Aluminosilicates-based nanosorbents for heavy metal removal - A review.

Contamination of water bodies with heavy metals poses a significant threat to human health and the environment, requiring the development of effective treatment techniques. In this context, aluminosilicates emerge as promising sorbents due to their cost-effectiveness and natural abundance. This review provides a clear, in-depth, and comprehensive description of the structure, properties, and characteristics of aluminosilicates, supporting their application as adsorbents and highlighting their diversity and adaptability to different matrices and analytes. Furthermore, the functionalization of these materials is thoroughly addressed, detailing the techniques currently used, exposing the advantages and disadvantages of each approach, and establishing comparisons and evaluations of the performances of various functionalized aluminosilicates in the extraction of heavy metals in aqueous matrices. This work aims not only to comprehensively review numerous studies from recent years but also to identify trends in the study of such materials and inspire future research and applications in the field of contaminant removal using aluminosilicates.

Assessing the Adjuvant Effect of Layered Double Hydroxides (LDH) on BALB/c Mice.

The discovery and validation of new adjuvants are critical areas for vaccinology. Mineral materials (e.g., alum microparticles) have been used for a long time as adjuvants in human vaccine formulations. Nonetheless, the use of nanosized materials is a promising approach to diversify the properties of adjuvants. Nanoclays are potential adjuvants proposed by some research groups. However, their adjuvant mechanisms and safety have not been fully elucidated. Herein, we aimed at expanding the knowledge on the potential adjuvanticity of layered double hydroxide (LDH) nanoparticles by reporting a detailed method for the synthesis and characterization of LDHs and the adsorption of a model antigen (bovine serum albumin, BSA). LDHs varying in diameter (from 56 to 88 nm) were obtained, and an in vitro evaluation revealed that the LDHs are not inherently toxic. BSA was passively adsorbed onto the LDHs, and the immunogenicity in mice of the conjugates obtained was compared to that of free BSA and BSA co-administered with alum (Alum-BSA). The LDH-BSA conjugates induced a higher humoral response that lasted for a longer period compared with that of free BSA and Alum-BSA, confirming that LDH exerts adjuvant effects. The 56 nm LDH particles were deemed as the more efficient carrier since they induced a higher and more balanced Th1/Th2 response than the 88 nm particles. This study is a contribution toward expanding the characterization and use of nanoclays in vaccinology and justifies further studies with pathogen-specific antigens.

Dynamic Fracture Resistance under Plane Strain Conditions of High-Density Polyethylene Nanoclay Composites.

Polymer nanoclay composites have received significant attention due to their substantially enhanced mechanical, thermal and barrier properties. However, the effect of these nanoclays on the dynamic fracture resistance of a polymer matrix during fast fracture events has not been documented. In this study, the effect of nanoclay addition on the rapid crack propagation (RCP) resistance of high-density polyethylene (HDPE) was investigated through the high-speed double torsion test. Results showed that the addition of 1, 3, and 5% of nanoclays improved the dynamic fracture resistance under the plane strain conditions (Gd1) of HDPE up to 65%. An increase in the storage and loss modulus, and a decrease in crystallinity and melt flow index with nanoclay content was also found. Although the presence of agglomerates can hinder the enhancement of Gd1 as it promotes agglomerate fracture and debonding, the increase in energy consumption through fibrillation and crazing promoted by the nanoclay prevails, suggesting that the nanoclay's toughening effect that has been extensively reported under quasi-static and impact tests, is also present under RCP conditions, and that the HDPE nanocomposites could be used in applications in which RCP must be prevented.

Influence of Organically-Modified Montmorillonite and Synthesized Layered Silica Nanoparticles on the Properties of Polypropylene and Polyamide-6 Nanocomposites.

Nanocomposites of layered silica nanoparticles (LSN) obtained by the sol⁻gel method, and commercial montmorillonite clay Cloisite®20A with polypropylene (PP) and Cloisite®30B with polyamide-6 (PA6) were prepared by melt blending in order to study their effects on barrier, mechanical properties, and thermal stability. Transmission electron microscopy (TEM) showed that all of the nanocomposites present agglomerated nanoparticles with some degree of individual particles. In barrier properties, LSN dramatically increased the oxygen and water vapor permeability of PP at low loadings (<5 wt %) due to the percolation effect. However, in PP and PA6 nanocomposites with clays, the permeability showed increases and decreases depending on the solubility of the permeating gases with the clays and the polymers. Tensile stress-strain tests otherwise showed that the nanocomposites with clays present an enhancement in the elastic modulus. Meanwhile, with the LSN, a decrease was found due to the formation of agglomerations and voids. Finally, thermogravimetric analysis under inert conditions showed the nanoparticles do not have a significant effect on the thermal stability of the nanocomposites. These results expose the relevance of the type of layered nanoparticle and polymer matrix on the barrier, mechanical, and thermal behaviors of the resulting nanocomposites.