Double Hydroxide Nanocomposites Research Articles

Wearable Self‐Powered Smart Sensors Enabled by 2D Flower‐Like Ni–Co Layered Double Hydroxides for Copper Monitoring in Sweat

AbstractThe growing power demands of wearable electronic devices have stimulated the development of self‐powered systems in noninvasive healthcare. Herein, ultrathin homogeneous 2D flower‐like nickel–cobalt layered double hydroxide (Ni–Co LDH) nanocomposites are prepared by a one‐step hydrothermal method to integrate a self‐powered system for wearable sweat copper ions (Cu2+) monitoring. The Ni–Co LDH nanocomposites with a lamellar structure and numerous active sites, exhibit sensitive selectivity and low detection limits for Cu2+. In addition, the optimized Ni–Co LDH provides favorable capacitive characteristics as supercapacitors for self‐powering sensors, ensuring continuous sensing energy sources. By connecting wirelessly to a smart device, a self‐powered system is constructed to achieve wearable sensing of Cu2+ in the practical application of sweat. This simple yet effective strategy provides new opportunities for the development of self‐powering health monitoring sensors, as well as smartsensing more heavy metals.

Synergistic adsorption removal of heavy metal oxoanions and cations from aqueous solution by a polyacrylate-coated ferrous sulfide and layered double hydroxide nanocomposite

Heavy metal oxoanions and cations often co-exist in the environment and it is a critical challenge to achieve their simultaneous and efficient removal due to their presence of opposite charges. Here, a polyacrylate-coated ferrous sulfide and layered double hydroxide (PAA/FeS@LDH) nanocomposite was developed. Results illustrated that PAA/FeS@LDH exhibited excellent reductivity and stability due to the dispersion of PAA and the support by LDH. The removal efficiency of single Cr(VI) (9.73 mg/L) using PAA/FeS@LDH reached 100 % within 120 min, which was significantly higher than that of LDH (35.39 %), FeS (73.13 %), and FeS/LDH (96.47 %). Attractively, an enhanced removal of Cr(VI) (19.46 mg/L) by PAA/FeS@LDH in the presence of Cu(II), Ni(II), or Cd(II) was observed, with Cr(VI) removal efficiency increasing from 49.63 % (single Cr(VI)) to 99.51 %, 82.46 %, and 72.18 % within 30 min, respectively. The adsorption capacities of Cr(VI) significantly enlarged from 140 mg Cr/g (single Cr(VI)) to 221, 175, and 171 mg Cr/g when co-existing with Cu(II), Ni(II), or Cd(II), respectively. Another interesting outcome was the significant enhancement of reusability of PAA/FeS@LDH by the co-existence of Cr(VI) and Cu(II). After 5 cycles, PAA/FeS@LDH could still remove 96.97 % of Cr(VI) together with >70 % of Cu(II) in the mixed solution, by contrast, the removal efficiency of Cr(VI) was only 38.04 % in a single solution. The characterization analysis and density functional theory calculations demonstrated that besides surface reduction, complexation and precipitation, the cation-anion bridge interaction was an essential mechanism of achieving the synergistic removal of heavy metal oxoanions and cations.

Tailored thymoquinone intercalated Layered Double Hydroxide (LDH) nanocomposites to accelerate mineralization for enhanced osteogenesis

The tunable nature of two-dimensional nanostructured Layered Double Hydroxides [LDH] and their effective intercalation ability with biomolecules make them inevitable functional hybrid materials for versatile biomedical applications. In an attempt to meet the limitations in existing bone reconstruction practice, the present work reports the synthesis of zinc and iron-based LDH [Zn-Fe LDH] and its subsequent intercalation with thymoquinone [TQ-Zn-Fe LDH] to augment osteoblastic differentiation and proliferation for accelerated bone mineralization. Structural studies depicted the polycrystalline and amorphous nature of ZnFe LDH and TQ-Zn-Fe LDH respectively. The biocompatible nature of LDHs was proven by negative cytotoxicity, cell adhesion, and proliferation assays studied in MG-63 cell lines. Gene expression studies of the nanocomposites showed a fold change of 5–10 in osteoblastic differentiation and proliferation. However, TQ-Zn-Fe LDH treated cells showed significantly higher protein translation levels of osteogenesis markers and elevated alkaline phosphatase secretion and calcium deposition on day 21, confirming their osteogenic efficiency. Thus, acquired results speculate the osteogenic potential of thymoquinone intercalated TQ-Zn-Fe-LDH to meet the limitations in bone reconstruction practice.

Carbon supported ternary layered double hydroxide nanocomposite for Fluoxetine removal and subsequent utilization of spent adsorbent as antidepressant

Fluoxetine (FLX) is one of the most persistent pharmaceuticals found in wastewater due to increased use of antidepressant drugs in recent decades. In this study, a nanocomposite of ternary ZnCoAl layered double hydroxide supported on activated carbon (LAC) was used as an adsorbent for FLX in wastewater effluents. The nanocomposite was characterized using Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), and surface area analysis (BET). The adsorption investigations showed that the maximum removal capacity was achieved at pH 10, with a 0.1 g/L adsorbent dose, 50 mL volume of solution, and at a temperature of 25 °C. The FLX adsorption process followed the Langmuir–Freundlich model with a maximum adsorption capacity of 450.92 mg/g at FLX concentration of 50 µg/mL. Density functional theory (DFT) computations were used to study the adsorption mechanism of FLX and its protonated species. The safety and toxicity of the nanocomposite formed from the adsorption of FLX onto LAC (FLX-LAC) was investigated in male albino rats. Acute toxicity was evaluated using probit analysis after 2, 6, and 24 h to determine LD50 and LD100 values in a rat model. The FLX-LAC (20 mg/kg) significantly increased and lengthened the sleep time of the rats, which is important, especially with commonly used antidepressants, compared to the pure standard FLX (7 mg/kg), regular thiopental sodium medicine (30 mg/kg), and LAC alone (9 mg/kg). This study demonstrated the safety and longer sleeping duration in insomniac patients after single-dose therapy with FLX-LAC. Selective serotonin reuptake inhibitors (SSRIs) like FLX were found to have decreased side effects and were considered the first-line mood disorder therapies.

Elongational flow‐induced microstructure evolutions in polypropylene/layered double hydroxides nanocomposites

AbstractIn this work, the effect of the non‐isothermal elongational flow on the morphology and mechanical properties of polypropylene (PP)‐based nanocomposites containing Mg‐Al layered double hydroxides (LDHs) modified with stearate or oleate functional groups has been investigated. In particular, nanocomposites containing 5 and 10 wt% of LDHs prepared through melt compounding were subjected to uniaxial elongational flow at the exit of the extruder, leading to the formation of fibers characterized by different draw ratios (DRs). The mechanical characterization of the fibers demonstrated a progressive enhancement of the tensile strength as a function of the DR with increasing the content of nanofillers. Notably, for the fibers stretched at a DR of 200 and containing 10 wt% of LDHs modified with oleate groups, the tensile strength increased fourfold as compared to that of the unfilled matrix. These results have been attributed to a progressive enhancement of the extent of the dispersions of the embedded LDHs induced by the application of the elongational flow, as also confirmed by morphological analyses. In all, the obtained results demonstrated the beneficial effect of the elongational flow in promoting the achievement of superior mechanical properties in LDHs‐containing nanocomposites, hence widening the application field of these nanostructured materials.Highlights PP/organomodified LDH nanocomposites were obtained through melt compounding. Nonisothermal elongational flow was applied to the extrudates at the die exit. Anisotropic fibers showed progressively enhanced tensile strength values. Elongational flow promoted a gradual evolution of the material microstructure. A gradual improvement of the nanofiller dispersion was observed upon elongation.

A Tablet-Operated Portable Wireless Sensing Platform for Field Simultaneous Rapid Detection of both Cd (II) and Pb (II) Using CaAl-Layered Double Hydroxide Nanocomposite Modified Integrated Screen-Printed Three-Electrode

It’s very essential to exploit a portable wireless integrated sensing platform for field simultaneous, on-site detection of heavy metal ions pollution that has been exhibited to Serious ecological and health risks even under trace levels, including Cd (II) and Pb (II) ions. In this work, we developed a portable sensing platform, consisting of an integrated screen-printed electrode (SPE) with the calcium/aluminum-layered double hydroxide (CaAl-LDH) nanocomposite based on carboxyl functionalized multi-walled carbon nanotubes (MWCNTs-COOH), a hand-held wireless electrochemical potentiostat and a tablet with a specially designed app, for field simultaneous rapid detection of both Cd (II) and Pb (II) in water environmental sample. The CaAl-LDH was produced through a facilely hydrothermal method, and the CaAl-LDH nanocomposite with MWCNTs-COOH was prepared by a one-step ultrasonic route, which demonstrated superior sensing performance for simultaneous determination of both Cd (II) and Pb (II) with a broad detection range (2–250 μg L−1 for Cd (II) and 5–250 μg L−1 Pb (II)) and low limit of detection (LOD) (0.96 μg L−1 Cd (II) and 0.74 μg L−1 for Pb (II)).Furthermore, the proposed tablet-operated portable wireless sensing platform was utilized for detection of both Cd (II) and Pb (II) in farmland irrigation canals with acceptable recoveries.

Development of polysaccharide-coated layered double hydroxide nanocomposites for enhanced oral insulin delivery.

Oral insulin (INS) is predicted to have the most therapeutic advantages in treating diabetes to repress hepatic glucose production through its potential to mimic the endogenous insulin pathway. Many oral insulin delivery systems have been investigated. Layered double hydroxide (LDH) as an inorganic material has been widely used in drug delivery thanks to its appealing features such as good biocompatibility, low toxicity, and excellent loading capability. However, when used in oral drug delivery, the effectiveness of LDH is limited due to the acidic degradation in the stomach. In this study, to overcome these challenges, chitosan (Chi) and alginate (Alg) dual-coated LDH nanocomposites with the loading of insulin (Alg-Chi-LDH@INS) were developed by the layered-by-layered method for oral insulin delivery with dynamic size of ~ 350.8nm, negative charge of ~ - 13.0mV, and dispersity index 0.228. The insulin release profile was evaluated by ultraviolet-visible spectroscopy. The drug release profiles evidenced that alginate and chitosan coating partially protect insulin release from a burst release in acidic conditions. The analysis using flow cytometry showed that chitosan coating significantly enhanced the uptake of LDH@INS by Caco-2 cells compared to unmodified LDH and free insulin. Further in the in vivo study in streptozocin-induced diabetic mice, a significant hypoglycemic effect was maintained following oral administration with great biocompatibility (~ 50% blood glucose level reduction at 4h). This research has thus provided a potential nanocomposite system for oral delivery of insulin.

Molecular-polaron-coupling-enhanced photocatalytic CO2 reduction on copper phthalocyanine/NiMgFe layered double hydroxide nanocomposites

We built CuPcS/NiMgFe-LDHs composites and probed the unique photogenerated-carrier transfer mechanism. A series of long-range Forster energy transfers prolonged the lifetime of photogenerated carriers to match the timescale of surface reaction.

Magnetic graphene oxide/Mg-Al layered double hydroxide nanocomposite as an efficient adsorbent for removal of methylene blue: A study of equilibrium isotherms, kinetics, thermodynamic and reusability

Dye pollution, mainly caused from textile industry, has become a global environmental problem. Methylene blue (MB) is a cationic dye commonly used in textile industry and needs to be removed from textile effluents. This work reports the synthesis of magnetic graphene oxide and Mg-Al layered double hydroxide (MGO/LDH) nanocomposite as an efficient adsorbent for the removal of MB from wastewater. The influence of different parameters including, pH, adsorbent amount, contact time, temperature, and initial concentration of MB were evaluated and optimized. Thermodynamic studies showed that the reaction was spontaneous and exothermic. The data were more compatible with the pseudo-second-order kinetic model with a high correlation coefficient (R2 = 0.994). Equilibrium isotherms demonstrated that the data were fitted well by a Langmuir model. Due to the synergistic effects of MGO and LDH in the nanocomposite, the removal efficiency was improved to 93.8 % for MB from wastewater by MGO/LDH.

Sandwich-type immunosensor based on aminated 3D-rGOF-NH2 and CMK-3-Fc-MgAl-LDH multilayer nanocomposites for detection of CA125

Cancer antigen 125 (CA125)11Cancer antigen 125 (CA125). is the most important biological screening indicator used to monitor epithelial ovarian cancers, and it plays a vital role in distinguishing ovarian cancers from benign diseases. Biosensors show great potential in the analysis and detection of disease markers. In this study, we designed electrochemical sensors based on three-dimensional amino-functionalized reduced graphene oxide (3D-rGOF-NH2),22three-dimensional amino-functionalized reduced graphene oxide (3D-rGOF-NH2). MgAl layered double hydroxide nanocomposites containing ordered mesoporous carbon (CMK-3),33ordered mesoporous carbon (CMK-3). and ferrocene carboxylic acids（Fc-COOH）44ferrocene carboxylic acids（Fc-COOH）.for the detection of CA125. 3D-rGOF-NH2 possesses good conductivity, a large surface area, and high porosity, enabling more immobilized nanoparticles to be deposited on its surface with excellent stability. CMK-3@Fc@MgAl-LDH nanocomposite was used as a carrier to enhance the immobilization of antibodies and the loading of Fc, conductors to enhance conductivity, and enhancers to gradually amplify the signal of Fc.The surface morphology, elemental composition, and surface groups of the materials were characterized using scanning electron microscopy (SEM),55scanning electron microscopy (SEM). transmission electron microscopy (TEM),66transmission electron microscopy (TEM). and X-ray diffraction (XRD)77X-ray diffraction (XRD). techniques. The response signal of the electrochemical sensor was measured by DPV. Under the optimal conditions, the electrochemical sensor obtained a linear detection range of 0.01 U/mL-100 U/mL with a detection limit of 0.00417 U/mL.

Development of ultrathin nanoflakes of Ni–Co LDH films by hydrothermal route for energy storage application

For energy storage systems, high capacitance, long cycling life, superior energy density, and ultrafast charge-discharge rates are important characteristics to meet the energy demands of various modern areas. Recently, the combination of Nickel (Ni) and Cobalt (Co) binary hydroxides has been recognized as a class of new materials due to their excellent electrochemical activity, high capacitance, excellent redox reversibility, spatial structure, and good electrical conductivity. Herein, Ni–Co layered double hydroxides (LDH) nanocomposites were prepared from different Ni–Co precursors under optimized preparation conditions by hydrothermal technique for supercapacitor application. As-obtained Ni–Co LDH exhibits an exceptionally high specific capacitance of 700.42 F/g was achieved at a current density of 1 A/g. Moreover, the Ni–Co LDH electrode showed a superior specific energy density of 19.69 Wh/kg and a specific power density of 2.8 Wh/kg. These excellent electrochemical results illustrate the potential of utilizing Ni–Co LDH materials for supercapacitor application and provide innovative direction for the development of future high-performance energy storage systems.

Exploring the therapeutic potential of layered double hydroxides and transition metal dichalcogenides through the convergence of rheumatology and nanotechnology using generative adversarial network

Two-dimensional Layered double hydroxides (LDHs) are highly used in the biomedical domain due to their biocompatibility, biodegradability, controlled drug loading and release capabilities, and improved cellular permeability. The interaction of LDHs with biological systems could facilitate targeted drug delivery and make them an attractive option for various biomedical applications. Rheumatoid Arthritis (RA) requires targeted drug delivery for optimum therapeutic outcomes. In this study, stacked double hydroxide nanocomposites with dextran sulphate modification (LDH-DS) were developed while exhibiting both targeting and pH-sensitivity for rheumatological conditions. This research examines the loading, release kinetics, and efficiency of the therapeutics of interest in the LDH-based drug delivery system. The mean size of LDH-DS particles (300.1 ± 8.12 nm) is −12.11 ± 0.4 mV. The encapsulation efficiency was 48.52%, and the loading efficacy was 16.81%. In vitro release tests indicate that the drug's discharge is modified more rapidly in PBS at pH 5.4 compared to pH 5.6, which later reached 7.3, showing the case sensitivity to pH. A generative adversarial network (GAN) is used to analyze the drug delivery system in rheumatology. The GAN model achieved high accuracy and classification rates of 99.3% and 99.0%, respectively, and a validity of 99.5%. The second and third administrations resulted in a significant change with p-values of 0.001 and 0.05, respectively. This investigation unequivocally demonstrated that LDH functions as a biocompatible drug delivery matrix, significantly improving delivery effectiveness.

Exfoliated Poly (styrene-co-urethane) Grafted - Polymethylmethacrylate /Layered Double Hydroxide Nanocomposite Synthesized by Metal Catalyzed Living Radical Polymerization and Solvent Blending Method

Exfoliated Poly (styrene-co-urethane) Grafted - Polymethylmethacrylate /Layered Double Hydroxide Nanocomposite Synthesized by Metal Catalyzed Living Radical Polymerization and Solvent Blending Method

A New Cu/Fe Layer Double Hydroxide Nanocomposite Exerts Anticancer Effects against PC-3 Cells by Inducing Cell Cycle Arrest and Apoptosis.

Prostate cancer treatment poses significant challenges due to its varying aggressiveness, potential for metastasis, and the complexity of treatment options. Balancing the effectiveness of therapies, minimizing side effects, and personalizing treatment strategies are ongoing challenges in managing this disease. Significant advances in the use of nanotechnology for the treatment of prostate cancer with high specificity, sensitivity, and efficacy have recently been made. This study aimed to synthesize and characterize a novel Cu/Fe layer double hydroxide (LDH) nanocomposite for use as an anticancer agent to treat prostate cancer. Cu/Fe LDH nanocomposites with a molar ratio of 5:1 were developed using a simple co-precipitation approach. FT-IR, XRD, SEM, TEM, TGA, and zeta potential analyses confirmed the nanocomposite. Moreover, the MTT cell viability assay, scratch assay, and flow cytometry were utilized to examine the prospective anticancer potential of Cu/Fe LDH on a prostate cancer (PC-3) cell line. We found that Cu/Fe LDH reduced cell viability, inhibited cell migration, induced G1/S phase cell cycle arrest, and triggered apoptotic effect in prostate cancer cells. The findings also indicated that generating reactive oxygen species (ROS) formation could improve the biological activity of Cu/Fe LDH. Additionally, Cu/Fe LDH showed a good safety impact on the normal lung fibroblast cell line (WI-38). Collectively, these findings demonstrate that the Cu/Fe LDH nanocomposite exhibited significant anticancer activities against PC-3 cells and, hence, could be used as a promising strategy in prostate cancer treatment.

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

Purpurin(pp) can be used as a photosensitive molecule in photocatalytic systems due to its excellent absorption of visible light, but its application is limited due to its poor stability under light. Layered double hydroxides (LDHs) can act as molecular containers due to their interlayer anion exchangeability, introducing target anions into the interlayer of LDHs and improving the instability of anions by utilizing the 2D confinement environment between LDHs layers. A series of co-intercalation materials with different ratios of pp and dodecyl sulfonate (SDS) were prepared through the hydrothermal method in this work, denoted as SDS-pp(x%)/LDHs. Compared with pp, the absorbance retention rate of SDS-pp(x%)/LDHs increased from 12.5% to 90% after 5 h of light exposure. Then its potential application in visible photocatalytic reduction of CO2 was explored. When the intercalation ratio of pp is 3%, the performance is optimal. Compared with ZnAl LDHs, the yield of CO produced by SDS-pp(3%)/LDHs was increased by 12 times and a small amount of 8-electron reduction product CH4 appeared. Through mechanism exploration, the matching energy level relationship between pp and LDHs promotes electron transfer from pp to LDHs. In addition, the catalyst exhibits good cyclic photocatalytic reduction performance for CO2 due to its stable intercalation structure.

A magnetic sorbent based on Zn-NiFe2O4@Ni-Al layered double hydroxide nanocomposite for the pre-concentration and quantification of mefenamic acid by differential pulse voltammetry

A novel magnetic sorbent was introduced involving a zinc–nickel ferrite@nickel–aluminum layered double hydroxide (Zn-NiFe2O4@Ni-Al LDH) nanocomposite. The Zn-NiFe2O4@Ni–Al LDH was synthesized through a co-precipitation method, and characterized using several techniques. The nanocomposite was shown to be an efficient sorbent for the pre-concentration of mefenamic acid prior to its detection by differential pulse voltammetry using a glassy carbon electrode modified with carbon nanotubes. To achieve the best extraction efficiency, the effects of various parameters such as pH, the sorbent dosage, extraction time, elution conditions, and sample volume were studied and optimized. Under the optimized experimental conditions, the calibration plot was linear in two concentration ranges from 50 to 100 nM (R2 = 0.9944) and 100–700 nM (R2 = 0.9913). The limit of detection was calculated to be 6.3 nM, and the precision of the method in the terms of intra-day and inter-day relative standard deviations (n = 5; mefenamic acid concentration = 100 nM) were 1.4% and 2.4%, respectively. The accuracy of the method was assessed by analyzing a pharmaceutical dosage form of the analyte, and comparing the results with those obtained from a standard method. To evaluate the applicability of the method, it was applied for trace determination of mefenamic acid in tablet, human plasma, urine, and pharmaceutical wastewater samples, and the satisfactory relative recovery values (96.0–103.1%) were attained for the spiked samples. The easy separation from the solution by applying an external magnet, high surface area, high stability in the strong alkaline solutions, and high reusability (more than 60 adsorption/desorption cycles) are some advantages of the synthesized nanosorbent.

Preparation of sisal fiber/polyaniline/bio-surfactant rhamnolipid-layered double hydroxide nanocomposite for water decolorization: kinetic, equilibrium, and thermodynamic studies

Sisal fiber is a potent economical biomaterial for designing composites because of its low density, high specific strength, no toxic effects, and renewability. The present study utilized sisal fiber as a starting material and subjected it to modification to produce a sisal fiber/polyaniline/bio-surfactant rhamnolipid-layered double hydroxide nanocomposite material denoted as SF@PANI@LDH@RL. The composite was evaluated for its efficacy in removing reactive orange 16 (RO16) and methylene blue (MB) from aqueous solutions. The synthesized adsorbent was characterized by FTIR, XRD, and SEM–EDS techniques; these analyses indicated the successful modification of the sisal fiber. The primary factors, including contact time, adsorbent dosage, dye concentration, temperature, and pH, were optimized for achieving the most excellent adsorption efficiency. On the one hand, methylene blue removal is enhanced in the basic solution (pH = 10). On the other hand, reactive orange 16 adsorption was favored in the acidic solution (pH = 3). The highest adsorption capacities for methylene blue and reactive orange 16 were 24.813 and 23.981 mg/g at 318 K, respectively. The Temkin isotherm model, which proves the adsorption procedure of methylene blue and reactive orange 16 could be regarded as a chemisorption procedure, supplies the most suitable explanation for the adsorption of methylene blue (R2 = 0.983) and reactive orange 16 (R2 = 0.996). Furthermore, Elovich is the best-fitting kinetic model for both dyes (R2 = 0.986 for MB and R2 = 0.987 for RO16). The recommended SF@PANI@LDH@RL adsorbent was reused six consecutive times and showed stable adsorption performance. The results demonstrate that SF@PANI@LDH@RL is a perfect adsorbent for eliminating cationic and anionic organic dyes from aqueous media.

NiFe-Layered Double Hydroxide Nanocomposites with Functionalized Bentonite Clay to Attenuate Lead Ions in Wastewater: Isothermal and Kinetic Studies

NiFe-Layered Double Hydroxide Nanocomposites with Functionalized Bentonite Clay to Attenuate Lead Ions in Wastewater: Isothermal and Kinetic Studies

Fabrication of graphene nanoplatelets/MgAl-layered double hydroxide nanocomposites as efficient support for gold nanoparticles and their catalytic performance in 4-nitrophenol reduction

The catalytic reduction of 4-nitrophenol is of considerable importance to a multitude of applications and industries. The present work introduces a new catalyst (AuNP/GNP/MgAl-LDH) containing gold nanoparticles (AuNP) supported on graphene nanoplatelets (GNP) intercalated in Mg Al layered double hydroxides (MgAl-LDH) for the reduction of 4-nitrophenol to 4-aminophenol using NaBH4 as a reducing agent. The catalyst was characterised by FTIR, XRD, STEM, TEM, and BET specific surface area. The XRD analysis showed the presence of crystalline phases of gold on the supports, while TEM demonstrated that MgAl-LDH provided uniform binding sites for AuNPs and prevented agglomeration. Similar reaction rate constant was determined for the disappearance of 4-nitrophenol and for the appearance of 4-aminophenol. The reaction rate constant was the highest for AuNP/GNP/MgAl-LDH, followed by AuNP/MgAl-LDH and AuNP/GNP. AuNP/GNP/MgAl-LDH was found stable after five repeated cycles.

Efficient Removal of Congo Red, Methylene Blue and Pb(II) by Hydrochar–MgAlLDH Nanocomposite: Synthesis, Performance and Mechanism

Organic dyes and heavy metals often coexist in industrial effluents, and their simultaneous removal is a grand challenge. Herein, a hydrochar and MgAl layered double hydroxide (HC-MgAlLDH) nanocomposite was prepared via a facile one-step hydrothermal route, and applied to remove anionic Congo red (CR), cationic Methylene blue (MB) and Pb(II) from aqueous solutions. The nanocomposite was formed by interweaving amorphous HC and crystalline MgAlLDH nanoplates and possessed more functional groups, lower zeta potential and larger specific surface area than uncomposited MgAlLDH. Batch removal experiments showed that the components HC and LDH dominated the CR and MB removals, respectively, whereas Pb(II) removal was conjointly controlled by the two components. The maximum Langmuir removal capacities of the nanocomposite to sole CR, MB, or Pb(II) were 348.78, 256.54 or 33.55 mg/g. In binary and ternary systems, the removal capacities of CR and MB only slightly decreased, while the capacity of Pb(II) increased by 41.13-88.61%. The increase was related to the coordination of Pb(II) with the sulfur-containing groups in dyes and the precipitation of PbSO4. Therefore, the simultaneous removal of CR, MB and Pb(II) was involved in a synergistic effect, including electrostatic adsorption, π-π interaction, coordination and precipitation. The present work shows that the HC-MgAlLDH nanocomposite has great potential for wastewater integrative treatment.