Nano-sized Layered Double Hydroxides Research Articles

Nanoparticles of (calcium/aluminum/CTAB) layered double hydroxide immobilization onto iron slag for removing of cadmium ions from aqueous environment

The novel point of this study represents by manufacturing new material for treating of aqueous solution laden with cadmium ions. This can achieve through utilizing of alum as cheapest and available substance, plaster kiln dust wastes from gypsum industry, and cetyl trimethyl ammonium bromide surfactant in the preparation of nano-sized layered double hydroxide of aluminum and calcium in the existence of mentioned surfactant. The gel-solution of nanoparticles can be co-precipitated on the iron slag to obtain new sorbent identified “iron-slag coated with (calcium/aluminum- cetyl trimethyl ammonium bromide) layered double hydroxide” and composition of all materials was characterized by analysis of X-ray diffraction. The outcomes proved that the area of slag surfaces was increased significantly from 0.49 to 10.21 m2/g due to the surfactant intercalation and precipitation of nanoparticles. The synthesis parameters require surfactant 0.035 g/50 mL, pH 10, molar ratio of (calcium/aluminum) 2, and mass of slag 1 g/50 mL. Batch tests proved that more than 99.3% cadmium can remove at time 60 min, initial pH 7, coated slag mass 0.5 g/50 mL, and speed 250 rpm for 50 mg/L initial concentration to obtain highest capacity of sorption of 14.50 mg/g. The measurements of kinetic tests were well followed the model of Pseudo second-order and; accordingly, the chemisorption mechanism will predominate the removal process. Model of intra-particle diffusion demonstrate that the electrostatic attraction, hydrogen bonding and diffusion are major mechanisms required in the cadmium removal onto the prepared sorbent. Also, Langmuir model is an ideal formula for representing the sorption data with determination coefficient = 0.99. Characterization tests certified that the nanoparticles on the slag can play a prime role in the enhancement of cadmium sorption. In addition, the exhausted sorbent can be regenerated and its efficiency was not less than 83% for removal of cadmium after 9 regeneration cycles.

Immobilization of hexavalent chromium in contaminated soil by nano-sized layered double hydroxide intercalated with diethyldithiocarbamate: Fraction distribution, plant growth, and microbial evolution

Soil contamination by hexavalent chromium (Cr(VI)) poses great risks to human health and ecosystem safety. We introduced a new cheap and efficient layered double hydroxide intercalated with diethyldithiocarbamate (DDTC-LDH) for in-situ remediation of Cr(VI)-contaminated soil. The content of Cr(VI) in contaminated soil (134.26 mg kg−1) was rapidly reduced to 1.39 mg kg−1 within 10 days by 0.5% of DDTC-LDH. This result attains to or even exceeds the effectiveness of most of reported soil amendments for Cr(VI) removal in soils. The production cost of DDTC-LDH ($4.02 kg−1) was relatively low than some common materials, such as nano zero-valent iron ($22.80–140.84 kg−1). The growth of water spinach became better with the increase of DDTC-LDH dose from 0% to 0.5%, suggesting the recovery of soil function. DDTC-LDH significantly altered the structure and function of soil microbial communities. The species that have Cr(VI)-resistant or Cr(VI)-reductive ability were enriched in DDTC-LDH remediated soils. Network analysis revealed a significant functional niche differentiation of soil microbial communities. In addition to the enhancement of Cr(VI) reduction, the stimulation of plant growth promoting traits, including siderophore biosynthesis, oxidation resistance to reactive oxygen species, and phosphorus availability by DDTC-LDH was another essential mechanism for the immediate remediation of Cr(VI)-contaminated soil.

Fabrication of layered double hydroxide microspheres by spray drying of nanoparticles: Effects of process conditions

Microspherical agglomerates of nano-sized layered double hydroxide (LDH) particles were prepared using a spray drying technique without addition of dispersant and binder. The effects of process conditions were investigated on the agglomerate size distribution, morphology and specific surface area. The spray-dried agglomerates were spherical in shape, with diameter of 2–15μm and with smooth surface without cracks and holes. The agglomerate surface area ranged from 49 to 101m2/g depending on process conditions. The smallest agglomerates with narrowest size distribution were obtained at the highest flow rate of spraying air, while the agglomerates of highest specific surface area were fabricated at the lowest spraying air flow rate. Drying at low temperature and using slurry of low concentration also resulted in formation of small agglomerates. The change in specific surface area was related to the variations in drying rate. Drying at low rate led to the fabrication of agglomerates with high surface area. Thus, by adjusting the spray drying parameters, one could produce LDH microspheres satisfying requirements and utilize them as an intermediate product in the manufacturing of functional materials.

PH sensitive nano layered double hydroxides reduce the hematotoxicity and enhance the anticancer efficacy of etoposide on non-small cell lung cancer

Etoposide (VP16), used for the treatment of many carcinomas, can cause leukopenia, thrombocytopenia and hair loss. To overcome the side effects and achieve target therapy, layered double hydroxides (LDHs), a pH sensitive layered double hydroxide nanohybrid, was used here as a nano-carrier. The functions of LDHs-VP16 on non-small cell lung cancer (NSCLC) were firstly explored both in vitro and in vivo. In A549 cell line, LDH-VP16 induced apoptosis 2.3-fold as that of plain VP16 by targeting to mitochondrial, stocking cells in G1 phase. The cellular uptake demonstrated the delivery of LDH for VP16 to pass through the membrane and accumulate in mitochondria. As a carrier, LDH greatly decreased the liver toxicity and hematotoxicity of VP16. The detected liver parameters, including glutamic-oxaloacetic transaminase (AST), alkaline phosphatase (ALP), alanine aminotransferase (ALT), were all turn back to normal range after the delivery of LDH, except ALP. In vivo, LDH-VP16 reduced A549 tumor growth significantly by 60.5%, whereas native VP16 exerted no significant anticancer activity. In LDH-VP16 treated mice, the AUC was increased by 6.26 folds as the native drug, and t1/2 of LDH-VP16 was prolonged from 6.68 to 98.78h. LDH-VP16 showed a targeting effect, which largely increase the concentration in tumor and lung. The phosphorylation antibody array and Western Blot of proteins from xenografts revealed that PI3K–AKT signaling was suppressed in the LDH-VP16 treated tumor, while in VP16 treated mice, ERBB signaling pathway was involved. These results suggested that LDH-VP16 diminishes hematotoxicity, targets NSCLC tumor, performs more effectively than VP16, and different signaling pathway is involved compared to VP16. Statement of significanceThis paper explored that nano-sized layered double hydroxide (LDH) could be used as a pH sensitive delivery system to overcome hematotoxicity and enhance the bioavailability and anticancer efficacy of etoposide (VP16) against non small cell lung cancer, which was not reported before, as the best of our knowledge. We found that the liver and hematotoxicity is nearly recovered after the loading of VP16 in pH sensitive LDH, which prongs the half time from 6.68h to 98h, helps target VP16 to tumor and lung, and protects white blood cells by its pH sensitive and nano-size property. LDH-VP16 achieve markedly performance on non-small cell lung cancer by targeting to mitochondria of A549 cells in vitro and effectively inhibiting the PI3K–AKT signaling pathway in vivo. The inhibition ratio of VP16 on A549 tumor growth is increased from less than 20% (no significance compared to control) to 60.5% after the delivery of LDH. This work provides a novel system for the safe and efficient use of etoposide on non-small cell lung cancer and explores the mechanism of the function of nano carrier in cancer therapy both in vitro and in vivo.

Corrosion resistance of in-situ Mg–Al hydrotalcite conversion film on AZ31 magnesium alloy by one-step formation

In situ growth of nano-sized layered double hydroxides (LDH) conversion film on AZ31 alloy was synthesized by a urea hydrolysis method. The formation mechanism of the film was proposed. Firstly, the dissolved Mg2+ ions deposited into a precursor film consisted of MgCO3 and Mg5(CO3)4(OH)2· 4H2O; secondly, the precursor translated into the crystalline Mg(OH)2 in alkaline conditions; finally, the Mg2+ ions in Mg(OH)2 were replaced by Al3+ ions, Mg(OH)2 translated into the more stable LDH structure, simultaneously, the OH− ions in the interlayer were exchanged by, thus led to the formation of the LDH (Mg6Al2(OH)16CO3·4H2O) film. The results indicated that the LDH film characterized by interlocking plate-like nanostructures and ion-exchange ability significantly improved the corrosion resistance of the AZ31 Mg alloy.

The effects of soil amendments on arsenic concentrations in soil solutions after long-term flooded incubation

We investigated the effects of various soil amendments on the concentration of arsenic (As) in soil solutions under flooded anaerobic conditions. Ten amendments (six As adsorbents and four general agricultural amendments) were used with two soil samples (Aquepts). The time-course changes in the concentrations of As, iron (Fe) and silicon (Si) in soil solutions with or without amendments were measured after incubations of approximately 30, 60 and 100 d. We conclude that a precipitate of polysilicate-iron solution (1.1 mol L‒1 Fe) shows promise as a novel As adsorbent for flooded anaerobic soils such as paddy soils. The precipitate is present in sludge from water purification plants and is therefore potentially cost effective. Moreover, it could increase the concentration of Si in soil solution, which could decrease As uptake by rice plants. Ferrihydrite and aluminum-substituted ferrihydrite were also effective for decreasing the dissolved As in both soils and nano-sized layered double hydroxides, and magnesium oxides worked in one soil. Poultry manure significantly increased dissolved As in both soils, but composted bark and silicate fertilizers did not change As in either soil. Some amendments had different effects in the two soil samples; further comprehensive studies will need to focus on how soil properties influence the effects of amendments.

Ultrasound-assisted one-pot preparation of organo-modified nano-sized layered double hydroxide and its nanocomposites with polyvinylpyrrolidone

In this contribution, polyvinylpyrrolidone (PVP) nanocomposites (NCs) with novel chiral diacid intercalated layered double hydroxides (LDHs) as nanofillers were prepared via ultrasonic irradiation. Chiral LDH was synthesized in one step via a co-precipitation reaction in aqueous solution under ultrasonic irradiation. The modified Mg-Al LDH shows an increase in interlayer distance as compared to the unmodified Mg-Al LDH by X-ray diffraction (XRD). Different NCs of organo-modified chiral LDHs and PVP were constructed by means of an ultrasonic process. The structures of these new materials were investigated by XRD, Fourier transform infrared, field emission scanning electron microscopy and transmission electron microscopy techniques. XRD and electron microscopy results confirmed the delaminated state of the LDH in the PVP matrix. Furthermore, thermal analysis was evaluated and the prepared NCs show significantly improved thermal stability at higher temperature because of the homogeneous and good dispersion of modified LDH in polymeric matrix.

Drug Delivery Using Nanosized Layered Double Hydroxide, an Anionic Clay

A study was conducted to demonstrate drug delivery using nanosized layered double hydroxide (LDH), which was an anionic clay. Investigated revealed that layered double hydroxides represented one of the most promising materials in the areas such as nanomedicine, adsorbents, catalysis and catalyst supports , electrode modifier, and magnetic precursors, processing of selective chemical nanoreactors, and separation and membrane technology. Layered nickel hydroxide was used as an electrode for alkaline secondary cells in electrochemistry. The layered structure, wide chemical compositions, variable layer charge density, ion-exchange properties, reactive interlayer space, swelling in water, and rheological and colloidal properties made LDH look and behave like clay.

New Insights on the Incorporation of Lanthanide Ions into Nanosized Layered Double Hydroxides

Nanosized Layered Double Hydroxides (LDH) were prepared in confined environment through the microemulsion method in the presence of different lanthanide cations (Ln(III) = Eu(III), Yb(III), Tb(III), and Nd(III)). To investigate the effects of lanthanide insertion in the sheets of LDH materials, several samples were prepared upon progressively increasing the content of Ln ions and properly reducing the Al(III) amount; the samples were characterized in terms of metal content, structure, morphology, thermal behavior, and spectroscopic properties. The data revealed that Ln(III) content in the LDH samples depends on the ionic radius of the lanthanide cations and on its concentration in the starting microemulsion. X-ray powder diffraction (XRPD) indicated that Eu(III) can be inserted into the LDH structure in average atomic percentages lower than 2.7%, leading to the formation of a low symmetry phase, as confirmed by steady state luminescence spectra; while Yb(III) can be incorporated into the layer structure up to about 10% forming a pure layered phase containing the lanthanide in the sheet. The incorporation of Yb(III) and Eu(III) into the LDH sheets is also supported by FT-IR measurements. Coupled thermogravimetrical (TG) and differential scanning calorimetric (DSC) studies indicated that water molecules are essential in the coordination sphere of incorporated Ln cations; this observation accounts for the lower thermal stability of Ln-doped LDH compared to the undoped ones. Furthermore, Eu-luminescence measurements indicates that the lanthanide inclusion does not compromise its luminescence although the spectral position and brightness can be tuned by the loading.

Modification of nano-sized layered double hydroxides by long-chain organic aliphatic surfactants

The inter-layer anion of layered double hydroxides (LDH) with a hydrotalcite (HT)-like structure was ion-exchanged with various organic surfactants, particularly with long chain aliphatic surfactants. After the ion-exchange process, the basal spacing of the LDH was increased and the increase of the basal spacing depended on various factors, such as the intercalation capacity functionality and orientation capability of the surfactant. Of the employed surfactants, stearic acid intercalated LDH showed the highest increase of the basal spacing, which was confirmed by XRD analysis. FTIR results supported the interaction of the surfactants with the LDH. In addition, an increase in the thermal stability of the dodecanedioic acid intercalated HT was evidenced by the TGA method.

Polylactide (PLA)/layered double hydroxides composite fibers by electrospinning method

Inorganic nanosized layered double hydroxides (LDHs) modified with dodecyl sulfate (DS) ions were incorporated into semi-crystalline polylactide (PLA) nanofiber non-woven membranes by combining a nanocomposite technique and the solution electrospinning process. The structure, morphology and thermal property of the electrospun membranes were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential thermal analysis (DTA). It was found that the melting point of PLA decreased upon the increase of LDHs content in the membranes.