Synthesis of Microporous Aluminosilicate by Direct Thermal Activation of Phenyl-Substituted Single-Source Aluminosilicate Molecular Precursors

The construction of aluminosilicates from versatile molecular precursors (MPs) represents a promising alternative strategy to conventional processes based on monomeric molecular or polymeric Al and Si sources. However, the use of MPs often suffers from drawbacks such as the decomposition of the core structures in the presence of solvents, acids, or bases. In this work, we demonstrate a simple thermal synthesis of porous aluminosilicates from single-source spiro-7-type MPs that consist of a tetrahedral Al atom and six Si atoms functionalized with 12 phenyl (Ph) groups, (C⁺)[Al{Ph₂Si(OSiPh₂O)₂}₂]^- (C⁺[AlSi₆]^-; C⁺ = pyridinium cation (PyH⁺), Na⁺, K⁺, Rb⁺, or Cs⁺), without using a solvent or activator. Microporous aluminosilicates synthesized via the thermal treatment of C⁺[AlSi₆]^- under a 79% N₂ + 21% O₂ atmosphere exhibited extremely low carbon contents (0.10-1.28%), together with Si/Al ratios of 3.9-6.7 ± 0.2 and surface areas of 103.1-246.3 m²/g. The solid-state ²⁷Al and ²⁹Si MAS NMR spectra suggest that the obtained aluminosilicates with alkali cations retain a tetrahedral Al site derived from the spiro-7-type core structure. After a proton-exchange reaction, the aluminosilicates showed almost 1.5 times higher reactivity in the catalytic ring-opening of styrene oxide than the aluminosilicate before proton exchange due to the catalytically active OH site being predominantly bridged by tetrahedral Al and Si atoms. These results suggest that the present MP strategy is a promising method for the introduction of key structures into active inorganic materials.

Performance of surfactant-modified *BEA-type zeolite nanosponges for the removal of nitrate in contaminated water: Effect of the external surface

Hierarchical *BEA-type nanosponges zeolite with a high external surface area (116 m².g^-1) and small crystal size, synthesized in the presence of a dual-porogenic organic compound, were modified with a cationic surfactant (HDTMA⁺Br^-: hexadecyltrimethyl ammonium bromide) in order to create a new anion exchanger system: the surfactant-modified zeolite nanosponges (SMZ_NS). For comparison, two other surfactant-modified *BEA-type zeolite materials, SMZ_MC and SMZ_NC, were obtained by modifying the synthesized conventional micron-size microcrytals and nanocrystals *BEA-type zeolite with HDTMA⁺Br^-, respectively. Textural and structural properties were determined for the three prepared materials using N₂ adsorption/desorption analysis, XRD, SEM, and TEM. Nitrate adsorption isotherms were drawn in a large concentration range [0.8-24.2 mmol.L^-1] and fitted with Langmuir isotherm model. The maximum nitrate removal capacity (1338 mmol.Kg^-1/83 mg.g^-1) was obtained for SMZ_NS material. This value is the highest ever observed for nitrate removal using surfactant-modified zeolite. The nitrate removal kinetics were fitted with the pseudo second-order model for both materials SMZ_NS and SMZ_NC.

Synthesis of Binderless ZK-4 Zeolite Microspheres at High Temperature

Binderless zeolite macrostructures in the form of ZK-4 microspheres were prepared using anion-exchange resin beads as shape-directing macrotemplates. The particles were synthesized under hydrothermal conditions at different temperatures and treatment times. The influence of the different synthesis parameters was investigated by X-ray diffraction, scanning electron microscopy, fluorescence X, nitrogen adsorption measurements and ²⁹Si solid-state NMR. Fully crystalline spheres similar in size and shape to the original resin beads were obtained by a hydrothermal treatment at the highest temperatures (150⁻180 °C) for a short treatment time of 24 h. The synthesized microspheres showed to be promising in the molecular decontamination of volatile organic compounds (VOCs).

Study of the antimicrobial and antifouling properties of different oxide surfaces

Membrane separation processes find applications in an array of fields as they use far less energy and chemical agents than competing processes. However, a major drawback of membrane technology is that biofilm formation alters membrane performances. Preventing biofilm formation is thus a pivotal challenge for larger-scale development of membrane processes. Here, we studied the comparative antibacterial activities of different inorganic membranes (ceramic and zeolite-coated ceramic with or without copper exchange) using several bacterial strains (Escherichia coli, Staphylococcus aureus, and Bacillus subtilis). In static conditions, alumina plates coated with Cu-exchanged zeolite showed significant bactericidal activity. In dynamic mode (circulation of a contaminated nutrient medium), there was no observable bacterial adhesion at the surface of the Cu-exchanged material. These results confirm the antifouling properties of the Cu-mordenite layer due to both the increased hydrophilicity and antibacterial properties of the active layer.Tests performed with tubular filtration membranes (without copper exchange) showed a significant decline in membrane hydraulic properties during filtration of culture media containing bacteria, whereas copper-exchanged membranes showed no decline in hydraulic permeability. Filtration tests performed with concentrated culture media containing spores of B. subtilis led to a significant decrease in membrane hydraulic permeabilities (but less so with Cu-exchanged membranes). The surfaces showed less effective global antifouling properties during the filtration of a concentrated culture medium due to competition between bacterial growth and the bactericidal effect of copper. Analyses of copper leached in solution show that after a conditioning step, the amount of copper released is negligible.

Influence of LiCl aqueous solution concentration on the energetic performances of pure silica chabazite

Stored energy is increased by a factor of 5.5 for the “Si-CHA–20 M aqueous LiCl” system compared to the “Si-CHA–water” system.

The influence of the nature of organosilane surfactants and their concentration on the formation of hierarchical FAU-type zeolite nanosheets

Hierarchical FAU-type zeolite nanosheets were successfully synthesized by using different organosilane surfactants.