Cu-Al Layered Double Hydroxide Research Articles

In situ XPS study of methanol oxidation over a copper catalyst derived from layered double hydroxides

Copper nanoparticles supported on alumina have been synthesized from CuAl-layered double hydroxide and have been studied in methanol oxidation at different molar ratios of the components of the reaction feed by in situ XPS and mass-spectrometry.

Composition Effect on the Formation of Oxide Phases by Thermal Decomposition of CuNiM(III) Layered Double Hydroxides with M(III) = Al, Fe.

The thermal decomposition processes of coprecipitated Cu-Ni-Al and Cu-Ni-Fe hydroxides and the formation of the mixed oxide phases were followed by thermogravimetry and derivative thermogravimetry analysis (TG - DTG) and in situ X-ray diffraction (XRD) in a temperature range from 25 to 800 °C. The as-prepared samples exhibited layered double hydroxide (LDH) with a rhombohedral structure for the Ni-richer Al- and Fe-bearing LDHs and a monoclinic structure for the CuAl LDH. Direct precipitation of CuO was also observed for the Cu-richest Fe-bearing samples. After the collapse of the LDHs, dehydration, dehydroxylation, and decarbonation occurred with an overlapping of these events to an extent, depending on the structure and composition, being more pronounced for the Fe-bearing rhombohedral LDHs and the monoclinic LDH. The Fe-bearing amorphous phases showed higher reactivity than the Al-bearing ones toward the crystallization of the mixed oxide phases. This reactivity was improved as the amount of embedded divalent cations increased. Moreover, the influence of copper was effective at a lower content than that of nickel.

Engineering g-C3N4 with CuAl-layered double hydroxide in 2D/2D heterostructures for visible-light water splitting

CuAl layered double hydroxide (LDH) and polymeric carbon nitride (g-C3N4, GCNN) were assembled to construct a set of novel 2D/2D CuAl-LDH/GCNN heterostructures. These materials were tested towards H2 and O2 generation from water splitting using visible-light irradiation. Compared to pristine materials, the heterostructures displayed strongly enhanced visible-light H2 evolution, dependent on the LDH content, which acts as a cocatalyst, replacing the benchmark Pt. The optimal LDH loading was achieved for 0.2CuAl-LDH/GCNN that exhibited an increased number of active sites and showed a trade-off between charge separation efficiency and light shading, resulting in a 32-fold increase in the amount of evolved H2 compared with GCNN. In addition, the 0.2CuAl-LDH/GCNN heterostructure generated 1.5 times more O2 than GCNN. The higher photocatalytic performance was due to efficient charge carriers’ separation at the heterojunction interface via an S-scheme (corroborated by work function, steady-state and time-resolved photoluminescence studies), enhanced utilisation of longer-wavelength photons (>460 nm) and higher surface area available for the catalytic reactions.

Activated biochar loaded CuAl-layered double hydroxide composite for the removal of aniline aerofloat in wastewater: Synthesis, characterization, and adsorption mechanism

It is challenging to completely biodegrade and oxidise aniline aerofloat wastewater. Rapid and efficient treatment of aniline aerofloat wastewater remains a challenge. Herein, inspired by the structural characteristics of aniline aerofloat and the fact that it can collect chalcopyrite well, a CuAl-layered double hydroxide composite-activated biochar adsorbent was studied. It was subsequently applied to aniline aerofloat wastewater treatment. In this study, a CuAl-layered double hydroxide/K2CO3 activated biochar composite (CKBC) was synthesised by hydrothermal method with K2CO3 activated biochar (KBC) as a carrier. KBC was prepared from rice straw biochar activated by K2CO3. The materials were characterised using a scanning electron microscope (SEM), X-ray diffraction (XRD), nitrogen adsorption analysis, and Fourier transform infrared spectroscopy (FTIR) analysis. The effects of pH, initial aniline aerofloat concentration, and adsorption time were investigated. The results demonstrated that under the conditions of pH 6, 80 mg/L concentration, and adsorption for 2 h, 96.6 % aniline aerofloat could be removed. The KBC and CKBC adsorption kinetics demonstrated a higher fitting degree with the Elovich equation, KBC adsorption isotherm data followed the Freundlich model, and CKBC could be better described by the Temkin model. X-ray photoelectron spectroscopy (XPS), FTIR, and SEM were used to explore the adsorption mechanism. The results demonstrate that the interaction between CKBC and aniline aerofloat predominantly includes pore filling, hydrogen bonding, π–π interactions, complexation, and electrostatic attraction. Based on the above merits, designing comprehensive composites offers new insights into adsorbents and reveals their applications.

Photo‐Driven Hydrogen Production from Methanol and Water using Plasmonic Cu Nanoparticles Derived from Layered Double Hydroxides

AbstractMethanol steam reforming (MSR) is viewed as an important technology in the growth of a future hydrogen economy, with methanol serving as an easily transportable and storable liquid hydrogen carrier. However, the thermocatalytic MSR reaction is energy intensive as it requires high temperatures. Herein, a novel L‐Cu catalyst is successfully fabricated for photo‐driven MSR through reduction of CuAl layered double hydroxide (CuAl‐LDH) nanosheets. L‐Cu offers outstanding activity for the photothermal conversion of methanol and water to hydrogen (160.5 µmol gcat−1 s−1) under ultraviolet‐visible irradiation, with this rate being much higher than that achieved for L‐Cu at the same temperature in the dark. Characterization studies using X‐ray diffraction, X‐ray photoelectron spectroscopy, X‐ray absorption spectroscopy, and high‐resolution transmission electron microscopy determine that L‐Cu catalyst comprise Cu nanoparticles on an amorphous alumina support. Computational calculations reveale that Cu localized surface plasmon resonance effects promote the activation of H2O, thereby underpinning the remarkable hydrogen production rates achieved during photo‐driven MSR. This study introduces a novel photothermal strategy for hydrogen generation from methanol, demonstrating the enormous potential of photothermal catalysis in the chemical and energy sectors.

In-situ activation of CuAl-LDH nanosheets to catalyze bioorthogonal chemistry in vivo in tumor microenvironment for precise chemotherapy and chemodynamic therapy

Precise activation of therapeutic molecules in tumor tissues is the key step to ensure targeted antitumor performance and reduce adverse effects towards normal tissues and organs. Although the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), i.e., bioorthogonal chemistry, has been used for the rapid synthesis of anticancer drugs in cells, it remains a great challenge to realize precise in vivo drug synthesis in tumor sites for precise cancer treatment. In this work, we first report the in-situ activation of CuAl-layered double hydroxide (CuAl-LDH) nanosheets to realize Cu(I)-catalyzed bioorthogonal chemistry in vivo in tumor microenvironment (TME) for precise chemotherapy and chemodynamic therapy (CDT). The Cu(II) ions in the biocompatible CuAl-LDH nanosheets can be in-situ reduced to Cu(I) ions partially by the overexpressed glutathione in TME. The generated Cu(I) can serve as a catalyst to catalyze the CuAAC reaction between alkyne and azide in TME, thus realizing in vivo drug synthesis for precise chemotherapy. Meanwhile, the generated Cu(I) can catalyze the Fenton-like reaction to generate toxic hydroxyl radicals (⋅OH) from H2O2 in TME for CDT. Therefore, CuAl-LDHs can be used for the targeted synergistic chemotherapy and CDT to achieve highly precise and efficient elimination of cancer cells in vitro and inhibition of tumors in vivo.

Synthesis of linear and cyclic organic sulfonic acid-modified Cu-Al layered double hydroxides and their adsorption properties

Over the past few years, many substances have been investigated for their potential application as adsorbent materials. The combination of a layered double hydroxide (LDH) and CH/π interactions enables selective adsorption through the differences in the electron density of the aromatic ring. Thus, in this study, two organic anions, namely the linear 1-octane sulfonate (OS-) and cyclic sulfonated-β-cyclodextrin (SCD13-), were intercalated into the interlayers of a Cu-Al LDH by coprecipitation (Cu/Al ratio, 3.0; chemical ratio, 2.0). The SCD13- anion was selected because β-cyclodextrin comprises hydrophobic cavities that allow the formation of inclusion compounds. X-ray diffraction (XRD), total organic carbon (TOC) analysis, and inductively coupled plasma-atomic emission spectrometry (ICP-AES) revealed that the as-synthesized OS-Cu-Al LDH and SCD-Cu-Al LDH were both oriented perpendicular to the LDH layer. Subsequent absorption experiments with m-aminophenol (AP) and m-nitrophenol (NP), which have similar structures but different aromatic ring electron densities, confirmed a Freundlich-type adsorption mechanism and revealed that adsorption occurred on a non-uniform surface for both LDHs. The results also revealed excellent NP and AP adsorptions for the linear OS•Cu-Al LDH and cyclic SCD•Cu-Al LDH, respectively. This was attributed to the strong hydrophobic interactions in the former and strong CH/π interactions in the latter. This study shows the potential of using linear and cyclic organic sulfonic acid-modified LDHs for the selective recovery of the desired aromatic organic compounds.

Creation of Highly Reducible CuO Species by High-Temperature Calcination of a Cu-Al Layered Double Hydroxide: Selective Hydrogenation of Furfural into Furfuryl Alcohol with Formic Acid

Abstract Highly reducible CuO species were created by the calcination of a Cu-Al layered double hydroxide (CuAl LDH) at 1073 K under air. After this heat treatment, the original layered double hydroxide structure was completely transformed into CuO and CuAl2O4 phases. The synthesized calcined CuAl LDH (calc-CuAl LDH) promoted the catalytic hydrogenation of furfural (FALD) into furfuryl alcohol (FOL) with formic acid (FA) as a hydrogen donor. In the initial stage of the above catalytic reaction, the CuO species in the calc-CuAl LDH matrix transformed into active Cu0 species via the formation of a Cu(HCOO)2-1,4-dioxane complex in the liquid phase. The spent catalyst was also reusable without loss of its high catalytic performance.

Unique Adsorption Properties of Malachite Green on Interlayer Space of Cu-Al and Cu-Al-SiW12O40 Layered Double Hydroxides

Cu-Al layered double hydroxide (LDH) was intercalated with Keggin ion of polyoxometalate K4[a-SiW12O40] to form Cu-Al-SiW12O40 LDH. The obtained materials were analyzed by X-ray Diffraction (XRD), Fourier Transform Infra Red (FTIR) spectroscopy, and Brunaur-Emmett-Teller (BET) surface area analysis. Furthermore, the materials were used as adsorbents of malachite green from aqueous solution. Some variables for adsorption, such as: effect of adsorption times, malachite green concentration, and also adsorption temperature, were explored. The results showed that diffraction at 11.72° on Cu-Al LDH has interlayer distance of 7.56 Å. The intercalation of that LDH with [a-SiW12O40]4− ion resulted increasing interlayer distance to 12.10 Å. The surface area of material was also increased after intercalation from 46.2 m2/g to 89.02 m2/g. The adsorption of malachite green on Cu-Al and Cu-Al-SiW12O40 LDHs followed pseudo second order kinetic and isotherm Langmuir model with adsorption capacity of Cu-Al and Cu-Al-SiW12O40 LDHs was 55.866 mg/g and 149.253 mg/g, respectively. That adsorption capacity is equal with increasing interlayer space and surface area properties of material after intercalation. Thus, the adsorption of malachite green on Cu-Al and Cu-Al-SiW12O40 LDHs is unique and dominantly occurred on interlayer space of LDH as active site adsorption. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Improving Flame Retardancy of Epoxy Resin Nanocomposites by Carbon Nanotubes Grafted CuAl-Layered Double Hydroxide Hybrid.

To solve the issues of the poor dispersion performance of the inorganic flame retardant filler in epoxy resin (EP) matrix, the three-dimensional (3D) hybrid carbon nanotubes-copper aluminum (sodium dodecyl sulfate)-layered double hydroxide (CNTs-OLDH) is designed and synthesized by co-precipitation. The results indicate that the CNTs-OLDH hybrid with 3D-structure is successfully fabricated and well dispersed in EP matrix. The thermostability of EP/CNTs-OLDH nanocomposites is raised and the residue is obviously increased. When the amount of CNTs-OLDH is only 4 wt%, limit oxygen index value of EP/CNTs-OLDH nanocomposites reaches 28.5. Compared with pure EP, the heat release, smoke and gas of EP/FePP nanocomposites are inhibited by CNTs-OLDH hybrid, and the PHRR, THR and SPR values of EP/4CNTs-OLDH nanocomposites decrease by 41.7%, 27.8% and 31.7%. The improved fire retardant performances and thermal stability are attributed to the excellent homogeneous dispersion, the network structure formed by the 3D hybrid in the matrix and the outstanding flame retardant effect of CNTs and OLDH.

Comprehensive study of the formation of stable colloids of Cu[sbnd]Al layered double hydroxide assisted by double hydrophilic block copolymers

The formation of stable aqueous colloidal suspensions of CuAl layered double hydroxide (LDH) assisted by double-hydrophilic block copolymers was investigated. It was of utmost importance since the direct preparation LDH colloids of controlled size is still a major challenge; moreover, regarding the CuAl system, the mechanism of formation of the LDH phase is not well understood yet. CuAl LDH nanoparticles were obtained by complexing Cu2+ and Al3+ cation mixture (Cu2+/Al3+ = 2) with an asymmetric poly(acrylamide)-b-poly(acrylic acid) block copolymer, followed by metal cation hydroxylation. The mechanism of formation of the CuAl LDH was studied and compared to that of MgAl LDH. ICP-MS analysis of the hybrid polyion complex (HPIC) micelles obtained at increasing complexation ratio, i. e. the ratio of the molar concentration of complexing acrylate group of DHBC to M2+ and Al3+ cations (R = AA/(M2+ + Al3+)), showed higher selectivity of DHBC toward Al3+ and, among M2+ cations, for Cu2+ than for Mg2+. Hydroxylation of the HPIC micelles led to macroscopic precipitates at R values below flocculation thresholds, i. e. R1 = 0.43 for DHBC/Cu-Al and 0.13 for DHBC/Mg-Al suspensions, while stable suspensions were formed above R1. The hydrodynamic diameter (Dh) of the colloids determined by DLS decreased from 160 to 50 nm and from 350 to 50 nm in the DHBC/Cu-Al and DHBC/Mg-Al colloids, respectively, when R increased from R1 to 1. XRD and TEM analyses of the dried colloidal suspensions (R > R1) revealed the presence of CuAl LDH and MgAl LDH phases and elemental analyses confirmed that M(II)/Al = 2. Particle sizes were lower in CuAl LDH than in MgAl LDH. Titration curves corresponding to progressive hydroxylation of DHBC/Cu(or Mg)-Al solutions at fixed complexation ratio R allowed establishing that formation of CuAl and MgAl LDH obeyed to a similar sequential mechanism in two steps but involving different aluminum hydroxide precursors according to the different pH values of precipitation. CuAl LDH was obtained by combination of aluminum poly(hydr)oxide species with dissolved copper-based species at pH ~ 5.5, while MgAl LDH resulted from combination of Al(OH)3 and dissolved Mg2+ at pH ~ 8.

Insight into Cu2O/CuO collaboration in the selective catalytic reduction of NO with NH3: Enhanced activity and synergistic mechanism

Cu-based catalysts have drawn much attention in ammonia-selective catalytic reduction (NH3-SCR) of NOx because of their outstanding low-temperature denitration (de-NOx) potential. Although satisfactory SCR performance was obtained with support from the catalytic activity of CuOx species in recent studies, the effect of the valence distribution of CuOx species on NH3-SCR reaction is still ambiguous, and elaborate exploration is necessary. Here, a series of CuAl-layered double oxide/carbon nanotubes-x (CuAl-LDO/CNTs-x) nanocatalysts with a tunable valence distribution of highly dispersed CuOx species was constructed from the topotactic transformation of CuAl-layered double hydroxide (CuAl-LDH) precursor and a controllable carbothermal reduction reaction. Multiple characterization techniques, including XRD, NH3-TPD, H2-TPR, NOx-TPD, XPS, in situ DRIFTS, and HR-TEM, were employed to elucidate the inherent relationship between the chemical properties and catalytic activity of the as-prepared catalysts. The obtained CuAl-LDO/CNTs-2 catalyst exhibited optimum catalytic performance, with NOx conversion exceeding 90% in the temperature range 180–305 °C. Such high catalytic efficiency can be attributed to the appropriate valence distribution of CuOx species, which can significantly improve the redox capacity and surface acidity of the catalysts, thereby promoting the adsorption and activation of the reactants. Combined with further theoretical calculation, a synergistic catalytic mechanism of Cu2O/CuO in the NH3-SCR reaction is tentatively proposed. Notably, the CuO active center can function as the dominant adsorption site of NO and NH3 to promote the formation of NO+ active species and the dehydrogenation activation of NH3. The Cu2O active center can act as the adsorption site for O, promoting the formation of active oxygen species O−. Consequently, the synergistic effect between Cu2O and CuO can lead to the rapid formation of reactive intermediates, proceeding via the Langmuir–Hinshelwood (reaction between adsorbed NH3 and adsorbed NOx) or Eley–Rideal (reaction between adsorbed NH3 and gaseous NO) mechanism reaction routes to complete the catalytic cycle. This work provides a fundamental understanding on Cu2O/CuO synergistic catalysis of NH3-SCR, which is propitious for the rational design and optimization of Cu-based oxide de-NOx catalysts.

Characteristics of Low-Temperature Polyvinyl Chloride Carbonization by Catalytic CuAl Layered Double Hydroxide

A good way to make carbon materials was presented in low-temperature polyvinyl chloride (PVC) carbonization by catalysis. The process of low-temperature PVC carbonization by CuAl-layered double hydroxide (CuAl-LDH) was investigated by thermogravimetric analysis (TGA) and tubular furnace. The results show that CuAl-LDH accounting for 5% of PVC mass enabled acceleration of the dehydrochlorination in PVC as soon as possible and maximized the yield of the PVC carbonized product. The vacuum with 0.08 MPa, 20 °C/min heating rate and 90 min carbonized maintenance time were optimal for PVC carbonization. Moreover, the best morphology and yield of the carbonized product was provided at a carbonization temperature of 300 °C.

Improving Fire Safety of Epoxy Resin with Alkyl Glycoside Modified CuAl-Layered Double Hydroxide.

To further improve carbonization efficiency of epoxy resin (EP) composites to form compact protective layers during combustion process, alkyl glycoside modified CuAl layered double hydroxide (CuAl-(APG)LDH) was designed and synthesized via one-step coprecipitation method, which was incorporated into EP matrix for preparing EP/CuAl-(APG)LDH nanocomposites. The results of XRD and TEM confirmed that EP nanocomposites with low incorporation of CuAl-(APG)LDH were exfoliated structures. The TGA results showed that the incorporation of CuAl-(APG)LDH remarkably increased the residues at 700 °C. The improved flame retardancy of EP/CuAl-(APG)LDH nanocomposites was proved by cone calorimeter test. The peak heat release rate, total heat release, peak smoke production rate and total smoke production value of EP/4 wt%CuAl-(APG)LDH nanocomposites dramatically decreased, which were attributed to the formation of hard and condensed residual layers on the surface of EP/CuAl-(APG)LDH nanocomposites.

Synergistic catalysis of Cu+/Cu0 for efficient and selective N-methylation of nitroarenes with para-formaldehyde

In this paper, an inexpensive heterogeneous copper nanoparticles catalyst derived from CuAl-layered double hydroxide via an in situ topotactic transformation process was developed. Cu nanoparticles with uniform size were homogeneously dispersed on amorphous Al2O3 with strong metal-support interaction. Characterization results reveals that the Cu0 and Cu+ were simultaneously formed with Cu+ species as the dominant sites on the surface during the reduction process. The resultant catalyst Cu/Al2O3 demonstrates high catalytic activity, selectivity and durability for the reductive N-methylation of easily available nitroarenes in a cost-efficient, environmentally friendly and cascade manner. A broad spectrum of nitroarenes could be efficiently N-methylated to their corresponding N,N-dimethyl amines with good compatibility of various functional groups. The protocol is also applicable for the late-stage functionalization of biologically and pharmaceutically active nitro molecules. A structure-function relationship discloses that Cu0 and Cu+ sites on the surface pronouncedly boosts the reaction efficiency in a synergistic manner, in which Cu0 could facilitate H2 production and N-methylation of anilines, while Cu+ is considerably more active and participates in the overall process of the selective N-methylation of nitroarenes. Moreover, the catalyst also showed a strong stability and could be easily separated for successive reuses without an appreciable loss in activity and selectivity.

Insights into the adsorption mechanism of carbon cellulose fiber loaded globular flowers bimetallic layered double hydroxide for efficiency pollutant removal

An environmentally-friendly CuAl-layered double hydroxide (LDH)/carbon cellulose fiber (CuAl-LDH/CCF) synthesized via one-pot precipitation and green hydrothermal method. The prepared cellulose-based immobilized carrier was prepared using sisal as the natural precursor and attempted to fabricate hierarchical structure materials. The XRD, BET, FTIR, RS and EDS techniques were employed for characterization of the as-prepared materials and elucidation of their adsorption mechanism. The characterization results indicated that the LDHs nanosheets with the sizes of about 5–10 μm were successfully anchored on the surface and dispersed into the walls of natural carbon fiber matrix, and the resultant nanocomposites have a uniform mesostructure with a high specific surface area and large pore volume. The obtained CuAl-LDH/CCF sample exhibited the better adsorption performance of phosphorus, in comparison with pure LDH and Cu/Al-LDH, the high adsorption capacity of the as-prepared adsorbent can be attributed to the synergetic effect of the CuAl-LDH nanosheets and carbon cellulose fiber. The adsorption isotherm and kinetic studies show that adsorption of phosphorus on the as-prepared materials were better described by the Langmuir equilibrium model and the pseudo-second order kinetic model. The maximum adsorption capacity of the CuAl-LDH/CCF was determined to be 105.26 mg/g, and the adsorption process was spontaneous and exothermic. The results indicated that phosphorus ions were adsorbed mainly mechanism including electrostatic attraction, ligand exchange and ion exchange. The CuAl-LDH/CCF still has >85% of the phosphorus removal percentage after fifth adsorption-desorption recycles of reuse. The hierarchical CuAl-LDH/CCF can be considered as a potentially adsorbent for applied in waste water treatment.

Improving the flame-retardant efficiency of layered double hydroxide with disodium phenylphosphate for epoxy resin

CuAl layered double hydroxide (CuAl-LDH) was synthesized by co-precipitation. Sodium phenyl phosphate (SPP) and sodium dodecyl sulfate (SDS) are used to modify CuAl-LDH for preparing CuAl-(SPP)LDH and CuAl-(SDS)LDH, which were incorporated into epoxy resin (EP) to obtain EP/CuAl-(SPP)LDH and EP/CuAl-(SPP)LDH nanocomposites. The results indicate that SPP and SDS are intercalated into the interlayers of CuAl-LDH, and CuAl-(SPP)LDH has larger layer spacing than CuAl-(SDS)LDH. The thermal stability and flame-retardant performances of EP/CuAl-(SPP)LDH nanocomposites were better than those of EP/CuAl-(SDS)LDH composites. Compared with those of EP/4CuAl-(SDS)LDH nanocomposites, the peak heat release rate (PHRR) of EP/4CuAl-(SPP)LDH nanocomposites is reduced 25.8% and 55.6%, and peak smoke production rate (PSPR) value of EP/4CuAl-(SPP)LDH nanocomposites is reduced 27.6% and 46.2%, value of EP/4CuAl-(SPP)LDH nanocomposites is reduced 27.6% and 46.2%, respectively. The improved flame retardancy and smoke suppression performances of EP/CuAl-(SPP)LDH nanocomposites were attributed to the combination of copper compounds and SPP, promoting the formation of swollen, continuous and compact char layers on the surface of EP nanocomposites during combustion, eventually restraining the decomposition of EP nanocomposites.

Hierarchical sheet-like Cu/Zn/Al nanocatalysts derived from LDH/MOF composites for CO2 hydrogenation to methanol

The CO2 hydrogenation to generate methanol is one of the most promising techniques to turn waste CO2 into useful fuel and chemicals in a sustainable manner. Herein, we have designed several hierarchical sheet-like Cu/Zn/Al nanocatalysts to efficiently produce methanol from CO2 hydrogenation by a rational integration of layered double hydroxide (LDH) nanosheets and metal-organic frameworks (MOF) nanoparticles as double solid precursors. Specifically, the uniform loading of Zn-BTC nanoparticles on CuAl LDH surface was achieved by an in-situ growth method at mild conditions. It was found that the pretreatment of the LDH with acetone could effectively exfoliate the sheet-like structure, increase the specific surface area, and facilitate the immobilization of Zn-BTC nanoparticles, which remarkably improved CO2 hydrogenation performance with respect to methanol selectivity (>90% at 200°C). It was found that both the existence of Zn-BTC and the pretreatment of LDH with acetone significantly reduced CO selectivity by increasing the activation energy (Δ(Ea) up to 20 KJ/mol). Moreover, in-situ DRIFTS study indicates that the promoting effect of ZnO (derived from Zn-BTC) on methanol formation is mainly associated with the formation of a higher amount of *CH3O intermediate rather than *CO and *HCOO species on the catalyst surface.

Development of Copper-Aluminum Layered Double Hydroxide in Thin Film Nanocomposite Nanofiltration Membrane for Water Purification Process.

This study aims to fabricate a thin film composite (TFC) membrane, modified with copper-aluminium layered double hydroxide (LDH) nanofillers via interfacial polymerization technique for nanofiltration (NF) processes. It was found that Cu-Al LDH nanofillers possessed layered structured materials with typical hexagonal plate-like shape and positive surface charge. The study revealed that TFN membrane exhibits a relatively smooth surface and a less nodular structure compared to pristine TFC membrane. The contact angle of TFN progressively decreased from 54.1° to 37.25°, indicating enhancement in surface hydrophilicity. Moreover, the incorporation of LDH nanofillers resulted in a less negative membrane as compared to the pristine TFC membrane. The best NF performance was achieved by TFN2 membrane with 0.1° of Cu-Al LDH loading and a water flux of 7.01 Lm-2h-1.bar. The addition of Cu-Al LDH resulted in excellent single salt rejections of Na2SO4 (96.8%), MgCl2 (95.6%), MgSO4 (95.4%), and NaCl (60.8%). The improvement in anti-fouling properties of resultant TFN membranes can be observed from the increments of pure water flux recovery and normalized water flux by 14% and 25% respectively. The findings indicated that Cu-Al LDH is a promising material in tailoring membrane surface properties and fouling resistance. The modification of the LDH-filled TFN membrane shows another alternative to fabricating a high-performance composite membrane, especially for water softening and partial desalination process.

Synthesis of Cu-Al LDH nanofluid and its application in spray cooling heat transfer of a hot steel plate

In the current study, authors have synthesized Cu-Al Layered Double Hydroxide nanofluid at different molar ratios of Cu and Al by using co-precipitation technique and utilized this as a coolant in a pressure atomized spray to achieve high cooling rates in the temperature range of 900–600 °C for a 6 mm thick steel plate. The study initially focuses on the effect of Cu: Al molar ratio variation on thermal conductivity, stability as well as its heat transfer potential in steel quenching. Post thermal conductivity and stability analysis, spray cooling experiments were conducted in two parts. The first part involves optimization of Cu: Al molar ratio by varying the ratio (Cu: Al = 2:1, 4:1 and 6:1) at a fixed nanofluid concentration (120 ppm) to select the best Cu: Al molar ratio based on heat transfer results. The results show that the highest cooling rate and average heat flux were achieved at a Cu and Al molar ratio of 4:1 among all molar ratio combinations. Once, the optimized molar ratio is selected, the second part of the spray cooling experiments was performed to study the effect of nanofluid concentration variation (40–240 ppm, at an optimized molar ratio of Cu: Al = 4:1) on spray cooling results. With respect to concentration optimization, the maximum cooling rate of 168.6 °C/s was attained at a concentration of 160 ppm which is 26% higher than what was achieved by normal water spray. Results obtained from the spray cooling experiments were further verified by the thermal conductivity analysis where highest enhancement of 15.17% was also observed at 160 ppm nanofluid concentration.