Structure Of Layered Double Hydroxides Research Articles

Royal Jelly Nanoparticle Alleviates Experimental Model of Breast Cancer Through Suppressing Regulatory T Cells and Upregulating TH1 Cells.

Royal jelly, a natural product from bees' hypopharyngeal glands, is commonly used in biomedicine due to its antioxidant and anti-tumor activities. The aim of this study was to compare royal jelly in free form and loaded in layered double hydroxide (LDH) nanoparticle for the treatment of breast cancer with a focus on Th1 and T regulatory parameters in an animal model. Nanoparticles were produced using the coprecipitation method and characterized using DLS, FTIR, and SEM techniques. Forty female BALB/c mice were inoculated with 7.5 x 105 4T1 cells and treated with royal jelly in free and nanoparticle form. Clinical signs and tumor volume were assessed weekly. The effect of royal jelly products on the serum level of IFN-γ and TGF-β was measured by ELISA. In addition, the mRNA expression of these cytokines and Th1 and regulatory T cells' transcription factors (T-bet and FoxP3) was assessed by real-time PCR in the splenocytes of tumor-bearing mice. The physicochemical analysis of nanoparticles confirmed the synthesis of LDH nanoparticles and loading of royal jelly into the LDH structures (RJ-LDH). Animal studies showed that royal jelly and RJ-LDH significantly reduced the size of tumor in BALB/c mice. Additionally, treatment with RJ-LDH significantly inhibited TGF-β and increased IFN-γ production. The data also revealed that RJ-LDH inhibited the differentiation of regulatory T cells, while promoting Th1 cell differentiation via regulating their master transcription factors. These results indicated that royal jelly and RJ-LDH could inhibit breast cancer progression by in-hibiting regulatory T cells and expansion of Th1 cell. Furthermore, the current study demonstrated the therapeutic efficacy of royal jelly is enhanced by LDH nanoparticles; hence, RJ-LDH is significantly more efficient than Free-RJ in the treatment of breast cancer.

Self-protection concrete measures as prevention measure from chloride transport and corrosion of reinforcement

Incorporation of additives into a reinforced concrete matrix to delay or even completely avoid the initiation of corrosion during the service-life of the construction is a widely pursued topic. One of the new promising technologies achieving increased interest is to incorporate corrosion inhibitors encapsulated in layered double hydroxide (LDH). LDH structures follow a controlled release of the inhibitor while chloride is efficiently trapped at the same time. Another type of nanostructure additive offering self-protection ability in concrete is polyhedral oligomeric silsesquioxanes (POSS) developed to exhibit water-repellent functionalities protecting the reinforcement from corrosive attack. In the present laboratory work, the enhanced performance of concrete infrastructures in a marine environment was studied using a SCC design. The addition of LDH (0.5, 1 and 2 % by mass of binder (bmb)) and POSS (2 and 4 % additive level) was explored. Migration and diffusion Cl transport tests have been performed towards corrosion protection of reinforcing bars. The results showed that Cl transport decreases with the concrete maturity, and this is even more effective for concretes with LDH and POSS. This delay effect is more pronounced in the unidirectional diffusional Cl transport. LDH is significantly retarding the initiation of rebar corrosion.

Delamination of Layered Double Hydroxide in Ionic Liquids under Ambient Conditions.

Liquid phase delamination of layered materials into single- or few-layer nanosheets leads to stable nanoscale dispersions of 2D materials. The delamination of layered double hydroxide (LDH) to double hydroxide nanosheets was studied in two ionic liquids (ILs): ethylammonium nitrate (EAN) and 1-butyl-3-methylimidazolium thiocyanate (BMIMSCN). The as-prepared lamellar structure of LDH disappeared upon dispersing it in ILs due to delamination into 2D nanosheets confirmed by X-ray scattering and diffraction techniques and further evaluated by height profile assessment of the nanoparticles by atomic force microscopy. The results showed that both the thickness and lateral size of the dispersed particles decreased in the IL-based samples, indicating that cleavage of the LDH materials can be observed in addition to delamination. The findings prove the concept of delamination of layered materials by ILs under ambient conditions─an excellent way to prepare 2D double hydroxide nanosheet dispersions in one step using nonvolatile green solvents.

Bioregulation of FeNi LDH morphology and electronic structure to highly promote electrocatalytic oxygen evolution

NiFe-based layered double hydroxides (LDHs) are currently the most efficient oxygen evolution reaction (OER) catalysts in alkaline medium. However, their shortcomings such as insufficient electron transport ability, few exposed active sites and susceptibility to aggregation hindered their further development. In this paper, soluble extracellular polymer substances (s-EPS) modified by urea was used as biosurfactant and pH regulator, micro-morphology and electronic structure of FeNi LDH were accurately regulated to upgrade its stability, electrical conductivity, electrochemical active surface area and kinetic process. Tryptophan residue protein in EPS is mainly responsible for the interaction between s-EPS and FeNi LDH. Experimental and theoretical calculation results demonstrate that the introduction of s-EPS can coordinate the morphology and electron distribution of active centers, consequently optimizing the adsorption energy of reaction intermediates and enhancing the inherent catalytic activity for OER. As expected, s-EPS@FeNi LDH exhibited excellent OER performance under alkaline conditions, and only had an overpotential of 220 mV at a current density of 10 mA cm−2, which is superior to other promising FeNi-based catalysts. This work sheds light on realizing the efficient assembly of LDH and s-EPS, and provides a reliable method for the morphology and electronic structure modification of LDH for more efficient OER.

Layered Double Hydroxide/Graphene Quantum Dots as a New Sorbent for the Dispersive Solid-Phase Microextraction of Selected Benzophenones, Phenols, and Parabens

In this study, the synthesis of a layered double hydroxide (LDH) composite with graphene quantum dots (GQDs) and its utilization for the development of a dispersive solid-phase extraction procedure are described. To this end, a carbonate-free Mg-Al LDH was synthesized. The development of the composite material made feasible the use of GQDs in a sample preparation procedure, while the incorporation of the GQDs in the LDH structure resulted in an 80% increase in extraction efficiency, compared to the bare LDH. As a proof of concept, the composite material was used for the development of an analytical method for the extraction, and preconcentration, of benzophenones, phenols, and parabens in lake water using high-performance liquid chromatography, coupled to a diode array detector. The analytical method exhibits low limits of quantification (0.10-1.33 μg L-1), good recoveries (92-100%), and satisfactory enrichment factors (169-186). Due to the abovementioned merits, the easy synthesis and simple extraction, the developed method can be used for the routine analysis of the target compounds.

Pretreatment of membrane dye wastewater by CoFe-LDH-activated peroxymonosulfate: Performance, degradation pathway, and mechanism

When a membrane is used to treat dye wastewater, dye molecules are continually concentrated at the membrane surface over time, resulting in a dramatic decrease in membrane flux. Aside from routine membrane cleaning, the pretreatment of dye wastewater to degrade organic pollutants into tiny molecules is a facile solution to the problem. In this study, the use of layered double hydroxide (LDH) to activate peroxymonosulfate (PMS) for efficient degradation of organic pollutant has been thoroughly investigated. We utilized a simple two-drop co-precipitation process to prepare CoFe-LDH. The transition metal components in CoFe-LDH effectively activate PMS to create oxidative free radicals, and the layered structure of LDH increases the number of active sites, and thereby considerably enhancing the reaction rate. It was found that the reaction process produced non-free and free radicals, including singlet oxygen (1O2), sulfate radicals (SO4•−), and hydroxyl radicals (•OH), with 1O2 being the dominant reactive species. Under the optimal conditions (pH 6.7, PMS dosage 0.2 g/L, catalyst loading 0.1 g/L), the degradation of Acid Red 27 dye in the CoFe-LDH/PMS system reached 96.7% within 15 min at an initial concentration of 200 mg/L. The CoFe-LDH/PMS system also exhibited strong resistance to inorganic ions and pH during the degradation of organic pollutants. This study presents a novel strategy for the synergistic treatment of dye wastewater with free and non-free radicals produced by LDH-activated PMS in a natural environment.

Characterization and Syngas Production at Low Temperature via Dry Reforming of Methane over Ni-M (M = Fe, Cr) Catalysts Tailored from LDH Structure

Bimetallic layered double oxide (LDO) NiM (M = Cr, Fe) catalysts with nominal compositions of Ni/M = 2 or 3 were tailored from layered double hydroxides (LDH) using a coprecipitation method to investigate the effects of the trivalent metal (Cr or Fe) and the amount of Ni species on the structural, textural, reducibility, and catalytic properties for CH4/CO2 reforming. The solids before (LDH) and after (LDO) thermal treatment at 500 °C were characterized using TGA-TD-SM, HT-XRD, XRD, Raman, and IR-ATR spectroscopies; N2 physical adsorption; XPS; and H2-TPR. According to the XRD and Raman analysis, a hydrotalcite structure was present at room temperature and stable up to 250 °C. The interlayer space decreased when the temperature increased, with a lattice parameter and interlayer space of 3.018 Å and 7.017 Å, respectively. The solids fully decomposed into oxide after calcination at 500 °C. NiO and spinel phases (NiM2O4, M = Cr or Fe) were observed in the NiM (M = Cr, Fe) catalysts, and Cr2O3 was detected in the case of NiCr. The NiFe catalysts show low activity and selectivity for DRM in the temperature range explored. In contrast, the chromium compound demonstrated interesting CH4 and CO2 conversions and generally excellent H2 selectivity at low reaction temperatures. CH4 and CO2 conversions of 18–20% with H2/CO of approx. 0.7 could be reached at temperatures as low as 500 °C, but transient behavior and deactivation were observed at higher temperatures or long reaction times. The excellent activity observed during this transient sequence was attributed to the stabilization of the metallic Ni particles formed during the reduction of the NiO phase due to the presence of NiCr2O4, opening the path for the use of these materials in periodic or looping processes for methane reforming at low temperature.

Layered double hydroxides for corrosion-related applications-Main developments from 20years of research at CICECO.

This work describes the main advances carried out in the field of corrosion protection using layered double hydroxides (LDH), both as additive/pigment-based systems in organic coatings and as conversion films/pre-treatments. In the context of the research topic "Celebrating 20years of CICECO", the main works reported herein are based on SECOP's group (CICECO) main advances over the years. More specifically, this review describes structure and properties of LDH, delving into the corrosion field with description of pioneering works, use of LDH as additives to organic coatings, conversion layers, application in reinforced concrete and corrosion detection, and environmental impact of these materials. Moreover, the use of computational tools for the design of LDH materials and understanding of ion-exchange reactions is also presented. The review ends with a critical analysis of the field and future perspectives on the use of LDH for corrosion protection. From the work carried out LDH seem very tenable, versatile, and advantageous for corrosion protection applications, although several obstacles will have to be overcome before their use become commonplace.

Regulation of Structure and Anion-Exchange Performance of Layered Double Hydroxide: Function of the Metal Cation Composition of a Brucite-like Layer.

As anion-exchange materials, layered double hydroxides (LDHs) have attracted increasing attention in the fields of selective adsorption and separation, controlled drug release, and environmental remediation. The metal cation composition of the laminate is the essential factor that determines the anion-exchange performance of LDHs. Herein, we review the regulating effects of the metal cation composition on the anion-exchange properties and LDH structure. Specifically, the internal factors affecting the anion-exchange performance of LDHs were analyzed and summarized. These include the intercalation driving force, interlayer domain environment, and LDH morphology, which significantly affect the anion selectivity, anion-exchange capacity, and anion arrangement. By changing the species, valence state, size, and mole ratio of the metal cations, the structural characteristics, charge density, and interlayer spacing of LDHs can be adjusted, which affect the anion-exchange performance of LDHs. The present challenges and future prospects of LDHs are also discussed. To the best of our knowledge, this is the first review to summarize the essential relationship between the metal ion composition and anion-exchange performance of laminates, providing important insights for regulating the anion-exchange performance of LDHs.

Effect of layered double hydroxides Ca-Al LDHs and polycarboxylate ethers on the hardening of Portland limestone cement

The use of layered double hydroxides (LDHs) is a new direction in chemistry of cement. The influence of calcium/aluminum double hydroxides (Ca-Al LDHs) and polycarboxylate ethers (PCE) on the strength development of Portland limestone cement has been investigated. It has been shown that Ca-Al LDHs form in cement slurry with the introduction of alkaline aluminate accelerator Na[Al(OH)4]. It was determined that this contributes to a significant increase in the early strength of cement stone. However, this reduces the setting time of hardening, and there is a decrease in strength with age. At an early stage of structuring in cement paste with the addition of Na[Al(OH)4], metastable high-water hydrate phases of Ca-Al LDHs of type C4AH19 ([Ca2Al(OH)6]2(ОН)2·12H2O) are formed, which, due to the conversion phenomenon, transform to cubic C3AH6. Such processes are accompanied by an increase in overall porosity and decreases in the strength of cement stone. Stabilization of the Ca-Al LDH structure is achieved by introducing anions [NO3]- into the interlayer space with the formation of Ca-Al-NO3 LDHs through the use of sol-gel technology. X-ray phase analysis, IR spectroscopy, and electron microscopy proved the fact of synthesis of AFm-phases of type [Ca2Al(OH)6]2(NO3)2.6H2О. When modifying such hydrates with polycarboxylate ethers, a nanocomposite Ca-Al-NO3 LDHs-РСЕ is formed. It was found that when the Ca-Al-NO3 LDHs-РСЕ nanocomposite was introduced to СЕМ ІІ/A-LL 42,5 R, the strength over the period of 8...24 hours increases by 2.0–1.5 times, and, after 2 and 28 days, 58 and 144 % of the standard strength is achieved (Rс28=62.5 MPa). The obtained nanomodified Portland limestone cement refers to extra rapid-hardening and high-strength cement, which makes it possible to solve the task of carrying out work on the rapid restoration of reinforced concrete structures' elements

Atomic Dispersed Ce/Ti Onto Layered Double Hydroxide Substrate Via Atomic Layer Deposition for Efficient Oxygen Evolution Reaction

Recently, transition metal based layered double hydroxides (LDHs) based materials have attracted attention for the enhancement of oxygen evolution reaction (OER) performances due to their unique structural property, high specific capacitance, facile synthesis process and low cost. [1,2] Atomic layer deposition (ALD) is a powerful technique for realizing highly dispersed nano-species at the atomic level with a precise control over the size, shape, and composition by leveraging its self-limiting nature of surface reactions. ALD precursors could be readily combined with LDH structures due to the abundant hydroxy group on the surface of LDH structure. The additional ALD-derived doping can regulate the electronic structures of original LDH and further strength the synergetic effects between the host and doped metals for enhancing electrocatalytic activities.[3] In this study, a simple and effective method of introducing Ce as a third metal was used to prepare high-performance Ni/Co-LDH based electrodes: hydrothermal approach followed by an ALD process, using Ni foam as the substrate to achieve the growth of Ni/Co nanostructures. Smooth 2D LDH plates of a uniform structure with high surface area and abundant active sites were synthesized. The resultant CoNi-LDH@5Ce and CoNi-LDH@5Ti exhibit optimal activity and stability toward OER. In particular, CoNi-LDH@5Ce exhibits excellent OER performance with a small overpotential of 270 mV to reach 50 mA cm-2. ALD-treated samples exhibit a decreased charge transfer resistance, indicating a more efficient OER. Furthermore, both CoNi@5Ti and CoNi@5Ce show lower ohmic resistance of 1.5 Ω, which is additionally beneficial to OER performance. The enhanced performance could be attributed to a synergic effect between the doped elements (Ce, Ti) and base transitional metals (Co, Ni). Furthermore, metal oxides – especially cobalt oxide – generated on the surface during ALD process is conjectured to have contributed to an acceleration of O-O bond formation during OER process.

3D Metal-Organic Framework Based Layered Double Hydroxide Core Shell Structure for Enhanced Oxygen Evolution Reaction

Electrochemical water splitting, an effective approach of generating high purity hydrogen in a clean way, is composed of two half reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).[1] OER is the main rate-limiting half reaction for water splitting due to its sluggish four-electron transfer process.[2] , [3] An efficient electrocatalyst is indispensable to minimize the activation barrier for the reaction and achieve a high efficiency.Recently, two-dimensional (2D) layered double hydroxides (LDHs) have shown promises as one of the most effective electrocatalysts towards OER. However, the confined nanostructure with poor electronic conductivity inhibits their further enhanced catalytic performance towards OER. Herein, a 3D core-shell LDH structure is synthesized through a facile one-step reaction strategy, in which the terephthalic acid and urea is employed as the organic ligand for the metal organic framework (MOF) precursor and surface coordination buffer between LDH and MOF. Benefiting from the hierarchical 3D microstructure with uniformly nanosheets grown on the surface, the as prepared electrocatalyst exhibits rich edge active sites and enormous electrochemical surface area. The representative sample (namely, CoNi-LDH@BDC) achieves an excellent OER activity with a low overpotential of 280 mV at 100 mA cm-2 and robust cyclic stability. In addition, quasi-operando studies using X-ray absorption and X-ray photoelectron spectroscopy further elucidate that the Co-Ni dual metal sites act as the main active site while Ni of high valence state is a favorable site to oxygen for the O-O bond formation. The prominent OER performance is also attributed to the synergistic effect between different transition metal atoms.

Chemiresistive gas sensors based on layered double hydroxides (LDHs) structures: A review

A wide range of materials and nanomaterials have been considered gas sensors due to the growing needs of developed and developing societies. It has been more than six decades since Taguchi introduced the first commercial gas sensor, yet the development of sensors has grown exponentially and has not slowed down. Researchers always look for new materials with more efficient morphologies. It can probably be said that one of the newest materials discussed is LDH nanosheets, which has been discussed for less than two decades. Thus, in this review, after defining the general structure of LDH and giving a general description of nanomaterials, we have discussed the relevant terms and various methods of synthesis. The film preparation of nanomaterial sensor is then discussed in detail as a scalable approach in line with the various methods of nanomaterial synthesis (especially with a focus on LDH nanosheets). The following is discussed the unique properties of LDH nanosheets and their effect on the detection of various contaminants. Since LDH nanomaterials fall into both n- and p-type categories, the pollutant (gas) measurement approach has been investigated in both categories. This creates a specific comparative approach for the reader. Concisely, this study describes the use of LDH nanosheets in the field of gas sensors and may provide the idea for more extensive and practical research on LDHs.

Influence of the aggregated structures of layered double hydroxide nanoparticles on the degradation behavior of poly(butyleneadipate-co-terephthalate) composites

Layered double hydroxides (LDH) modified with sodium dodecyl sulfate (LDH-SDS) and stearic acid (LDH-SA) were added into the poly(butyleneadipate-co-terephthalate) (PBAT) matrix for the preparation of PBAT/LDH nanocomposite films. In the matrix, pristine LDH, LDH-SDS, and LDH-SA were present in the form of aggregated nanoparticles, intercalated, and exfoliated layers, respectively. In comparison with pristine LDH, the intercalated and exfoliated LDH exhibited better dispersibility in PBAT and greater capacity to promote the mechanical properties and crystallization performance of PBAT. More importantly, in the hydrolysis degradation experiment, the degradation behaviors were significantly affected by hydrophilic nature of modified LDH and its organic–inorganic interfaces caused by various aggregated state structures. Thus, an important method of tuned the degradation behaviors of PBAT films by adjusting the aggregated structures of LDH was established.

SYNTHESIS, PROPERTIES AND PRACTICAL APPLICATIONS OF DOPED AND UNDOPED, ZINC-CONTAINING LAYERED DOUBLE HYDROXIDES – A BRIEF REVIEW

Recently, layered double hydroxides (LDHs) have been developed for more potential applications in various industry fields. Many synthesis methods of LDHs in the literature have been considered and classified by changing properties. However, the property change by the synthesis method does not happen in the same way in all LDHs. Also, when LDH with the same composition is synthesized by the same synthesis method, it is possible to obtain LDHs with the same composition but different properties due to the change of reaction parameters. Recently, the doping of semiconductor nanocomposites with different element atoms has led to new properties. The effect of the elements used in the doping process on the properties of zinc-containing LDHs was investigated and explained in the review article. The synthesis's techniques differ from each other by the reaction parameters and they impact the crystal structure, physicochemical properties, and morphology of LDHs. Finding more additional effects of doping processes and doping elements' nature on the zinc-containing LDHs' properties, the synthesis procedures, and the determination of reaction parameters are shown in this review article. It was revealed that rare earth elements are not selected as three valence metals for the main structure of LDHs, they are mainly used as a doping element which is replaced by three valence metals (Al, Cr, Ti, Fe(III)) as dopants because of the ionic radius and various factors.

Activation of persulfate via Mn doped Mg/Al layered double hydroxide for effective degradation of organics: Insights from chemical and structural variability of catalyst.

Considerable interest has been focusing on the activation of peroxydisulfate (PDS) by layered double hydroxide (LDH) for degradation of organic pollutants. However, understanding the structure and chemistry of LDH by which the activation of PDS could achieve a high degradation efficiency of organic compounds is an unsolved and fundamental question in advanced oxidation processes (AOPs), and one which, if harnessed, could enable the rational design of LDH with desired material properties. In this work, Mg/Al-LDH was synthesized with variable structures and compositions through doping different proportions of Mn2+. We advanced to understand this question of how LDH by these characteristics can affect the activation of PDS for degradation of organic pollutants. At a relatively low dosage of Mn (˂ 1%) in Mg/Al-LDH, the degradation rate of phenol by LDH activated PDS increased with the increase content of Mn, which was achieved by an increase of catalytic sites in Mg/Al-LDH interlayer. Rather, higher content of Mn (˃ 1%) significantly lowered the degradation performance of phenol as the decrease of interlayer space resulted in reduction of PDS intercalation in LDH and the formation of secondary Mn-related minerals (i.e., Mn3O4) led to meaningless consumption of PDS. Finally, the degradation of phenol by LDH activated PDS followed a non-radical (1O2) mechanism. Our ability to quantify how the chemical and structural variability of LDH influence the activation of PDS for organic degradation could mark an important step toward synthesis strategies for advanced catalysts.

Synthesis, Characterization and Photocatalytic Activity of Eco-friendly ZnCr/C-LDH Nanocatalyst

ZnCr/C layered double hydroxide (LDH) was synthesized using the co-precipitation method. The LDH photo-Catalyst was characterized using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy dispersive Spectroscopy (EDS), Fourier transformed infrared (FTIR) and Thermo gravimetric analysis (TGA). The 2ϴ values at 13.5, 24.5 and 32.5 in XRD confirmed the formation of the Layered double hydroxide structure. The lower band gap energy at 1.84eV suggests that the catalyst works well in the UV-visible region. The photocatalytic activity of the LDH under UV-Irradiation in aqueous Congo red (CR) was studied under optimal operational parametric conditions (Concentration, catalytic dosage and pH). The kinetics of the photocatalytic activity was investigated using the Langmuir Hinshelwood model. The LDH Shows excellent recyclability, durability and stability even after the fourth cycle.

Mechanically Reinforced Flame-Retardant Epoxy Resins by Layered Double Hydroxide In Situ Decorated Carbon Nanotubes

Epoxy resins (EPs) are widely used as structural materials in airplane compartments due to their lightweight merits and corrosion resistance. However, the flammability of polymers necessitates the exploration of high-performance flame retardants to improve aircraft fire safety. In this study, an in situ composite structure of layered double hydroxides (LDHs) and carbon nanotubes (CNTs) is constructed via a one-pot strategy in which LDH nanosheets are grown in situ on the skeleton of interwoven CNTs. The composite structure of LDH–CNTs acts as a mechanical support to further accommodate nanoparticles of 9,10-dihydro-9-oxa-10-phosphorus-10-oxide (DOPO) to obtain the flame retardant LDH–CNTs–DOPO. The in situ composite structure of LDH–CNTs realizes the uniform dispersion of the nanoscale flame-retardant components in the polymer substrate and endows the flame-retardant-treated EP substrate with both desirable mechanical strength and flame retardancy. Notably, the total heat release and smoke release of the flame-retardant composite EP@LDH–CNTs–DOPO are reduced by 19.0 and 25.56%, respectively, relative to those of neat EP, and a limiting oxygen index (LOI) of 31.0% and a flame-retardancy level of V-1 are achieved. A synergistic flame-retardant mechanism coordinated by LDH nanosheets, a supportive LDH–CNTs composite structure, and DOPO nanoparticles is proposed and elaborated by extensive fire-resistance evaluations and intensive analysis of the char residue after combustion.

Construction of 3D Ni2+-Al3+-LDH/γ-Fe2O3-Cd2+-Ni2+-Fe3+-LDH structures and multistage recycling treatment of dye and fluoride-containing wastewater

The construction of three-dimensional (3D) Ni2+-Al3+-LDH/γ-Fe2O3-Cd2+-Ni2+-Fe3+-layered double hydroxide (LDH) structures (S1–S6) with magnetic properties and different (γ-Fe2O3-Cd2+-Ni2+-Fe3+-LDH)/(Ni2+-Al3+-LDH) ratios were successfully prepared. The effects of these ratios in these 3D LDH constructions on physicochemical properties were investigated using XRD, SEM, VSM, UV–vis, and BET analyses. The specific surface area and band gap of these materials decreased with increased ratio, while the saturation magnetization increased. The synergistic combination of saturation magnetization, adsorption characteristics, and band gap of six sample types were evaluated. S3 samples were used in a multistage recycling treatment study of dye wastewater and fluoride ion (F−)-containing wastewater, effectively degrading methyl orange (MO) due to its high photocatalytic activity. After this, the memory effect of the calcined product (S3, 300 °C) significantly enhanced the migration and diffusion of F−, resulting in a F− adsorption capacity of 49.25 mg/g. The recycling properties of this composite material for photocatalytic degradation and adsorption capabilities for F− removal were evaluated, showing a reduction in efficiency of only 1 % and 8.6 % for degradation of MO and F− removal respectively, with no significant loss of efficiency after 10 cycles. Adsorption experiments and subsequent sample characterization showed that the F− adsorption mechanism of S3 involved ion exchange mechanism and sorption sites (interlayer, basal, edges and junction sites). The existence of oxygen vacancies and formation of S-scheme heterojunction between γ-Fe2O3-Cd2+-Ni2+-Fe3+-LDH and Ni2+-Al3+-LDH, resulted in the improvement of the photocatalytic activity. The results obtained in this study demonstrated that Ni2+-Al3+-LDH/γ-Fe2O3-Cd2+-Ni2+-Fe3+-LDH composites were a promising adsorbent for degradation of MO and F− removal in practical multilevel utilization due to its simple synthesis, low-cost, recyclability, and high removal capability.

Vital Role of Synthesis Temperature in Co–Cu Layered Hydroxides and Their Fenton-like Activity for RhB Degradation

Cu and Co have shown superior catalytic performance to other transitional elements, and layered double hydroxides (LDHs) have presented advantages over other heterogeneous Fenton catalysts. However, there have been few studies about Co–Cu LDHs as catalysts for organic degradation via the Fenton reaction. Here, we prepared a series of Co–Cu LDH catalysts by a co-precipitation method under different synthesis temperatures and set Rhodamine B (RhB) as the target compound. The structure-performance relationship and the influence of reaction parameters were explored. A study of the Fenton-like reaction was conducted over Co–Cu layered hydroxide catalysts, and the variation of synthesis temperature greatly influenced their Fenton-like catalytic performance. The Co–Cut=65°C catalyst with the strongest LDH structure showed the highest RhB removal efficiency (99.3% within 30 min). The change of synthesis temperature induced bulk-phase transformation, structural distortion, and metal–oxygen (M–O) modification. An appropriate temperature improved LDH formation with defect sites and lengthened M–O bonds. Co–Cu LDH catalysts with a higher concentration of defect sites promoted surface hydroxide formation for H2O2 adsorption. These oxygen vacancies (Ovs) promoted electron transfer and H2O2 dissociation. Thus, the Co–Cu LDH catalyst is an attractive alternative organic pollutants treatment.