PREPARATION OF BACTERICADAL FILLERS FROM GEORGIAN HEULANDITE-CLINOPTILOLITE AND THEIR APPLICATION FOR PAPER PRODUCTION. II. BACTERICADAL PAPER

The purpose of present work was to obtain bactericidal materials using heulandite-clinoptilolite from the Rkoni plot of the Tedzami deposit, Eastern Georgia, and to use them as a filler for the production of bactericidal paper. Materials remaining the zeolite crystal structure, containing over 130 mg/g of silver, 70 mg/g of copper, and 55 mg/g of zinc, and showing bacteriostatic activity towards pathogenic bacteria and fungi were prepared in laboratory and the filled papers were manufactured on the production lines of the GPM company. It was found that the introduction of zeolite fillers leads to an increase in the grammage, thickness and density of the paper, as well as to a certain decrease in the tensile strength in the machine direction. The introduction of zeolite fillers containing divalent metals causes a significant change in surface properties, and samples with a certain copper content become absolutely waterproof. Testing of bacteriostatic activity by disc diffusion method revealed only activity of paper with a silver-containing filler against E. coli and staphylococcus, while the colony forming unit assay indicates the activity of all metal-containing samples against staphylococcus and all zinc-containing samples against E. coli. The greatest activity against E. coli is shown by paper with a high content of zinc, against staphylococcus, paper with a high content of copper. These results are very important from a practical point of view, since they open up the possibility of replacing silver with copper and zinc.

Time-resolved dissolution elucidates the mechanism of zeolite MFI crystallization

Zeolite crystal growth mechanisms are not fully elucidated owing to their complexity wherein the formation of a particular zeolite can occur by more than one crystallization pathway. Here, we have conducted time-resolved dissolution experiments of MFI-type zeolite crystals in ammonium fluoride medium where detailed structural analysis allowed us to extrapolate and elucidate the possible mechanism of nucleation and crystal growth. A combination of electron and scanning probe microscopy shows that dissolution initiates preferentially at lattice defects and progressively removes defect zones to reveal a mosaic structure of crystalline domains within each zeolite crystal. This mosaic architecture evolves during the growth process, reflecting the changing conditions of zeolite formation that can be retroactively assessed during zeolite crystal dissolution. Moreover, a more general implication of this study is the establishment that dissolution can be used successfully as an ex situ technique to uncover details about crystal growth features inaccessible by other methods.

In-situ structural reconstruction triggers the hydrothermal synthesis of hierarchical Ti-Beta zeolites for oxidative desulfurization

Fabricating hierarchical porosity in metallosilicate zeolite crystal is a facile and efficient approach to increase the accessibility of active sites and to enhance diffusion performance in the process of catalytic...