Advances in layered double hydroxide (LDH)-based elastomer composites

Adsorptive removal of phosphate from secondary effluents in WWTPs by ZnAl layered double hydroxides granules

Selenium adsorption on Mg–Al and Zn–Al layered double hydroxides

The role of dispersion of LDH in fire retardancy: The effect of different divalent metals in benzoic acid modified LDH on dispersion and fire retardant properties of polystyrene– and poly(methyl-methacrylate)–LDH–B nanocomposites

Layered double hydroxides (LDHs) are considered promising photocatalytic materials for the efficient removal of heavy metals like Cr(VI), a toxic metal commonly present in industrial wastewater. In this context, a practical way to do that is by applying a photocatalytic process to reduce Cr(VI) previously adsorbed in LDH materials to non-toxic Cr(III). This work aimed to obtain a hybrid ZnFeAl material with a better charge transfer efficiency by the in-situ incorporation of Fe(II, III) during the synthesis by the co-precipitation method, to decrease the electron-hole recombination rate and improve the photoreduction reaction of Cr(VI) to Cr(III). The synthesized ZnAl and ZnFeAl LDH materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), physisorption of nitrogen, UV-vis DRS analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and photoelectrochemical techniques.

Comparison of adsorption and desorption of phosphate on synthesized Zn-Al LDH by two methods in a simulated soil solution

Zn-Al layered double hydroxide as an inhibitive conversion coating developed on AA2024-T3 by one-step hydrothermal crystallization: Crystal structure evolution and corrosion protection performance

Purpurin intercalated layered double hydroxide nanocomposites for improved CO2 visible photocatalytic reduction: Dye-intercalation stabilization and sensitization

Synthesis and evaluation of layered double hydroxide based sorbent for hot gas cleanup of hydrogen chloride

Technetium has a long half life of up to 2.13×105 years. It is separated from liquid waste streams with tetraphenylphosphonium bromide [1], which upon degradation releases Tc as the pertechnetate anion, TcO4−. Pertechnetate is highly mobile in groundwater and it is therefore highly desirable to capture and immobilise this anion within a solid for interim and ultimately long term storage. Layered Double Hydroxide (LDH) materials are known to possess excellent anion sorption capabilities due to their structure which consists of ordered positively charged sheets intercalated with interchangeable hydrated anions. The composition can be tailored to produce suitable precursors for ceramic phases by varying the divalent and trivalent cations and the anions. LDHs with the general formula Ca1-x (Fe1-y, Aly)x (OH)2 (NO3)x . nH2O were produced by a co-precipitation method from a solution of mixed nitrates. Calcination leads to the formation of Brownmillerite Ca2(Al,Fe)2O5 like compounds for temperatures as low as 400°C, this is close to the lowest temperature at which Tc is known to volatilise (310.6 °C Tc2O7). It was shown that after calcining up to 600°C, the LDH structure is recovered in water allowing rapid ion capture to occur. This suggests that these materials have potential for both capture and as a storage medium for Tc.

Layered Double Hydroxides (LDHs) coatings were developed for corrosion protection of AZ31 Mg alloy. LDH coatings were fabricated under co-precipitation conditions and applied under hydrothermal conditions. Two different systems Zn-Al LDH and Li-Al LDH were studied. Specimens were post-treated via immersion for 2 h at 45 ºC in Na2WO4·H2O or LiNO3 baths respectively, to produce Zn-Al LDH(W) and Li-Al LDH(Li). The characterization of the coatings was carried out by field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The corrosion process was studied by electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). Surface was also evaluated by water drop contact angle and paint adhesion test by using an epoxy primer. The characterization of the coating revealed two-layered coatings with a denser inner layer and a flaky outer layer. Both coatings improved the corrosion resistance of the AZ31 alloy. Loading with inhibitor further increased the corrosion resistance by one order of magnitude (Bare substrate, Z10mHz ⁓ 102 Ω cm2; LDH, Z10mHz ⁓ 103-4 Ω cm2; LDH-inhibitor, Z10mHz ⁓ 105 Ω cm2)

Layered double hydroxides (LDHs) are versatile materials with diverse applications, including catalysis, water separation, adsorption, biomedicine, and fire retardancy. This study investigates the thermal evolution of ZnAl LDH ([Zn2+2Al3+(OH)6]+ [CO32-0.5]-) using in situ scanning nanobeam electron diffraction, high-resolution transmission electron microscopy, and energy-dispersive X-ray analysis. The structural and morphological changes are examined during heating in both ambient air and vacuum. The pristine ZnAl LDH exhibited edge dislocations and irregular interlayer distances, leading to significant diffuse scattering in the electron diffraction patterns. Both upon heating in ambient air conditions and in vacuum, the characteristic hexagonal LDH morphology transformed into a porous nanostructure. The exact crystal structure transitions differed as a function of the environment. Heating under vacuum conditions first led to a ZnAl2O4 phase with a spinel-type structure, and subsequently to ZnO particles embedded within an Al2O3 matrix. When heated in a closed cell filled with ambient air, the LDH initially transitioned to an Al-doped ZnO-type structure, followed by conversion to a ZnAl2O4 phase. This study is the first gas in situ TEM LDH study and shows the recrystallization behavior of the LDH into the different phases upon heating and uncovers the nanoscale distribution of these phases within the particles, forming ZnAl2O4, ZnO, and Al2O3 composites.

Layered double hydroxide (LDH)-based nanomaterials are known for their good biocompatibility, pH-dependent stability, biodegradation properties, anion exchange capacity, easy surface modification, and high chemical stability. More recently, with the rise of oligonucleotide therapeutics and the related delivery challenges, LDHs are emerging as an alternative delivery therapeutic tool for oligonucleotide delivery because of their ability to bind effectively to the negatively charged phosphate backbone of oligonucleotides and release it once it is in the cell. However, based on our knowledge, the potential of using LDHs for short interfering RNA (siRNA) delivery has not been fully explored. In fact, this is the first study of its kind that systematically evaluates several LDHs for siRNA binding, gene silencing, and toxicity. The results of this research reveal that NiAl-NO 3 -LDH/h (h = hydrothermal method) has a comparable gene knockdown to siRNA delivered using common transfection agents such as Lipofectamine 2000™ (Invitrogen), Lipofectamine 3000™ (Invitrogen), and Interferin (ThermoFisher), with gene knockdown of 62.7 %, 62.6 %, 79.3 %, and 78.6 %, respectively. Exploring alternatives to transfection agents is important in driving oligonucleotide therapeutic applications forward because some of them, for example, Lipofectamine 2000™, is well known to exhibit toxicity across various cell lines. • Short interfering RNA delivery to cells remains an ongoing challenge • A comprehensive analysis of the physical properties of several LDH materials and the effect of these properties on short interfering RNA binding, gene silencing and cell toxicity were examined • LDH material NiAl-NO 3 -LDH/h (h = hydrothermal method) produces a potent gene silencing effect of 62 % when complexed with short interfering RNA • All LDH materials synthesized are non-toxic to HeLa and A549 cells

Perishable food post-harvest loss is a major global concern, and research is currently concentrated on creating active packaging materials. This research is focused in multiple antioxidants intercalated Layered Double Hydroxides (LDH) that are combined in one matrix, and their overall effect that defines as synergism, which successfully preserves perishable food by releasing antioxidants slowly. For this purpose, a hybrid LDH material of ascorbic-LDH (AA-LDH), salicylic-LDH (SA-LDH), and citric-LDH (CA-LDH) was synthesized, characterized and incorporate into electrospun nanofiber mat to be used as a potential active packaging material. Antioxidants intercalated Mg/Al LDH was synthesized and successfully characterized by PXRD, FTIR, XPS, Raman, SEM, and EDS. The shifts in the LDHs’ peaks in PXRD indicated the successful incorporation of antioxidants into LDH. FTIR, Raman, and XPS data clearly indicated the establishment of metal-oxygen bonds by observing the characteristic peaks. Morphological features and the layered structure were clearly observed by SEM images. Antioxidants were slowly released from the LDHs, and it was evaluated for time intervals up to 24 h. The hybrid LDH material exhibited the highest antioxidant activity with an IC50 value of 132.5 μg ml−1, where 234.1, 354.5, and 402.2 μg ml−1 were reported for ascorbic-LDH, salicylic-LDH, and citric-LDH respectively. The hybrid LDH material incorporated electrospun mats showed the best antibacterial activity against the tested bacteria and clearly evidenced the synergistic activity of the combination of the nanohybrids. It has showed a minimal bacterial growth compared to the other control samples (∼2.41 log CFU/ml). The shelf life of cherry tomatoes was studied at different physiochemical parameters with and without hybrid LDH material incorporated electrospun mats. The fabricated mat showed an extended shelf life of 42 days for cherry tomatoes, whereas the control sample showed a shelf life of 17 days. It is concluded that hybrid LDH material exhibited synergistic performance and the best antioxidant activity when comparing with mono LDH materials.

Progress in pre-treatment and extraction of organic and inorganic pollutants by layered double hydroxide for trace-level analysis

The study of the physicochemical process of volatile organic compound (VOC) adsorption on porous materials is significant for design and screening of adsorbent materials and treatment of VOCs. Traditional measurement methods for studying the adsorption process require lots of adsorbates and adsorbents and are time-consuming. We proposed a facile strategy to study the adsorption process of trace gaseous aldehydes on layered double hydroxide (LDH) using surface-enhanced Raman spectroscopy (SERS). We prepared a composite of Ag nanocubes@hollow Co-Ni LDH (AgNCs@Co-Ni LDH) with a strong adsorption capability and high SERS sensitivity. The adsorption properties of LDH for benzaldehyde in terms of general kinetics and isotherms were investigated. The kinetic adsorption process could be fitted better by the pseudo-first-order kinetics with a higher correlation coefficient than by the pseudo-second-order model, and the adsorption rate of 0.0308 min-1 was obtained from the fitting curve. The isotherm adsorption fits the Langmuir isotherm model, and its adsorption constant is 6.25 × 106 L/mol. Taking advantage of the excellent adsorptive performance and SERS activity, the AgNCs@Co-Ni LDH composite can be used as an effective SERS probe to detect gaseous aldehydes, and it shows a linear dynamic range (5-100 ppb) with a limit of detection reaching 1.83 ppb for benzaldehyde, better than that achieved by previous studies. Therefore, this work has not only established a new measurement method for probing the adsorption process with extremely low consumption of both adsorbates and adsorbents, but also may lay the groundwork for the construction of rapid and ultra-sensitive SERS sensors for probing VOCs in the future.