Layered Double Hydroxides Layers Research Articles

Corrosion-oriented self-healing coating based on ZnMg MOF for efficient corrosion protection of aluminum alloy via in-situ LDH film formation

A corrosion-oriented self-healing coating system relying on metal–organic framework (MOF) based nanofiller is designed for aluminum alloy protection. The nanofiller is comprise of ZnMg MOF nanoparticle as a framework, salicylaldoxime corrosion inhibitors inside the MOF, and a polydopamine layer on the MOF surface. The Al3+ ions generated from the aluminum alloy substrate at the damaged coating area can etch the nanofiller, causing the collapse of the nanofiller and releasing the corrosion inhibitors to suppress the corrosion process in time. Subsequently, Zn2+ and Mg2+ ions from the nanofiller co-precipitate with Al3+ to form a dense AlZnMg layered double hydroxide (LDH) film, which provides further protection performance at the exposed alloy surface. Electrochemical impedance spectroscopy results demonstrate that the intact MOF@S/P coating exhibits a remarkable corrosion resistance property. For the damaged coating, the self-healing performance originated from the formation of LDH layer and the release of corrosion inhibitors gradually took effect, with the |Z|0.01Hz value increasing 2.27 times within 14 days. Moreover, under near-infrared irradiation, the photothermal effect of polydopamine will accelerate the release of corrosion inhibitor, the formation of LDH film, as well as the shape memory effect of coating defect for an efficient recovery of the corrosion resistance property. This novel coating system enables a corrosion-driven and location-specific repair with in-situ deposition of both an inhibitor film and an LDH film. As the first work to fully utilize and consume nanofillers on demand, this approach prevents inadequate use of healing agents, addressing a significant challenge in corrosion-driven self-healing coatings. The self-healing mechanism ensures target-oriented corrosion protection that makes the most efficient use of the healing substances.

Layered Double Hydroxides as Systems for Capturing Small-Molecule Air Pollutants: A Density Functional Theory Study.

Air pollutants are usually formed by easily spreading small molecules, representing a severe problem for human health, especially in urban centers. Despite the efforts to stem their diffusion, many diseases are still associated with exposure to these molecules. The present study focuses on modeling and designing two-dimensional systems called Layered Double Hydroxides (LDHs), which can potentially trap these molecules. For this purpose, a Density Functional Theory (DFT) approach has been used to study the role of the elemental composition of LDHs, the type of counterion, and the ability of these systems to intercalate NO2 and SO2 between the LDH layers. The results demonstrated how the counterion determines the different possible spacing between the layers, modulating the internalization capacity of pollutants and determining the stability degree of the system for a long-lasting effect. The variations in structural properties, the density of states (DOS), and the description of the charge transfer have been reported, thus allowing the investigation of aspects that are difficult to observe from an experimental point of view and, at the same time, providing essential details for the effective development of systems that can counteract the spread of air pollutants.

Effects of interlayer-modified layered double hydroxides with organic corrosion inhibiting ions on the properties of cement-based materials and reinforcement corrosion in chloride environment

Developing novel, environmentally friendly, and efficient corrosion inhibitors is of great significance for improving the durability of marine concrete against chloride ion erosion. This paper aims to explore the potential of layered double hydroxides (LDHs) as nanocontainers, incorporating organic corrosion inhibitors between LDHs layers to synergistically enhance their effectiveness. In this study, Mg/Al-pAB-LDH was synthesized through the interlayer modification of LDHs with an organic corrosion inhibitor, p-aminobenzoic acid (pAB), employing a calcination-rehydration method. Chloride ion (Cl−) adsorption behavior was quantitatively and qualitatively analyzed and the effect on mortar properties was investigated. The corrosion resistance of steel bars in the mortar was assessed under chloride salt simulated concrete pore solution (SCPs) and chloride salt wet-dry cycles via electrochemical tests and microscopic characterization of Mg/Al-pAB-LDH. The results demonstrate that Mg/Al-pAB-LDH efficiently captures Cl− and releases corrosion-inhibiting ions pAB, with the adsorption process conforming to pseudo-second-order kinetics and Langmuir adsorption isotherm. Mg/Al-pAB-LDH enhances the pore structure of mortar, effectively improving mechanical properties and resistance to chloride ion penetration, with the optimal effect observed at a 4 % addition rate. Mg/Al-pAB-LDH demonstrates outstanding corrosion resistance to steel bars in both SCPs and mortar. In SCPs, it serves as a corrosion inhibitor by adsorbing Cl− and releasing pAB, whereas in mortar, it functions as a corrosion inhibitor by enhancing the physical barrier effect of mortar, adsorbing Cl−, and releasing pAB. This study demonstrates the promising potential of utilizing Mg/Al-pAB-LDH as a novel corrosion inhibitor to mitigate the corrosion of steel bars in marine concrete.

Enhancement of corrosion, biocompatibility and drug delivery properties of nitinol implants surface by Al-Zn-LDH nanohybrids

This study investigates the enhancement of drug delivery and corrosion resistance by incorporating dexamethasone sodium phosphate into aluminum-zinc layered double hydroxide (LDH) coated nickel-titanium alloys. The nickel-titanium samples were fabricated from titanium and nickel powders using spark plasma sintering (SPS) and cold press sintering (CPS), followed by electrophoretic deposition of LDH nanoparticles. This composite construction aims to utilize the biocompatibility and mechanical properties of nickel-titanium, combined with the controlled drug release and corrosion resistance properties of LDH coatings. Structural and microstructural characterizations were performed using X-ray diffraction and scanning electron microscopy. The results indicated that SPS samples exhibited superior microstructural homogeneity and corrosion resistance compared to CPS samples. Dexamethasone sodium phosphate was successfully intercalated into the LDH layers, as evidenced by an increase in layer spacing from 7.14 Å to 20.130 Å. The LDH-coated nickel-titanium with intercalated dexamethasone sodium phosphate demonstrated a 5 % lower drug release rate and significantly improved corrosion resistance compared to uncoated samples. Cell adhesion studies confirmed good biocompatibility between cells and the coated surface. This composite material shows promise for enhanced performance in biomedical applications, particularly in drug delivery and corrosion resistance.

Synergetic integration of photothermal and self-cleaning features in a composite phase change material based on layered double hydroxides and polypyrrole

Composite phase change materials (PCMs) with photothermal functionality play a crucial role in efficiently storing and utilizing solar energy. However, the challenge of effectively removing of contaminants on photothermal conversion coatings has long puzzled researchers. In this study, we propose a novel approach to enhancing both photothermal conversion performance and self-cleaning properties of wood-based composite phase change materials, ultimately facilitating the sustainable and effective utilization of solar energy. The method utilized metal-organic frameworks (MOFs) as a precursor to form rough layered double hydroxides (LDH) on the wood surface through hydrolysis-induced exchange. Subsequently, polypyrrole (PPy) was deposited through vapor phase onto the LDH, and paraffin wax (PW) is utilized as the phase change material to prepare a novel composite phase change material. This modified wood structure facilitates leak-proof PW encapsulation and effective heat storage (167.6 J/g). PPy acts as a proficient photothermal converter and improves the composite material's heat transfer efficiency by establishing thermal conduction pathways, resulting in an 87.4 % enhancement in thermal conductivity compared to pure PW. The rough surface of LDH promotes multiple light reflections and scattering within the material, leading to increased light absorption by the PPy coating and achieving a photothermal conversion efficiency of up to 96.4 %. Furthermore, the high roughness of the LDH layer combined with the low surface energy of PW imparts superhydrophobic self-cleaning properties to the material, ensuring sustained effectiveness of the photothermal conversion coating over time. This research presents a viable approach for maintaining the cleanliness and efficiency of solar energy systems.

Rational Construction of Heterostructures with n‐Type Anti‐Barrier Layer for Enhanced Electrochemical Energy Storage

AbstractAs a type of 2D materials, layered double hydroxides (LDHs) have emerged as potential candidates for electrochemical energy storage materials. To address their challenges of limited active sites and sluggish charge transfer kinetics, etc., this work presents an ingenious synchronous topochemical pathway (STP) method that enables the in situ anchoring of numerous nanosized Co9S8 on the rigid layers of LDHs. These n‐type anti‐barrier layers, generated by the ohmic contact between a quasi‐metal (Co9S8) and n‐type semiconductor (LDHs), alter the energy band structure and electron states near the Fermi level, optimizing the intrinsic conductivity and deprotonation reaction barriers of LDH materials. The prepared NiCoAl‐LDHs@Co9S8 (LCS) electrode exhibits remarkable electrochemical capacity (473.2 mAh g−¹ at 1 A g−¹) and operational stability (91.2% capacity retention after 20,000 cycles). Furthermore, an aqueous battery device constructed with LCS cathode and Fe‐Ni sulfide (FNS) anode demonstrates an impressive energy density of 118.5 Wh kg−¹ at a power density of 800 W kg−¹. This generalized structural design strategy achieves multiple enhancements in active sites, charge transfer efficiency, and structural stability of LDH materials, providing insights into the potential relationships between energy band and electrochemical performance in energy storage materials.

Ball-Milling Enhanced UV Protection Performance of Ca2Fe-Sulisobenzone Layered Double Hydroxide Organic Clay.

Using a co-precipitation technique, the anionic form of sulisobenzone (benzophenone-4) sunscreen ingredient was incorporated into the interlayer space of CaFe-hydrocalumite for the first time. Using detailed post-synthetic millings of the photoprotective nanocomposite obtained, we aimed to study the mechanochemical effects on complex, hybridized layered double hydroxides (LDHs). Various physicochemical properties of the ground and the intact LDHs were compared by powder X-ray diffractometry, N2 adsorption-desorption, UV-Vis diffuse reflectance, infrared and Raman spectroscopy, scanning electron microscopy and thermogravimetric measurements. The data showed significant structural and morphological deformations, surface and textural changes and multifarious thermal behavior. The most interesting development was the change in the optical properties of organic LDHs; the milling significantly improved the UV light blocking ability, especially around 320 nm. Spectroscopic results verified that this could be explained by a modification in interaction between the LDH layers and the sulisobenzone anions, through modulated π-π conjugation and light absorption of benzene rings. In addition to the vibrating mill often used in the laboratory, the photoprotection reinforcement can also be induced by the drum mill grinding system commonly applied in industry.

Zipper‐Like Interlocked Heterostructure of NiFe Layered Double Hydroxide‐WN for Super‐Stable Oxygen Evolution over 4500 h

AbstractThe nickel‐iron based materials are widely studied as excellent oxygen evolution reaction (OER) electrocatalysts. However, its relatively poor OER stability limits its practical applications. Herein, a zipper‐like interlocked heterostructure of NiFe layered double hydroxide (LDH)‐WN is constructed. The NiFe LDH‐WN exhibits not only ultrahigh OER activity of 228 mV overpotential at a current density of 50 mA cm−2, but also extremely long‐term stability over 4500 h at 50 mA cm−2 and over 550 h at an industrial current density ≈350 mA cm−2, which is ascribed to its special zipper‐like interlocked structure. Moreover, in situ Raman confirms that the presence of WN can efficiently achieve NiFe LDH reconstruction to slower the metal dissolution during OER, and therefore boosts its stability. DFT calculations reveal that WN not only can increase the *O adsorption capability and conductivity of NiFe LDH layer, but also can anchor the metal atoms of NiFe LDH layer to improve the dissolution energy barrier. In short, this work presents a new method of constructing the interlocked heterostructure to improve the OER stability of Ni‐Fe‐based catalysts, which would accelerate its practical application.

Development of a low carbon binder system based on metakaolin: Focus on corrosion inhibitor-intercalated layered double hydroxides

In this work, MgO-CaO activated blends were produced by using metakaolin (MK). Roles of sodium nitrite (NaNO2) corrosion inhibitor on phase assemblance, micro-structure, and chloride binding of layered double hydroxides (LDH) in the systems were systematically studied. The results showed that the compressive strength in the middle and late stages were increased for 32.78% and 73.74% with the addition of CaO, and pore structure of the MgO-CaO-MK blends was optimized. After the addition of 5% NaNO2, NO2− anions were preferably intercalated into the layers of self-formed MgAl LDH and CaAl LDH. The chloride binding capacity of the samples was stronger than that of cement paste, which was attributed to the generation of more LDH by accelerating hydration of the system.

Desorption behavior of phosphate species from layered double hydroxides

In phosphate species recovery, layered double hydroxides (LDHs) are good adsorbent, but show difficulties in its desorption. In this study, the desorption behavior was systematically investigated by changing several factors, which were drying condition, change with time, crystallinity and solution for desorption. Interlayer space of PO4-exchanged LDHs could swell by adding water one day after synthesis when the LDHs were vacuum dried at 25 °C. However, the swelling ability was deteriorating with time, and was also lost by oven-drying at 110 °C. In the case of high-crystallinity LDH, clear results were observed: desorption ratio of phosphate species from the vacuum-dried LDH decreased with time even by 1 M NaOH which was the most effective, and desorption ratios of phosphate species from the oven-dried LDH dropped sharply. In contrast, SO4-exchanged LDH, which were used for comparison, did not lose their swelling ability, and desorption ratios of sulphate were almost unchanged over time or by oven-drying at 110 °C. PO4-exchanged LDH stored in aqueous suspensions did not lose their swelling ability with time, and their desorption ratios of phosphate species remained unchanged over time. Therefore, above results suggest that interaction between phosphate species and host layers of LDHs in dried state causes the changes. In conclusion, the result that phosphate species desorption from dried high-crystallinity LDH deteriorated with time has not been reported previously, which will give a great impact on applications such as recovery of phosphate and slow release of phosphate.

A Novel Coating System Based on Layered Double Hydroxide/HQS Hierarchical Structure for Reliable Protection of Mg Alloy: Electrochemical and Computational Perspectives.

Growing research activity on layered double hydroxide (LDH)-based materials for novel applications has been increasing; however, promoting LDH layer growth and examining its morphologies without resorting to extreme pressure conditions remains a challenge. In the present study, we enhance LDH growth and morphology examination without extreme pressure conditions. By synthesizing Mg-Al LDH directly on plasma electrolytic oxidation (PEO)-treated Mg alloy surfaces and pores at ambient pressure, the direct synthesis was achieved feasibly without autoclave requirements, employing a suitable chelating agent. Additionally, enhancing corrosion resistance involved incorporating electron donor-acceptor compounds into a protective layer, with 8-Hydroxyquinoline-5-sulfonic acid (HQS) that helps in augmenting Mg alloy corrosion resistance through the combination of LDH ion-exchange ability and the organic layer. DFT simulations were used to explain the mutual interactions in the LDH system and provide a theoretical knowledge of the interfacial process at the molecular level.

Tungstate Intercalated NiFe Layered Double Hydroxide Enables Long-Term Alkaline Seawater Oxidation.

Renewable electricity-driven seawater splitting presents a green, effective, and promising strategy for building hydrogen (H2)-based energy systems (e.g., storing wind power as H2), especially in many coastal cities. The abundance of Cl- in seawater, however, will cause severe corrosion of anode catalyst during the seawater electrolysis, and thus affect the long-term stability of the catalyst. Herein, seawater oxidation performances of NiFe layered double hydroxides (LDH), a classic oxygen (O2) evolution material, can be boosted by employing tungstate (WO4 2-) as the intercalated guest. Notably, insertion of WO4 2- to LDH layers upgrades the reaction kinetics and selectivity, attaining higher current densities with ≈100% O2 generation efficiency in alkaline seawater. Moreover, after a 350h test at 1000mAcm-2, only trace active chlorine can be detected in the electrolyte. Additionally, O2 evolution follows lattice oxygen mechanism on NiFe LDH with intercalated WO4 2-.

Waterborne epoxy coating with excellent barrier and self-healing properties for long-term corrosion protection

Herein, an intelligent anticorrosive coating with superior barrier and self-healing properties was prepared. Molybdate (MoO42−) intercalated layered double hydroxide (MIH) was synthesised and polydopamine (PDA) shell was grown on MIH surface to prepare MIH@PDA (PMIH) material. PMIH was assembled on graphene (Gr) sheet through π–π interaction to obtain the Gr@PMIH composite. The anticorrosive coating was prepared by incorporating Gr@PMIH into the epoxy resin. The PMIH material demonstrated a stimulus-response capacity due to the solubility of polydopamine in acidic conditions. In addition, the ion-exchange properties of the layered double hydroxide (LDH) facilitated the release of the encapsulated molybdate corrosion inhibitor between LDH layers and the adsorption of chloride ions. This mechanism was corroborated by ultraviolet–visible (UV–vis) spectroscopy results. Electrochemical impedance spectroscopy (EIS) results revealed that the incorporation of MIH and Gr@PMIH materials considerably enhanced the low-frequency (0.01 Hz) impedance modulus. Among the tested ratios, Gr@PMIH/waterborne epoxy coatings (WECs) (3:7) exhibited the most effectively long-term corrosion protection. EIS measurements of the scratched coatings confirm the superior corrosion resistance and inhibition properties of Gr@PMIH/WECs (3:7). Furthermore, after 400 h of salt spray testing, substrates coated with Gr@PMIH/WECs (3:7) showed the least amount of corrosion products and blisters around surface scratches, affirming its exceptional long-term corrosion protection performance. Thus, the excellent barrier and stimuli-responsive characteristics of the Gr@PMIH material endowed the coating with enhanced long-term corrosion resistance and intelligent protection capabilities.

Sustained antibacterial release of zwitterionic globular hyperbranched polymer dots intercalated into layered double hydroxides.

This study introduces zwitterionic hyperbranched polymer (HBP) dots intercalated into layered double hydroxides (LDHs) for sustained antibacterial release. The proposed zwitterionic HBPs possess a three-dimensional spherical structure; unconventional blue fluorescent luminescence; water solubility; abundant COOH, amine, and amide functional groups; anionic exchangeability for intercalating into LDH interlayers; and sustained-release antibacterial activity. The intercalation for the layered nanomaterials was determined by adding different weight ratios of HBPs to Mg-Al LDHs to investigate the changes in the interlayer distance. X-ray diffraction revealed that the LDH layer spacing increased from 8.6 to 25.5 Å, effectively expanding the interlayer spacing with increasing HBP intercalation. Additionally, Fourier-transform infrared spectroscopy revealed the functional groups of the intercalated nanohybrids. Because the peripheral functional groups of HBPs are amino (-NH2) groups, preliminary evaluations revealed that pristine HBPs exhibited antibacterial properties. We further examined the antibacterial properties of the HBP/LDH nanohybrids. The results showed that HBPs combined with LDHs' controllable release properties can effectively achieve long-term sustained antibacterial release.

Preparation of hydrophobic layered double hydroxide-based composite pigments via octyltriethoxysilane surface modification for cosmetic applications.

Pigments play a pivotal role in the cosmetic industry, in which the development of pigments with concurrent color diversity, hydrophobicity, biocompatibility and photostability remains a great challenge. Herein, we report organic-inorganic composite pigments synthesized via a combination of organic dye anions (Ponceau SX and acid green (AG)), layered double hydroxides (LDHs) and octyltriethoxysilane (OTEOS) (denoted as O/Dye-LDHs: O/SX-LDHs and O/AG-LDHs).The prepared composite pigments were characterized via a comprehensive investigation based on X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS-mapping), Fourier transform infrared (FT-IR) spectroscopy, CIE 1976 L*a*b* color scales, static contact angle measurement and HET-CAM assay. The results confirm the successful intercalation of organic dye anions into the interlayer region of LDHs via host-guest interactions and the surface modification of OTEOS on the layer surface, forming a new kind of hydrophobic organic-inorganic composite pigment with a sandwich structure. LDH layer protection and OTEOS coating play crucial roles in the high photostability, good hydrophobicity and satisfactory biocompatibility of pigments. In addition, O/Dye-LDHs exhibit rich color and color adjustability. Impressively, we applied mixture composite pigments with different O/SX-LDH-to-O/AG-LDH ratios to formulate an eye shadow cream, which present a series of popular and natural colours with water resistance to enhance one's attractiveness and appearance. This work provides a promising strategy for the design of safe and efficient composite pigments, demonstrating their potential application in the field of makeup.

Multifunctional Biocompatible Nanoparticles: Surface Modification and Synthesis of Layered Double Hydroxides for Biomedical Applications

Layered Double Hydroxides (LDHs) are considered versatile materials owing to their distinctive features resulting from the isomorphous substitution of metal cations, namely M(II) and M(III), inside their octahedral locations. The LDH layer structure is characterized by a balanced arrangement of exchangeable hydrated or solvated anions within the interlayer and outer regions. This arrangement gives rise to a two-dimensional heterostructure with an ABAB pattern. Various metal cations have a role in LDHs composition, leading to their classification as hydrocalumites and hydrotalcite. Pristine-LDHs that include diverse inorganic anions have shown significant potential in biological applications. These substances have been investigated for their potential use in many applications, including but not limited to antacids, vaccination adjuvants, etc. The attainment of monodispersity in the size of LDHs is of utmost importance for their efficacy in biomedicine. This research emphasizes that the potential of LDHs is contingent upon effectively resolving difficulties, including those associated with size polydispersity. This study suggests using Surface Modified and Synthesized Layered Double Hydroxides for Biomedical Applications (SMS-LDH-BMA). The present study presents a novel approach that incorporates various enhancements, such as a decreased hydrodynamic diameter of 44.6 nm, a zeta potential of -23.86 mV, a high encapsulation efficiency of 91.2%, a substantial drug loading capacity of 14.6%, a favorable cell viability of 96.44%, and a controlled release rate of GLIB at 3.73 μg/mL/min. These findings demonstrate the efficacy of SMS-LDH-BMA in tackling these obstacles and augmenting the drug delivery capabilities and biomedical applications of LDHs.

Improving corrosion and wear resistances of 2195 Al–Li alloy by PEO and LDHs composite coating

In this study, a composite coating comprising a ceramic film and layered double hydroxide (LDHs) layer was prepared on the surface of extruded 2195 Al–Li alloy. The preparation method, surface morphology, and chemical composition of the coating were described and characterized in detail. The corrosion and wear protection of the coating on the Al–Li alloy substrate were tested, and the mechanisms of corrosion and wear resistance were discussed. The results indicate that plasma electrolytic oxidation processing can form a thick ceramic film with good interface bonding on the surface of 2195 Al–Li alloy. Hydrothermal reaction in an alkaline solution produces a nanoscale layer of Mg/Al LDHs on the surface of the ceramic film. The LDHs layer fills the micro-pores and cracks in the film and effectively prevents the corrosion medium from permeating and damaging the alloy matrix. The composite coating reduces the surface corrosion efficiency by 99.98 %. Moreover, the composite-coated samples exhibit long-lasting corrosion resistance in seawater and exfoliation corrosion environments. Additionally, the composite-coated Al–Li alloy exhibits wear resistance 1-2 orders of magnitude higher than that of the bare alloy at both room and high temperatures. This study proposes a novel strategy for corrosion and wear protection of Al–Li alloys.

Influence of Mg substrate on the formation mechanism and corrosion resistance of LDH films

Layered double hydroxides (LDH) layer has been synthesized on various Mg substrates (pure Mg, MgLi and AZ91 alloy) under atmospheric pressure. Presence of alloying elements resulted in formation of a new composition and accelerated film growth rate. Li promoted homogeneous growth of LDH film, while the cathodic intermetallics in AZ91 Mg resulted in heterogeneous growth and formation of a porous LDH film, leading to deteriorated corrosion resistance. The dense MgLi LDH layer demonstrated high impedance value (4030 Ω·cm2) after 240 h electrochemical impedance spectroscopy (EIS) test, which was much higher than that of the substrate (146 Ω·cm2).

Study on the Thermal Stabilizing Process of Layered Double Hydroxides in PVC Resin

Poly(vinyl chloride) (PVC) is widely used in various fields and requires the use of thermal stabilizers to enhance its thermal stability during processing because of its poor thermal stability. Layered double hydroxides (LDHs) are widely considered to be one kind of highly efficient and environmentally friendly PVC thermal stabilizer. To investigate the thermal stabilizing process of layered double hydroxides (LDHs) in PVC resin, PVC and MgAl-LDHs powders with different interlayer anions (CO32−, Cl−, and NO3−) were physically mixed and aged at 180 °C. The structure of LDHs at different aging times was studied using XRD, SEM, and FT-IR. The results show that the thermal stabilizing process of LDHs on PVC mainly has three stages. In the first stage, the layers of LDHs undergo a reaction with HCl, which is released during the thermal decomposition of PVC. Subsequently, the ion exchange process occurs between Cl− and interlayer CO32−, resulting in the formation of MgAl-Cl-LDHs. Finally, the layers of MgAl-Cl-LDHs react with HCl slowly. During the thermal stabilizing process of MgAl-Cl-LDHs, the peak intensity of XRD reduces slightly, and no new XRD peak emerges. It indicates that only the first step happens for MgAl-Cl-LDHs. The TG-DTA analysis of LDHs indicates that the interaction of LDHs with different interlayer anions has the following order: NO3− < CO32− < Cl−, according to the early coloring in the thermal aging test of PVC composites. The results of the thermal aging tests suggest that LDHs with a weak interaction between interlayer anions and layers can enhance the early stability of PVC significantly. Furthermore, the thermal aging test demonstrates that LDHs with high HCl absorption capacities exhibit superior long-term stabilizing effects on PVC resin. This finding provides a valuable hint for designing an LDHs/PVC resin with a novel structure and excellent thermal stability.

Layered double hydroxide loaded pinecone biochar as adsorbent for heavy metals and phosphate ion removal from water

This study modified pinecone biochar with a novel layered double hydroxide (LDH) to enhance its capacity to adsorb heavy metal and phosphate ions from water. The unmodified pinecone biochar demonstrated moderate adsorption capacities for Cu2+ (25.0 mg/g), Co2+ (24 mg/g), Pb2+ (22.9 mg/g), and phosphate (36.0 mg/g). However, after LDH modification, the LDH-biochar showed significantly improved adsorption capacities for Pb2+ (135.9 mg/g) and phosphate (160.8 mg/g) and a slight increase for Cu2+ (30.6 mg/g) and Co2+ (28.0 mg/g). The LDH layer enhances the adsorption of Pb2+ through ion exchange, phosphate through surface precipitation, and Cu2+ and Co2+ through surface complexation. The integration of LDH creates a multifaceted layer that utilizes various mechanisms to boost the biochar's adsorption capacity.