Layered Double Hydroxides Surface Research Articles

Hydrogen bond-induced configuration and electron transfer on layered double hydroxide for high-performance sodium-iodine batteries

Sodium-iodine (Na-I2) batteries are appealing electrochemical energy storage devices owing to the low cost and high energy density. However, they are constrained by shuttle effect due to the high solubility of iodine/iodide in electrolyte and the sluggish reaction kinetics of I2 ↔ 2I−. Accordingly, Na-I2 batteries with superficial redox mechanism and superior rate capability almost seem impossible. Herein, a layered double hydroxide (LDH) formulated as Ni2Al(OH)4.2(CO3)1.4·2H2O (NiAl-LDH) and an iodine-decorated LDH (NiAl-LDH-I2) were synthesized. When used as the Na-I2 battery cathode in the NaClO4 electrolyte, NiAl-LDH-I2 exhibits an increasing capacity, accompanied with a transformation from the (de)intercalation to the surface-controlled (pseudo)capacitive behavior. This is ascribed to irreversible reduction reaction of ClO4− → Cl− and the formation of I+-Cl− on the LDH surface over an overcharge process. Density functional theory (DFT) calculations reveal that the adsorbed I2 and I-Cl both exhibit zigzag chain-like configurations, which are not easily intercalated into the interlayer space of NiAl-LDH, but can be anchored on the NiAl-LDH surface via multiple hydrogen bonds. These hydrogen bonds can stabilize I+ to boost the multi-electron redox reaction of 2I− ↔ I2 ↔ 2I+. The adsorbed I2 is activated by the electron transfer and the elongation of I-I bond, then fasten the reaction kinetics of I2 ↔ 2I−. Therefore, NiAl-LDH-I2 shows outstanding rate capability and cycling performance with a large capacity of 310/ 210 mAh/g at 0.3/ 1.5 A/g and excellent capacity retention over 2700 cycles.

Removal of Metribuzin and Bentazon by LDH-HA Modified Material: Kinetic and Equilibrium Study

ABSTRACT This study investigates the adsorption behavior of herbicides Metribuzin and Bentazon using a soil model incorporating Layered Double Hydroxide (LDH) and humic acid. Mg3AlCl-LDH, synthesized at pH 10, was combined with humic acid to produce two distinct materials: Mg3–5%HA and Mg3–10%HA. These materials were characterized using FTIR, XRD, and SEM techniques. The research confirms that humic acid adsorbs onto the LDH surface without altering its structure, resulting in negatively charged materials. While both materials fully adsorb Metribuzin at 20 mg/L, their adsorption capacities diverge at higher concentrations, with Mg3–10%HA exhibiting a higher capacity than Mg3–5%HA. In contrast, Bentazon’s adsorption is unaffected by humic acid content, displaying identical adsorption capacities in both materials at different concentrations. Both herbicides exhibit rapid adsorption kinetics, reaching equilibrium in 15 minutes. The Avrami model accurately predicts equilibrium adsorption capacities, with Metribuzin primarily adsorbed through electrostatic attraction and hydrogen bonding, while Bentazon’s adsorption is limited due to electrostatic repulsion. The adsorption of both herbicides by Mg3-HA materials is not influenced by pH variations, likely due to the surface charge of the materials. Metribuzin retention in soil containing LDH and humic acid is effective, increasing with higher humic acid concentrations, whereas Bentazon demonstrates greater mobility and resistance. These findings provide valuable insights for developing efficient water decontamination techniques, with implications for environmental protection and public health. Policymakers, researchers, and professionals in water management and pollution control should consider these findings to enhance current practices and technologies.

Efficient phosphate removal by Mg-La binary layered double hydroxides: synthesis optimization, adsorption performance, and inner mechanism.

Layered double hydroxides (LDH) hold great promise as phosphate adsorbents; however, the conventional binary LDH exhibits low adsorption rate and adsorption capacity. In this study, Mg and La were chosen as binary metals in the synthesis of Mg-La LDH to enhance phosphate efficient adsorption. Different molar ratios of Mg to La (2:1, 3:1, and 4:1) were investigated to further enhance P adsorption. The best performing Mg-La LDH, with Mg to La ratio is 4:1 (LDH-4), presented a larger adsorption capacity and faster adsorption rate than other Mg-La LDH. The maximum adsorption capacity (87.23 mg/g) and the rapid adsorption rate in the initial 25 min of LDH-4 (70 mg/(g·h)) were at least 1.6 times and 1.8 times higher than the others. The kinetics, isotherms, the effect of initial pH and co-existing anions, and the adsorption-desorption cycle experiment were studied. The batch experiment results proved that the chemisorption progress occurred on the single-layered LDH surface and the optimized LDH exhibited strong anti-interference capability. Furthermore, the structural characteristics and adsorption mechanism were further investigated by SEM, BET, FTIR, XRD, and XPS. The characterization results showed that the different metal ratios could lead to changes in the metal hydroxide layer and the main ions inside. At lower Mg/La ratios, distortion occurred in the hydroxide layer, resulting in lower crystallinity and lower performance. The characterization results also proved that the main mechanisms of phosphate adsorption are electrostatic adsorption, ion exchange, and inner-sphere complexation. The results emphasized that the Mg-La LDH was efficient in phosphate removal and could be successfully used for this purpose.

Oleic acid-modified layered double hydroxide for Pickering emulsions: (I) Interfacial properties

Layered double hydroxides (LDHs) are one type of potential emulsifiers for Pickering emulsions. Surface modification can regulate their surface properties, thereby affecting their emulsifying behavior. However, there is still a lack of full understanding of the impact of surface modification on their surface properties. In the current work, one Mg3Al-Cl LDH was modified using oleic acid (OA), obtaining six OA-modified products with different OA loadings. Their contact angles and relative dielectric constants were determined, and their surface properties including the interfacial free energies (γ) and solubility parameters (δ) were then estimated from the data. Their apparent molar volumes were estimated using the γ and δ data. OA molecules are coated on the LDH surface via the bidentate bonding mode to form monolayers. The OA modification has no obvious impact on the structure and morphology of LDH particles, but can significantly affect their surface properties. This work provides a better understanding of the dependence of surface properties of LDHs on the surface modification.

Surface-Modified LDH Nanosheets with High Dispersibility in Oil for Friction and Wear Reduction.

Surface and interfacial engineering of nanomaterials is essential for improving dispersion stability in liquids. In this study, we report that oleic acid (OA)- and stearic acid (SA)-functionalized layered double hydroxide (LDH) nanosheets as lubricant additives can achieve high dispersion and reduce friction and wear. LDH is a typical layered structure, and OA and SA are long-chain organic molecules that are not only compatible with base oils but also act as friction-reducing agents. The OA and SA molecules were branched onto ZnMgAl LDH nanosheets using dehydration condensation between the exposed OH groups on the surface of LDH and the COOH groups on the OA and SA molecules. Compared with that of the pristine ZnMgAl LDH, the dispersion of OA-ZnMgAl LDH and SA-ZnMgAl LDH was significantly improved. The surface-modified LDH exhibited superior tribological properties and great stability due to the synergistic lubrication effect between OA, SA, and LDH. Even at an ultralow concentration (0.15 wt %), the coefficient of friction and wear volume were reduced by ∼65 and ∼99%, respectively, compared to those of the base oil. Due to the green and simple synthesis method and excellent tribological properties, surface-functionalized LDH has enormous possibilities for future industrial applications.

The preparation of layered double hydroxide wrapped with triazine-based organic framework to enhance the flame retardancy for polypropylene

Layered double hydroxide (LDH) can be used as a flame retardant (FR) for polypropylene (PP) because of its excellent flame retardancy and smoke-suppression effects. However, the agglomeration of LDH seriously affects its dispersity in the PP matrix, thus limiting its application as a FR polymer. This study aimed to enhance the dispersion of LDH in the PP matrix for improving its flame retardancy performance. Herein, a reactive triazine-based organic framework (TOF) was designed and formed by the in situ polymerisation of cyanuric chloride and melamine, and then the LDH surface was covered with TOF to obtain a novel core–shell FR (LDH@TOF), with TOF as the ‘shell’ and LDH as the ‘core’. Subsequently, LDH@TOF was melted into the PP matrix as nanofillers to prepare PP and LDH@TOF composites (PP/LDH@TOF). As expected, the PP/LDH@TOF composites exhibited superior flame-retarding performance (limiting oxygen index of 29.2% and UL-94 V-0 rating) and favourable smoke-suppression performance at 20 wt% of LDH@TOF loading. Moreover, the peak heat release rate, total heat release and total smoke production of PP/LDH@TOF composites decreased by 29.9%, 12.1% and 12.4%, respectively, compared with those of PP and LDH composites. The outstanding flame retardancy properties of the PP/LDH@TOF composites were attributed to the better dispersibility of LDH@TOF in the PP matrix, the synergy of the physical barrier effect of nanosheets and the dense carbonisation acceleration of LDH@TOF. The findings of this study provide a highly efficient approach for functionalising LDH for expanding its application value of PP composites.

Evaluation of surface organic layered double hydroxides on the anti-ageing performance of asphalt

To promote the anti-ageing performance of asphalt, layered double hydroxides (LDHs) modified by propyl trimethoxylsilane (MPMS) was prepared and applied to modify asphalt. Fourier transform infrared spectroscopy (FTIR) showed that MPMS was chemically-grafted on the surface of LDHs. The interaction between LDHs and asphalt was significantly enhanced after MPMS organic modification, and MPMS organic LDHs (OMLDHs) exhibited better compatibility in asphalt. OMLDHs and LDHs could enhance the high-temperature properties of asphalt, particularly OMLDHs. After ageing, the properties and structure of asphalt were dramatically degenerated. The incorporation of LDHs could inhibit the oxygenic groups increase in asphalt molecules during ageing, and retard the gelatinization of colloidal structures. LDHs could alleviate the negative effect of ageing on asphalt, and improve the anti-ageing performance of asphalt. The improvement effectiveness of LDHs on the anti-ageing performance of asphalt was remarkably improved after MPMS modification.

Development of anti-corrosive coating on AZ31 Mg alloy modified by MOF/LDH/PEO hybrids

The self-assembly of hybrid inorganic-organic materials on stationary platforms plays a critical role in improving their structural stability and wide usability. In this work, a novel two-step hydrothermal approach is proposed for synthesizing stable and advanced hybrid coatings on metal-oxide platforms through the surface modification of layered double hydroxide (LDH) films using novel metal-organic frameworks (MOFs). Initially, Mg-Al LDH nanocontainers, grown on a magnesium oxide layer produced through plasma electrolytic oxidation (PEO) of AZ31 Mg alloy substrate, were intercalated with cobalt via an oxidation route, providing the metallic coordination center for the MOF formation. In the subsequent step, a pioneering technique is introduced, utilizing tryptophan as the organic linker for the first time at a pH of 10. The self-assembly of cobalt- tryptophan complex, driven by the strong bonding between electrophilic sites of monomers and nucleophilic sites, facilitated the formation of a MOF network having a cloud-like structure on the surface of MgAl LDH's film. The resulting MOF-LDH encapsulation containers demonstrate exceptional electrochemical stability when exposed to a 3.5 wt.% NaCl solution, surpassing the performance of PEO and pure LDH coatings. This enhanced stability is attributed to the development of a dense top layer and a stable composition within the self-assembled MOF, effectively sealing flaws and preventing the infiltration of corrosive ions into the underlying metallic substrate. The formation mechanism of MOFs on LDH galleries is investigated using density functional theory calculations.

Tetrahydrobiopterin inhibitor-based antioxidant metabolic strategy for enhanced cancer ferroptosis-immunotherapy

The induction of immunogenic ferroptosis in cancer cell is limited by the complex and delicate antioxidant system in the organism. Synergistic induction of oxidative damage and inhibition of the defensive redox system in tumor cells is critical to promote lethal accumulation of lipid peroxides and activate immunogenic death (ICD). To address this challenge, we present a multifunctional and dual-responsive layered double hydroxide (LDH) nanosheet to enhance immunogenic ferroptosis. The MTX-LDH@MnO2 nanoplatform is constructed by intercalating methotrexate (MTX) into LDH interlayers and electrostatically absorbing biomineralized ovalbumin (OVA)-MnO2 onto the LDH surface. Specifically, the released Mn2+ from the incorporated MnO2 triggers a Fenton-like reaction, leading to reactive oxygen species (ROS) accumulation, while the depletion of reduced glutathione (GSH) further intensifies oxidative stress, resulting in the induction of ferroptosis. MTX is released in response to the acidic environment of tumor cells and inhibits the regeneration of tetrahydrobiopterin (BH4), modulating the GTP cyclic hydrolase 1 (GCH1)/BH4 axis. MTX disrupts the antioxidant metabolic activity regulated by GCH1/BH4 axis and inhibits ROS consumption, further boosting the ferroptosis effect, which promoted the release of damage-associated molecular patterns (DAMPs) and triggered ICD in the tumor. This activation subsequently leads to significant antitumor immune reactions, including DCs maturation, infiltration of CD4+/CD8+ T cells and cytokines release. The redox-controllable nanoplatform demonstrates promising anticancer efficacy in a mouse breast model providing a novel strategy for cancer immunotherapy.

Synergy between Cu and Co in a Layered Double Hydroxide Enables Close to 100% Nitrate-to-Ammonia Selectivity.

Nitrate electroreduction (NO3RR) holds promise as an energy-efficient strategy for the removal of toxic nitrate to restore the natural nitrogen cycle and mitigate the adverse impacts caused by overfertilization from suboptimal agricultural practices. However, existing catalysts suffer from limited electrocatalytic activity, poor selectivity, inadequate durability, and low scalability. To address this quadrilemma, in this study, we developed a cost-effective layered double hydroxide (LDH) electrocatalyst with a lamellar structure that presents trimetallic CuCoAl active sites on the nanomaterial surface. This codoping design enabled electrochemical upcycling of nitrate into ammonia exclusively and efficiently with an onset potential at 0 V vs RHE, where the electrocatalytic process is less energy intensive and has a lower carbon footprint than conventional practices. The synergistic interaction among Cu, Co, and Al further afforded a 99.5% Faradic efficiency (FE) and a yield rate of 0.22 mol h-1 g-1 for nitrate-to-ammonia electroreduction, surpassing the performance of state-of-the-art nonprecious metal NO3RR electrocatalysts over an extended operation period. To gain insights into the origin of the catalytic performance observed on LDH, control materials were employed to elucidate the roles of Cu and Co. Cu was found to improve the NO3RR onset potential despite displaying limited FE for ammonia synthesis, while Co was discovered to suppress the formation of nitrite byproduct though requiring large overpotential. Simulated wastewater containing phosphate and sulfate, which are typically present in industrial effluents, was used to further investigate the effect of electrolytes on NO3RR. Intriguingly, the use of phosphate buffer resulted in a superior yield rate and FE for ammonia production while simultaneously inhibiting nitrite byproduct formation compared with the sulfate case. These experimental findings were supported by density functional theory (DFT) calculations, which explored the adsorption strength of nitrate adducts adjacent to coadsorbed electrolytes on the LDH surface. Additionally, the relative free energies of NO3RR species were also computed to examine the proton-coupled electron transfer (PCET) mechanism on CuCoAl LDH, shedding light on the potential-dependent step (PDS) and the exclusive selectivity for nitrate-to-ammonia conversion. The CuCoAl LDH developed here offers scalability by eliminating the need for precious metals, rendering this earth-abundant catalyst particularly appealing for sustainable nitrate electrovalorization technology.

Intercalation vs Adsorption Strategies of Myo-Inositol Hexakisphosphate into Zn-Fe Layered Double Hydroxide: A Tiff between Anion Exchange and Coprecipitation.

Myo-inositol hexakisphosphates (IHPs) or phytates are the most abundant organic phosphates having the potential to serve as a phosphorus reserve in soil. Understanding the fate of IHP interaction with soil minerals tends to be crucial for its efficient storage and utilization as a slow-release organic phosphate fertilizer. We have systematically compared the effective intercalation strategy of a phytate onto Zn-Fe layered double hydroxide (LDH) acting as storage/carrier material through coprecipitation and anion exchange. Powder X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, thermogravimetric analysis, FTIR spectra, and molecular modeling demonstrated the formation of phytate-intercalated Zn-Fe LDH through coprecipitation with a maximum loading of 41.34% (w/w) in the pH range of ∼9-10 in a vertical alignment through monolayer formation. No intercalation product was obtained from the anion exchange method, which was concluded based on the absence of shifting in the XRD (003) peak. A change in the zeta potential values from positive to negative and subsequent increase in solution pH, with decreasing phytate concentration, are suggestive of adsorption of IHP onto the LDH surface. The batch adsorption data were best fitted with Langmuir isotherm equation and followed the pseudo-second-order kinetic model. The maximum adsorption capacity was found to be 45.87 mg g-1 at a temperature of 25 ± 0.5 °C and pH 5.63.

Molecular-level insights into the corrosion protection mechanism of Mg/Al CO32−-LDH films on steel in aqueous chloride environments

Despite their thickness of only a few microns, layered double hydroxide (LDH) films offer excellent corrosion protection for steel. However, the lack of molecular-level comprehension of this protective mechanism has hindered the optimal design of LDH films. Herein, we developed a molecular model of Mg/Al-CO32−-LDH and investigated the nanoscale characteristics of water and ions in proximity to the LDH surface. Results underscore a robust attachment of water and ions to the LDH surface, accompanied by the attenuation of diffusion as they approach. The diffusion of interfacial water is predominantly influenced by H-bond interactions stemming from hydroxyl groups on the LDH surface. Additionally, the impediment of Cl− diffusion can be attributed to both anionic competition adsorption and the chemical bonding interactions of LDH.

Clay-based durable catalyst membranes of porous layered double hydroxide and gold nanoparticle nanocomposites for fast and continuous-flow reactions

We synthesized the hybrid catalyst of a porous layered double hydroxide (LDH) decorated with ultrasmall Au nanoparticles. The porous LDH was prepared by coprecipitation and ethanol washing, producing thin LDH nanoplatelets. Thereafter, spray drying was carried out, affording a few hundred nm of the hydrangea-like structure of the LDH with an extensive open network and a Brunauer–Emmett–Teller surface area of 386 m2/g. Its sizable open frame and active hydroxide surface enabled the uniform decoration of average 4-nm-diameter Au nanoparticles (Au/P-LDH) through one-pot chemical reduction using NaBH4 at room temperature. We applied the Au/P-LDH for the fabrication of catalyst membranes, which are potentially valuable for the continuous flow of catalytic reactions, e.g., the hydrogenation of p-nitrophenol. This study suggested that their porous structure and active Au nanoparticle catalyst allowed fast and mass catalytic functions by simple filtration without washing or catalyst recovery steps. We found no significant damage to the hybrid membrane during the reactions with a few liters; thus, we expect strong bindings of the Au nanoparticles on the surface of the porous LDH.

Regulating Surface Charge by Embedding Ru Nanoparticles over 2D Hydroxides toward Water Oxidation.

Exploring highly active and earth-abundant electrocatalysts for the oxygen evolution reaction (OER) is considered one of the prime prerequisites for generating green hydrogen. Herein, a competent microwave-assisted decoration of Ru nanoparticles (NPs) over the bimetallic layered double hydroxide (LDH) material is proposed. The same has been used as an OER catalyst in a 1 M KOH solution. The catalyst shows an interesting Ru NP loading dependency toward the OER, and a concentration-dependent volcanic relationship between electronic charge and thermoneutral current densities has been observed. This volcanic relation shows that with an optimum concentration of Ru NPs, the catalyst could effectively catalyze the OER by obeying the Sabatier principle of ion adsorption. The optimized Ru@CoFe-LDH(3%) demands an overpotential value of only 249 mV to drive a current density value of 10 mA/cm2 with the highest TOF value of 14.4 s-1 as compared to similar CoFe-LDH-based materials. In situ impedance experiments and DFT studies demonstrated that incorporating the Ru NPs boosts the intrinsic OER activity of the CoFe-LDH on account of sufficient activated redox reactivities for both Co and lattice oxygen of the CoFe-LDH. As a result, compared with the pristine CoFe-LDH, the current density of Ru@CoFe-LDH(3%) at 1.55 V vs RHE normalized by ECSA increased by 86.58%. First-principles DFT analysis shows that the optimized Ru@CoFe-LDH(3%) possesses a lower d-band center that indicates weaker and more optimal binding characteristics for OER intermediates, improving the overall OER performance. Overall, this report displays an excellent correlation between the decorated concentration of NPs over the LDH surface which can tune the OER activity as verified by both experimental and theoretical calculations.

Enhancing the Surface-Active Sites of Bimetallic 2D Hydroxide Materials by Introducing Fe2+ Ions toward Effective Hydroxide Adsorption for the Water Oxidation Reaction

Here, in this work, via a simple wet chemical method, we have modified the CoFe layered double hydroxide (LDH) surface by doping active Fe2+ ions which function as an excellent electrocatalyst for the oxygen evolution reaction (OER) in 1 M KOH. Variations in the amount of Fe2+ ions show a noteworthy concentration dependency on the electrochemical performance of the catalyst. The catalyst shows an interesting Fe2+ ion dependency toward the OER, and a volcanic relationship between accumulated electronic charge and thermoneutral current densities is observed. This volcanic relation shows that with an optimum concentration of Fe2+ ions, the catalyst could effectively catalyze the OER by following the Sabatier principle of ion adsorption. The LDH having an intermediate amount of Fe2+ loading {FeII-LDH (0.04 M)} shows the highest OER activity, and it demands just a 268 mV overpotential to drive a 10 mA/cm2 current density, whereas the pristine CoFe-LDH displays an overpotential of 345 mV. Also, as a result of introducing Fe2+ ions, a 4-fold increase in the turnover frequency (TOF) value was noticed. Operando in situ impedance analysis reveals that the introduction of Fe2+ ions in the pristine CoFe-LDH lattice largely improvises the charge transfer kinetics at the interface by providing a greater number of surface-active sites toward OH– adsorption. Overall, this study shows an interesting Fe2+ ion loading dependency over the LDH surface toward the water oxidation reaction.

The Effect of Lithium Ion Leaching from Calcined Li-Al Hydrotalcite on the Rapid Removal of Ni2+/Cu2+ from Contaminated Aqueous Solutions.

A layered double hydroxide (LDH) calcined-framework adsorbent was investigated for the rapid removal of heavy metal cations from plating wastewater. Li-Al-CO3 LDH was synthesized on an aluminum lathe waste frame surface to prepare the sorbent. The calcination treatment modified the LDH surface properties, such as the hydrophilicity and the surface pH. The change in surface functional groups and the leaching of lithium ions affected the surface properties and the adsorption capacity of the heavy metal cations. A zeta potential analysis confirmed that the 400 °C calcination changed the LDH surface from positively charged (+10 mV) to negatively charged (-17 mV). This negatively charged surface contributed to the sorbent instantly bonding with heavy metal cations in large quantities, as occurs during contact with wastewater. The adsorption isotherms could be fitted using the Freundlich model. The pseudo-second-order model and the rate-controlled liquid-film diffusion model successfully simulated the adsorption kinetics, suggesting that the critical adsorption step was a heterogeneous surface reaction. This study also confirmed that the recovered nickel and/or copper species could be converted into supported metal nanoparticles with a high-temperature hydrogen reduction treatment, which could be reused as catalysts.

Synergistic enhancement of flame retardancy of epoxy resin by layered zirconium phenylphosphate modified layered double hydroxides

While water-based epoxy coatings have been welcomed by the market due to their excellent environmental performance and low volatile organic compounds emission, its poor flame retardancy has led to limited applications. Herein, the catalytic char formation effect of zirconium phenylphosphonate (ZrPP) and the excellent flame retardant properties of layered double hydroxide (LDH) were fully combined to obtain a high-performance composite flame retardant coating. Specifically, polydopamine (PDA) with excellent adhesion properties was encapsulated on the surface of LDH to enhance its dispersibility in water. The introduction of PDA provided abundant active sites for the adsorption of ZrPP precursor cations, which contributed to the uniform loading of ZrPP on LDH to obtain well-structured LDH@PDA@ZrPP (LPZP) hybrids. The synergistic effect of LDH and ZrPP on the flame retardant properties of the epoxy resin matrix was investigated. The LPZP4%/EP sample showed the lowest backside temperature (173.6 °C), maximum expansion height (25.10 mm) and expansion rate (20.10), proving its highest thermal insulation effect. In the TGA test, the residual char of LPZP4%/EP increased to 26.8 %, proving the excellent thermal stability of the coating. The SEM images showed that the internal char layer of the composite coating formed a honeycomb network structure, which increased the heat absorption property of the char layer.

Effect of different organic layered double hydroxides on the anti-aging property of bitumen

Two organic layered double hydroxides (LDHs) were synthesized and utilized to enhance the anti-aging property of bitumen. Fourier infrared spectroscopy and X-ray diffraction showed that sodium dodecyl sulfate was intercalated into the interlayers of LDHs (I-LDHs), and γ-(2,3-Epoxypropoxy)propyltrimethoxy silane was chemically grafted onto the surface of LDHs (S-LDHs). Compared with LDHs, organic LDHs possessed better compatibility and organic LDHs modified bitumen exhibited better performance in high-temperature regions, especially S-LDHs. After aging, the rheological properties dramatically deteriorated. The content of aromatic in bitumen evidently decreased, and the asphaltene noteworthy increased, the colloid structure verged on the gel system. The incorporation of LDHs could relieve the damage of aging on the rheological properties and colloid structure, and strengthen the anti-aging property of bitumen. Moreover, the consequence of LDHs had been further enhanced obviously after organic modification, and S-LDHs exhibited more excellent performance compared with I-LDHs.

Synergetic Removal of Pb(II)- and Sulfonamide-Mixed Pollutants using Ni/Co Layered Double Hydroxide Nanocages Coupled with Peroxymonosulfate

Organic pollutants are often present in wastewater coupled with toxic metallic ions, which are harmful to both human beings and the ecological environment, and their simultaneous removal is of great significance. In this work, hollow Ni/Co layered double hydroxide (LDH) nanocages were synthesized through the hydrothermal method by using zeolitic imidazolate framework-67 as a self-sacrificial template, and it was further used as a catalyst to activate peroxymonosulfate (PMS) for sulfonamide (SA) degradation and an adsorbent for Pb(II) removal simultaneously. The materials were characterized using various techniques, and the effect of parameters including the dosage of the catalyst and PMS, initial temperature, and pH on the performances of the LDH nanocage was investigated. Nearly 80% of SA (15 mg/L) could be degraded via PMS activation, whereas ∼93% of Pb(II) (20 mg/L) could be removed simultaneously within 60 min. During the reaction, there were redox cycles for both Co and Ni over the surface of LDH, but Pb did not participate in the process, and it had a slightly negative effect on SA degradation. The quenching experiments and the electron paramagnetic resonance results showed that the radicals (•OH, •SO4–, O2•–, and 1O2) generated from PMS activation participated in the process. Finally, the possible mechanism and degradation pathways were proposed, based on the intermediate products identified, and the toxicity of the intermediate products was evaluated.

New findings on the contribution of Mg-Al-NO3 layered double hydroxides to the hydration and chloride binding capacity of cement pastes

The impact of the addition of layered double hydroxides (LDHs) on binding of chloride ions was studied by pore expression experiments. A Mg-Al-NO3 type of LDHs was added to paste samples blended with 3 % NaCl in different proportions (4 % and 10 % by mass of the binder). In addition, the influence of LDHs on the hydration process, morphology and porosity of samples containing Portland cement, calcium sulphoaluminate cement and silica fume was investigated. The potential physical and chemical contributions of LDHs to the system (e.g. AFm formation) were discussed comprehensively. According to the results, addition of LDHs by 10 % could reduce the chloride content in the pore solution by over 25 % and increase the carbonate AFm phases. Moreover, formation of reaction products on the LDH grains was observed. Finally, it was clear that a part of the Cl− ions is bound to the surface of LDHs and can be washed out.