Synthesis of Hydrotalcites from Waste Steel Slag with [Bmim]OH Intercalated for the Transesterification of Glycerol Carbonate.

Ca-Mg-Al hydrotalcites were prepared by coprecipitation from Type S95 steel slag of Shanghai Baosteel Group as supports of ionic liquid in this paper. Five basic ionic liquids [Bmim][CH3COO], [Bmim][HCOO], [Bmim]OH, [Bmim]Br and ChOH were prepared and their catalytic performance on the synthesis of glycerol carbonate by transesterification between dimethyl carbonate and glycerol was investigated. The characterization results indicated that [Bmim]OH is the best ionic liquid (IL) for the transesterification reaction of glycerol carbonate. The hydrotalcites before and after intercalation by ionic liquid were characterized by XRD, FTIR, SEM, EDS and the IL were characterized by FT-IR, 13C-NMR and basicity determination via the Hammett method. The analysis results implied that the dispersion of [Bmim]OH in hydrotalcites reduced the alkali density appropriately and facilitated the generation of glycerol carbonate. The yield of glycerol carbonate and the conversion rate of glycerol reached 95.0% and 96.1%, respectively, when the molar ratio of dimethyl carbonate and glycerol was 3:1, the catalyst dosage was 3 wt%, the reaction temperature was 75 °C and the reaction time was 120 min. The layered structure of hydrotalcites increased the stability of ionic liquid intercalated in carriers, thus the glycerol conversion and the GC yield still remained 91.9% and 90.5% in the fifth reaction cycle.

Enhanced bactericidal activity of brucite through partial copper substitution.

Brucite Mg(OH)2 belongs to a family of two-dimensional compounds with a CdI2-type structure built up from layers of edge-sharing octahedra delineating 2D galleries. In the current study, nanometer-sized platelets of copper substituted Mg(OH)2 were prepared by co-precipitation at room temperature in mixed alkaline (NaOH/Na2CO3) medium. Very weak substitution of a few hydroxyl ions by carbonate groups was highlighted at first by infrared spectroscopy and then quantified by thermogravimetric (TG) and mass spectrometric (MS) evolved gas analyses. The presence in a very low amount of water molecules in the galleries induces disorder in the stacking of layers of edge-sharing octahedra along the c-axis. The dehydration of the hydroxides taking place below 225 °C preserves the brucite-type structure of the samples while suppressing the stacking disorder. Copper substitution greatly enhances the bactericidal activity of nanometer-sized platelets of brucite against two bacteria frequently involved in healthcare-associated-infections. 10 mol% of cupric ions in Mg(OH)2 (a copper loading of 0.102 mg mL-1 in the suspension) were sufficient to induce, after 3 h in contact, 100% and 99.3% reductions in viability of Gram-negative E. coli and Gram-positive S. aureus, respectively (reductions as low as 23% and 48% are reported for the parent compound Mg(OH)2 in the same conditions). A good compromise between fast bactericidal kinetics and a high reduction in viability is reached by the 15 mol% copper-substituted Mg(OH)2 hydroxide. Its use gives the opportunity to five-fold reduce the copper loading of the bactericidal agent while being at least equally or even more efficient compared to the conventional CuO (a Cu loading of 0.799 mg mL-1 and 0.154 mg mL-1 in the suspension of CuO and 15 mol% copper substituted Mg(OH)2 particles, respectively).

Oxidative Dehydrogenation of Ethanol over Vanadium- and Molybdenum-modified Mg-Al Mixed Oxide Derived from Hydrotalcite.

Hydrotalcite or Mg-Al LDHs were synthesized by co-precipitation method. The Mg-Al mixed oxide was then derived by calcination of hydrotalcite at 450°C. The metal modified catalysts (Mo/Mg-Al and V/Mg-Al) were prepared by incipient wetness impregnation method. The obtained catalysts were characterized by several useful techniques and tested the reactivity for dehydrogenation and oxidative dehydrogenation of ethanol (gas-phase) to produce acetaldehyde. The catalytic reactions were performed at temperature range from 200 to 400°C for both non-oxidative and oxidative atmospheres. The results showed that the vanadium-modified hydrotalcite (V/Mg-Al) exhibited the highest ethanol conversion (34.3%) and acetaldehyde yield (15.5%) at 400℃ in the non-oxidative atmosphere. For the oxidative dehydrogenation of ethanol, the V/Mg-Al catalyst showed the highest activity at 400°C giving the ethanol conversion and acetaldehyde yield of 73.7% and 29.5%, respectively. This result probably related to the highest base density of V/Mg-Al catalyst (6.13 µmol CO2/m2) measured by CO2-TPD. The catalytic activity of Mg-Al catalyst and metal modified catalyst slightly decreased upon time-on-stream test for 10 h on oxidative dehydrogenation of ethanol due to carbon deposition.

Characterization and Structure⁻Property Relationships of Organic⁻Inorganic Hybrid Composites Based on Aluminum⁻Magnesium Hydroxycarbonate and Azo Chromophore.

In this study, novel organic⁻inorganic composites were prepared by the complexation of dicarboxylic azo dye (AD) with aluminum⁻magnesium hydroxycarbonate (AlMg⁻LH). This procedure provides an effective method for the stabilization of dicarboxylic organic chromophores on an AlMg-LH host. The structures of the hybrid composites were examined by X-ray diffraction (XRD), secondary ion mass spectrometry (TOF-SIMS), 27-Al solid-state nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA) and scanning transmission electron microscopy (STEM). The TOF-SIMS method was applied to investigate the metal⁻dye interactions and to monitor the thermal stability of the organic⁻inorganic complexes. Secondary ion mass spectrometry confirmed the presence of a characteristic peak for C18H10O5N2Mg22+, indicating that both carboxylic groups interacted with AlMg-LH by forming complexes with two Mg2+ ions. Modification with hybrid pigments affected the crystal structure of the AlMg-LH mineral, as shown by the appearance of new peaks on the X-ray diffraction patterns. Adsorption of the dicarboxylic chromophore not only led to significantly enhanced solvent resistance but also improved the thermal and photostability of the hybrid pigments. We propose a possible arrangement of the azo dye in the inorganic matrix, as well as the presumed mechanism of stabilization.

Removal of boron from oilfield wastewater via adsorption with synthetic layered double hydroxides.

Hydrotalcite is a layered double hydroxide (LDH) consisting of brucite-like sheets of metal ions (Mg-Al). In this work, hydrotalcites were synthesized, and boron removal from oilfield wastewater was evaluated. LDHs were synthesized using the co-precipitation method. The calcined products (CLDHs) were obtained by heating at 500°C and characterized using X-ray diffraction, X-ray fluorescence, thermogravimetric analysis and the specific surface area (BET). The affinity of LDHs for borate ions was evaluated for calcined and uncalcined LDHs as a function of contact time, initial pH of the oilfield wastewater (pH ∼ 9) and the LDH surface area. The tests were conducted at room temperature (approximately 25ºC). The results indicated that 10 min were needed to reach a state of equilibrium during boron removal for calcined LDHs due to the high surface area (202.3 m(2) g(-1)) regardless of the initial pH of the oilfield wastewater, which resulted from the high buffering capacity of the LDHs. The adsorption capacity increased as the adsorbents levels increased for the range studied. After treatment of the oilfield wastewater containing 30 mg L(-1) of boron with Mg-Al-CO3-LDHs, the final concentration of boron was within the discharge limit set by current Brazilian environmental legislation, which is 5 mg L(-1). Pseudo-first-order and pseudo-second-order kinetic models were tested, and the latter was found to fit the experimental data better. Isotherms for boron adsorption by CLDHs were well described using the Langmuir and Freundlich equations.

Coupling physical chemical techniques with hydrotalcite-like compounds to exploit their structural features and new multifunctional hybrids with luminescent properties.

Hydrotalcite-like compounds (HTlc), belonging to the large class of Layered Double Hydroxides (LDH), have excited wide interest owing to the incredible number of their potential and achieved applications in physical, chemical and bio-chemical fields. This perspective review deals with recent advances in the application of physical-chemical techniques for the study of HTlc structure and for the design and synthesis, using intercalation chemistry routes, of new hybrid materials. Firstly, a rapid survey on the most common synthetic strategies for the attainment of HTlc with different crystallinity degree and crystal size and for their modification to obtain hybrids has been made, and the use of coupled techniques (XRPD, luminescence, Solid State MAS NMR and Molecular Dynamics) to gain structural information is reported. Then, the design, synthesis and photophysical characterization of azoic dyes-intercalated and co-intercalated HTlc hybrid materials are described. Hybrids constituted of ZnAl-HTlc, co-intercalated with stearate anions and methyl orange or methyl yellow dyes, have been used as nanofillers of hydrophobic polymers. The polymeric nano-composites obtained have been characterized by means of XRPD patterns, Thermo-Gravimetric Analysis and Confocal Fluorescence Microscopy. This latter technique has been found to be an excellent, complementary and non-invasive tool to probe the dispersion degree of the fluorescent fillers into the polymeric matrices and their stability in the compounding process. Finally, the synthesis and spectroscopic characterization of nanoparticle (NP) decorated HTlc for advanced antimicrobial and photo-catalytic applications are also reported. The review terminates with a concluding short note and future trends.

Removal of bisphenol A from aqueous solution by a dodecylsulfate ion-intercalated hydrotalcite-like compound.

A Mg-Al hydrotalcite-like compound (HTlc) and a dodecylsufate ion-intercalated Mg-Al HTlc (MHTlc) were prepared. The effects of temperature, ionic strength, and initial pH on the adsorptions ofbisphenol A (BPA) on both HTlc and MHTlc were studied in detail. The adsorption capacity of the pristine HTlc for BPA was low, and the adsorption was due to the substitution of surface anions within the pristine HTlc by the hydroxybenzene anion that was dissociated from BPA. The adsorption capacity for BPA increased notably with modification. The high adsorption capacity of MHTlc for BPA was mainly due to the dissolution of BPA molecules into the hydrophobic organic phase formed in the interlayers of MHTlc. The adsorption capacity of MHTlc for BPA decreased with increasing temperature and initial pH, but increased when increasing the ionic strength.

Competitive adsorption characteristics of fluoride and phosphate on calcined Mg-Al-CO3 layered double hydroxides.

With synthetic wastewater, competitive adsorption characteristics of fluoride and phosphate on calcined Mg-Al-CO(3) layered double hydroxides (CLDH) were investigated. A series of batch experiments were performed to study the influence of various experimental parameters, such as pH, contact time, and order of addition of the anions on the competitive adsorption of fluoride and phosphate on CLDH. It was found that the optimal pH is around 6 and it took 24 h to attain equilibrium when fluoride and phosphate were simultaneous added. The order of addition of anions influenced the adsorption of fluoride and phosphate on CLDH. The kinetic data were analyzed using the pseudo first-order and pseudo second-order models and they were found to fit very well the pseudo second-order kinetic model. Data of equilibrium experiments were fitted well to Langmuir isotherm and the competitive monolayer adsorption capacities of fluoride and phosphate were found to be obviously lower than those of single anion at 25 °C. The results of X-ray diffraction, Scanning Electron Microscopy with energy-dispersive X-ray analyses, and ATR-FTIR demonstrate that the adsorption mechanism involves the rehydration of mixed metal oxides and concomitant intercalation of fluoride and phosphate ions into the interlayer to reconstruct the initial LDHs structure.

The synthesis and spectroscopic characterisation of hydrotalcite formed from aluminate solutions.

Raman spectroscopy has been used to characterise nine hydrotalcites prepared from aluminate and magnesium solutions (magnesium chloride and seawater). The aluminate hydrotalcites are proposed to have the following formula Mg(6)Al(2)(OH)(16)(CO(3)(2-))·xH(2)O, Mg(6)Al(2)(OH)(16)(CO(3)(2-),SO(4)(2-))·xH(2)O, and Mg(6)Al(2)(OH)(16)(SO(4)(2-))·xH(2)O. The synthesis of these hydrotalcites using seawater results in the intercalation of sulfate anions into the hydrotalcite interlayer. The spectra have been used to assess the molecular assembly of the cations and anions in the hydrotalcite structures. The spectra have been conveniently subdivided into spectral features based upon the carbonate anion, the hydroxyl units and water units. This investigation has shown the ideal conditions to form hydrotalcite from aluminate solutions is at pH 14 using a magnesium chloride solution at a volumetric ratio of 1:1. Changes in synthesis conditions resulted in the formation of impurity products aragonite, thenardite, and gypsum.

Total oxidation of toluene over calcined trimetallic hydrotalcites type catalysts.

Two trimetallic ZnCuAl and MnCuAl hydrotalcites have been successfully synthesized by a co-precipitation method. The manganese based material was identified as a new hydrotalcite phase. Both lamellar precursors were calcined at 450 and 600 degrees C and the resulting catalysts were tested on reaction of total oxidation of toluene. The solids were characterized by X-ray diffraction, thermal analysis, atomic absorption spectroscopy, Fourier transformed infrared spectroscopy, N(2) adsorption and H(2) temperature-programmed reduction. It was found that ZnCuAl materials are composed of copper and zinc oxides supported on alumina; while MnCuAl ones comprise basically spinel phases, which were not completely identified. The catalytic behavior of the calcined samples showed that Mn hydrotalcite calcined at 450 degrees C exhibited the best catalytic performance that corresponds to 100% toluene conversion into CO(2) at about 300 degrees C.

Nitrate sorption by thermally activated Mg/Al chloride hydrotalcite-like compound.

A laboratory study was conducted to investigate the ability of Mg-Al-Cl hydrotalcite-like compound for the removal of nitrate from synthetic nitrate solution. In the present study Mg-Al-Cl hydrotalcite was synthesized by co-precipitation method and was characterized using SEM, XRD, FTIR and TGA-DSC. To know the practical applicability, a detailed removal study of nitrate ion was carried out. The removal of nitrate was 87.6% under neutral condition, using 0.3g of adsorbent in 100mL of nitrate solution having initial concentration of 10mg/L. Adsorption kinetic study revealed that the adsorption process followed first-order kinetics. Adsorption data were fitted to linearly transformed Langmuir isotherm with R(2) (correlation coefficient)>0.99. Thermodynamic parameters were also calculated to study the effect of temperature on the removal process. In order to understand the adsorption type, equilibrium data were tested with Dubinin-Radushkevich isotherm. The percentage removal was found to decrease gradually with increase in pH and the optimum pH was found to be 6. The process was rapid and equilibrium was established within first 40 min.

First identification of O,S-diethyl Thiocarbonate in Indian Cress absolute and odor evaluation of its synthesized homologues by GC-sniffing.

Indian cress (Tropaeolum majus L.) absolute was studied by GC-olfactometry (VIDEO-Sniff method) in order to identify odor-active aroma compounds. Because of its fruity-sulfury odor note, a compound that has never been identified in plant extracts before stood out: O,S-diethyl thiocarbonate, present at 0.1% (percentage of the total GC/FID area) in the extract. GCxGC-TOFMS allowed for a clean mass spectrum to be obtained, and isolation by preparative GC followed by NMR studies allowed its identification. Here, we report on the first detection of O,S-diethyl thiocarbonate in Indian cress absolute by GC-olfactometry/VIDEO-Sniff and on its isolation and identification. The synthesis and odor evaluation of its homologues are presented.

Magnesium hydroxide nanoparticles synthesized in water-in-oil microemulsions.

Well-dispersed magnesium hydroxide nanoplatelets were synthesized by a simple water-in-oil (w/o) microemulsion process, blowing gaseous ammonia (NH(3)) into microemulsion zones solubilized by magnesium chloride solution (MgCl(2)). Typical quaternary microemulsions of Triton X-100/cyclohexane/n-hexanol/water were used as space-confining microreactors for the nucleation, growth, and crystallization of magnesium hydroxide nanoparticles. The obtained magnesium hydroxide was characterized by field-emission scanning electron microscopy (FESEM), high-resolution transmission election microscopy (HRTEM), X-ray powder diffraction (XRD), laser light scattering, Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis-differential scanning calorimetry (TGA-DSC). The mole ratio of water to surfactant (omega(0)) played an important role in the sizes of micelles and nanoparticles, increasing with the increase of omega(0). The compatibility and dispersibility of nanoparticles obtained from reverse micelles were improved in the organic phase.

Treatment of high fluoride concentration water by MgAl-CO3 layered double hydroxides: kinetic and equilibrium studies.

MgAl-CO(3) layered double hydroxides (LDHs) have been employed to treat high fluoride concentration solution. The influences of solution pH, initial fluoride concentration and other anions in the solution were investigated by a series of batch experiments. A marked decrease in the amount of adsorbed fluoride by LDHs is observed with increasing pH. The extent of fluoride removal in the presence of other anions decreases in the order HCO(3)(-)>Cl(-)>H(2)PO(4)(-)>SO(4)(2-). The equilibrium isotherm for fluoride uptake corresponds closely to the Langmuir-Freundlich (L-F) model. The maximum capacity of LDHs for fluoride ions and the Gibbs free energy (DeltaG(0)) for the defluoridation process were calculated to be 319.8+/-5.7mg/g and -9.0+/-0.66kJ/mol, respectively. The negative value of DeltaG(0) indicates the spontaneous nature of the treatment process. Four kinetic models have been evaluated in order to attempt to fit the experimental data, namely the pseudo-first order, the pseudo-second order, the modified multiplex and the double exponential models. It was found that the modified multiplex model, involving a rapid first order step and a slow second order step most closely described the kinetics. The activation energies for the two steps are 37.2+/-5.26 and 72.6+/-4.52kJ/mol, respectively, suggesting that the rapid step is controlled by diffusion processes, whilst the second step is controlled by the reaction of fluoride with the LDHs.

Synthesis and sulfate ion-exchange properties of a hydrotalcite-like compound intercalated by chloride ions.

To reduce the generation of hydrogen sulfide gas from sulfate ions, we synthesized a layered double hydroxide hydrotalcite-like compound intercalated with chloride ions in the interlayer (HT-Cl) using a coprecipitation reaction. The resultant HT-Cl material had a Mg/Al molar ratio of approximately 2, and the molar fraction of the chloride ions on the intercalated anion layer of the HT was 0.90. A higher molar fraction of chloride ions can be inserted into the interlayers of the HT by increasing the initial concentration ratio of chloride ions to aluminum ions [Cl(-)](0)/[Al(3+)](0) in the solution. Approximately 98% of the sulfate ions in the solution were removed within 10 min after adding 1.12 times the stoichiometric quantity of synthesized HT-Cl, which contained a Mg/Al molar ratio of 2 equal to a solution containing a 12 mM calcium sulfate solution.

Emission reduction of aluminium anodising industry by production of Mg2+-Al3+-SO4(2-) -hydrotalcite-type compound.

The synthesis of Mg(2+)-Al(3+)-SO(4)(2-)-hydrotalcite-type compound from the acid wastewaters of the aluminium anodising industry has been studied as a possible way of reducing the emissions to the environment, recovering simultaneously resource materials as a valuable mineral. The process of synthesis was carried out using rinse wastewater solutions generated from the anodising treatment when a cascade rinsing system is employed. The method of co-precipitation at constant pH was employed for such a process, using MgO as a source of magnesium. The synthesis was studied as a function of precipitation pH (8-10) and flow rate of reagent mixture (5-30 ml min(-1)). High pH of precipitation and low flow rate of reagent mixture (5-15 ml min(-1)) were found optimal to improve the crystallinity of the synthesised product. The mineral characterisation was performed using X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis and differential thermal analysis, all of which indicated characteristics typical of the desired compound. Almost 100% of the aluminium initially present in the acid wastewater solutions was recovered in the form of Mg(2+)-Al(3+)-SO(4)(2-)-hydrotalcite-type compound.

Mg,Al layered double hydroxides with intercalated indomethacin: synthesis, characterization, and pharmacological study.

Magnesium aluminium layered double hydroxides (LDH) with a molar Mg/Al ratio of 2.0 have been prepared with intercalated indomethacin following two routes: reconstruction from a previously calcined Mg(2)Al-CO(3) LDH, and coprecipitation from the corresponding chlorides. The solids have been characterized by powder X-ray diffraction, FTIR, and (13)C CP/MAS NMR spectroscopies and thermal stability (differential thermal analysis and thermogravimetric analysis). Intercalation of the drug is attained by both routes; however, while coprecipitation leads to a single layered structure, contamination with another layered MgAl-CO(3) phase occurs by the reconstruction method. The amount of drug intercalated, as well as the height of the gallery, are larger by the coprecipitation than by the reconstruction one. The data obtained support a somewhat tilted, upwards orientation of the drug molecules forming an interdigited bilayer, in the case of the sample prepared by coprecipitation, with the carboxylate groups pointing towards the hydroxyl layers. However, in the case of the sample prepared by reconstruction, the molecules are forming a tilted, upwards monolayer. The solids prepared are stable up to 250 degrees C. Pharmacological studies in vivo show that intercalation of the drug in the LDH reduces the ulcerating damage of the drug.

Concentration of simple aldehydes by sulfite-containing double-layer hydroxide minerals: implications for biopoesis.

Environmental conditions play an important role in conceptual studies of prebiotically relevant chemical reactions that could have led to functional biomolecules. The necessary source compounds are likely to have been present in dilute solution, raising the question of how to achieve selective concentration and to reach activation. With the assumption of an initial 'RNA World', the questions of production, concentration, and interaction of aldehydes and aldehyde phosphates, potential precursors of sugar phosphates, come into the foreground. As a possible concentration process for simple, uncharged aldehydes, we investigated their adduct formation with sulfite ion bound in the interlayer of positively charged expanding-sheet-structure double-layer hydroxide minerals. Minerals of this type, initially with chloride as interlayer counter anion, have previously been shown to induce concentration and subsequent aldolization of aldehyde phosphates to form tetrose, pentose, and hexose phosphates. The reversible uptake of the simple aldehydes formaldehyde, glycolaldehyde, and glyceraldehyde by adduct formation with the immobilized sulfite ions is characterized by equilibrium constants of K=1.5, 9, and 11, respectively. This translates into an observable uptake at concentrations exceeding 50 mM.

[Drug interactions during storage of mixtures of the antacid group. II. Effect of temperature on the formation of hydrotalcite in neutralizing suspensions]. / Badanie oddzialywan zachodzacych podczas przechowywania mieszanin z grupy antacida. II. Wplyw temperatury na powstawanie hydrotalcytu w zawiesinach zobojetniajacych.

Eight antacid mixtures were stored for 110 days at 25 degrees C, 35 degrees C and 45 degrees C in the form of suspensions in water. Changes in pH were followed, and the structural changes in suspension components were studied by X-ray analysis. It has been stated that formation of hydrotalcite, the product od interaction of the mixture components depends mainly on the kind and ratio of the suspension reactants, and only to a little degree on the storage temperature.