Magnetic Layered Double Hydroxide Research Articles

Magnetic nano composites for gallic acid delivery

A new magnetic layered double hydroxide (MLDH) composed of Fe, Mg, and Al was designed to improve gallic acid delivery to breast tumors. The metals formed the octahedrons within the layers, while the gallate ions were dissolved in the aqueous interlayer space. The drug loading was 30 %, determined with UV/Vis spectrophotometry. The material exhibited superparamagnetic behavior with a saturated magnetization of 5.5 emu/gr. This magnetic property enables the compound to be directed towards the therapeutic target using an external magnetic field, while the superparamagnetic attribute prevents the material from remaining magnetized in the body after the external magnetic field is removed. The diameter of the composites, measured from TEM images, was 110 nm: small enough for systemic circulation. For comparison, a conventional layered double hydroxide composed of Mg and Al was loaded with gallic acid and impregnated with Fe3O4 magnetic nanoparticles (LDH-NP). The drug loading was slightly lower (23 %), and the material demonstrated a combination of superparamagnetic and ferromagnetic behavior. However, the saturated magnetization was higher, 15 emu/gr for the superparamagnetic-like component and 13 emu/gr for the ferromagnetic-like component. From TEM images, the diameter of the composites was 57 nm. Drug release was studied with Franz diffusion cells. Both systems showed fast release at the lysosomal pH (4.8), but the MLDH avoids the release at the blood pH (7.4) more than the LDH-NP. Lastly, the systems were tested against breast cancer cells. After 48 h, the new composite demonstrated a 77 % reduction in cell viability, while the conventional composite impregnated with NPs showed a 66 % reduction. The designed Fe/Mg/Al magnetic nano composite loaded with gallic acid is easier to manufacture and holds promise for breast cancer treatments.

Magnetic biochar-supported layered double hydroxide for simultaneous remediation of As and Cd in soil: Effectiveness, retention durability, and insight into a new immobilization mechanism

Immobilization/stabilization is a common technique for remediating As and Cd-contaminated soil. However, the effectiveness of employed stabilizer plays a crucial role in determining the fate of these contaminants. This study investigated the effectiveness and durability of a magnetic biochar-supported Ca–Mg–Al layered double hydroxide composite (FLBC) and its components in simultaneous remediation of As and Cd in Phaeozem (BS) and Krasnozem soils (RS). Results demonstrated that 5 wt% FLBC amendment immobilized >85% of As and Cd and converted them into immobile fractions even in a reduction environment. Moreover, FLBC treatment effectively resisted leaching of As and Cd by > 70% under acidic rainwater filtration, thus displaying excellent retention durability. The new immobilization mechanisms were proved using transmission electron microscope technology, where layered double hydroxide (LDH) acted as a nano-bridge to bind FLBC and soil colloids ensuring FLBC stability and synergistic immobilization. During this process, X-ray photoelectron analysis demonstrated the re-oxidation of As(III) to As(V) driven by ferric reduction that resulted in the formation of multiple stable species on the soil surface via the confirmation of X-ray absorption near fine structure and extended X-ray absorption fine structure. This species included Ca/Fe/Cd–As(V) and γ-Cd(OH)2 co-precipitation, as well as As(V)–O–Fe(III)/Ca and As–Fe tridentate-hexanuclear corner-sharing complexes. Furthermore, FLBC amendment favored the immobilization of As and Cd in RS soil compared to BS soil due to a weaker reduction potential and an increased participation of metal-(hydr)oxides for As and Cd complexation. This study provides valuable references for predicting the impact of LDH-coupled magnetic biochar technology on the fate of As and Cd in actual soil environments.

Enhancing adsorption capacity of magnetic magnesium-aluminum layered double hydroxide by surface modification with sodium dodecyl sulfate for efficient removal of organic contaminants

A magnetic magnesium-aluminum layered double hydroxide (Mag-MgAl) was prepared, and its surface was modified using surfactant sodium dodecyl sulfate (SDS) and utilized as adsorbents for antibiotic ciprofloxacin (CIP) and dyes ponceau red (PR) and methylene blue (MB). Mag-MgAl/SDS demonstrated twice the adsorption capacity for CIP compared to Mag-MgAl, confirming that the surface modification by SDS aided the adsorption capacity. At pH 3.5, Mag-MgAl removed CIP and PR, attributed to electrostatic effect and hydrogen bonding, whereas it did not interact with MB. Conversely, Mag-MgAl/SDS successfully removed both MB and CIP, suggesting that SDS micelles acted as nanoreactors attracting cationic contaminants. The PR removal efficiency was low, possibly due to electrostatic repulsion. A binary dye system adsorption assessment was performed by mixing MB and PR aqueous solutions with Mag-MgAl and Mag-MgAl/SDS as selective adsorbents. Mag-MgAl removed around 80% of PR and 45% of MB, whereas Mag-MgAl/SDS removed less than 40% of PR and 80% of MB. SDS remains adsorbed on the surface of Mag-MgAl/SDS after the adsorption process of CIP, MB, or PR. The inversion in the affinity for the target molecules suggests that the surface of the composite can be adjusted to modulate the behavior of the adsorbent toward organic contaminants.

Size-based selectivity of magnetic-layered double hydroxide (MLDH) for efficient removal of oxytetracycline in the presence of natural organic matter

While the adsorption process plays an essential role in antibiotics removal from water, one major problem for applying absorbents in actual wastewater is competitive adsorption that is commonly caused by natural organic matter (NOM). Therefore, we aimed to investigate size-based selectivity of magnetic layered double hydroxides (MLDH) as the absorbent in the mixture of oxytetracycline (OTC) and NOM, as MLDH are generally characterized by high specific surface area, limited intercalation, and ion-exchange properties. MLDH were synthesized by the one-step solvothermal method with four different Fe:Mg ratios and then applied in a series of adsorption experiments. In addition, the role of limited interlayer space of MLDH in the adsorption of OTC and NOM was investigated based on molar mass distribution of those organic components. As results, the adsorption behavior of OTC/NOM on MLDH in the binary systems was found to involve chemisorption and multi-layer coverage. Although the competitive adsorption reduced OTC adsorption, Freundlich coefficient of MLDH (KF) for OTC was higher than KF for NOM, indicating that MLDH selectively adsorbed OTC molecules in the presence of NOM. Moreover, the selectivity (α) value of all MLDH, except MLDH with a Fe:Mg ratio of 1:4, indicating substantial selective adsorption. Among the four MLDH, MLDH11 exhibited the highest α, because its smallest interlayer space offers size-based selectivity, which was also supported by the molar mass distribution. The type of NOM did not significantly affect the OTC adsorption efficiency on MLDH. The results confirmed the benefits of limited interlayer space of MLDH, which offers selectivity for adsorption of OMP in water and shows potential applicability for removing other organic micropollutants.

The “Plus” of the Outer Surface of a Magnetic Layered Double Hydroxide for Arsenic Removal from Water: Synthesis and Adsorption Aspects

The “Plus” of the Outer Surface of a Magnetic Layered Double Hydroxide for Arsenic Removal from Water: Synthesis and Adsorption Aspects

Natural deep eutectic solvent-decorated magnetic layered double hydroxide as a sorbent for the enrichment of organochlorine pesticides in environmental samples

A newly designed magnetic layered double hydroxide composite modified with a natural deep eutectic solvent derived from choline chloride and sucrose was synthesized and applied as a sorbent for the enrichment of organochlorine pesticides. The magnetic solid phase extraction (MSPE) procedure was optimized via a small central composite design and response surface methodology. The MSPE method was able to preconcentrate the organochlorine residues in environmental samples prior to GC–MS analysis. Good analytical performance of the proposed method was observed with an enrichment factor of up to 158 and low limits of detection in the ranges of 0.002–0.015 µg·L−1 and 0.03–0.10 ng·g−1 for water and soil, respectively. Satisfactory recoveries for spiked water and soil samples were obtained in the ranges of 80.9–104.7% (RSDs<7.9) and 88.8–104.1% (RSDs<7.3), respectively. This finding highlights the role of natural deep eutectic solvents as modifying agents for magnetic layered double hydroxides, which enhance the efficiency of extraction of the target analytes. The developed MSPE/GC–MS procedure was sensitive and reliable for the determination of trace organochlorine residues in environmental samples.

One-step synthesis of magnetic–layered double hydroxide and its application for oxytetracycline removal from water

Layer double hydroxide (LDH) is abundantly available for water treatment as its large surface area and large porosity satisfy the important requisite properties of adsorption. However, it is still intricate to integrate LDH with magnetic particles to enable magnetic separation from water after treatment. Therefore, we aimed to demonstrate one-step solvothermal method integrating iron reduction for preparing magnetic layered double hydroxide (MLDH) and optimize it for the oxytetracycline (OTC) adsorption by applying four different Fe:Mg ratios. The results confirmed that the synthesized MLDH by the one-step method (1S-MLDH) had typical structure of LDH and sufficient magnetic property. The adsorption efficiency of 1S-MLDH is higher than MLDH provided by two-step method (2S-MLDH). Among the four different Fe:Mg ratios of 1S-MLDH, the ratio of 1:3 showed maximum adsorption efficiency of OTC (217 mg g−1) under pH 7, which was characterized by monolayer chemisorption. This maximum efficiency was also higher than that of other materials reported in the literature, possibly because the d-spacing of 1S-MLDH1:3 is close to size of OTC molecule, thereby allowing well intercalation and adsorption in interlayers. Under environmentally relevant conditions, anions showed weak interference in OTC adsorption, and the adsorption capacities of 1S-MLDH1:3 decreased by 2.0–14.5%. Furthermore, 1S-MLDH exhibited the photo-assisted regeneration ability for adsorbent recovery and the adsorption efficiency remained over 80% after five cycles of adsorption and regeneration. Besides the higher adsorption performance, the preparation of 1S-MLDH is more convenient and less time-consuming than 2S-MLDH synthesis, and thus applicable for organic pollutants treatment with economic benefit.

Removal of perchlorate from aqueous solution using quaternary ammonium modified magnetic Mg/Al-layered double hydroxide

The magnetic and non-magnetic layered double hydroxide (LDH@Fe3O4 and LDH) were developed via simple co-precipitation method. After modified by methyltrioctylammonium chloride (N8881Cl), the absorption capability of the materials for inorganic pollutant perchlorate (ClO4-) improved obviously through ion exchange. Then the characteristics of studied materials were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectronic spectroscopy (XPS) and Zeta potential measurements. The removal performance of ClO4- from water was investigated, and the effects of adsorption parameters on the efficiency were studied, such as contact time, initial concentration, pH and co-existing anions. The adsorption process was quite rapid and the removal rate could reach over 90% on N8881Cl-LDH@Fe3O4 within just 1 min. Maximum adsorption capacities were observed as 50.58 and 60.68 mg g−1 for N8881Cl-LDH and N8881Cl-LDH@Fe3O4 at 303 K. Moreover, the pH and common co-existing anions had little effects on adsorption capacity of ClO4-. It was found that the equilibrium adsorption process could be well described by pseudo-second-order kinetic model and Langmuir adsorption isotherm model. In brief, the N8881Cl-LDH@Fe3O4 synthesized in this study has the characters of low cost, mild conditions and easy operation, showing satisfactory absorption performance such as fast adsorption and low pH-dependence, which is potential on ClO4- removal from aqueous solution.

One-Step Synthesis of Magnetic–Layered Double Hydroxide and its Application for Oxytetracycline Removal from Water

One-Step Synthesis of Magnetic–Layered Double Hydroxide and its Application for Oxytetracycline Removal from Water

Enhanced Removal Performance and Mechanistic Study of Cu2+, Cd2+ and Pb2+ by Magnetic Layered Double Hydroxide Nanosheets Assembled on Graphene Oxide

Enhanced Removal Performance and Mechanistic Study of Cu2+, Cd2+ and Pb2+ by Magnetic Layered Double Hydroxide Nanosheets Assembled on Graphene Oxide

A new magnetic bio-sorbent for arsenate removal from the contaminated water: Characterization, isotherms, and kinetics

Background: Arsenic (AS) is a heavy metal pollutant in water that has been known as one of the most important environmental contaminants due to its serious effects on both human health and the environment. This study was conducted to investigate the efficiency of calcined Co/Fe/Al LDH@Fe3 O4 @ PA as a new magnetic bio-sorbent for AS removal from the polluted water. Methods: At first, magnetic ternary calcined layered double hydroxide (Co/Fe/Al LDH) was synthesized through co-precipitation procedure. The synthesized CLDH was modified with phenylalanine amino acid, named CLDH@Fe3 O4 @PA. Infrared spectroscopy, X-ray diffraction, transmission, and field emission scanning electron microscopy (FESEM) were used to confirm the synthesis of the sorbent. The removal time, pH, and the sorbent dose were studied and optimized as the effective parameters on the As (V) removal. Results: The XRD, FTIR, TEM, SEM, EDS, and VSM techniques confirmed the properties of the synthesized magnetic bio-sorbent. Based on the optimization study, pH=6, the sorbent concentration of 30 mg, and the removal time of 5 minutes were considered as the optimum conditions with about 91% AS removal. The Langmuir isotherm with higher R2 value was matched well with the obtained results, and values obtained for qm and RL were 167 mg g–1 and 0.976 to 0.993, respectively. The kinetics studies were fitted well with the linear pseudo-first-order model with higher R2 at sorption process. Conclusion: The real samples results confirmed the excellent As (V) sorption capacity of the synthesized magnetic bio-sorbent in comparison with other sorbents. Therefore, CLDH@Fe3 O4 @PA sorbent is introduced as a new suitable sorbent for removal of As (V) from the polluted water.

Synthesis and Characterization of Copper(I)‐Cysteine Complex Supported on Magnetic Layered Double Hydroxide as an Efficient and Recyclable Catalyst System for Click Chemistry Using Choline Azide as Reagent and Reaction Medium

In this study, Fe3O4@LDH@cysteine–Cu(I) nanoparticles as a novel and recyclable catalytic system was designed and successfully synthesized. These nanoparticles show high catalytic activity for preparation of the triazole family through reaction of the organic halides with alkynes in the presence of choline azide as reagent and reaction medium. In addition, Fe3O4@LDH@cysteine–Cu(I) could be easily recovered and reused for five times without any significant loss in catalytic activity.

Adsorption of phosphorus by using magnetic Mg-Al-, Zn-Al- and Mg-Fe-layered double hydroxides: comparison studies and adsorption mechanism.

Mg-Al, Zn-Al and Mg-Fe magnetic layered double hydroxide (LDH) adsorbents were synthesized. The adsorption effect and influencing factors of these adsorbents were explored, and the adsorption mechanism of phosphorus was studied with advanced instruments. The results showed that the best adsorption performance was observed when the molar ratio of metals was 3 for the magnetic LDH adsorbents, and the maximum adsorption amount for phosphorus was 74.8, 80.8 and 67.8mg/g for Mg-Al, Zn-Al and Mg-Fe LDHs, respectively. Pseudo-second-order kinetics could be used to describe the adsorption process of phosphorus onto the magnetic LDHs. The adsorption of phosphorus onto the magnetic LDHs was an exothermic process. Lower temperatures were favourable for adsorption, and the adsorption of phosphorus onto the magnetic LDHs was a spontaneous process. When the solid-liquid ratios were 0.10g/L, 0.10g/L and 0.05g/L for Mg-Al, Zn-Al and Mg-Fe magnetic LDHs, respectively, the highest adsorption amount of phosphorus was achieved for each magnetic LDH. The maximum adsorption amount was observed at pH values of 6.0-8.0. The inhibitory effect of HCO3- on the adsorption capacity of phosphorus onto the magnetic LDHs was the strongest at a higher HCO3- concentration level. The relative content of -OH significantly reduced after adsorption of phosphorus by the FTIR analysis, which indicated that the mechanism of phosphorus removal was mainly through the exchange between hydroxyl on the adsorbent surface and phosphorus in water. XPS studies showed that oxygen provided electrons during the adsorption of phosphorus.

Recombination of CdHgTe Quantum Dot and “Dextran - Magnetic Layered Double Hydroxide - Fluorouracil” System for Cell Imaging

In this paper, we synthesized a CdHgTe type water-soluble quantum dots, combined in the next time with the drug delivery system "dextran - magnetic layered double hydroxide - fluorouracil" (DMF), built a new nanostructures platform QD@DMF for blending the fluorescent probe function of quantum dot together with the magnetic targeting curative effect of the DMF system. The Fluorescence spectrophotometer, Ultraviolet spectrophotometer, TEM and XRD were used to characterize the luminescent properties, particle morphology and phase characteristics of the QD@DMF samples. The experiments on cell imaging were carried out by laser con-focal scan microscopy technique. Results showed that the CdHgTe QDs could be successfully grafted onto the surface of the DMF system through electrostatic coupling, forming a special structure based on magnetic layered double hydroxide with a near-infrared emission wavelength in 575~780 nm. Compared with QDs, the QD@DMF composite could significantly improve the cell imaging effect, the label intensity increased with the magnetic field intensity and obeyed the linear relationship Dmean = 1.760+0.013B. The fluorescent magnetic nanoparticles maintained not only the super-paramagnetic of DMF but also the photoluminescence properties of the QDs, implicating that the QD@DMF composite may be an effective multifunction tool for optical bio-imaging and magnetic targeted therapy.

Preparation and Characterization of the Magnetic Layered Double Hydroxide - DNA Delivery System

The purpose of this paper is to prepare and evaluate a gene delivery system resulted from the intercalation of DNA with magnetic layered double hydroxide (MLDH). The structure and property of the MLDH/DNA hybrids were studied using XRD, FTIR and TG characterization. The cytotoxicity and protection effect of MLDH were evaluated by MTT assay and gel electrophoresis assay. MLDH exhibited lower cytotoxicity than other inorganic nanoparticles. Under physiological conditions, MLDH could protect DNA from enzymatic degradation. Our results confirmed that MLDH can be used safely and effectively as non-viral vectors for gene targeting therapy in form of MLDH/DNA composite.

Enhanced adsorption of anionic diazo dye by magnetic layered double hydroxide (Zn0.5Cu0.5Fe2O4@SiO2@Ni-CrLDH) from aqueous solution

A novel magnetic layered double hydroxide known as Zn0.5Cu0.5 Fe2O4@SiO2@Ni−Cr layered double hydroxide was synthesized with Zn0.5 Cu0.5Fe2O4, SiO2 and Ni−CrLDH by using coprecipitation method. In order to compare the adsorption efficiency, the Ni−CrLDH sample also was synthesized. The synthesized samples were characterized by X−ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The adsorption of Congo red (CR) by magnetic layered double hydroxide depended upon the contact time, initial dye concentration and pH. The adsorption of the Congo red (CR) reached equilibrium at 180 min and followed the pseudo−second−order kinetic equation. The adsorption capacity of the magnetic layered double hydroxide changed significantly between pH 4−10 and the maximum dye removal were 88% for CR. Moreover, the magnetic layered double hydroxide can be quickly separated from the aqueous solution by an external magnet before and after adsorption process. This indicated that the Zn0.5Cu0.5Fe2O4@SiO2@Ni−CrLDH composite was an effective adsorbent for CR dye removal with quick separation. The adsorption performance of the synthesized Zn0.5 Cu0.5Fe2O4, SiO2 and Ni−CrLDH and comparing with Ni−CrLDH show that the Zn0.5Cu0.5Fe2O4@SiO2@Ni−CrLDH can be more efficient than Ni−CrLDH for removal of CR dye.

Removal of As(V) and Sb(V) in water using magnetic nanoparticle-supported layered double hydroxide nanocomposites

To remove As(V) and Sb(V) in water, magnetic nanoparticles (MNPs) supported calcined layered double oxide (MLDO) was prepared in order to enhance the separability and removal capacity. MLDO was successfully prepared using a flocculation method and the MNPs stably attached onto the surface of LDH by both chemical bonding and physical attachment. MLDO rapidly separated As(V) and Sb(V) from water due to its external magnetic field, with the saturation magnetism of raw MNPs and MLDO being 63.2emu/g and 14.3emu/g, respectively. In addition, MLDO enhanced the removal capacity for As(V) and Sb(V) by reconstruction process. A kinetic study revealed that the removal of As(V) and Sb(V) rapidly reached equilibrium within 120min for an initial concentration of 50mg/L, and that the maximum removal capacities for As(V) and Sb(V) as calculated from the Langmuir isotherm are 83.01mg/g and 180.96mg/g, respectively. The regeneration rate of As(V) could be maintained at about 70% for five regeneration cycles for 0.5M NaOH and 5M NaCl solutions, whereas Sb(V) displayed a lower regenerability due to its higher irreversible fraction in MLDO. Nevertheless, the effective removal efficiency for As(V) and Sb(V), with its easy magnetic separation, implies that MLDO has a potential for use in field applications of wastewater treatment.

Preparation and characterization of magnetic thermosensitive fluorouracil micelles

In this study, we synthesized P(NIPAM-co-DMAM)-b-PLA polymers with free radical polymerization and ring-opening addition polymerization, and immediately assembled ‘dextran magnetic layered double hydroxide fluorouracil’ (DMF) magnetic particles into the core of the amphiphilic polymer micelles with synchronous hydration and dialysis, to generate a magnetic thermosensitive fluorouracil drug delivery system. The basic properties of the micelle particles, such as the core–shell-type structure, size, and zeta potential, were studied with 1H-NMR, FTIR, TEM, TGA, laser nanoparticle size analysis, and other characterization techniques. The thermosensitivity of the micelles was investigated by measuring parameters such as the lower critical solution temperature (LCST) and the relationship between the particle size variation and temperature. The drug release curves for the micelles at different temperatures were constructed with a dialysis method. The LCST of the triblock polymers was 42 °C. The particle sizes of the blank micelles and DMF-loaded micelles were 493.6 ± 1.8 nm and 464.9 ± 4.1 nm, respectively, at 25 °C. When the temperature was higher than LSCT, a contraction phase change in the micelle structure occurred, a significant characteristic of the core–shell-type structure, and reversible phase transition phenomena. The release behavior of the drug-loaded micelles showed obvious variations with temperature. Therefore, the magnetic thermosensitive fluorouracil drug delivery system has a good magnetic response and excellent temperature controlled release characteristics, so it can be used as a drug delivery system in magnetically and thermally targeted chemotherapy for tumors.

Synthesis pretreatment and characterization of a magnetic layered double hydroxides fluorescent probe

Abstract Using magnetic layered double hydroxide (MLDH) as carrier of fluorescein (FLU), a fluorescent composite of MLDH-FLU was prepared via intercalation reaction of ion change. The crystal properties of MLDH-FLU were investigated through XRD, IR, TEM and TG-DSC characterization. It is shown that the crystal type of MLDH-FLU composite matched well with R-hexagonal crystal system of MLDH, with crystal cell parameters of a , c and channel height h equal to 0.3199, 2.411 and 0.3267 nm respectively. The superabundant pigment adsorbed outside the composite should be cleared before interference with cells, but excessive wash would decrease stability and cause crystal phase transformation of MLDH.

Preparation and Characterization of the Magnetic Layered Double Hydroxide Fluorescence Composite

A fluorescence composite of magnetic layered double hydroxide (MLDH) and fluorescein (FLU) was synthesized by ion change reaction. The crystal structure and properties of the intercalated compound MLDH-FLU were investigated through XRD, IR, TEM and TG-DSC characterization. Results show that fluorescein is suited for intercalation assembly with MLDH, producing MLDH-FLU composite which could be used as a fluorescence probe to test the cell-transmission efficiency of MLDH delivery system.