Antioxidant intercalated hydrocalumite as multifunction nanofiller for Poly(propylene): Synthesis, thermal stability, light stability, and anti-migration property

Layered double hydroxide-based antioxidant dispersions with high colloidal and functional stability

Highly stable antioxidant dispersions were designed on the basis of ring-opened ellagic acid (EA) intercalated into MgAl-layered double hydroxide (LDH) nanoparticles. The morphology of the composite was delicately modified with ethanolic washing to obtain EtOH-EA-LDH with a high specific surface area. The colloidal stability was optimized by surface functionalization with positively charged polyelectrolytes. Polyethyleneimine (PEI), protamine sulfate (PS) and poly(acrylamide-co-diallyl dimethyl ammonium chloride) (PAAm-co-DADMAC) was adsorbed onto the surface of the oppositely charged EtOH-EA-LDH leading to charge neutralization and overcharging at appropriate doses. Formation of adsorbed polyelectrolyte layers provided remarkable colloidal stability for the EtOH-EA-LDH. Modification with PEI and PAAm-co-DADMAC outstandingly improved the resistance of the particles against salt-induced aggregation with a critical coagulation concentration value above 1 M, while only limited stability was achieved by covering the nanoparticles with PS. The high antioxidant activity of EtOH-EA-LDH was greatly preserved upon polyelectrolyte coating, which was proved in the scavenging of radicals in the test reaction applied. Hence, an active antioxidant nanocomposite of high drug dose and remarkable colloidal stability was obtained to combat oxidative stress in systems of high electrolyte concentrations.

CuAl LDH/Rice Husk Biochar Composite for Enhanced Adsorptive Removal of Cationic Dye from Aqueous Solution

The preparation of CuAl LDH and biochar (BC) composite derived from rice husk and its application as a low-cost adsorbent for enhanced adsorptive removal of malachite green has been studied. The composite was prepared by a one-step coprecipitation method and characterized by X-ray Diffraction (XRD), Fourier Transform Infra Red (FTIR), Brunauer-Emmett-Teller (BET), and Scanning Electron Microscopy - Energy Dispersive X-ray (SEM−EDX). The result indicated that CuAl LDH was successfully incorporated with the biochar that evidenced by the broadening of XRD peak at 2θ = 24° and the appearance of a new peak at 1095 cm−1 on the FTIR spectra. The BET surface area analysis revealed that CuAl/BC composite exhibited a larger surface area (200.9 m2/g) that the original CuAl LDH (46.2 m2/g). Surface morphological changes also confirmed by SEM image, which showed more aggregated particles. The result of the adsorption study indicated the composite material was efficient in removing malachite green with Langmuir maximum adsorption capacity of CuAl/BC reaching 470.96 mg/g, which is higher than the original CuAl LDH 59.523 mg/g. The thermodynamic analysis suggested that the adsorption of malachite green occurs spontaneously (ΔG < 0 at all tested temperature) and endothermic nature. Moreover, the CuAl/BC composite showed strong potential as a low-cost adsorbent for cationic dye removal since it showed not only a high adsorption capacity but also good reusability. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Antioxidant Materials Based on 2D Nanostructures: A Review on Recent Progresses

Counteracting reactive oxygen species (ROS, e.g., superoxide radical ion, H2O2 and hydroxyl radical) is an important task in fighting against oxidative stress-related illnesses and in improving product quality in industrial manufacturing processes. This review focuses on the recent advances on two-dimensional (2D) nanomaterials of antioxidant activity, which are designed for effective decomposition of ROS and thus, for reduction of oxidative stress. Some materials featured in this paper are of uni- or multi-lamellar structures modified with small molecular or enzymatic antioxidants. Others are enzyme-mimicking synthetic compounds (the so-called nanozymes) prepared without antioxidant additives. However, carbon-based materials will not be included, as they were extensively reviewed in the recent past from similar aspects. Given the landmark development around the 2D materials used in various bio-applications, sheet-like antioxidant compounds are of great interest in the scientific and technological communities. Therefore, the authors hope that this review on the recent progresses will be helpful especially for researchers working on novel developments to substantially reduce oxidative stress either in biological systems or industrial liquors.

Melt-Mixed Thermoplastic Nanocomposite Containing Carbon Nanotubes and Titanium Dioxide for Flame Retardancy Applications

The study of polymeric nanocomposites is a possible alternative to conventional flame retardants. The aim of the present work is to investigate the effects of carbon-nanotubes (CNT) and TiO₂ nanoparticles (NPs) on the thermo-mechanical, flammability, and electrical properties of polypropylene (PP). In this work, PP-TiO₂/CNT nanocomposites were obtained with TiO₂/CNT mixtures (ratio 1:2) through the melt extrusion process, with different weight percentage of nanoparticles (1, 5, and 10 wt %). The PP-TiO₂/CNT nanocomposites were characterized by DSC, TGA, MFI, FTIR, XRD, and SEM. It was possible to determine that the thermal stability of the PP increases when increasing the content of NPs. A contrary situation is observed in the degree of crystallinity and thermo-oxidative degradation, which decreased with respect to pure PP. The TiO₂ NPs undergo coalition and increase their size at a lower viscosity of the nanocomposite (1 and 5 wt %). The mechanical properties decreased slightly, however, the Young's modulus presented an improvement of 10% as well as electrical conductivity, this behavior was noted in nanocomposites of 10 wt % of NPs. Flammability properties were measured with a cone calorimeter, and a reduction in the peak heat release rate was observed in nanocomposites with contents of nanoparticles of 5 and 10 wt.

Co-intercalated layered double hydroxides as thermal and photo-oxidation stabilizers for polypropylene

An elegant and efficient approach consisting in the co-intercalation of stabilizing molecular anions is described here. The thermal stabilizer calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] (Irganox 1425, MP-Ca) and a photo-oxidation stabilizer (hindered amine light stabilizer, HALS) are co-intercalated into the interlayer regions of layered double hydroxides (LDH) in a one-step coprecipitation. These hybrid organic-inorganic materials are successively dispersed in polypropylene to form H _n M _{n '}-Ca₂Al/PP composite films (with H = HALS and M = MP) through a solvent casting method. The corresponding crystalline structure, chemical composition, morphology as well as the resistance against thermal aging and photo-oxidation are carefully investigated by various techniques. The results show that the powdered H _n M _{n '}-Ca₂Al-LDHs hybrid materials have a much higher thermal stability than MP-Ca and HALS before intercalation. In addition, the H _n M _{n '}-Ca₂Al/PP composites exhibit a higher overall resistance against thermal degradation and photo-oxidation compared to LDHs intercalated with only HALS or MP. This underlines the benefit of the co-intercalation. The co-intercalated LDH materials pave a new way in designing and fabricating high-performance multifunctional additives for polymers.

Effect of anion co-existence on ionic organic pollutants removal over Ca based layered double hydroxide

The effects of co-existing anions (NO₃^- or SO₄^2-) on the removal of sodium dodecylsulfate (SDS), representing anionic organic pollutants, by Ca-based layered double hydroxide (CaAl-LDH-Cl) are investigated to provide fundamental insights on the ionic surfactant removal in the presence of co-existing anions, and facilitate the establishment of a practical and advanced water treatment for environmental remediation. The SO₄^2- system shows higher adsorption capacity (4.43 mmol·g^-1) and larger d-spacing of adsorption resultant (3.4 nm) than the control system with no co-existing anion (3.64 mmol·g^-1, 3.25 nm) and the NO₃^- system (3.82 mmol·g^-1, 3.27 nm). The macroscopic and microscopic analyses reveal that, NO₃^- had a little influence on the SDS removal due to strong electrolysis, while SO₄^2- could significantly promote the SDS removal. Moreover, the reaction mechanism varies under different molar ratios of DS^-/SO₄^2-.