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Chemical looping with oxygen uncoupling, a variant of chemical looping combustion, requires chemically and physically stable oxygen carriers over long‐term redox cycling. Copper‐based oxygen carriers are characterised by high oxygen release rates but experience sintering at high temperatures. The use of layered double hydroxides (LDHs), prepared via co‐precipitation, as oxygen carrier precursors has been shown to effectively limit deactivation of copper‐based mixed metal oxides (MMOs) over extended redox cycling. The LDH‐derived MMOs have highly dispersed metal oxide within a stable support; the high dispersion of metals is due to the LDH precursor structure. In this work, a fluidised bed reactor (FBR) was used to study the intrinsic kinetics of oxygen release from CuO/MgAl2O4 oxygen carriers synthesised via the LDH‐MMO design strategy. The long‐term performance of MMOs with higher loadings of CuO, calcined from LDHs with higher Cu contents, was also investigated using an FBR. The intrinsic kinetics were determined using a kinetic model incorporating an effectiveness factor. By minimising the effects of intra‐ and inter‐particle mass transfer, the activation energy and the pre‐exponential factor of the lower loading MMOs were determined to be 51 ± 3 kJ mol−1 and 0.0567 s−1, respectively. All MMOs showed excellent stability over 100 redox cycles in a thermogravimetric analyser. However, the pH during co‐precipitation of the LDHs affected the stability of the MMOs in an FBR. The MMOs calcined from LDHs synthesised at pH 9.5 disintegrated during operation, whilst those produced from LDHs synthesised at pH 11 maintained high conversion and physical integrity over 100 redox cycles. © 2023 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

The Cu/ZnO/Al 2 O 3 catalysts (CuZnAl) can be utilized to directly synthesize isobutanol from syngas at low temperatures, and complexants are new and efficient modifiers for the catalysts used to synthesize higher alcohols. However, little is known about effects of the complexants such as ethylene diamine tetra-acetic acid (EDTA) and triethanolamine (TEA) on structure and catalytic activity of CuZnAl. In this work, the precursors of CuZnAl, hydrotalcite-like compounds (HTLCs), were treated with EDTA and TEA to obtain the CuZnAl modified by EDTA (CuZnAl-EDTA) and TEA (CuZnAl-TEA). The catalytic performances of CuZnAl, CuZnAl-EDTA and CuZnAl-TEA were evaluated. Addition of EDTA or TEA increased CO conversion and selectivity for isobutanol and ethanol compared with pure CuZnAl. All the samples were characterized by BET, XRD, SEM, CO–TPD, CO 2 –TPD, H 2 –TPR and FTIR spectroscopy to further disclose the reason for better catalytic performance of CuZnAl-EDTA and CuZnAl-TEA. We found that the EDTA and TEA promote reduction of CuO, increase in concentration of basic sites and formation of floccule-like structure, which efficiently improves catalytic activity of CuZnAl-EDTA and CuZnAl-TEA for synthesis of isobutanol and ethanol. However, EDTA restrains CO desorption from the surface of the catalysts, and thus the strongly adsorbed CO molecules may lead to lower catalytic activity of CuZnAl-EDTA compared with CuZnAl-TEA. [ABSTRACT FROM AUTHOR]

Benzoin methyl ether (BME) is an important photosensitizer for coatings and printing technologies, and Cu/Cr hydrotalcite-like compounds (CuCr-HTLcs) is promising to be used as pollution-free catalyst for BME synthesis. However, little is known about effect of CuCr-HTLcs structure on catalytic synthesis of BME. In this work, a series of CuCr-HTLcs with different ratios of Cu to Cr (n Cu /n Cr ) was successfully prepared by a co-precipitation method. The structure of CuCr-HTLcs were systematically characterized. The copper and chromium in CuCr-HTLcs mainly exist in the form of Cu 2+ and Cr 3+ , respectively. The n Cu /n Cr has significant effects on crystallinity, acidity, and textural properties of CuCr-HTLcs. Subsequently, catalytic performance of CuCr-HTLcs was tested for BME synthesis. We found that BME synthesis is mainly influenced by combined effects of acid-site concentration and pore size. Moderate acid-site concentration and pore size (mesopores) are the critical factors for improving catalytic activity of CuCr-HTLcs and BME selectivity. [ABSTRACT FROM AUTHOR]

Ni catalysts with high surface areas were prepared from Mg–Al hydrotalcite-like compounds containing Ni with different Mg-to-Al ratios for the production of hydrogen via ammonia decomposition. At atomic ratios of Mg-to-Al from 3:1 to 6:1, Ni reduction was greater than 90%, and the amounts of Ni0 exposed were kept at more than 200 μmol g−1. With the increase in Mg-to-Al ratio, turnover frequency was increased due to an increase in the basicity of the support. Of the catalysts examined, Ni_MgAl(6:1) exhibited the highest NH3 conversion, which was attributed to its relatively high basicity and large amount of Ni0 exposed. [ABSTRACT FROM AUTHOR]

Hydrotalcite-like compounds, also known as layered double hydroxides (LDH) are synthetic compounds that have been widely researched due to their many potential applications. These compounds are usually produced by a co-precipitation method that requires a metallic solution. Some previous works have reported the use of wastewater in LDH synthesis. This paper proposes a sustainable way to reduce waste in the lab. First, hydrotalcite-like compounds were synthesized using wastewater from metal analyses and then they were applied for phenol and chromium removal. In this process, a highly metallic acid residue has not been previously tested in LDH synthesis. It is first reported herein. The obtained materials were characterized and the results demonstrated that LDH with Mg-Al or Zn-Al structures were achieved and that the acidic features from lab wastes do not affect LDH production. The hydrotalcite-like compounds were also thermally treated and reconstructed, indicating that the memory effect appeared to play an important role in phenol and chromium VI adsorption. The thermally treated LDH with Mg-Al adsorbs 111 mg phenol/g and 5.92 mg Cr(VI)/g. Finally, both pollutants were used to prove that the synthesized LDH-like compounds could be used as an adsorbent. [ABSTRACT FROM AUTHOR]

• Mortar using BFS improves freezing and thawing resistance under chloride environment. • Mortar using BFS has improved electrical resistivity and chloride ion diffusion coefficient. • The improvement in electrical resistivity e is due to densification of the BFS-cement paste ITZ. • Hydrotalcite-like compound forms at the BFS-cement paste ITZ, improving the chloride ion diffusion coefficient. The effect of BFS (Blast Furnace Slag Fine Aggregate) on the freezing and thawing resistance under chloride environment was evaluated, and the freezing and thawing resistance was proven to be improved by using BFS with fine grain size and by increasing the mixing ratio of BFS to natural sand. The electrical resistivity and effective chloride ion diffusion coefficient were measured in order to evaluate the effect of BFS on the resistance of the penetration of chloride ions into concrete, and the mortar using BFS had higher electrical resistivity and lower effective chloride ion diffusion coefficient than the mortar using mountain sand. In order to elucidate the reaction products at the interface between cement paste and BFS, which cause densification of the BFS interface when BFS is used as fine aggregate in concrete, an investigation and analysis of the reaction products were conducted using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). As a result, it was found that a reaction phase is formed in the BFS-cement paste interfacial transition zone (ITZ), and its thickness is 0.45 to 1.4 μm. TEM observation and selected-area diffraction (SAD) analysis revealed the existence of hydrotalcite-like compounds in the BFS-cement paste ITZ. The chloride enrichment in hydrotalcite-like compounds at ITZ was confirmed by TEM observation and TEM-EDS of mortar with BFS after freeze–thaw tests under chloride environment. Therefore, it was considered to contribute to the improvement of the resistance of the penetration of chloride ions into concrete mixed with BFS. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is known to have wide ranging toxicities not only as a gas but also as dissolved forms in aquatic environments. The diversity of aquatic organisms can be severely affected by hydrogen sulfide at very low concentrations, indicating the urgent necessity to develop an efficient method for removal of hydrogen sulfide in water. In this study, the removal capacity for hydrogen sulfide of our originally developed hydrotalcite-like compound composed of magnesium and iron (MF-HT) was investigated and its potential application for reduction of toxicity to aquatic organisms was evaluated. The MF-HT experimentally showed a high adsorption capacity of 146.5 mg/g with a fast adsorption equilibrium time of 45 min, both of which are top-class compared with those of other adsorbents previously reported. In fact, removal of hydrogen sulfide (1.2–152.5 mg/L) at an average rate of >97.6% was achieved in groundwater samples (n = 16) by the MF-HT within 60 min. The toxicities of groundwater, indicated by inhibition rate for microalgae (primary producers) and immobilization rate for crustaceans (secondary consumers), were reduced by 96.1% and 82.5% in 2-fold and 4-fold diluted groundwater, respectively, after treatment with the MF-HT for 60 min. These results indicate that MF-HT has an excellent safety record for aquatic organisms. After clarifying the adsorption mechanism, excellent reusability of MF-HT was also confirmed after regeneration using 1 M Na 2 CO 3 solution. Considering the efficacy, speed, safety and cost of MF-HT, it could be a novel promising material for solving the problem of hydrogen sulfide pollution in the hydrosphere. [Display omitted] • No study for H 2 S removal in water using hydrotalcite-like compounds (HT). • Top-class adsorption capacity of our HT consisted of Mg and Fe (MF-HT) for H 2 S. • Top-class equilibrium time in addition to adsorption capacity of the MF-HT for H 2 S. • MF-HT-mediated reduced toxicities for water microorganism in groundwater with H 2 S. • MF-HT as a novel, efficient and safe depurator for H 2 S removal in the hydrosphere. [ABSTRACT FROM AUTHOR]

The syntheses of Mg–Fe(III) layered double hydroxides with different compositions at varied temperature through a co-precipitation method were attempted. The well-crystallized and white colored layered double hydroxides with chloride anions were obtained from the samples adjusted to the composition of Mg/Fe = 4 and aged at higher temperature. The Fe species in the white colored Mg–Fe layered double hydroxides were evaluated as all Fe(III) species by a Mössbauer measurement. The synthesized Mg–Fe(III) layered double hydroxide was treated with a sugar alcohol at temperature above its melting point in order to reduce Fe(III) incorporated into the hydroxide layers. The Mg–Fe layered double hydroxide resulting from a sugar alcohol treatment showed the reduction property in an aqueous solution. [ABSTRACT FROM AUTHOR]

Hydrotalcite-type solids of the form NiAl- R, where R refers to the ratio of Ni to Al ( R = 2, 3, 5, 8, and 10), were successfully synthesized following co-precipitation method at pH = 12. The obtained solids were calcined at 800 °C, except for NiAl- R where calcination was performed at temperatures ranging between 300 and 800 °C. Following calcination, the resulting materials were evaluated for their catalytic activity and stability during the process of dry reforming of methane. Factors affecting the catalytic activity of the obtained materials such as the ratio R and calcination temperature were also studied. Prior to calcination, X-ray diffraction analyses clearly illustrated the typical hydrotalcite structure of the synthesized materials (when R ≤ 5). On the other hand, calcination at various temperatures prompted decomposition of all solids to form NiO, with exception to NiAl- R, which upon calcinations at 800 °C was decomposed to form NiO and a second phase spinel containing NiAlO. The chemical composition of the obtained solids was determined by atomic absorption spectroscopy. Further characterization was performed using several techniques, including: surface area measurements ( S), scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. The reducibility of nickel species was studied via temperature-programmed reduction. The catalytic performance of the as-prepared samples was studied for dry reforming of methane under atmospheric pressure at temperatures ranging between 400 and 700 °C. The catalytic activity of the designed substances highlighted the importance of molar ratios i.e. Ni/Al on the success of the overall dry reforming of methane process. The catalytic activity of the synthesized materials was also found to be directly proportional to the ratio of Ni/Al as well as the calcination temperature, with exception to NiAl- R which was found to exhibit the highest activity of all. The latter observation was perhaps associated with the lower size of the crystalline particles in conjunction with the presence of a second phase containing NiAlO. In this study, it is shown that the calcination temperature has a significant effect on the catalytic property and the crystallite size of the metal. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of Zn-Al oxide were obtained from ZnAl hydrotalcite-like compound. • Zn-Al oxide was used as catalysts to remove carbonyl sulfide. • Sm dopant and the replacement of base can improve the removal efficiency. • KOH and K 2 CO 3 was used as the precipitation base. In this work, a series of Zn-Al oxides calcined from ZnAl hydrotalcite-like catalysts were prepared using the co-precipitation method and then applied to remove COS. The effects of the content of Sm and the species of rare earth metal on the catalytic activities of COS hydrolysis are investigated. Experimental results show that the prepared catalyst doped with 20 wt% Sm performs better catalytically. Based on the optimization of Sm dopant, the effect of the precipitation base in the ZnAl hydrotalcite-like compounds on the catalytic activities of the catalysts is further investigated. The results show that the prepared catalyst using KOH and K 2 CO 3 as the precipitation base exhibits the best catalytic performance. The characterization results show that the doping of rare earth metals can weaken the crystallinity and the introduction of an appropriate amount of Sm ions can significantly enhance the proportion of adsorbed oxygen species. Moreover, the results show that the synergistic effect of the doping of Sm and the replacement of precipitating alkali contribute to the enhancement of the number of basic sites, especially weak and medium basic sites. Furthermore, combined with in-situ DRIFTS, the catalytic mechanism of COS hydrolysis on ZnAl-20Sm-Na MMO is proposed. [ABSTRACT FROM AUTHOR]

A pre-combustion removal option, coupling water-gas shift and CO2 capture is the well-known sorption- enhanced water-gas shift (SEWGS): the removal of CO2 produced by WGS reaction, shifting the thermodynamic equilibrium, enhances H2 production. Among the different CO2 sorbents, hydrotalcite-like compounds work at the required intermediate temperature (T 200- 400°C). Using low supersaturation method, three different sorbents were synthesized. Sieved fractions were impregnated with 20%w/w K2CO3 and then dried and subjected to thermal treatment. Sample characterization was performed by means of FT-IR spectroscopy, XRD analysis and TG-DTA analysis. Sample analysis was carried out after synthesis, thermal treatment (calcination) and after fixed bed reactor capture tests. Sorption and desorption tests were performed in a fixed bed microreactor, under cyclic conditions, at temperature level of T = 350°C and P = 5 bar in dry and wet condition. The amount of CO2 captured by the sorbent in each test was quantified by means of a first order with dead time flow distribution model applied to the experimental system. Sorption capacity of sorbents in dry conditions increases of 30% with respect to previous atmospheric pressure results obtained in fluidized bed. These sorbents seem to be good candidates to be used as a bi-functional sorbent-catalyst for SEWGS. [ABSTRACT FROM AUTHOR]

A series of MgZnAl hydrotalcite-like compounds with different zinc content (1-25 mass % of nominal zinc content) were prepared by a simple and environmentally-friendly method. The solids were characterized by X-ray powder diffraction (XRD), thermogravimetric (TG), nitrogen adsorption-desorption at −196°C (BET), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and CO temperature-programmed desorption (CO-TPD). Transesterification of castor oil with methanol was selected as a probe reaction to stress the effect of zinc incorporation. From the XRD analysis of fresh samples it was demonstrated that the incorporation of zinc is feasible in the nominal range of 1-10 mass % while in the samples with higher zinc content, zinc nitrate and ZnO as secondary crystalline phases were observed. Furthermore, the analysis of samples calcined at 450°C indicated the coexistence of the ZnO and MgO crystalline phases. From the EDS and TG characterizations, the zinc percentage and thermal decomposition of the samples were determined. It was revealed that the samples exhibited the characteristic platy-like habit of hydrotalcite-like compounds. The BET analysis confirmed that the calcined samples presented an increment in their specific surface area values compared with the pristine ones. It was established that the amount of basic sites diminished with the zinc incorporation, which also affected the conversion degree of the transesterification reaction. [ABSTRACT FROM AUTHOR]

A series of mixed oxide catalysts with different composition of Co-M-Al and Co-M-Ce-Al (M=Zn, Ni, Cu) were prepared by co-precipitation method from hydrotalcite-like compounds. The experimental results revealed the catalytic activity of Co-Ni-Al is slightly higher than that of Co-Zn-Al and much higher than that of Co-Cu-Al for direct decomposition of N2O. Moreover, addition of small amounts of CeO2 improved the catalytic activity significantly and made the decomposition temperatures at which the N2O conversion was 50% and 90% (T50 and T90) both decreased 80°C than those of Co-M-Al catalysts without CeO2 added. Further, potassium-load also promoted the catalytic activity, and the decomposition temperatures of T50 and T90 both decreased approximately 50°C. It is significant for decomposing N2O from industries and reducing carbon emission from atmosphere. [ABSTRACT FROM AUTHOR]

Highlights: [•] Waste product of oil shale industry was utilized as sorbent for uranium. [•] Hydrotalcite-like compound was synthesized using oil shale ash. [•] Composition, microstructure and absorptive property were investigated. [•] It was an Mg–Al-based hydrotalcite compound with a lamellar morphology. [•] The maximum adsorption capacity toward uranium is 156mg/g at 298K. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the simultaneous sorption of Cu2+ and p-cresol, which are frequently encountered together in waste waters, into Mg–Al hydrotalcite-like compound (HTlc) modified with dodecylsulfate and ethylenediaminetetraacetate ions (SDS–EDTA-HTlc) was described and compared to a single adsorbate situation. Modification can decrease the specific surface area of the Mg–Al HTlc but promote the sorption for Cu2+ and p-cresol, respectively. Pseudo-second order equations were fitted to the kinetic data, and the rate constants were evaluated. The effect of pH on the simultaneous sorption efficiency was also studied. Freundlich isotherm model was used to analyze the equilibrium data for each adsorbate in both single and binary systems. In binary mixtures, competition for binding sites was identified. The equilibrium Cu2+ uptake decreased with an increased initial p-cresol concentration, whereas the existence of Cu2+ in the solution enhanced the p-cresol removal. [Copyright &y& Elsevier]

Abstract: Ni/Cu/Al/Fe hydrotalcite-like compound was synthesized by a co-precipitation method. The activity of the reduced hydrotalcite-like precursor for the hydrogenation of fructose was investigated. The effects of various reaction conditions on the production of sorbitol and mannitol were investigated in detail. The properly high reduction temperature could obviously enhance catalyst activity. XRD and XPS tests provided the essential properties of the precursor and prepared catalyst. A catalyst recycling experiment demonstrated that Ni4.63Cu1Al1.82Fe0.79 was a better magnetic catalyst and it could be reused more than three times. [Copyright &y& Elsevier]

Potassium-promoted hydrotalcite-like material was prepared with potassium nitrate as the K precursor. The highest ever reported CO2 adsorption capacity (1.13 mol kg-1) was obtained at 656 K with p [ABSTRACT FROM AUTHOR]

Abstract: Nickel based mixed oxide catalysts derived from Ni–Mg–Zn–Al hydrotalcite-like precursors are prepared and evaluated for H2-rich gas production via ethanol steam reforming. It has been found that the catalyst properties (e.g. BET surface area, Ni dispersion and reducibility) and catalytic performance depend on the Mg:Zn molar ratio. MgO and ZnO have a synergetic effect. At 700°C, the quaternary catalyst with a Mg:Zn ratio of 4 exhibits the highest H2 yield and best stability, viz. no apparent variation of the product distribution over 100h operation, whereas the ternary catalyst without Mg suffers severe coke accumulation after 7h on-stream. Two types of carbon (filamentous and amorphous) are found deposited on the catalyst surface. The carbon deposited is dominated by filamentous carbon, which is likely originated from the decomposition of methane, and does not cause immediate deactivation. [Copyright &y& Elsevier]

Abstract: The stearate anions intercalated Ni–Al hydrotalcite-like compounds were prepared by a coprecipitation method coupled with the microwave-hydrothermal treatment. Their structures were characterized using FT-IR, XRD, contact angle, SEM, TEM and thermal analysis. The XRD results indicate that the interlayer anions of the microwave radiation samples have better order and stronger electrostatic interactions with hydroxyl layers than those of the conventional aging 12h samples, the crystallinity of stearate anions intercalated Ni–Al hydrotalcite-like compounds can be rapidly enhanced in a short period of microwave treatment, and the stearate anions arrange in the form of a monolayer in the interlayer space for all samples. The morphology analysis results show that all samples consist of irregular and very thin platelets, while the crystals size of microwave treated samples was obviously smaller than that of the conventional aged samples. Based on the contact angle results, the surfaces of all samples show the hydrophobic property. This is due to the intercalation of stearate anions. The thermal analysis results point out that the sample obtained from microwave radiation 60min possesses the best thermal stability. The rapid synthesis method explored in this paper is a promising method for studying other anionic surfactant intercalated HTLc. [ABSTRACT FROM AUTHOR]

Abstract: Biodiesel produced by transesterification is a promising green fuel in the future. A new heterogeneous catalyst, Zn/Al complex oxide, was prepared for biodiesel production. The results showed that the catalyst derived from a hydrotalcite-like precursor with a zinc/aluminum atom ratio of 3.74:1 and calcined at 450°C gave the highest conversion of 84.25%. Analysis of XRD, XPS, FI-IF, TG-DTA, BET and alkalinity tests demonstrated that it is the unique structure of hydrotalcite-like compound precursor that gave the catalyst a high alkalinity greater than 11.1. The optimal reaction condition for Zn/Al complex oxide was under methanol sub-critical condition: 200°C, 2.5MPa, 1.4% (wt) catalyst dosage, and 24:1 methanol to oil ratio. Under these conditions, the conversion reached 84.25% after 90min, which was better than Mg/Al complex oxides. The excellent tolerance to water and free fatty acid was exhibited when the oil feed had fewer than 6% FFA or 10% water content with a conversion greater than 80%. [Copyright &y& Elsevier]

A novel strong-fluorescent Eu-containing hydrotalcite-like compound (Eu-HTlc) was synthesized using the coprecipitation method, in which aluminum(III) was partially substituted by Europium (III) in the hydrotalcite-like layers, and thenoyltrifluoroacetone, 1,10-phenanthroline were dispersed into the anions in the interlayer region. The sample was characterized by XRD, XPS, FT-IR, ICP, TG-DSC, TEM and fluorescence spectra, and its composition and structure were determined. The results indicated that the sample exhibited a characteristic red light (614 nm). The fluorescent lifetime and fluorescence quantum yield of Eu-HTlc were measured to be respectively 893 μs and 66.44%, higher than those of Eu(III)-thenoyltrifluoroacetone-1,10-phenanthroline complex [Eu(TTA)3phen]. The result of TG-DSC measurement showed the enhanced thermal stability of Eu-HTlc compared with that of MgAl-LDHs and Eu(TTA)3phen. With excellent photoluminescent property and thermal stability, low contents of rare earth ions and ligands, the Eu-HTlc may become one of the novel fluorescent materials with potential applications. [ABSTRACT FROM AUTHOR]

Hydrotalcite and similar compounds are found to be a potential adsorbent for removal of different metal ions. In present work we have synthesized a low-cost hydrotalcite-like compound, takovite, using the co-precipitation method. Further, part of the synthesized material was calcined at 773 K. Both normal and calcined takovite were characterized by XRD. Using this hydrotalcite-like compound the adsorption of Zn was studied in industrial effluents in a batch system by keeping different agitation times (15-1020 min), varying pH in the range 2-6 and varying the temperature in the range 283-313 K. In the controlled conditions, the percentage adsorption of Zn was found to be 76% and 93% for normal and calcined takovite respectively. The equilibrium isotherm data were analysed using Freundlich isotherm model. The values of log a and 1/b were found to be 0.778 and 0.083 for normal and 0.88 and 1.44 for calcined takovite, respectively, and the correlation coefficient (r²) was 0.9849 and 0.9945 for normal and calcined takovite, respectively. [ABSTRACT FROM AUTHOR]

A novel strong-fluorescent hydrotalcite-like compound (Al-HTLc) was synthesized by coprecipitation. In the sample, the content of aluminum(III) in the layers was decreased to a proper value. The Al3+ ions coordinated with 8-hydroxyquinolines (8-HQ) which were dispersed into the anions in the interlayer region. The sample was characterized by XRD, XPS, FT-IR, TG-DSC, UV-Vis, and fluorescence spectroscopy; its composition and structure were also determined. The results indicate that the sample can emit fluorescence (487 nm) with a strong fluorescence intensity (4.9×105 (a.u.)). The fluorescent lifetime and fluorescence quantum yield of Al-HTLc were measured to be 21.24 ns and 67%, respectively, higher than those of pure 8-hydroxyquinoline aluminum (Alq3). The result of TG-DSC measurement clearly shows the enhanced thermal stability of Al-HTLc compared with that of MgAl-LDH and pure Alq3. Al-HTLc may be used as a novel luminescent functional material. [ABSTRACT FROM AUTHOR]

In this study, we confirmed that the characteristics of anion intercalation into the interlayer of a hydrotalcite-like compound (HT) during synthesis are similar to those of the anion-exchange reaction of HTs as well as the reconstruction reaction of HTs from Mg-Al oxide. We demonstrated that (i) Cl-, which has a higher charge density than NO3-, more easily reacted with Mg and Al species to form HT structure, resulting in greater intercalation of Cl- into the HT interlayer; and (ii) for HTs with lower Mg : Al molar ratios, OH-, which has a higher charge density than Cl- and NO3-, was more likely to interact with Mg and Al species to form HT structure, blocking the intercalation of Cl- and NO3-. Furthermore, we showed that high concentrations of Cl- and NO3- in solution regulated their intercalation into the HT interlayer. The high activity of Cl- and NO3- in solution would facilitate the anions' reactions with Mg and Al species to form HTs, resulting in a high degree of anion intercalation into the interlayer of HTs. [ABSTRACT FROM AUTHOR]

Magnesium–aluminum oxide (Mg–Al oxide) prepared by the thermal decomposition of a hydrotalcite-like compound was found to have potential for treating NaBF4 wastewater. The Mg–Al oxide removed the and F− and H3BO3 from the NaBF4 solution. With increasing Mg–Al oxide quantity and time, the concentration decreased and the degree of , F−, and boron removal increased. The decrease in the concentration resulted from uptake by the Mg–Al oxide and not hydrolysis. The Mg–Al oxide took up F− from the solution preferentially. The Mg–Al oxide also converted the H3BO3 in the aqueous solution into , which it took up. [Copyright &y& Elsevier]

Magnesium—aluminum oxide (Mg—Al oxide), which was prepared by the thermal decomposition of a hydrotal-cite-like compound, was found to take up fluoride and borate ions in low concentrations in aqueous solution. The degree of fluoride and borate removal increased with the quantity of Mg—Al oxide and temperature. When Mg—Al oxide with a Mg/Al molar ratio of 4.0 was added to 1 mM NaF or H3BO3 solution at five times the stoichiometric amount, the degree of fluoride and borate removal at 60 °C for 1 h reached 92.8 and 95.7%, respectively. The fluoride and borate concentrations decreased from 20 and 10 mg L-1 to 1.4 and 0.5 mg L-1, respectively. Borate was thought to be removed from the solution via combination of the Mg—Al oxide and orthoborate ion, i.e., H2BO3- produced with increasing pH. The fluoride and borate removal reactions could be described as first-order for the fluoride and borate concentrations. The apparent activation energies for the fluoride and borate removal were 33.8 and 51.2 kJ mol-1, respectively, indicating that the reaction proceeded under chemical reaction control. The apparent activation energy for borate removal was higher than that for fluoride removal, indicating that the combination of H2BO3- with Mg—Al oxide was more difficult than that of the fluoride ion. This was attributable to the lower charge density of H2BO3- compared to the fluoride ion. [ABSTRACT FROM AUTHOR]

Abstract: We examined the dehydrochlorination of a chloride ion-intercalated hydrotalcite-like compound (Cl−-HT) on thermal treatment under water vapor, and the subsequent recovery of hydrochloric acid. The degree of dehydrochlorination increased with increasing temperature, partial pressure of water vapor, and time, whereas the hydrochloric acid concentration decreased with increasing partial pressure of water vapor and time. Greater than 90% dehydrochlorination and greater than 20 wt.% recovery of hydrochloric acid could be obtained by thermal treatment of Cl−-HT in the conditions as follows; temperature: 550 °C, time: 0.5 h, water vapor: 7%. [Copyright &y& Elsevier]

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/[Al3+]0 in the solution. Approximately 98% of the sulfate ions in the solution were removed within 10min 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 12mM calcium sulfate solution. [Copyright &y& Elsevier]

Abstract: We prepared a chloride ion-intercalated hydrotalcite-like compound (Cl−-HT) in a co-precipitation reaction, and investigated its thermal properties using thermogravimetry-differential thermal analysis (TG–DTA) and simultaneous thermogravimetry-mass spectrometry (TG-MS). In addition, we examined the effects of temperature and atmosphere on the dehydrochlorination of Cl−-HT during thermal treatment. The thermal decomposition of the Cl−-HT was divided into three stages: the evaporation of surface adsorbed water and interlayer water in the Cl−-HT, the dehydroxylation of the brucite-like octahedral layers in the Cl−-HT, and the elimination of HCl from the Cl−-HT. H2O was produced at four steps: the evaporation of surface adsorbed water and interlayer water in the first stage, two steps of H2O production caused by the dehydroxylation of the parts of Cl−-HT with properties similar to Mg(OH)2 and Al(OH)3, respectively, in the second stage, and H2O production due to the dehydroxylation of the part of Cl−-HT with properties similar to Al(OH)3 in the third stage. HCl was produced at two steps: the dehydrochlorination of the parts of Cl−-HT with properties similar to AlOCl and Mg(OH)Cl, respectively, in the third stage. Hydrochloric acid was obtained from the Cl−-HT on thermal treatment. The degree of dehydrochlorination of the Cl−-HT increased with temperature. The degree was greater under water vapor than under nitrogen at all temperatures, indicating that water vapor promoted the dehydrochlorination of Cl−-HT. However, the concentration of hydrochloric acid obtained under water vapor was lower than that under nitrogen. [Copyright &y& Elsevier]

Abstract: Our results demonstrate that magnesium–aluminum oxide (Mg–Al oxide) can be advantageous in treating hydrochloric acid waste at temperatures between 10 and 30°C, by acting as both a neutralizer and fixative for Cl−. The Mg–Al oxide was prepared by the thermal decomposition of a hydrotalcite-like compound. The extent of Cl− removal by Mg–Al oxide increased with increases of temperature, oxide quantity and Mg/Al molar ratio. The initial pH had little effect on Cl− removal; the pH increased rapidly from the start of the reaction and attained a nearly constant value. The reaction involved in Cl− removal from HCl by Mg–Al oxide proceeded under surface chemical reaction control, with apparent activation energy of 65.6kJmol−1. [Copyright &y& Elsevier]

Mn/Al catalysts for hydrogenation of methyl benzoate to benzaldehyde were prepared by different methods. The catalyst prepared from hydrotalcite-like precursor, the mesoporous MSU- γ supported Mn catalyst and the Mn-incorporated MSU- γ catalyst are more active than conventional Mn/ γ-Al2O3 catalyst. The reaction temperature for the same yield level can be reduced by 20–60 °C. High specific surface area, high dispersion of manganese oxide species and strong interaction of manganese oxide species with γ-Al2O3 are of benefit to the reaction. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the removal of chloride from various solutions (NaCl, HCl, MgCl2, AlCl3, CaCl2, and NH4Cl) at 60°C for 3h using magnesium–aluminum oxide, Mg0.80Al0.20O1.10, prepared by the thermal decomposition of a hydrotalcite-like compound, Mg0.80Al0.20(OH)2(CO3)0.10·0.78H2O. The degree of Cl− removal from solution increased with the amount of Mg0.80Al0.20O1.10 used. When Mg0.80Al0.20O1.10 was added to 0.5M Cl− solutions of HCl, MgCl2, AlCl3, and NH4Cl in a Mg0.80Al0.20O1.10/Cl− molar ratio of 8.75, the degree of Cl− removal exceeded 95%. The degree of Cl− removal from NaCl and CaCl2 solutions was slightly lower, approximately 80 and 90%, respectively. These results reveal that both the amount of Mg0.80Al0.20O1.10 added to chloride solution and the nature of the cations in the solution affect the efficiency of Cl− removal from solution. [Copyright &y& Elsevier]

We investigated the removal of Ca2+ and Cl− from CaCl2 solution at 20–60°C, using magnesium–aluminum oxide, Mg0.80Al0.20O1.10, prepared by the thermal decomposition of a hydrotalcite-like compound, Mg0.80Al0.20(OH)2(CO3)0.10·0.78H2O. The degree of Ca2+ and Cl− removal from the solution increased with increasing initial CaCl2 concentration, temperature, and quantity of Mg0.80Al0.20O1.10 added. When Mg0.80Al0.20O1.10 was added to 0.25 M CaCl2 solution in a Mg0.80Al0.20O1.10/CaCl2 molar ratio of 20, the degree of Ca2+ and Cl− removal from the solution at 60°C after 0.5 h was 93.0% and 98.2%, respectively. These results reveal that Mg0.80Al0.20O1.10 has the capacity to remove Ca2+ and Cl− simultaneously from aqueous solution. [Copyright &y& Elsevier]

Water pollution caused by tannery wastewater is an important issue in developing countries. Most studies have focused on inorganic chemicals represented by chromium as a tannery-related main pollutant. This is the first study in which pollution of water by tannery-related organic chemicals was assessed by a combination of qualitative and quantitative analyses. Our quantitative analysis showed that the maximum concentration of total phenolic compounds (phenols), consisting of phenol, bisphenol F, p-cresol and chlorocresol, in canal water in a tannery built-up area in Bangladesh was >67-fold higher than the Environmental, Health and Safety (EHS) guideline value. Mapping of our results indicated tanneries as the sources of phenols pollution. Our original depurative, a hydrotalcite-like compound consisting of magnesium and iron (MF-HT), could adsorb all kinds of phenols and exhibited the highest phenol adsorption ability (115.8 mg/g) among reported hydrotalcite-like compounds. The levels of phenols in canal water samples were reduced to levels below the guideline value by using MF-HT with assistance of a photocatalytic reaction. Moreover, the mean level of chromium (112.2 mg/L) in canal water samples was decreased by 99.7% by using the depurative. Thus, the depurative has the potential for solving the problem of tannery-related water pollution by phenols and chromium. [Display omitted] • No data from qualitative and quantitative analyses of tannery-related organic pollution. • Phenol level in canal water that is 100-fold higher than the US-EPA guideline value. • Higher phenol removal ability (116 mg/g) of our original adsorbent of MF-HT in theory. • An MF-HT adsorbent with highest ability to remove Cr, a main pollutant in tanneries. • An effective adsorbent to remove both Cr and phenols from tannery wastewater. [ABSTRACT FROM AUTHOR]

• ATMP promotes synthesis of iso -butanol and ethanol from syngas. • ATMP leads to lattice strain and defects. • ATMP changes layered structure of HTDO. Ethanol and iso -butanol have received considerable interest to be used in automobiles as additives or as potential substitutes for gasoline. The Cu–Zn–Al hydrotalcite-derived oxides (CuZnAl-HTDO) can be used to catalyze synthesis of higher alcohols from syngas, and the complexing agents such as amino trimethylene phosphonic acid (ATMP) were used as novel modifiers to improve the catalytic activities of CuZnAl-HTDO. However, there is some lack of knowledge about the intrinsic relation between structure of the ATMP-modified CuZnAl-HTDO and its catalytic activities. Therefore, characterization techniques including FT–IR, XRD, N 2 adsorption–desorption, H 2 –TPR, CO–TPD, CO 2 –TPD and SEM were carried out to investigate the composition, crystal structure, textural properties, reducibility, alkalinity, CO adsorption behavior and morphology of the ATMP-modified CuZnAl-HTDO and its precursors. The complexation reaction between Cu2+ ions and ATMP leads to expansion of crystal structure for the precursors (Cu–Zn–Al hydrotalcite-like compounds), and thus the amount of strained and defective lattices in CuZnAl-HTDO increases after calcination of the precursors. The lattice strain and defects improve hydrogen reduction of CuO in CuZnAl-HTDO and enhance CO adsorption and dissociation on Cu active sites. In addition, a network structure formed by Cu(II)-ATMP chelate delays desorption of alcohols from Cu active sites and thus promotes CO insertion reaction. These structural changes caused by ATMP promote catalytic synthesis of iso -butanol and ethanol from syngas. [ABSTRACT FROM AUTHOR]