Zn-Al Layered Double Hydroxides Research Articles

Elucidating the Photo-Induced Electronic Structure and Mechanisms of ZnAl-Layered Double Hydroxides: A DFT Study.

Layered double hydroxides (LDHs) have been regarded as excellent catalysts for a variety of photocatalytic applications including the hydrogen production, carbon dioxide reduction, and nitrogen fixation, etal. The elucidation of the photocatalytic mechanism of LDH-based photocatalysts under light irradiation, especially at the ultraviolet (UV) and deep ultraviolet (DUV) region, at the molecular level has remained elusive. In this study, the photo-induced electronic structure of ZnAl-LDH materials were investigated, and a comprehensive understanding of its underlying mechanism, both in the UV and DUV region, was gained using density functional theory (DFT) calculations. The UV and DUV regions exhibit distinct excitation characteristics, revealing the complex interactions between electrons and holes within the system. The DUV region significantly promotes electron transfer, indicating the potential application of LDH materials as a DUV catalysis material. This study elucidates the electron transfer kinetics in LDHs upon UV and DUV irradiation, thereby offering new perspective for the development of photocatalytic materials under different light region.

Synthesis of eco-friendly CaCO3@Zn-Al MMO core-shell nanoflowers photocatalyst using bio–eggshell waste for improved photocatalytic degradation of RhB under visible light irradiation

In this study, a type-I heterojunction was synthesized based on eggshell waste doped mixed metal oxide (ES@ZnAl MMO) for the degradation of RhB dye under visible light irradiation. The ES@ZnAl MMO core-shell was synthesized using waste eggshell and layered double hydroxide (LDH) as primary precursors. After their mechanochemical assembly and thermal treatment, CaCO3 was formed in both calcite and vaterite forms, alongside mixed metal oxides derived from the LDH (ZnO and Al2O3). The formation of a heterojunction between the semiconductors results in an improved activation of sites, a decrease in bandgap energy from 5.72 to 3.44 eV, and an increase in degradation capacity. The elemental composition, morphology, structural, and optical properties of the ES@ZnAl MMO nanocomposite were analyzed using various techniques. The optimal ES@ZnAl MMO photocatalyst demonstrated superior performance, reaching over 98% of RhB dye degradation under optimal conditions, outperforming pure ZnAl LDH, ZnAl MMO, and ES. After five run cycles, the ES@ZnAl MMO heterojunction still maintained a high photocatalytic performance for RhB dye (99%). Furthermore, it displayed high performance in degrading various other pollutants, including OG, IC, MB, and 2.4-DP, with degradation efficiencies of 97%, 99%, 99%, and 87%, respectively. This economically advantageous heterojunction showed its importance in environmental remediation, presenting a promising solution for addressing diverse pollution challenges.

Assessing the efficiency, selectivity, and reusability of ZnAl-layered double hydroxide and Eucheuma cottonii composite in removing anionic dyes from wastewater

This study synthesised ZnAl-Eucheuma cottonii (ZnAl-EC) composites made from ZnAl-Layered Double Hydroxide (ZnAl-LDH) and Eucheuma cottonii (EC) with the aim of making the composites have better stability. ZnAl-EC was tested for its ability to absorb anionic dyes. The thermal stability of ZnAl-EC was high % weight reduction decomposed by 3.64% and left a residue of 95.96%. The maximum adsorption capacity (Qmax) of ZnAl-EC was 384.61 mg/g. The ZnAl-EC can be reused up to 4–5 cycles with 4th and 5th cycle % adsorption of 75.10% and 48.83%. Kappa-carrageenan functional groups were identified by FTIR interacting on the surface and dyes adsorbed on the surface of ZnAl-EC seen from the d-space from 7.79 Å to 7.65 Å from XRD data analysis reinforced by XPS analysis in the Al2p spectrum with a binding energy of 72.91 eV and in S2p spectra showing a shift in binding energy and an increase in SO3- intensity. The success of this study shows the success of ZnAl-EC in regeneration and has a large adsorption capacity and shows the stability of the material as an adsorbent.

Mussel-inspired polydopamine (PDA)-grafted 2D-Ti3C2 MXene nanosheets tailored ZnAl-layered double hydroxides (LDH); Toward designing a smart self-healing epoxy composite coating

The constant challenge of corrosion significantly compromises the durability and functionality of metal substrates, propelling the demand for advanced protective solutions. This study introduces a novel smart epoxy coating system modified with a three-component nanocomposite integrating polydopamine (PDA)-modified Ti3C2 MXene with ZnAl-layered double hydroxides (LDH), intercalated with phosphate (P) and glutamate (Gl) ions as corrosion inhibitors. The innovative approach leverages the synergistic impacts of barrier protection, ion exchangeability, and self-healing capabilities to offer superior anti-corrosion performance. In the solution phase, the EIS results revealed a notable increase in resistance values, with MPLG samples exhibiting a 2.45-fold and MPLP samples a 2.17-fold enhancement compared to the blank specimen after 96 h of immersion. Furthermore, the data obtained from EIS demonstrated a significant enhancement in the barrier effects of the epoxy coating upon the addition of MPLG and MPLP. This enhancement was evidenced by a significant increase in the impedance values, which were observed to be 103-fold higher following a prolonged immersion period of 140 days. The self-healing properties, confirmed through EIS, FE-SEM, and EDX/Mapping analyses, indicated the formation of a stable corrosion-protective layer over the damaged areas, thus providing active protection. Adhesion assessments further underscored the coatings' durability, with MPLG and MPLP samples demonstrating minimal delamination. Collectively, these findings emphasize the potential of the proposed PDA-modified MXene@ZnAl-LDH nanocomposite as a multifaceted solution to corrosion challenges, promising significant advancements in the longevity and reliability of coated metal surfaces.

Antibacterial and Healing Potential of Zn-Al LDHs/Cellulose Acetate Nanocomposite in Burns and Wounds: A Study on Earthworms as a Human Skin Model

AbstractProtection against microbial invasion has gained much attention to accelerate wound healing. Layered double hydroxides (LDHs) have antimicrobial properties due to their partial release of metallic ions. In this study, Zn-Al LDHs was chemically prepared and then supported on cellulose acetate (CA) in the form of nanocomposite. This novel Zn-Al LDHs/CA nanocomposite was in vitro characterized, and its antibacterial efficacy was determined using the agar well diffusion method. Moreover, healing capabilities of the nanocomposite were evaluated via topical application on wounds and burns induced in earthworms as a model of human skin like. The average crystallite sizes of Zn-Al LDHs and 50% Zn-Al/CA nanocomposite were 18.4 nm and 14.8 nm, respectively. TEM micrographs revealed that pure CA, pure Zn-Al LDHs, and 50% Zn-Al LDHs/CA nanocomposites had an average particle size of 27.7 ± 13.5, 296.2 ± 123, and 223.2 ± 83.4 nm, respectively. Pure Zn-Al LDHs showed antibacterial activity against different bacterial strains (Inhibition zone: 15 ± 2 to 20 ± 4 mm). However, when 50% Zn-Al LDHs was supported on CA, the inhibition zone was significantly higher (20 ± 3 to 26 ± 2 mm). Visual inspection, scanning electron microscopy and histological studies of earthworm skin revealed better morphology and shorter healing duration with Zn-Al LDHs/CA nanosystem (66 h for wounds and 144 h for burns) when compared with untreated control (> 400 h). In conclusion, these findings reveal that Zn-Al LDHs/CA nanocomposite is a promising promoter for wound and burn healing due to its biocompatibility and antibacterial activity.

Construction of ZnAl LDH-Derived Sulfides with Etching Modification to Trigger Photocatalytic H2 Production and Degradation Oxidation.

Constructing novel functional photocatalysts represents a promising approach to optimize the energy band structure and facilitate the separation of photogenerated carriers. Layered double hydroxides (LDHs) exhibit notable advantages in photocatalysis due to the exceptional photoelectrochemical properties and elevated number of active surface atoms. However, an unsuitable band gap and limited carrier migration have inhibited their development in photocatalysis. Herein, we propose a novel in situ topological vulcanization strategy for optimizing the photocatalytic activity of ZnAl LDH-derived sulfides (ZnAlSx). The subsequent etching process via a 1 M NaOH solution was introduced to construct the ZnSx photocatalysts. Then, the crystallinity of the crystals was enhanced by etching to further improve the catalytic activity and stability of ZnSx. The as-synthesized ZnSx shows an excellent photocatalytic hydrogen production rate (11.89 mmol/g/h) and tetracycline degradation efficiency (91.94%) under light illumination, and its hydrogen evolution efficiency is approximately 176 and 2 times greater than that of ZnAl LDH and ZnAlSx, respectively. The characterization and density functional theory (DFT) analysis confirmed that the surface electronic properties and energy band structure of ZnAl LDH were significantly optimized after experimental treatment, resulting in enhanced carrier separation and photooxidative reduction capacity. Combining in situ topological vulcanization and etching to realize the functional conversion of ZnAl LDH provides promising insights into the construction of high-performance, low-cost photocatalysts.

Simple incorporation and calcination of Zn-Al LDH during PEO processing in near-neutral pH solutions

Plasma electrolytic oxidation (PEO) process was employed for preparing oxide coatings on AA2024 aluminum alloy in solutions containing Zn-Al layered double hydroxide (LDH) particles. Sodium hexametaphosphate aqueous solution was selected as the standard solution, based on its almost neutral pH value considered as important for the LDH stability. Different additives to the standard solution were examined including 2-mecaptobenzothiazole (MBT) and different Zn-Al LDH compounds. The formed coatings underwent characterization regarding their morphology, chemical and phase composition, as well as assessment of their photocatalytic and corrosion protection efficiency. Coating thickening and compactness evolution were noted for all coatings with LDH additions to the standard solution. Obtained coatings are well-crystallized featuring γ-Al2O3 and two Zn-containing crystalline phases, namely ZnO and NaZnPO4, originating mainly from the LDH addition to the solution. PEO coatings obtained in this study demonstrated very reasonable photocatalytic activity for immobilized photocatalyst, reaching 51 % after 6 h under UV irradiation. The inclusion of Zn-Al LDH substantially boosted the impedance modules at low frequencies by two orders of magnitude compared to bare AA2024 alloy when exposed to a 3.5 % NaCl solution.

Fabrication of Vanadate-Exchanged Electrodeposited Zn-Al Layered Double Hydroxide (LDH) Coating on a ZX21 Mg Alloy to Improve the Corrosion Resistance

Fabrication of Vanadate-Exchanged Electrodeposited Zn-Al Layered Double Hydroxide (LDH) Coating on a ZX21 Mg Alloy to Improve the Corrosion Resistance

Chemical and Structural Transformations of M-Al-CO3 Layered Double Hydroxides (M = Mg, Zn, or Co, M/Al = 2) at Elevated Temperatures: Quantitative Descriptions and Effect of Divalent Cations.

Layered double hydroxides (LDHs) exhibit diverse chemical compositions and are being designed for promising applications such as CO2 adsorbents. Although many researchers have analyzed CO2 gas evolution and structural transformation behavior at elevated temperatures, there are still inconsistencies in results on the effect of different metal ions in LDHs. In this study, on the basis of atomic/molecular-level findings from our previous study on multistep structural/chemical transformation of Mg-Al LDHs, we analyzed the quantitative gas evolution behavior and structural transformations of M-Al-CO3 LDHs with different divalent metal ions (M = Mg, Zn, or Co, M/Al = 2) at elevated temperatures. Our quantitative analysis revealed that all three LDH samples undergo the three-step chemical transformations: release of interlayer water, partial dehydroxylation of the hydroxyl layers, and complete dehydroxylation of layers and decomposition of interlayer CO32-. However, the temperature range for each step differs, as do the structural transformations for each sample: the layered structure collapses in the first step for Zn-Al LDH and Co-Al LDH, and the third step for Mg-Al LDH. Our results provide for quantitative and concrete understanding of the effect of divalent metal ions in LDHs on thermal decomposition.

Synthesis and characterization of Ketotifen Fumarate Intercalated Zn–Al Layered Double Hydroxides as sustained-release carriers

The present study seeks to synthesize, characterize, and sustain the release of properties of Ketotifen Fumarate Intercalated Zn–Al Layered Double Hydroxides (Zn-Al-KF-LDHs) by the chemical co-precipitation method. A variety of techniques were used to analyze the synthesized products, including Elemental Analysis, X-ray diffraction (XRD), Scanning electron microscope (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Thermogravimetry Differential Thermal Analysis (TG-DTA). The XRD patterns successfully highlighted the remarkable crystallinity of the typical hydrotalcite-like materials, Zn-Al-KF-LDHs. While the FT-IR analysis indicates the chemical functional groups and interlayer anions of Zn-Al-KF-LDHs, the elemental analysis determines the content of Zn, Al, S, C, H, and N. The TG-DTA results show that Zn-Al-KF-LDHs possess improved thermal stability. These findings provide an empirical understanding of the supramolecular structure of Zn-Al-KF-LDHs, enabling its comprehensive structural analysis. Additionally, the sustained-release properties of simulated gastric juice and intestinal juice, which followed the theoretical models of Higuchi and Riger-Peppas, indicated that the layered double hydroxides have potential applications as sustained-release carriers for ketotifen fumarate.

Vitamin B3 Intercalated in Layered Double Hydroxides: A Drug Delivery System for Metabolic Regulation.

The organic compound niacin or nicotinic acid, also known as vitamin B3 (VitB3), is essential for human nutrition and metabolic regulation. However, in high doses, it can provoke side effects, such as hyperglycemia, liver damage, and flushing. Development of a controlled release system that slowly releases VitB3 into the organism would avoid high dosing peaks, thus contributing to decrease the occurrence of side effects in nutritional supplementation. Here, we show that the slow and controlled release of VitB3 in an acid environment can be achieved via its intercalation in layered double hydroxides (LDHs). The synthesis of a ZnAl-VitB3 system is shown, in which VitB3 is intercalated in a ZnAl LDH. The presence of VitB3 in the ZnAl-VitB3 system was confirmed by elemental analysis, infrared (FTIR) and NMR spectroscopy, while successful intercalation in the LDHs was revealed by powder X-ray diffraction (PXRD). In vitro release tests were carried out in a concentrated HCl solution of pH 1.5, a pH similar to the human stomach environment. The results showed a steady release of VitB3 from the LDH host, with 90% of the vitamin liberated in the first 60 min after the suspension of the LDH in the acidic solution.

Chelating agent stimulated LDH post-treatment of PEO coated AA2024

Layered double hydroxides (LDHs) are well known and broadly investigated on bare aluminum alloys, but not on PEO treated aluminum where source of aluminum ions is restricted. The additions of the chelating agents were tested in this work to stimulate the LDH formation on PEO (plasma electrolytic oxidation) coated aluminum alloy AA2024. 1,3-diamino-2-hydroxipropane-N,N,N’,N’-tetraacetic acid (DHPTA) was identified as the most effective one among tested additives. Its performance in terms of LDH growth stimulation was investigated. The DHPTA additive provides an increase of the pH of the LDH synthesis compared to previously known methods to achieve hydration of aluminum oxide from PEO as the initial stage of PEO etching, as well as the formation of soluble complex compounds of Zn-DHPTA, necessary for the formation of ZnAl LDH. The process of LDH formation was also followed by intercalation of DHPTA ions into LDH galleries. It was shown that LDH was formed both on the surface and insight the pores of parental PEO coating. Moreover, it imparted lubricating properties to the hybrid coating. Finally, PEO-LDH coating demonstrated higher corrosion resistance and long-term stability comparing to the PEO coated aluminum alloy.

Palladium Nanoparticles Decorated over Polydopamine-coated Zn–Al-layered Double Hydroxide (Zn-Al LDH@PDA/Pd NPs) as Recyclable Heterogeneous Nanocatalyst for Suzuki–Miyaura Coupling Reactions

Palladium Nanoparticles Decorated over Polydopamine-coated Zn–Al-layered Double Hydroxide (Zn-Al LDH@PDA/Pd NPs) as Recyclable Heterogeneous Nanocatalyst for Suzuki–Miyaura Coupling Reactions

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.

Chemical and physical modification of graphene oxide nano-sheets using casein, Zn-Al layered double hydroxide, alginate hydrogel, and magnetic nanoparticles for biomedical applications

In our study, we developed a novel nanobiocomposite using graphene oxide (GO), casein (Cas), ZnAl layered double hydroxide (LDH), sodium alginate (Alg), and Fe3O4 magnetic nanoparticles. To synthesize the GO, we used a modified Hummer's method and then covalently functionalized its surface with Cas protein. The functionalized GO was combined with as-synthesized ZnAl LDH, and the composite was conjugated with alginate hydrogel through the gelation process. Finally, we magnetized the nanobiocomposite using in-situ magnetization. The nanobiocomposite was comprehensively characterized using FT-IR, FE-SEM, EDX, and XRD. Its biological potential was assessed through cell viability, hemolysis, and anti-biofilm assays, as well as its application in hyperthermia. The MTT assay showed high cell viability percentages for Hu02 cells after 24, 48, and 72 h of incubation. The nanobiocomposite had a hemolytic effect lower than 3.84 %, and the measured bacterial growth inhibition percentages of E. coli and S. aureus bacteria in the presence of the nanobiocomposite were 52.18 % and 55.72 %, respectively. At a concentration of 1 mg.mL−1 and a frequency of 400 kHz, the nanocomposite exhibits a remarkable specific absorption rate (SAR) of 67.04 W.g−1, showcasing its promising prospects in hyperthermia applications.

Insight on Zn-Al LDH as electrocatalyst for CO2 reduction reaction: An in-situ ATR-IR study

Electrochemical reduction of CO2 (CO2RR) is expected to play a key role among the various strategies being explored to limit global warming. In this scenario, Layered Double Hydroxides (LDHs) are emerging as a promising class of electrocatalysts to replace the most used noble metals. In this work three Zn-Al LDH with different Zn2+/Al3+ ratio were synthesized and characterized by means of XRD, STEM-EDX and HR-TEM. Their suitability for CO2RR to CO was assessed by means of a custom-made three-compartment cell, showing an increase in CO selectivity by decreasing the Zn2+/Al3+ ratio. The CO2 interaction with the samples was firstly characterized by means of volumetric adsorption measurements, exhibiting an increase in capture capacity by decreasing the Zn2+/Al3+ ratio. The evolution of the samples in interaction with a CO2-saturated liquid flow was then deeply investigated by means of in-situ ATR-IR spectroscopy. The samples displayed a different evolution in the vibrational region of the carbonate-like species (1800–1200 cm−1). To better discriminate the different carbonate cyclohexane was also employed. A definitive assignment of the main IR bands of the carbonate was carried out by studying the spectral behavior of the different bands observed in the ATR-IR experiments and by comparing these results with the existing literature. Interestingly, Zn-Al 1:2 LDH, the most efficient electrocatalyst for CO2RR, is also the sole sample exhibiting a higher monodentate to total bidentate carbonates ratio, suggesting that the existence of a higher content of low coordination oxygen anions with stronger basic character can influence the final catalytic activity.

Development of a novel fluorescence spectroscopy based method using layered double hydroxides to study degradation of E. coli in water

Layered double hydroxides (LDHs) belong to a class of 2D nanomaterials having metallic ions of varying valences and interlayer spacing as in brucite. Since their discovery, they are being used everywhere. However, their biomedical properties are the most explored as they exhibit advantages like biodegradability, biocompatibility, and ease of making composites. In this research, two types of LDHs i.e. MgAl and ZnAl LDHs are synthesized via hydrothermal route. Two types of doping; Gd and Yb, are done to create GdMgAl, GdZnAl, YbMgAl and YbZnAl. After synthesis, LDHs are characterized by X-ray Diffraction, Scanning Electron Microscopy, Dynamic Light Scattering, Energy dispersive X-ray Spectroscopy, and UV–vis spectroscopy. Average length for LDHs was found out to be in the range of 275–467 nm whereas thickness was in between 67 nm and 135 nm via SEM. Hydrodynamic size came out to be between 331 nm and 1720 nm for all samples. Absorption wavelength for all samples was between 251 and 261 nm. A novel antibacterial approach utilizing LDHs was introduced, employing antibacterial photodynamic treatment. The results were quantified using fluorescence spectroscopy, taking tryptophan peak as bacterial indicator at 270 nm excitation. Spectra recorded in 285–550 nm range showed considerable bacterial degradation, notably with YbZnAl LDHs. The efficacy was further tested with Colony Forming Units. Notably, all synthesized particles outperformed UV light alone, demonstrating their versatility as photocatalysts for bacterial inactivation. This pioneering method provides a unique and effective strategy for antibacterial treatment.

ZnAl LDH-based Derivative Materials as Photocatalysts: Synthesis, Characterization, and Catalytic Performance in Tetracycline Degradation

Layered Double Hydroxide (LDH)-derived materials exhibited different characteristics from LDH precursors. The conversion of ZnAl LDH into its derivative material has been carried out to find the best catalyst for TC degradation. ZnAl (LDH)-based catalysts in this study have been effectively synthesized using coprecipitation, calcination, and restacking procedures. ZnAl Layered Double Oxide (LDO) is derived from the calcination of ZnAl LDH at 500°C. ZnAl LDH was also modified by adding Garcinia mangostana pericarp extract (GME). XRD, FT-IR, UV-DRS, and SEM-EDX were used to investigate the synthesized catalyst. ZnAl LDH exhibited the typical LDH FT-IR spectra, whereas ZnAl LDO showed metal oxide-like spectra, and the ZnAl-GME composite displayed the combination spectra of precursor material. The ZnAl LDH XRD diffraction pattern exhibited the attributes of a layered material, whereas the other three catalysts did not. Calcination destroyed the layered structure of ZnAl LDH, whereas the addition of GME to LDH and LDO generated a single-layered composite. The modified ZnAl-GME composite showed a decrease in both particle size and bandgap energy. At an ideal pH of 5, the synthesized catalyst was used in a batch system photodegradation of 5 mg/L Tetracycline (TC), employing solar light irradiation. ZnAl LDO holds the most significant catalytic activity and structural stability through the fifth regeneration cycle, degraded TC up to 100% in 90 minutes.

Zn-Al layered double hydroxide / polyurethane as a novel nanocomposite for cefixime antibiotic adsorption

Wastewater contaminated with antibiotics requires innovative solutions to remove such pollutants efficiently. In this work, Zn-Al layered double hydroxide (LDH) adsorbent supported on polyurethane (PU) (Zn-Al LDH/PU) was synthesized using a simple co-precipitation method. The synthesized material was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), zeta potential, and hydrodynamic size. This adsorbent was investigated for the removal of cefixime (CFX), which is a model third-generation cephalosporin antibiotic. The LDH phase showed a typical hexagonal layered morphology with layer sizes larger than 200 nm in diameter. CFX adsorption on PU, Zn-Al LDH and Zn-Al LDH/PU showed a maximum adsorption capacity of 94.43, 57.17, and 115.69 mg/g, respectively. The Redlich-Peterson and Baudu isotherm models were found to be the best fit models for CFX adsorption of Zn-Al LDH and Zn-Al/PU, respectively. The equilibrium time was found to be 175 and 250 min for CFX adsorption of Zn-Al LDH and Zn-Al/PU, respectively. CFX adsorption kinetics on Zn-Al LDH/PU best fitted the pseudo-second order model indicating chemisorption and diffusion limited adsorption process. Numerous types of bonding between functional groups of CFX and both Zn-Al LDH and PU could explain the adsorption mechanism. The selectivity study of CFX adsorption on Zn-Al LDH/PU using Sulfamethoxazole and Ciprofloxacin with different concentrations was investigated and discussed. The recyclability of this Zn-Al LDH/PU was also studied. Also, the effect of temperature was investigated at (23, 35, 45, 55 °C) and the thermodynamic parameters (∆H°, ∆S° and ∆G°) were calculated showing exothermic and spontaneous adsorption process.The methyl thiazolyl tetrazolium (MTT) assay indicated that the biocompatibility of Zn-Al LDH nanostructures was enhanced following modification with PU, demonstrating regulated and minimal cytotoxic effects towards normal liver cell line (WRL-68). The Zn-Al LDH/PU can be considered as a promising low-cost adsorbent for CFX antibiotic from wastewater streams.

Visible light-driven novel chlorine modified g-C3N4/ZnAl LDHs heterojunction with improved photodegradation activity towards organic pollutants

In this regard, an NH4Cl-modified g-C3N4/ZnAl-layered double hydroxides (CCN/LDHs) was successfully prepared by combining the calcine and hydrothermal treatment. The heterojunction samples are a hierarchical nanosheet structure self-assembled from the stacked hybrid flakes. The CCN/LDHs heterojunctions exhibited a superior synergistic effect between CCN and LDHs for decomposing typical tetracycline (TC) antibiotics in modulated seawater. The photodegradation kinetics constant of TC in seawater of CCN/LDHs hybrids showed 2.12 and 2.61 times higher than that of CCN and LDHs under visible light irradiation, respectively. The reusability and stability of the materials was also proved via cycling experiments. Additionally, the possible photo-degradation mechanism was illustrated based on the trapping experiments, EPR results and electron-hole pairs migration pathway analysis. With all results, this study complies the CCN/LDHs composite heterojunction and exhibits a tremendous synergistic effect for accelerating the separation of photogenerated charge carriers, which is beneficial for enhanced visible light photodegradation capacity. The exploration of CCN/LDHs in natural water systems (Xiangjiang River and underground water, Changsha, China) and heavy metal ions (Cr(VI)) demonstrated a great potential for its practical application.