydroxides

Layered double hydroxides (LDHs) or LDHs matrices used for water treatment have been reviewed in this article. These aggregated nanoparticles can be obtained by sol-gel, hydrothermal or coprecipitation method, therefore their shape, size, properties (such as magnetic, acido-bazic, red-ox, texture and assembly) and applications are tailored as a function of synthesis method and process parameters respectively. Among other materials used in water treatment we chose layered double hydroxides generally named LDHs or in particular case hydrotalcites (MgAlLDHs). During calcination layered structure is destroyed giving rise to new structures like mixed oxides partially crystallized. LDHs and calcined LDHs type materials were able to uptake selected products. An important issue for removal of undesirable species for human health was M2+/M3+ cation ratio. Results show a better uptake of anionic compounds for thermally activated LDHs due to their “memory effect”. A large variety of LDHs was investigated in order to demonstrate their adsorption capacity for anionic compounds, cations, gas compounds even microorganisms. Nowadays one of the atractive issues of nanoscience is both the synthesis of these nanostructures and the assembly and organization way but the interest of scientists is to find new properties and applications in order to protect the environment. These cost effective, eco-friendly materials revealed new opportunities for waste water treatment.

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Bio-DEE Synthesis and Dehydrogenation Coupling of Bio-Ethanol to Bio-Butanol over Multicomponent Mixed Metal Oxide Catalysts

Catalysts ◽

10.3390/catal11060660 ◽

2021 ◽

Vol 11 (6) ◽

pp. 660

Author(s):

Izabela S. Pieta ◽

Alicja Michalik ◽

Elka Kraleva ◽

Dusan Mrdenovic ◽

Alicja Sek ◽

...

Keyword(s):

Active Sites ◽

Internal Combustion Engines ◽

Mixed Oxides ◽

Catalyst Activity ◽

Product Distribution ◽

Coke Deposition ◽

Precipitation Method ◽

Mixed Metal Oxide ◽

Low Carbon ◽

Municipal Solid Wastes

Within the Waste2Fuel project, innovative, high-performance, and cost-effective fuel production methods from municipal solid wastes (MSWs) are sought for application as energy carriers or direct drop-in fuels/chemicals in the near-future low-carbon power generation systems and internal combustion engines. Among the studied energy vectors, C1-C2 alcohols and ethers are mainly addressed. This study presents a potential bio-derived ethanol oxidative coupling in the gas phase in multicomponent systems derived from hydrotalcite-containing precursors. The reaction of alcohol coupling to ethers has great importance due to their uses in different fields. The samples have been synthesized by the co-precipitation method via layered double hydroxide (LDH) material synthesis, with a controlled pH, where the M(II)/M(III) ≈ 0.35. The chemical composition and topology of the sample surface play essential roles in catalyst activity and product distribution. The multiple redox couples Ni2+/Ni3+, Cr2+/Cr3+, Mn2+/Mn3+, and the oxygen-vacant sites were considered as the main active sites. The introduction of Cr (Cr3+/Cr4+) and Mn (Mn3+/Mn4+) into the crystal lattice could enhance the number of oxygen vacancies and affect the acid/base properties of derived mixed oxides, which are considered as crucial parameters for process selectivity towards bio-DEE and bio-butanol, preventing long CH chain formation and coke deposition at the same time.

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Mixed Oxide Layered Double Hydroxide Materials: Synthesis, Characterization and Efficient Application for Mn2+ Removal from Synthetic Wastewater

Materials ◽

10.3390/ma13184089 ◽

2020 ◽

Vol 13 (18) ◽

pp. 4089

Author(s):

Cristina Modrogan ◽

Simona Cǎprǎrescu ◽

Annette Madelene Dǎncilǎ ◽

Oanamari Daniela Orbuleț ◽

Eugeniu Vasile ◽

...

Keyword(s):

Adsorption Capacity ◽

Layered Double Hydroxides ◽

Synthetic Wastewater ◽

Precipitation Method ◽

Metallic Ions ◽

Materials Synthesis ◽

Experimental Conditions ◽

Edx Analysis ◽

Co Precipitation ◽

Double Hydroxides

Magnesium–aluminum (Mg-Al) and magnesium–aluminum–nickel (Mg-Al-Ni) layered double hydroxides (LDHs) were synthesized by the co-precipitation method. The adsorption process of Mn2+ from synthetic wastewater was investigated. Formation of the layered double hydroxides and adsorption of Mn2+ on both Mg-Al and Mg-Ni-Al LDHs were observed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDX) analysis. XRD patterns for prepared LDHs presented sharp and symmetrical peaks. SEM studies revealed that Mg-Al LDH and Mg-Al-Ni LDH exhibit a non-porous structure. EDX analysis showed that the prepared LDHs present uniformly spread elements. The adsorption equilibrium on these LDHs was investigated at different experimental conditions such as: Shaking time, initial Mn2+ concentration, and temperatures (10 and 20 °C). The parameters were controlled and optimized to remove the Mn2+ from synthetic wastewater. Adsorption isotherms of Mn2+ were fitted by Langmuir and Freundlich models. The obtained results indicated that the isotherm data fitted better into the Freundlich model than the Langmuir model. Adsorption capacity of Mn2+ gradually increased with temperature. The Langmuir constant (KL) value of Mg-Al LDH (0.9529 ± 0.007 L/mg) was higher than Mg-Al-Ni LDH (0.1819 ± 0.004 L/mg), at 20 °C. The final adsorption capacity was higher for Mg-Al LDH (91.85 ± 0.087%) in comparison with Mg-Al-Ni LDH (35.97 ± 0.093%), at 20 °C. It was found that the adsorption kinetics is best described by the pseudo-second-order model. The results indicated that LDHs can be considered as a potential material for adsorption of other metallic ions from wastewater.

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Study on synthesis of superparamagnetic spinel cobalt ferrite nanoparticles as layered double hydroxides by co-precipitation method

Russian Journal of General Chemistry ◽

10.1134/s1070363214110279 ◽

2014 ◽

Vol 84 (11) ◽

pp. 2205-2210 ◽

Cited By ~ 8

Author(s):

H. A. Hamad ◽

M. M. Abd El-latif ◽

A. B. Kashyout ◽

W. A. Sadik ◽

M. Y. Feteha

Keyword(s):

Layered Double Hydroxides ◽

Cobalt Ferrite ◽

Ferrite Nanoparticles ◽

Precipitation Method ◽

Cobalt Ferrite Nanoparticles ◽

Co Precipitation ◽

Double Hydroxides

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Study on synthesis of superparamagnetic spinel cobalt ferrite nanoparticles as layered double hydroxides by co-precipitation method

Russian Journal of General Chemistry ◽

10.1134/s1070363214100296 ◽

2014 ◽

Vol 84 (10) ◽

pp. 2031-2036 ◽

Cited By ~ 15

Author(s):

H. A. Hamad ◽

M. M. Abd El-latif ◽

A. B. Kashyout ◽

W. A. Sadik ◽

M. Y. Feteha

Keyword(s):

Layered Double Hydroxides ◽

Cobalt Ferrite ◽

Ferrite Nanoparticles ◽

Precipitation Method ◽

Cobalt Ferrite Nanoparticles ◽

Co Precipitation ◽

Double Hydroxides

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Photocatalytic Degradation of 2,4,6-Trichlorophenol by MgO–MgFe2O4 Derived from Layered Double Hydroxide Structures

Catalysts ◽

10.3390/catal9050454 ◽

2019 ◽

Vol 9 (5) ◽

pp. 454 ◽

Cited By ~ 5

Author(s):

Esthela Ramos-Ramírez ◽

Francisco Tzompantzi-Morales ◽

Norma Gutiérrez-Ortega ◽

Héctor G. Mojica-Calvillo ◽

Julio Castillo-Rodríguez

Keyword(s):

Photocatalytic Degradation ◽

Layered Double Hydroxides ◽

X Ray Diffraction ◽

Application Study ◽

Toxic Compounds ◽

X Ray ◽

Thermally Activated ◽

Double Hydroxide ◽

Double Hydroxides ◽

Scanning Electron

In recent years, the search for solutions for the treatment of water pollution by toxic compounds such as phenols and chlorophenols has been increasing. Phenols and their derivatives are widely used in the manufacture of pesticides, insecticides, paper, and wood preservers, among other things. Chlorophenols are partially biodegradable but not directly photodegradable by sunlight and are extremely toxic—especially 2,4,6-trichlorophenol, which is considered to be potentially carcinogenic. As a viable proposal to be applied in the treatment of water contaminated with 2,4,6-trichlorophenol, this paper presents an application study of the thermally activated Mg/Fe layered double hydroxides as photocatalysts for the mineralization of this contaminant. Activated Mg/Fe layered double hydroxides were characterized by X-ray diffraction, thermal analysis, N2 physisorption, and scanning electron microscopy with X-ray dispersive energy. The results of the photocatalytic degradation of 2,4,6-trichlorophenol in aqueous solution showed good photocatalytic activity, with an efficiency of degradation of up to 93% and mineralization of 82%; degradation values which are higher than that of TiO2-P25, which only reached 18% degradation. The degradation capacity is attributed to the structure of the MgO–MgFe2O4 oxides derived from double laminate hydroxide Mg/Fe. A path of degradation based on a mechanism of superoxide and hollow radicals is proposed.

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