Synthesis of X- and A-Type Zeolites from Waste Stone Powder and Aluminium Dross Using Alkali Fusion

Zeolites A and X, well-known as practical materials, were successfully synthesized with high cation exchange capacity (CEC) using two industrial wastes, waste crushed stone powder and aluminum dross, by alkali fusion treatment. Waste stone powder and aluminum dross are industrial wastes, and effective utilization of these wastes has been highly expected. Since the main components of the two wastes are Si, Al and O, those wastes can be used as starting materials for synthesis of zeolites. In this study, these industrial wastes were converted into crystalline zeolite-X and –A using alkali fusion. The stone powder, dross and the mixture of these wastes were transformed into a soluble phase via alkali fusion, and then agitated in distilled water at room temperature to give an intermediate gel-like solid, followed by synthesis at 80 °C to give the final product. The zeolites were successfully synthesized via the alkali fusion process, and selective synthesis of zeolites A and X was achieved by controlling the mixing ratio of aluminium dross to stone powder.

Hierarchization of Zeolites A and X Using Bacterial Cellulose as Macroporous Support

In this work, we studied the formation of hierarchical porous cartridges by means of bacterial cellulose impregnation with the zeolites A and X. Cellulose was successfully produced by Komagataeibacter genus and the zeolites were obtained by hydrothermal route. The composites were formed using both oxidized and non-oxidized cellulose. Different characterization techniques were used to analyze the resulting materials like powder X-ray diffraction, spectroscopic techniques (infrared vibrational spectroscopy and nuclear magnetic resonance), electron microscopy, thermal analyses, as well as ionic exchange experiments. The results show that the composites present layers with large voids among them, formed by cellulose nanofibrils tangling the particles in the oxidized samples, and shiftings in the bands referent to the carboxilyc groups and hydrogen bondings. The oxidation step for the cellulose seems to be important for the hierarchization and a positive effect on the cartridges is found for Ca2+ ionic exchange tests. Thus, these components can be successfully mixed to form cartridges with potential use at gas and liquid adsorption technologies.

Immobilization of Radioiodine via an Interzeolite Transformation to Iodosodalite

We described a technology for immobilizing radioiodine in the sod-cages by the interzeolite transformation of iodine-containing LTA (zeolite A) and FAU (zeolites X and Y) into a sodalite (SOD) structure. The immobilization of iodine in the sod-cage was confirmed using diverse characterization methods including powder XRD, elemental analysis, SEM–EDS, 127I MAS NMR, and I 3d XPS. Although both zeolites A (Na-A) and X (Na-X) were well converted into SOD structure in the presence of NaI and AgI, the iodide anions were fixed in the sod-cages only when NaI was used. The ability to adsorb methyl iodide (CH3I) was evaluated for zeolites A and X in which Na+ and/or Ag+ ions were exchanged, and Ag+ and zeolite X showed better adsorption properties than Na+ and zeolite A, respectively. However, when both CH3I adsorption ability and the successive immobilization of iodine by interzeolite transformation were considered, Na-X was determined to be the best candidate of adsorbent among the studied zeolites. More than 98% of the iodine was successfully immobilized in the sod-cage in the SOD structure by the interconversion of Na-X following CH3I adsorption, although the Na-X zeolite exhibited half the CH3I adsorption capacity of Ag-X.

Optimized cesium and potassium ion-exchanged zeolites A and X granules for biogas upgrading

Ion exchange of binderless zeolite A and X granules leads to high CO2/CH4 selectivity and CO2 uptake capacity.

Conditions of synthesis and structure of metakaolin-based geopolymers: application as heavy metal cation sorbent

This study presents the synthesis of geopolymer materials designed for application as self-supporting zeolite membranes. For this purpose, batches of metakaolin activated with sodium silicate and sodium hydroxide were used. During synthesis, it was assumed that low temperatures are sufficient to receive the membranes. The composition of raw materials and temperature of activation were selected in such a way so as to correspond to the basic chemical compositions and synthesis conditions of sodalite as well as zeolites A and X. Additionally, the structural and textural properties of geopolymers were determined. The results show that it is possible to obtain composite zeolite structures in an amorphous matrix. A number of synthesized materials were used in the sorption of selected heavy metal cations (Ni2+, Zn2+, Pb2+ and Cd2+). It was concluded that the investigated geopolymerization process may be applied to obtain a material with potential use as a heavy metal sorbent.