Selective separation of heavy metal ions from dilute aqueous solutions by foams and micelles of surfactants

Enhanced Tetracycline Adsorption of MoS2 via Defect Introduction Under Microwave Irradiation

Defect engineering is a promising method for improving the performance of MoS₂ in various fields. In this study, sulfur-defect-enriched MoS₂ (SD-MoS₂) nanosheets were fabricated via a facile microwave-hydrothermal strategy in 10 min for tetracycline (TC) adsorption applications. The introduction of sulfur defects in MoS₂ induced more exposed unsaturated sulfur atoms at the edge, enhancing the interaction between the adsorbent and antibiotic and improving the adsorption activity of the antibiotic. Density functional theory calculations further revealed that sulfur defects in MoS₂ could alter the electronic structure and exhibited low TC adsorption energy of -2.09 eV. This work provides a new method for fabricating MoS₂ nanosheets and other transition metal dichalcogenide-based adsorbents with enhanced antibiotic removal performance and a comprehensive understanding of antibiotic removal mechanisms in SD-MoS₂.

Ion-Specific Effects on Vesicle-to-Micelle Transitions of an Amino Acid Surfactant Probed by Chemical Trapping

Ion-specific effects widely exist in biological and chemical systems and cannot be explained by classical theories. The complexity of ion-specific effects in protein systems at the molecular level necessitates the use of mimetic models involving smaller molecules, such as amino acids, oligopeptides, and other organic molecules bearing amide bonds. Therefore, it is of theoretical value to determine the effect of additional salts on the aggregation transitions of acyl amino acid surfactants. Herein, the effects of specific tetraalkylammonium ions (TAA⁺) on sodium lauroyl glycinate (SLG) aggregation were studied by dynamic light scattering (DLS) and transmission electron microscopy. Although previous studies have shown that the kosmotropic TAA⁺ ions tend to induce micellar growth or micelle-to-vesicle transitions of some anionic surfactants, TAA⁺ addition in the present study induced partial vesicle-to-micelle transitions in SLG solutions. The chemical trapping (CT) method was employed to estimate changes in the interfacial molarities of water, amide bonds, and carboxylate groups during such transitions. The vesicle-to-micelle transitions were accompanied by a marked rise in interfacial water molarity and a decline in interfacial amide bonds molarity, suggesting that the hydrated TAA⁺ entered the interfacial region and disrupted hydrogen bonding, thus preventing the SLG monomers from packing tightly. Molecular dynamic simulation was also performed to demonstrate the salt-induced cleavage of amide-amide bonds between SLG headgroups. Furthermore, both CT and DLS results show that the ability of tetraalkylammonium cations to induce such transitions increased with increasing size and hydrophobicity of the cation, which follows the Hofmeister series. The current study offers critical molecular-level evidence for understanding the specific effects of tetraalkylammonium ions on the aggregation transitions of an acyl amino acid surfactant.

A small molecule with a big scissoring effect: sodium dodecyl sulfate working on two-dimensional metal–organic frameworks

In this paper, a SDS-directed solution method was developed to synthesize a series of well-dispersed two-dimensional non-layered metal–organic frameworks (MOFs) (ZIF-8 & ZIF-67) and layered MOFs (ZnTCPP & CuBDC).

Surface functionalization of MIL-101(Cr) by aminated mesoporous silica and improved adsorption selectivity toward special metal ions

Developing novel solid adsorbents with high efficiency and excellent selectivity is always an important target in the removal of toxic metal ions from waste water.