Layered Double Hydroxides Samples Research Articles

Interlayer anions modulated ZnAl-layered double hydroxides for enhanced photocatalytic CO2 reduction

Photocatalytic CO2 reduction has drawn widespread attention across all sectors of society. Layered double hydroxides (LDHs) have emerged as promising photocatalysts, renowned for their adjustable bandgaps and reaction sites. As a typical anionic layered material, LDHs exhibit intricate interactions between interlayer anions and brucite-like metal layers, greatly influencing their inherent physicochemical properties. In this work, we synthesized ZnAl-LDH samples intercalated with four distinct anions: carbonate (CO32–), chloridion (Cl–), nitrate (NO3–), and dodecyl sulfate (DS–), denoted as LDH-CO3, LDH-Cl, LDH-NO3, and LDH-DS, respectively. These LDHs samples have comparable crystallinity and morphology but differ in their interlayer spacing. XRD results reveal interlayer spacings of 0.77 nm for LDH-CO3, 0.78 nm for LDH-Cl, 0.88 nm for LDH-NO3, and 1.24 nm for LDH-DS, between adjacent brucite-like ZnAl hydroxide layers. Remarkably, LDH-NO3 demonstrates the highest photocatalytic CO2 reduction performance, with CO as the primary reduction product. Specifically, the average CO production rate of LDH-NO3 are 3.80 μmol g–1 h–1, surpassing that of LDH-CO3, LDH-Cl, and LDH-DS by 1.9, 2.1, and 2.5 times, respectively. This superior performance can be attributed to the intermediate interlayer spacing of LDH-NO3, which facilitates strong light absorption and a robust local built-in electric field. Theses properties enhance charge generation and separation abilities, leading to efficient photocatalytic reactions. The obtained results highlight the critical role of controlling small molecules within the interlayer, alongside defects, in the design and fabrication of layered-structure photocatalysts. This study provides valuable insights into optimizing the performance of LDH-based photocatalysts for CO2 reduction and potentially other photocatalytic applications.

Tribological Behavior of GTL Base Oil Improved by Ni-Fe Layered Double Hydroxide Nanosheets

The layered double hydroxide (LDH) has been practically applied in the field of tribology and materials science due to its unique physicochemical properties, weak bonding, flexible structural composition, and adjustable interlayer space. In this work, a series of ultrathin and flexible composition of Ni-Fe LDH samples were prepared via a cost-effective room-temperature co-precipitation process. Then, they were mechanically dispersed into GTL base oil and their lubricating performance were tested by a four-ball tribometer. It is found that the variation of Ni-Fe ratio of Ni-Fe LDH has a great influence on the improvement of lubricating performance of GTL base oil. At the same concentration (0.3 mg/mL), the Ni-Fe LDH with Ni/Fe ratio of 6 was demonstrated to exhibit the best lubricating performance and the AFC, WSD, the wear volume, surface roughness and average wear scar depth decreased 51.3%, 30.8%, 78.4%, 6.7% and 50.0%, respectively. SEM-EDS and X-ray photoelectron spectra illustrated that the tribo-chemical film consisting of iron oxides and NiO with better mechanical properties formed and slowly replaced the physical film, which resists scuffing and protect solid surface from severe collisions.

Oleic acid-modified layered double hydroxide for Pickering emulsion: (II) Emulsification behavior

Layered double hydroxides (LDHs) are plate-like particles, being potential Pickering emulsifiers. Surfactant modification can regulate their surface properties, and thus can influence their emulsifying behavior. However, there is a lack of full understanding on the correlation between the surface modification of LDHs and their emulsification behavior. In the current work, one LDH and five oleic acid (OA)-modified LDH (LDH@OA) samples were chosen as emulsifiers, and emulsifying tests for pentadecane (oil)-water mixtures were performed at different oil/water volume ratios (1/9−9/1) and solid dosages (Cs, 1.00−10.0 g/L). The type, droplet size, and stability of emulsions were determined. The interfacial adsorption energy (ΔGad) and the coverage of solid particles for droplet surfaces (Rcov) were estimated, and the oil-water interfacial tension and viscoelastic moduli were determined. Results showed that LDH and LDH@OA particles can emulsify the oil-water mixture, forming coalescence-stable Pickering emulsions. The emulsion type is only determined by the solid wettability, independent of the oil/water ratio and Cs. The OA modification can change the wettability of LDH from hydrophilic to hydrophobic, thereby can regulate the type of emulsions from oil-in-water (O/W) to water-in-oil (W/O). Enhancing solid hydrophobicity decreases droplet sizes and increases interfacial viscoelasticity, thus improving the stability of emulsions. The droplet size decreases with an increase in Cs, while it increases with an increase in the volume fraction of dispersed liquid, both independent of the type of emulsions. The solid particles can irreversibly adsorb at the oil-water interface (with |ΔGad|/kT > 107), forming interfacial particle-layers with Rcov ∼0.4 and strong viscoelasticity, which endow the Pickering emulsions with extremely strong stability against coalescence.

Antimicrobial properties of promising Zn–Fe based layered double hydroxides for the disinfection of real dairy wastewater effluents

Bacterial resistance to conventional antibiotics is a serious challenge that requires novel antibacterial agents. Moreover, wastewater from dairy farms might contain countless number of pathogens, organic contaminants and heavy metals that consider a threat to the terrestrial and aquatic environment. Therefore, the development of cost-effective, highly operation-convenient, recyclable multifunctional antimicrobial agents became an urgent necessity. Layered double hydroxides (LDH) have shown promising results as antibacterial agents. However, more work is required to further investigate and improve the antimicrobial performance of LDH structures against pathogens. In this study three Zn–Fe based LDH were investigated for real dairy wastewater disinfection. The three LDH samples were cobalt substituted Zn–Fe LDH (CoZnFe), magnesium substituted Zn–Fe LDH (MgZnFe) and MgZnFe-Triazol LDH (MgZnFe-Tz) nanocomposite. Seventy-five wastewater samples were collected from a dairy farm sewage system. The sensitivity of isolated pathogens was tested against two commonly used disinfectants (Terminator and TH4) and was assessed against the three LDH samples at different concentrations. The overall prevalence of S. agalactiae, S. dysgalactiae and Staph. aureus was significantly at 80.0% (P-value = 0.008, X2 = 9.700). There was variable degree of resistance to the tested disinfectants, whereas the antimicrobial activity of CoZnFe LDH was increased significantly at a concentration of 0.005 mg/L followed by MgZnFe LDH while MgZnFe-Tz LDH showed minor antibacterial potency. It was concluded that CoZnFe LDH showed a better biocidal activity in killing the isolated resistant pathogens, making it a good choice tool in combating the zoonotic microbes in wastewater sources.

Controlling Lateral Size and Thickness of Layered Double Hydroxide (LDH) Used as Conversion Layer for Corrosion Protection of AZ31 Mg Alloy

In the present study, Mg-Al layered double hydroxide (Mg-Al/LDH) was synthesized on the surface of AZ31 Mg alloy substrate via in-situ hydrothermal treatment. Synthesis parameters were changed to determine their effect on the lateral size of LDH. For this purpose, etching in nitric acid and anodizing in sodium hydroxide solution were performed as surface pretreatments. Moreover, the influence of LDH solution pH (10 and 11) on the lateral size of LDH coating was investigated. Morphology, chemical composition, and crystalline structure were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). The corrosion resistance of the coatings was investigated by H2 measurements, salt spray, and electrochemical impedance spectroscopy (EIS). Moreover, the epoxy coating was applied on the best anti-corrosive LDH sample for assessing the compatibility and effectiveness of LDH on the corrosion properties of the substrate with the epoxy layer. At pH = 11, the lateral size of LDH was smaller than samples at pH = 10. In addition, small-sized LDH, as well as LDH/epoxy coating, revealed enhanced corrosion protection.

A Comparison of Nitrate Release from Zn/Al-, Mg/Al-, and Mg-Zn/Al Layered Double Hydroxides and Composite Beads: Utilization as Slow-Release Fertilizers.

Nitrate-loaded Zn/Al, Mg/Al, and Mg-Zn/Al layered double hydroxides (LDHs) were synthesized using the coprecipitation method. The slow-release properties of LDHs were measured in powder form at various pH conditions. Sodium alginate was used to encapsulate Mg/Al LDH to produce composite beads (LB) to further slow down the release of nitrate ions. The prepared LDH samples and LB were characterized by X-ray diffraction, attenuated total reflectance Fourier transform infrared spectroscopy, thermogravimetric analysis, and inductively coupled plasma optical emission spectroscopy. The surface morphologies of LDHs and LB were obtained from scanning electron microscopy analysis. The slow-release properties of the materials were evaluated using a kinetic study of nitrate release in tap water, soil solution, as well as plant growth experiments using coriander (Coriandrum sativum). The nitrate release ability of LDHs and LB was compared with a soluble nitrate source. The plant growth experiments showed that all three LDHs were able to supply an adequate amount of nitrate to the plant similar to the soluble fertilizer while maintaining the availability of nitrate over extended periods. The ability of LDHs to increase soil pH was also demonstrated.

Surfactant Intercalation in Li-Al-Based Binary and Ternary Layered Double Hydroxides by the Microwave-Assisted Rapid Ion-Exchange Process and Its Application in Iodine Adsorption

Recognizing the extreme speeds of reactions with microwaves, anionic forms of surfactants (sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS)) have been intercalated successfully by ion-exchange reactions in binary Li-Al and ternary Li-M-Al (M = Mg, Co, Ni, Cu, and Zn) layered double hydroxide (LDH) systems with the aid of microwaves. The samples have been characterized extensively. The basal spacings of 28.2 and 30.4 Å have been estimated for Li-Al-DS and Li-Al-DBS LDH samples, respectively, suggesting a perpendicular arrangement of DS− and DBS− anions in the interlayer space. The characteristic vibration bands of both LDH and the surfactant (DS− and DBS−) in the FTIR spectra confirmed the binding mode of surfactant molecules within the interlayers. DS−-intercalated Li-Al LDH showed lower thermal stability than the DBS−-intercalated sample. The nitrate-intercalated Li-M-Al (M = Mg, Co, Ni, Cu, and Zn) LDHs were ion-exchanged with SDS and SDBS to yield DS−-and DBS−-intercalated systems. The expanded basal spacings and a change in crystallite morphology confirmed the vertical intercalation of DS− and DBS− in Li-M-Al LDHs. ICP-AES and elemental analyses determined the metal contents and the surfactant content. FTIR spectra of intercalated samples confirmed the surfactant’s presence in the interlayer. The presence of Co, Ni, and Cu in Li-M-Al LDHs has been confirmed from UV-visible spectra. The Li-Al-DBS sample adsorbed iodine efficiently from methanol solutions, and the Langmuir model could explain the adsorption data in a better way. The adsorption followed pseudo-second-order kinetics.

Efficient activation of peroxymonosulfate by MoS2 intercalated MgCuFe layered double hydroxide for phenol pollutant control

The application of MoS2 as an emerging cocatalyst in wastewater treatment is of great significance, but the efficiency of cocatalyst is often limited due to its easy agglomeration and insufficient interaction with the catalyst. Here, we used layered double hydroxide (LDH) as the catalyst and the growth template of MoS2 to achieve an efficient combination of catalyst and cocatalyst in the removal of organic pollutants by peroxymonosulfate (PMS) activation. The outcomes showed that the MoS2 intercalated LDH composite samples (MLDH) owned excellent phenol degradation performance, reaching nearly 100% removal within 10 min, and the calculated apparent rate constants were 2.3, 5.6, 17.7 and 19.8 times higher than that of the samples of directly growing MoS2 on the LDH (M@LDH), physically blended MoS2 and LDH samples, LDH and MoS2, respectively. Based on the results of electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), SO4•- had a major impact on the elimination of phenol, Mo(Ⅳ) in MoS2 also participated in and encouraged the Fe(Ⅲ)/Fe(Ⅱ) redox cycle, providing the driving force for the further activation of PMS. Moreover, the effects of pH value, anions, cations and water environment of MLDH during the activation of PMS were also determined, and it was found that under various catalytic environments, MLDH always maintained a high removal rate of phenol and showed strong anti-interference ability. Collectively, the results of this research would offer more possibilities and suggestions for creating highly effective catalysts for wastewater cleanup.

Сорбционные свойства слоистых двойных гидроксидов, полученных при ультразвуковом воздействии

Layered double hydroxides (LDH) can be classified as promising materials due to the ease of synthesis, as well as their wide scope of application. However, the process of LDH synthesis, depending on the LDH chemical composition, can take from tens of hours to several days. It was previously identified that ultrasound exposure during the LDH production significantly reduces the synthesis time, and LDHs produced in this way are interesting in relation to the study of their physicochemical properties and sorption capacity. In this work, the authors produced Mg/Fe LDHs in nitrate form by the traditional method and by the combined action of ultrasound and increased hydrostatic pressure. The resulting samples are characterized by a complex of physicochemical methods of analysis, including scanning electron microscopy (SEM), infrared spectroscopy (IR), X-ray phase analysis (XRD), and thermal gravimetric analysis (TGA) with differential scanning calorimetry (DSC). Experiments were carried out to study the sorption capacity of the obtained Fe/Mg LDH samples in relation to chromate ions under normal conditions and under the influence of ultrasound, including in combination with increased hydrostatic pressure. A photoelectric photometer was used to obtain and analyze data with quantitative values of the sorption process. Data of comprehensive analysis of the finished product indicate that the synthesized material is a Mg/Fe layered double hydroxide. X-ray phase analysis identified that the LDH synthesis using ultrasound and pressure increases the crystallinity degree of the finished product. It has been found that the sorption properties of LDHs produced by the conventional method and LDHs produced under the influence of ultrasound and pressure are different. In Mg/Fe LDHs synthesized by the conventional method, chromate sorption proceeds better than in samples synthesized using ultrasonic treatment in combination with increased hydrostatic pressure. The study shows that the sorption process of the examined LDH samples is described by different mathematical models.

Preparation of TPU/GO/Mg‐Al LDHs Hybrid Material With Enhancing Flame Retardancy and Smoke Suppression Performance

AbstractFlammability of Thermoplastic polyurethane (TPU) limits its application in automotive, wires and cables, sports and textile coatings. Endowing TPU with simultaneously improved flame retardancy and smoke‐suppressant will be highly beneficial. Herein, a novel green and efficient condensed phase GO/Mg−Al layered double hydroxides (LDHs) flame retardant for TPU was synthesized by the co‐precipitation of Mg2+ and Al3+ and assembled with graphene oxide (GO) by electrostatic interaction. The unique two‐dimensional layered structure of GO/LDHs has a large specific surface area, which can form a dense and uniform char layer during the combustion process, thus hindering mass and heat transfer between gaseous and condensed phases. The XRD, TEM, SEM and EDS results showed that Mg−Al LDHs and GO/LDHs were successfully synthesized. The thermal, flame retarding and smoke suppression properties of TPU/GO/Mg−Al LDHs were determinated by UL‐94, limiting oxygen index (LOI), cone calorimeter (CCT) and smoke density (SDT). UL‐94 testing results showed that all the TPU/GO/Mg−Al LDHs samples had a vertical combustion rating of V‐0. Compared with pure TPU (19.1±0.2 %), the LOI value of all TPU/GO/Mg−Al LDHs composites are above 27 %. CCT results showed TGAL3 sample displayed the lowest peaks of heat release rate (pHRR) value of 142.9±9.3 Kw m−2. The total heat release (THR) value of TGAL5 is almost 70 % lower than that of pure TPU. In addition, compared to pure TPU, GO/Mg−Al LDHs materials has excellent performance in smoke suppression. The digital photos and Raman spectra of char residue demonstrated that TPU/GO/Mg−Al LDHs materials has a denser carbon layer after combustion. Apart from flame retarding and smoke suppression, the mechanical properties of TPU/GO/Mg−Al LDHs can maintain more than 80 % of the original TPU after addition of GO/LDHs. These results indicates that GO/LDHs composites is a kind of two‐dimensional layered material with unique structure and excellent flame retardant and smoke suppression.

Influence of Structural Disorders on the Tribological Behavior of Phosphate-Intercalated Layered Double Hydroxide Additives in Polyalphaolefin.

In this work, several phosphate-intercalated Mg-Al layered double hydroxides (LDHs) were synthesized and evaluated as solid lubricant additives in polyalphaolefin (PAO-4) by means of tribotesting on coupled GCr15/cast iron contacts. The effects of test parameters such as normal loads, additive concentrations, and substrate surface roughness were investigated, while the LDH crystal structure received considerable attention. Several types of structural disorder after anion exchange were identified based on X-ray diffraction (XRD) analysis. The unstable structures promote feasible shearing during sliding to improve friction and wear. In addition, antiwear properties correlate well with the anion charge number or the quantity of anion in the interlayer region. Overall, the tribological performance increased in the order HPO42--LDH < PO43--LDH < P2O74--LDH < (PO3)66--LDH. (PO3)66--LDH demonstrated the best antiwear performance with a reduction of 69% of the ball volume loss compared to PAO-4 oil due to the synergy of the disordered stacking LDH sheets and flexible ring structure of the (PO3)66- anion. Furthermore, on polished surfaces, the coefficient of friction (COF) of the (PO3)66--LDH sample dropped significantly by 26%, while the wear loss reduction of more than 80% was also substantial compared to the base oil sample. A performance comparison between the best-performing LDH additive was also conducted against popular nanomaterials, such as hexagonal boron nitride (BN), graphene nanoplatelets (GNPs), and titanium oxide (TiO2). The performance of (PO3)66--LDH was close to that of GNPs.

Size and surface charge effect of layered double hydroxide particles upon blood cells

Biological behavior of layered double hydroxide (LDH) toward human blood cells was evaluated with respect to the particle size and surface charge parameters. Three kinds of LDHs with different particle sizes were prepared by different synthesis routes and surface charge of the LDH was controlled by coating with citrate, malate or serine. Powder X-ray diffraction patterns and scanning electron microscopic (SEM) analyses indicated that the three LDHs before surface coating had average diameter ~ 160 nm, ~ 340 nm and ~ 1980 nm with well-crystallized hydrotalcite-like structure. According to zeta potential measurement, the surface coating with citrate, malate, and serine gave controlled zeta potential of −15.28 mV, 5.68 mV, and 36.5 mV, respectively. It was confirmed that all the six LDH samples regardless of size and surface charge did not induce serious hemolysis toward human red blood cells (RBCs), of which the value was less than 2.5% even in a high administration concentration of 10 mg/mL. However, the LDH with the largest size showed statistically a higher hemolysis ratio than the others at the high administration dose and long exposure time. The SEM showed that the large LDH particles induced membrane disruption by direct attack, while most of the LDH particles were softly landed on the RBC surface. Comparative SEM study suggested that the membrane interaction of LDH toward RBC was different from that with adherent cells. The adherent cells showed massive attachment of LDH particles on membrane periphery with active endocytosis. It was therefore concluded that LDH particles with moderate size are highly compatible to human blood cells.

Adsorption characteristics of assembled and unassembled Ni/Cr layered double hydroxides towards methyl orange

The lamella aggregation state of layered double hydroxides (LDHs) may affect their sorption capacity for organic compounds. The dried LDH samples (Ni/Cr LDH-FA-D and Ni/Cr LDH-H2O-D) and the undried samples (Ni/Cr LDH-FA-W and Ni/Cr LDH-H2O-W) were flexibly prepared by a co-precipitation method in formamide (FA) and water, respectively. The results of X-ray diffraction (XRD) and transmission electron microscope (TEM) showed that the undried LDHs were unassembled, which had no the stacking layers but had a pseudohexagonal nanosheet lamella structure. And the unassembled LDH layers can be assembled again during the dry process. Ni/Cr LDH-FA-W and Ni/Cr LDH-H2O-W showed much greater adsorption capacities towards methyl orange (MO) than Ni/Cr LDH-FA-D and Ni/Cr LDH-H2O-D, as well as shorter time to reach equilibrium. The maximum adsorption capacity of MO could be calculated to 806 mg/g and 740 mg/g for Ni/Cr LDH-FA-W and Ni/Cr LDH-H2O-W by Langmuir-type simulation. The greater adsorption capacities of unassembled LDH could be attributed to the loosen structure and much more exposed adsorption sites. It could be concluded that unassembled LDHs were an effective and conducive preparation pathway for the exploration of the adsorption sites of LDHs.

Fabrication of NiO/Mg–Al layered double hydroxide with superior performance for peroxydisulfate activation

Mg–Al Layered double hydroxides (LDH) with weak alkalinity can improve the activity and stability of transitional metal oxides for peroxydisulfate (PDS) activation. Herein, NiO supported on LDH (Ni-LDH-TP) and Ni doped LDH samples (Ni-LDH-CP and Ni-LDH-SP) were prepared by two-step precipitation and co-precipitation methods, respectively. Their structure and surface properties were characterized and their performance for PDS activation was compared using ciprofloxacin as the target pollutant. The results indicate that Ni-LDH-TP exhibited much higher activity than Ni-LDH-CP and Ni-LDH-SP due to its more surface exposed NiO. The two-step precipitation method should be a better alternative for the synthesis of Ni-LDH catalyst for PDS activation. Ni-LDH-TP exhibited high activity over a wide pH range and good reusability in the presence of bicarbonate, demonstrating its potential application in real water treatment. Activated PDS and SO4•− should be the dominant reactive species for ciprofloxacin degradation. This finding provides an effective strategy for preparing Ni-based PDS catalyst.

Waterborne polyurethane nanocomposite incorporated with phytic acid intercalated layered double hydroxides: A highly stable aqueous dispersion with desired corrosion protection capability

AbstractIn this research, waterborne polyurethane (WPU) nanocomposites incorporated with MgAl‐NO3LDH layered double hydroxide (LDH) and phytic acid intercalated LDH (PA‐LDH) nanostructures were prepared as novel environmental‐friendly corrosion protective coatings. Fourier‐transform infrared spectroscopy, X‐ray diffraction (XRD), thermogravimetric analysis, field emission scanning electron microscope (SEM), and high‐resolution transmission electron microscopy analysis confirmed the prosperous preparation of LDHs nanosheets. Moreover, structural, thermal, thermo‐mechanical, and morphological investigations of prepared WPU/LDHs films were also evaluated. The SEM images exhibited that the intercalation of LDH nanosheets with PA could drastically overcome the agglomeration problem of unmodified LDH within the polyurethane matrix. Based on XRD results, WPU/LDHs films showed a lower micro‐phase separation degree and crystallinity compared to pure WPU film. According to wettability analysis, WPU/PA‐LDH film demonstrated the highest hydrophobicity among samples due to its lowest phase‐separation degree, which causes the castor oil and poly(tetramethylene ether) glycol segments to migrate toward the surface of film from the bulk. Furthermore, the potentiodynamic polarization scanning and electrochemical impedance spectroscopy analysis revealed that the WPU/PA‐LDH sample containing 1.0 wt% of PA‐LDH has a superlative anti‐corrosion performance for SS 304 steel with an inhibition efficiency of 99.9%. This superior anti‐corrosive property benefited from the barrier property and chloride absorption capability of well‐dispersed PA‐LDH nanosheets, deposition of PA on the steel substrate, and improved hydrophobicity of the WPU/PA‐LDH coating.

Cryogenic heat capacity measurements and thermodynamic analysis of lithium aluminum layered double hydroxides (LDHs) with intercalated chloride

Abstract Lithium aluminum chloride layered double hydroxide ([Li-Al-Cl] LDH) sorbents selectively recover lithium from geothermal brines, paving the way for increased domestic production of lithium for rechargeable batteries. In this work, cryogenic heat capacity measurements (CP) were performed from 1.8 to 300 K on several undoped and Fe-doped [Li-Al-Cl] LDH samples with a generalized compositions Li1–xAl2(OH)6Cl1–x (undoped) and LixFeyAl2–y(OH)6Clx (Fe-doped). Thermodynamic functions were generated from these measurements, and values of S298.15○ are reported based on both the CP measurements and configurational entropy (Sconfig○) arising from positional disorder in the layered structure. These results are combined with previous enthalpy of formation (ΔHf○) measurements to calculate the Gibbs energy of formation (ΔGf○) for the samples. In these samples, a higher water content results in a less negative ΔGf○ when doped and undoped samples are considered separately. Limited iron substitution for aluminum results in the most negative ΔGf○, but a larger dopant amount destabilizes the LDH structure. One of the samples had an anomaly in the heat capacity from 210 to 300 K, which is likely related to the movement of water in the structure due to the large H2O/Cl− ratio and the presence of vacancies in the interlayer where H2O resides. This indicates that the interactions between these species in the interlayer play an important role in stabilizing the LDH structure, and this effect should be further studied using different water/anion ratios.

Sorption of methyl orange dye by dodecyl-sulfate intercalated Mg-Al layered double hydroxides

The aim of this study is to evaluate the Mg-Al layered double hydroxides (LDHs) containing dodecyl sulfate and carbonate ions in the removal of methyl orange (MO) from aqueous solution. The prepared materials (Mg-Al-CO3 and Mg-Al-Ds) were characterized by XRD, TEM and FT-IR methods. XRD patterns of the two materialsshow the interlayer type structure with (00 l) reflections. TEM analysis showed that the LDH samples have nanoscale structures. FTIR spectroscopy confirmed the presence of the desired anions in the interlayer space. The results of the adsorption experiences for MO were performed as a function of solution pH and contact time. The adsorption ability of MO onto Mg-Al-CO3was practically influenced by pH solution. However, the adsorption capacity of MO by Mg-Al-Ds appears stable at the different values of solution pH. The maximum adsorption capacities were 185.06 and 97.5 mg/g for Mg-Al-Ds MB and Mg-Al-CO3, respectively. The adsorption tests recommend the use of organic LDHs as potential adsorbents for azo dye treatment in a wide range of pH.

Fumonisin B1 Interaction with Mg-Al and Mg-Fe Layered Double Hydroxides: Removal Efficiency and Mechanisms.

Mycotoxins in feed and food are highly toxic and pose a serious danger even at very low concentrations. The use of bentonites in animal diet can reduce toxin bioavailability. However, some mycotoxins like fumonisin B1 (FB1) form anionic species which excludes the use of negatively charged clays. Layered double hydroxides (LDH) with anion-exchange properties, in theory, can be perfect candidates to adsorb FB1. However, fundamental research on the use of LDH for mycotoxins removal is scarce and incomplete. Thus, the presented study was designed to explore such a possibility. The LDH materials with differing chemistry and layer charge were synthesized by co-precipitation both from metal nitrates and chlorides and were then tested for FB1 removal. XRD, FTIR, XPS, and chemical analysis were used for the LDH characterization and to obtain insight into the removal mechanisms. A higher adsorption capacity was observed for the Mg/Al LDH samples (~0.08–0.15 mol/kg) in comparison to the Mg/Fe LDH samples (~0.05–0.09 mol/kg) with no difference in removal efficiency between Cl and NO3 intercalated LDH. The adsorption capacity increased along with lower layer charge of Mg/Al and was attributed to the lower content of bonded carbonates and the increase of non-polar sites which led to matching between the adsorption domains of LDH with FB1. The FTIR analysis confirmed the negative effect of carbonates which hampered the adsorption at pH 7 and led to the highest adsorption at pH 5 (FB1 content ~15.8 ± 0.75 wt.%). The fast surface adsorption (1–2 min) was dominant and XRD analysis of the basal spacing indicated that no FB1 intercalation occurred in the LDH. The XPS confirmed a strong interaction of FB1 with Mg sites of LDH at pH 5 where the interaction with FB1 carboxylate moieties COO− was confirmed. The research confirmed a high affinity and selectivity of LDH structures towards anionic forms of FB1 mycotoxin.

Zn2Al‐CO3 Layered Double Hydroxide: Adsorption, Cytotoxicity and Antibacterial Performances

AbstractDue to the accelerating growth of civilian and industrial regime, chemical and bioremediation of water body become a major concern for society. Here, we report a facile and scalable process to get Zinc‐aluminium layered double hydroxide (LDH) with carbonate interlayer anion and present it as promising multifunctional material for potential applications in adsorption, antibacterial, and cytotoxicity performances. In this study, the sample was prepared by co‐precipitation method and the well crystalline LDH was characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), X‐Ray Diffraction (XRD), X‐Ray Photoelectron Spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) analysis. The study shows excellent adsorption capacity of Zn2Al‐CO3 LDH as high as 81.4 mg/g against the methyl orange (MO) dye taken as a model organic pollutant. Adsorption kinetics and adsorption isotherms have also been investigated in detail. Moreover, the prepared Zn2Al‐CO3 LDH sample shows commendable antimicrobial efficacy against both Gram‐negative and Gram‐positive bacteria. In addition to that, under cytotoxicity study, the sample exhibits a creditable inhibitory effect towards the cancerous cell HEPG2 cell. As a whole the results show the significant implication of the Zn2Al‐CO3 LDHas a multifunctional material towards environmental concern and also as an antimicrobial material.

Tribological behavior of layered double hydroxides with various chemical compositions and morphologies as grease additives

The layered double hydroxide (LDH) is a kind of natural mineral, which can also be manually prepared. It has been practically applied in various fields due to its unique crystal structure and diversity of composition, size, and morphology. In this work, LDHs with different chemical compositions (Co2+, Mg2+, Zn2+, and Ni2+) and topographical features (flower-like, spherical, and plate-like) were successfully prepared by controlling the reaction conditions. Then, they were mechanically dispersed into base grease and their tribological properties were evaluated by a ball-on-disk tester under a contact pressure of 2.47 GPa. It was found that the variation of morphology, instead of chemical composition, had great influence on the tribological performance. The “flower-like” LDH sample with high specific surface area (139 m2/g) was demonstrated to show the best performance. With 1 wt% additive, the wear volume was only about 0.2% of that lubricated by base grease. The tribofilm with unique microscopic structure and uniform composition was derived from tribochemical reaction between LDH additives and sliding solid surfaces, effectively improving tribological properties of the lubrication system. This work provided the guidance for optimizing lubricant additives and held great potential in future applications.