Layered Hydroxide Salts Research Articles

Light-assisted cyclohexane oxidation catalysis by a manganese(III) porphyrin immobilized onto zinc hydroxide salt and zinc oxide obtained by zinc hydroxide salt hydrothermal decomposition

Two manganese(III) porphyrin complexes prepared with the tetra anionic free base porphyrin (Na4[H2(TDFSPP)]) and two different manganese(II) salts (manganese(II) acetate - MnP(OAc) complex and manganese(II) chloride - MnP(Cl) complex) were immobilized onto zinc hydroxide nitrate (ZHN), a layered hydroxide salt, and also into zinc oxide (ZnO), obtained via hydrothermal decomposition of the ZHN. The resulting solids, MnP(OAc)-ZHN, MnP(Cl)-ZHN, MnP(OAc)-ZnO and MnP(Cl)-ZnO, were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), electronic paramagnetic resonance (EPR) and ultraviolet-visible spectroscopy (UV–vis) (solid samples). Manganese and consequently the immobilized manganese porphyrin complexes were quantified by ICP-OES. The materials were applied as catalysts for the oxidation of cyclohexane, using iodosylbenzene as the oxygen donor, under conventional conditions (absence of light) as well as using light assisted conditions. Good catalytic results were obtained and, in absence of light, an unusual selectivity for the ketone was observed when using MnP(OAc)-ZHN as catalyst different from what can be observed when the catalyst is the solid MnP(Cl)-ZHN, that present selectivity to alcohol, suggesting an influence of both axial ligand and support in the catalytic activity.

Immobilization of Salicylic Acid on Ni-Zn Layered Hydroxide Salts

Ni-Zn Layered hydroxide salt (Ni-Zn LHS) has been synthesized from equimolar Ni(NO3)2 and Zn(NO3)2 by co-precipitation method using NaOH. The formation of layered assembly is confirmed in X-ray diffractogram, i.e. by the appearance of peaks at 2θ: 9.60°, 19.40°, 33.48°, and 59.76° which corresponds to diffraction plane (001), (003), (020), and (040), respectively. The synthesized Ni-Zn LHSs possessed the point of zero charge (pHpzc) at pH 8 and nitrate as the interlamellar ion. The incorporation of salicylic acid into LHS can extend the property of LHS as a reductive adsorbent in the application of metal recovery. The immobilization of salicylic acid on the Ni-Zn-LHS was successfully done and indicated the strong pH-dependent property. The immobilization of salicylic acid on Ni-Zn LHSs was optimum at pH 7 and followed better the Langmuir than Freundlich isotherm models with immobilization capacity 64.93 mg/g. After the immobilization of salicylic acid, the basal spacing of Ni-Zn LHSs did not enlarge indicating that the immobilized salicylic acid was on the outer layer without entering the interlayer and this immobilized salicylic acid was stable at medium pH range 3 to 9.

Chemical and biological protection of food grade nisin through their partial intercalation in laminar hydroxide salts

The use of antimicrobial agents within a matrix, specifically layered compounds, is of growing interest for reducing contamination due to food borne pathogens and deteriorative microorganisms, one of the main health problems worldwide. In this study, zinc layered hydroxide nanoparticles were synthesized as a matrix for nisin immobilization. Layered materials were characterized by X-ray diffraction, Fourier-Transform Infrared and Ultra Violet-Visible spectra, Scanning Electron Microscopy, and by Thermogravimetric Analysis. Thermal, chemical, enzymatic, and biological stabilities were assessed against Lactobacillus brevis as control strain. Free and immobilized nisin in solution were previously subjected to 25 and 121°C, pH (7, 9) and inactivation with protease before antimicrobial tests that lasted 21days. Immobilized nisin was found to maintain the activity levels after the protease action while the pure nisin solution lost its activity gradually. Furthermore, immobilized nisin treated at 121°C and pH 7 showed higher activity than pure nisin after 21days. These results may support that immobilizing nisin in zinc layered hydroxide salts promoted extended nisin inhibitory activity in solution after thermal, chemical or enzymatic treatments. This research provides an alternative to nisin application that could be used in processes where such operating conditions take place, as in dairy products.

Self‐Supporting Ni‐M (M = Mo, Ge, Sn) Alloy Nanosheets via Topotactic Transformation of Oxometallate Intercalated Layered Nickel Hydroxide Salts: Synthesis and Application for Electrocatalytic Hydrogen Evolution Reaction

AbstractMetal alloys are valuable for achieving energy‐ and cost‐efficient electrocatalysis. To maximize active sites exposure and electron transport, a general method to prepare binder‐free Ni‐M (M = Mo, Ge, Sn) bimetallic alloy nanosheets electrocatalyst for the hydrogen evolution reaction (HER) is successfully developed for the first time, via topotactic transformation of layered nickel hydroxide salts (Ni‐LHS). The obtained bimetallic alloys show much improved HER performance to that of Ni. In particular, Ni4Mo alloy nanosheets exhibit HER activity with an overpotential of only 69.6 mV at 100 mA cm−2 and a low Tafel slope of 37 mV decade−1 in alkaline medium, due to large electrochemical active surface area and low charge transfer resistance. Moreover, Ni4Mo alloy nanosheets also show high HER activity in both acidic and neutral electrolytes with long‐term stability, demonstrating superior activity comparable to or better than state‐of‐the‐art commercial Pt/C catalyst. This topotactic transformation method using LHS precursors provides a way to design and fabricate cost‐effective and energy‐efficient ultrathin 2D bimetallic alloy nanosheets for electrocatalysis, greatly broadening the scope of the currently available self‐supporting metal alloy electrocatalysts.

Solvent-free mechanochemically synthesized Zn layered hydroxide salts for the adsorption of naphtholate AS dye

Solvent-free synthesis through a mechanochemical method is one of the most promising benign methodologies in the recent decades. In this study, a very simple solvent-free mechanochemical method for the synthesis of Zn layered hydroxide salts (Zn LHSs) by manual grinding in a mortar was reported in detail. With a single step grinding for fifteen minutes at ambient temperature, Zn LHSs were successfully synthesized from Zn(NO3)2·4H2O and NaOH with OH/Zn molar ratio 0.6. Based on the characterization results using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermal analysis (TGA/DTA) and scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), the as-synthesized Zn LHSs (mechano-Zn LHSs) showed similar characteristics as Zn LHSs prepared by conventional coprecipitation method (copre-Zn LHSs) but with slightly worse crystallinity and lower dehydroxylation temperature. Mechano-Zn LHSs were highly pure with only insignificant noticeable contamination from other phases. Adsorption of naphtholate AS dye on mechano-Zn LHSs and copre-Zn LHSs was optimum at pH 9.14 and matched well in Langmuir isotherm model with capacity and energy of adsorptions were 0.67 × 10−3 mol/g and 23.79 kJ/mol for mechano-Zn LHSs which were slightly higher than those of copre-Zn LHSs, i.e. 0.62 × 10−3 mol/g and 23.18 kJ/mol, respectively.

Adsorption mechanism of ReO4− on Ni–Zn layered hydroxide salt and its application to removal of ReO4− as a surrogate of TcO4−

The long-lived anionic radionuclide of 99Tc (pertechnetate ion TcO4−) is highly mobile under oxic conditions, and therefore long-term removal and immobilization of TcO4− from radioactively contaminated water have been major challenges. Mg–Al layered double-hydroxides (LDH) have been often investigated to remove anions from waste water. In this study, we propose Ni–Zn layered hydroxide salt (LHS) as an alternative adsorbent for anionic radionuclides. We prepared and characterized Ni–Zn LHS with the nominal composition of Ni0.77Zn0.46(OH)2(OCOCH3)0.46·0.96H2O, using X-ray diffraction (XRD) pattern, scanning electron microbe (SEM) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The formation of a layered structure was confirmed by XRD, and plate-like crystals of the Ni–Zn LHS were observed in SEM images. Analysis of Ni K-edge and Zn K-edge EXAFS spectra supported the structure proposed by previous works, where Ni ions form brucite-type layers with vacancies, and Zn ions were located at tetrahedral sites above and below the vacancy sites of the Ni hydroxide layers. The prepared Ni–Zn LHS was used for adsorption experiments of ReO4−, as a surrogate of TcO4−, in aqueous solutions with various initial Re and sodium salt concentrations. The maximum adsorption amount of Re was estimated at 127.7 mg/g (6.86 × 10−4 eq/g) by fitting adsorption isotherm of ReO4− to Langmuir plot. The adsorption of ReO4− at neutral pH was a reversible process by anion exchange, and decreased with increasing Cl−, NO3− and SO42− in solution. EXAFS analysis indicated that ReO4− was adsorbed as an outer-sphere complex on Ni–Zn LHS. The Ni–Zn LHS is a more robust adsorbent for ReO4− than the Mg–Al LDH in terms of solution pH and tolerance to competing anions, and may be an effective alternative to the traditional and more limited method of removing aqueous TcO4− by reductive precipitation.

Facile and Scalable Coating of Metal-Organic Frameworks on Fibrous Substrates by a Coordination Replication Method at Room Temperature.

Coating of metal-organic frameworks (MOFs) on flexible substrates is a crucial technology for applications such as purification/separation, sensing, and catalysis. In this work, a facile coordination replication strategy was developed to coat various MOFs onto flexible fibrous materials where a dense layer of an insoluble precursor template, such as a layered hydroxide salt, was first deposited onto a fiber substrate via a mild interfacial reaction and then rapidly transformed into a MOF coating in a ligand solution at room temperature. Spatiotemporal harmonization of solid precursor dissolution and MOF crystallization enabled precise replication of the precursor layer morphology to form a continuous MOF coating composed of intergrown crystals. The resulting flexible, highly robust, and processable fibrous MOF/textile composites demonstrated tremendous potential for industrially relevant applications such as continuous removal of the organosulfur compound dibenzothiophene from simulated gasoline and ammonia capture. This rapid, versatile, eco-friendly, and scalable MOF coating process at room temperature gives rise to new possibilities for preparing MOF-coated functional materials.

Interface Coupling of Ni–Co Layered Double Hydroxide Nanowires and Cobalt-Based Zeolite Organic Frameworks for Efficient Overall Water Splitting

Hydrogen is a source of sustainable and clean energy poised to replace fossil fuels. Bifunctional electrocatalysts are actively pursued to simultaneously drive the two key reactions, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), for hydrogen production by electrolysis water. One of the most promising candidates based on bimetallic layered double hydroxide salts (LHSs) and cobalt-based organic framework (ZIF-67) suffer from poor interface coupling. Herein, we present a new approach based on fusing NiCo LHSs nanowire arrays with ZIF-67 to fabricate three-dimensional flower-like structures on a Ni-Fe foam support. To improve interfacial coupling and catalytic performance, simple oxidation, carbonization, sulfurization, and selenization are performed to study the effects of different post-treatments and discover the optimum bifunctional electrocatalysts. The optimized S-doped catalyst reveals the highest electrocatalytic characteristic quantified by the low overpotentials of 170 and 100 mV for OER and HER at 10 mA cm -2 in 1 M KOH, respectively. This outstanding electrocatalytic property is ascribed to strong interfacial coupling between the NiCo-LHSs and ZIF-67 derivatives, as well as the rational electronic structures, dense catalytic active sites, and large specific surface area. This work opens new prospects for fabricating efficient and low-cost electrocatalysts for renewable hydrogen energy production.

Novel 2D materials from exfoliation of layered hydroxide salts: A theoretical study

Using density functional theory (DFT), we theoretically investigated the electronic and structural properties of monolayer and few-layer 2D materials obtained from the exfoliation of zinc-based layered hydroxide salts (LHSs). Four different compounds are investigated: Zn3(OH)4(NO3)2, Zn5(OH)8Cl2.H2O, Zn5(OH)8(NO3)2.2H2O and NaZn4(OH)6SO4Cl.6H2O. We found exfoliation energies in the range of 30 meV/Å̊2 for all cases. Monolayer structures remained semiconducting like the respective bulk compounds, although in some cases, the band gap changes its character from indirect to direct. We also explored the effects of dehydration, which can also change the gap character from indirect to direct in some monolayer structures. Finally, we found that the anion or cation removal from the interlayer region can turn the monolayer systems into metallic, by means of electron and hole doping, respectively.

Effect of layered hydroxide salts, produced by two different methods, on the mechanical and thermal properties of poly(methyl methacrylate)

In this study, eight different layered hydroxide salts (LHSs) based on copper and zinc, intercalated with stearate, myristate, azelate, and poly(ethylene glycol) (PEG) monolaurate, were prepared. All the LHSs were produced according two different methods: co‐precipitation (direct method) and synthesis of zinc hydroxide nitrate (ZHN) and copper hydroxide nitrate (CHN) followed by exchange reaction (indirect method). The synthetic layered compounds were characterized by X‐ray diffraction (XRD) and thermogravimetric analysis (TGA). TGA results revealed that higher thermal stability was observed for the LHSs synthesized by direct method. The effects of all these LHSs on the thermal and mechanical properties of poly(methyl methacrylate) (PMMA) nanocomposites were investigated. The LHSs percentage (wt%) in the PMMA was fixed at 1%. PMMA and PMMA nanocomposites were produced by in situ bulk polymerization. Compared to PMMA, all the nanocomposites exhibited higher thermal stability. The nanocomposite containing ZHN(stearate) by indirect method revealed both T50 (temperature at which a 50% loss of mass occurs) and T90 (temperature at which a 90% loss of mass occurs) 71°C higher than PMMA. Compared to PMMA, the nanocomposite with ZHN(PEG monolaurate) exhibited an increase of 14% in the elastic modulus, at 30°C. POLYM. ENG. SCI., 59:1065–1074, 2019. © 2019 Society of Plastics Engineers

Comparison between catalytic activities of two zinc layered hydroxide salts in brilliant green organic dye bleaching

This paper reports the use of two layered hydroxide salts (LHS) (zinc hydroxide nitrate – ZHN – Zn5(OH)8(NO3)2·2H2O, and zinc hydroxide chloride – ZHC – Zn5(OH)8Cl2·H2O) as catalysts for brilliant green (BG) organic dye bleaching, using hydrogen peroxide as oxidant. The LHS were prepared by precipitation reaction between an aqueous solution of zinc salts and an aqueous ammonia solution. The solids were characterized by powder X-ray diffraction (XRD), electron paramagnetic resonance (EPR), ultraviolet-visible electronic spectroscopy (UV–Vis) and Fourier-transform infrared spectroscopy (FTIR). The catalytic activity of the solids was investigated at temperatures of 25, 35 and 45 °C, using different molar ratios of oxidant:dye:Zn2+ ions (present in the catalyst), in the absence and presence of ambient light. The kinetic aspect of the reaction was investigated considering that the reaction showed pseudo-first order behavior in relation to BG dye concentration. We propose a mechanism where superoxide radicals account for most of the bleaching taking place. The catalytic results obtained, along with the low cost and low toxicity of zinc compounds, establish ZHN and ZHC as novel catalysts for dye wastewater treatment, an area with constant demand for new methods and materials given its relationship with environmental equilibrium and human health.

Intercalation, characterization and release behavior of imidacloprid into layered hydroxide salts by coupling of (3-glycidyloxypropyl) trimethoxysilane

The poorly water-soluble pesticide imidacloprid (IMP) was intercalated into NiZn-layered hydroxide salts (NZL) by the aid of (3-glycidyloxypropyl) trimethoxysilane (GPS). The resulting NZL-GPS-IMP composites were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), carbon solid state nuclear magnetic resonance (13C NMR), thermo gravimetric analysis and differential thermal analysis (TGA/DTA). The interlayer distance of NZL-GPS-IMP was 1.62 nm, which is different from those of NZL-SDS, NZL-GPS and NZL-IMP. XRD and 13C-NMR results showed that SDS anions leave the galleries, and adsorb on the surface. The incorporation mechanism of NZL-GPS-IMP was reasonably put forward. TGA/DTA data showed that the combustion temperatures of IMP and GPS in the gallery were enhanced by 40 and 170 °C, respectively. These indicated that GPS-IMP was intercalated into the gallery. The IMP release behaviors of NZL-GPS-IMP in the water and buffer solutions (pH 5.0 and 6.8) were studied and compared. The IMP release rate and equilibrium release amount were dependent on release environments. Moreover, the release behavior of NZL-GPS-IMP was well fitted with pseudo second-order and parabolic diffusion models. This work would be helpful to develop a potential controlled-release formulation.

Comparative Study of Ni-Zn LHS and Mg-Al LDH Adsorbents of Navy Blue and Yellow F3G Dye

Adsorption of disperse dyes from wastewater onto Ni-Zn LHS (layered hydroxide salts) and Mg-Al LDH (layered double hydroxides) has been compared in this study. Effects of initial pH solution, contact time and initial dye concentration were investigated. The ability of the adsorbent to be reused was also studied. The results showed that acidic condition was favorable for the adsorption of each dyes onto both adsorbent. The adsorption kinetics was studied using pseudo-first-order, pseudo-second-order and Santosa’s kinetics models. The experimental data fits well with the pseudo-second order kinetic model. The equilibrium adsorption data were analyzed using Langmuir and Freundlich isotherm models. The results showed that adsorption of navy blue onto both adsorbent followed Freundlich isotherm adsorption, while yellow F3G followed Langmuir isotherm adsorption. In the application for the adsorption the wastewater containing dyes, Ni-Zn LHS has a better adsorption capacity of 52.33 mg/g than that of Mg-Al LDH that 30.54 mg/g. Calcination of the adsorbent which has already been used increased the adsorption capacity of Mg-Al LDH to 84.75 mg/g, but decreased the adsorption capacity of the Ni-Zn LHS to 42.65 mg/g.

DFT study of the intercalation of layered double hydroxides and layered hydroxide salts with dodecylsulfate and dodecylbenzene sulfonate: Exfoliation and hydration properties

DFT calculations were performed for the simulation of the intercalations of Zn2Al-layered double hydroxide and Zn-layered hydroxide salts with dodecylsulfate and dodecylbenzene sulfonate. A structural and energetic analyses of the exfoliation processes were computed and compared with Perdew-Burke-Ernzerhof exchange-correlation (PBE) and Van der Waals-aware density (vdW-DF) functionals and with the semi-empirical approach DFT-D2. It could be concluded that the layers cell parameters were not affected by the applied approach. On the other hand, the basal spacing and the exfoliation energies presented variations with respect to the simulation. The influence of water molecules hydrating the polar heads of the anions intercalated in the interlayer region was also investigated. Furthermore, the interactions between the anions and the positive layers and the influence of hydration waters could be resolved by means of charge density difference plots and Bader charges. Projected density of states (PDOS) showed the possible acid and basic sites of these compounds for both dehydrated and hydrated structures.

Enhancement of Mechanical and Thermal Properties of Poly(L-lactide) Nanocomposites Filled with Synthetic Layered Compounds

The effects of a layered double hydroxide (LDH) (Zn/Al palmitate) and two layered hydroxide salts (LHS), intercalated with the anion salicylate or palmitate, on the properties of poly(L-lactide) (PLLA) nanocomposites were investigated. PLLA and the nanocomposites were synthesized by ring opening polymerization of the cyclic dimer of lactic acid (lactide), using tin(II) 2-ethylhexanoate (stannous octanoate) as catalyst. PLLA nanocomposites containing two different fillers concentrations (1 wt% and 2 wt%) were produced. Compared to PLLA, almost all the nanocomposites exhibited an enhancement on thermal resistance. The sample containing 1 wt% of Zn/Al palmitate exhibited a decomposition temperature 51°C higher than neat polymer. Results of flexural properties demonstrated that the nanocomposites containing Zn/Al palmitate displayed the highest values of maximum flexural stress and elongation at break. The sample with 2 wt% of this filler revealed values of maximum flexural stress and strain at break, 15% and 157%, respectively, higher than PLLA. Contrary to PLLA, which only exhibited break point, this nanocomposite showed a less fragile behavior, as a yield point was observed. In this case, it was possible to promote a higher flexibility without reducing the flexural stress, revealing an advantage of the Zn/Al palmitate under the plasticizers that have been used so far for PLLA.

Layered hydroxide anion exchanger and their applications related to pesticides: a brief review

Layered double hydroxides and layered hydroxide salts have generated enormous excitement in the inorganic field due to their potential to act as versatile host materials in fabricating novel host–guest layered materials. The ability of the layered hydroxide anion exchanger to be incorporated with a wide range of guest ions enable them to be exploited in various applications related to pesticides. This review sums up the different methods of preparing layered hydroxide anion exchanger, summarises the types of anion intercalated into these layered hydroxide anion exchanger based on their respective systems, and elucidates their potential applications in pesticide-related fields.

Recent Advances in Solid Catalysts Obtained by Metalloporphyrins Immobilization on Layered Anionic Exchangers: A Short Review and Some New Catalytic Results.

Layered materials are a very interesting class of compounds obtained by stacking of two-dimensional layers along the basal axis. A remarkable property of these materials is their capacity to interact with a variety of chemical species, irrespective of their charge (neutral, cationic or anionic). These species can be grafted onto the surface of the layered materials or intercalated between the layers, to expand or contract the interlayer distance. Metalloporphyrins, which are typically soluble oxidation catalysts, are examples of molecules that can interact with layered materials. This work presents a short review of the studies involving metalloporphyrin immobilization on two different anionic exchangers, Layered Double Hydroxides (LDHs) and Layered Hydroxide Salts (LHSs), published over the past year. After immobilization of anionic porphyrins, the resulting solids behave as reusable catalysts for heterogeneous oxidation processes. Although a large number of publications involving metalloporphyrin immobilization on LDHs exist, only a few papers have dealt with LHSs as supports, so metalloporphyrins immobilized on LHSs represent a new and promising research field. This work also describes new results on an anionic manganese porphyrin (MnP) immobilized on Mg/Al-LDH solids with different nominal Mg/Al molar ratios (2:1, 3:1 and 4:1) and intercalated with different anions (CO32− or NO3−). The influence of the support composition on the MnP immobilization rates and the catalytic performance of the resulting solid in cyclooctene oxidation reactions will be reported.

Intercalation of indigo carmine anions into zinc hydroxide salt: A novel alternative blue pigment

Zinc layered hydroxide salt was intercalated with indigo carmine (IC) anions, transforming a soluble dye into an insoluble pigment. The obtained material was characterized by X ray powder diffraction, where a basal distance of 19.07 Å was obtained. DFT simulation showed that the groups of the indigo carmine are held by electrostatic and hydrogen bonds to water molecules positioned in the tetrahedral zinc apex. Fourier transform infrared and UV–Vis spectra confirmed that the intermolecular bonds are broken, and intramolecular bonds prevail in the intercalated compound. Thermal analysis curves (thermogravimetry – TGA and differential scanning calorimetry – DSC) showed that the intercalated IC is stable up to 350 °C and the mass loss is consistent with the expected compound formula (Zn5(OH)8(IC)·H2O). The obtained material presents layered crystals with micrometer sizes, as shown by scanning electron microscopy, and consists of a novel blue pigment mimicking the Maya blue pigment, having potential industrial applications.

層状金属水酸化物を利用したヘテロ凝集構造体の作製とその充填層に関する研究

層状金属水酸化物を利用したヘテロ凝集構造体の作製とその充填層に関する研究

Rare earth and zinc layered hydroxide salts intercalated with the 2-aminobenzoate anion as organic luminescent sensitizer

Rare earth (RE=Eu, Y and Tb) and zinc layered hydroxide salts intercalated with nitrate anions were synthesized, followed by exchange with 2-aminobenzoate. The obtained compounds were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) and ultraviolet visible (UV–vis) spectroscopies, fluorescence measurements and thermal analysis (TGA/DTA). The results from FTIR spectroscopy suggest a direct coordination of 2-aminobenzoate to the metal cations of the inorganic layered structure. The organic derivative products from the intercalation reactions absorb a broader range of UV-light in relation to that shown by the parent material; the photoluminescence measurements present a strong violet, blue and green luminescence under UV-light excitation for layered compounds with, Zn, Y and Tb, respectively. Rare earth hydroxide salts (RE-LHS) are potential alternative matrices for the immobilization of organic species to produce luminescent materials.