One-step coprecipitation synthesis of Cl− intercalated Fe3O4@SiO2 @MgAl LDH nanocomposites with excellent adsorption performance toward three dyes

Targeted recognition and enhanced biotransformation of phytochemicals by a dual-functional cellulose-based hydrogel bioreactor

The combined technology of molecular imprinting and immobilization is a promising strategy for improving biocatalytic performance. In this work, a dual-functional cellulose-based hydrogel bioreactor with targeted recognition and transformation functions was innovatively designed by cellulose-based molecularly imprinted polymers (CM-MIPs) hydrogel coupled with layered double hydroxide immobilized enzyme (LDH-E). Firstly, CM-MIPs hydrogel was prepared by using phlorizin, 4-pinylpyridine, and cellulose microspheres as template molecule, functional monomer, and support material, respectively. Meanwhile, layered double hydroxide (LDH) taken as a carrier to immobilize β-glucosidase. The prepared LDH was layered sheet-like structure with ultra-thin thickness of approximately only 1.5 nm, and β-glucosidase was immobilized on both sides of the LDH. Further, the dual-functional bioreactor was constructed by the anion exchange, which possessed maximum targeted adsorption capacity to phlorizin of 15.25 mg/g, exhibited 1.2 folds higher transformation efficiency than LDH-E, and the phloretin content increased 26 folds to that in Lithocarpus litseifolius (Hance) Chu leaves extracts. Moreover, the transformation efficiency remained above 70 % even after five consecutive transformations. Overall, the dual-functional bioreactor has broad prospects for the application in targeted recognition and transformation of phytochemicals, and provides a new insight on multifunctional bio-based reactors in natural production field.

Effect of Interlayer Anions on NiFe Layered Double Hydroxides for Catalytic Ozone Decomposition

NiFe layered double hydroxides (NiFe-LDH) exhibited an outstanding performance and promising application potential for removing ozone. However, the effect of interlayer anions on ozone removal remains ambiguous. Here, a series of NiFe-LDH with different interlayer anions (F-, Cl-, Br-, NO3-, CO32-, and SO42-) were prepared to investigate the effect of the interlayer anion on ozone removal for the first time. It was found that the interlayer anions are a key factor affecting the water resistance of the NiFe-LDH catalyst under moist conditions. NiFe-LDH-CO32- exhibited the best water resistance, which was much better than that of NiFe-LDH containing other interlayer anions. The in situ DIRFTS demonstrates that the carbonates in the interlayer of NiFe-LDH-CO32- will undergo coordination changes through the interaction with water molecules under moist conditions, exposing new metal sites. As a result, the newly exposed metal sites could activate water molecules into hydroxyl groups that act as active sites for catalyzing ozone decomposition. This work provides a new insight into the interlayer anions of LDH, which is important for the design and development of LDH catalysts with excellent ozone removal properties.

Hybridization of layered double hydroxides with functional particles

Layered double hydroxides (LDHs) are a class of materials with useful properties associated with their anion exchange abilities as well as redox and adsorptive properties for a wide range of applications including adsorbents, catalysts and their supports, electrodes, pigments, ceramic precursors, and drug carriers. In order to satisfy the requirements for each application as well as to find alternative applications, the preparation of LDHs with the desired composition and particle morphology and post-synthetic modification by the host-guest interactions have been examined. In addition, the hybridization of LDHs with various functional particles has been reported to design materials of modified, improved, and multiple functions. In the present article, the preparation, the heterostructure and the application of hybrids containing LDHs as the main component are overviewed.

Rapid and efficient removal of methylene blue dye from aqueous solutions using extract-modified Zn-Al LDH

Environmental pollution, particularly water pollution caused by organic substances like synthetic dyes, is a pressing global concern. This study focuses on enhancing the adsorption capacity of layered double hydroxides (LDHs) to remove methylene blue (MB) dye from water. The synthesized materials are characterized using techniques like FT-IR, XRD, SEM, TEM, TGA, EDS, BET, BJH, AFM, and UV-Vis DRS. Adsorption experiments show that Zn-Al LDH@ext exhibits a significant adsorption capacity for MB dye compared to pristine LDH. In addition, Zn-Al LDH@ext shows a significant increase in stability, which is attributed to the presence of phenolic compounds in the extract and the interactions between the functional groups of the extract and LDH. The pH and adsorbent dosage optimizations show that pH 7 and 0.7 g of Zn-Al LDH@ext are optimal conditions for efficient MB removal. The study assessed adsorption kinetics through the examination of Langmuir, Freundlich, and Temkin isotherms. Additionally, four kinetic models, namely pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich, were analyzed. The results indicated that the Temkin isotherm (R2 = 0.9927), and pseudo-second-order (R2 = 0.9999) kinetic provided the best fit to the experimental data. This study introduces a novel approach to enhance adsorption efficiency using modified LDHs, contributing to environmentally friendly and cost-effective water treatment methods.