English

Synthesis and characterization of Ln-ZSM-5/MCM-41 (Ln = La, Ce) by using kaolin as raw material

Hydrothermal synthesis of galloaluminosilicate (MFI) zeolite crystals having uniform size, morphology and Ga/Al ratio

Synthetic investigation of CIT-5 catalyst

Several factors affecting Al-MCM-41 synthesis

Synthesis of zeolite Y from diatomite as silica source

A search was conducted for a Portland cement adequately low in radioactivity for use in the construction of a lowbackground counting enclosure. Raw materials from the operating cement plants in California and finished products from over 80 plants in the United States and Canada were subjected to gamma spectrographic evaluation. The rawmaterials study of 138 samples indicated that limestone, the principal cement ingredient, is low in radioactivity compared with sources of alumina and silica. Uranium is the principal contributor of gamma radioactivity in limestone, while thorium is the principal contributor in cementplant shale'' material. When the K contribution to the total gamma spectrum is normalized to a value of 1, the averaged K:U: Th contribution ratio for limestone is 1.0: 14.4: 4.5; for shale'', 1.0: 1.2 : 2.2; and for cement products,

During the nuclear fuel cycle, a large amount of radioactive cesium is produced, and at the same time, it is difficult to safely dispose of because of its extremely soluble in water and low boiling point. The safe disposal of radioactive cesium is a problem that needs to be solved urgently. The currently used methods to treat cesium-containing wastewater such as cement fixation, glass solidification and ion exchange, have certain drawbacks, and urgently need to be further optimized. Pollucite is an analcite molecular sieve. Many studies have shown that it is one of the potential final choices for radioactive cesium. Pollucite has an appropriate pore size, without destroying the structure of pollucite, radioactive cesium cannot diffuse out of pore of pollucite, pollucite also has a good stability and high cesium loading rate. In previous studies, pollucite needs to be synthesized under high temperature conditions above 1000°C. This method will cause the volatilization of cesium and increase the difficulty of exhaust gas treatment. How to quickly synthesize pollucite at a lower temperature has become an important research direction for the safe disposal of caesium. Different from the traditional calcination method to synthesize pollucite, this paper uses hydrothermal method to simulate the generation environment of zeolite in nature, and realizes the synthesis of pollucite at a lower temperature. Using cesium contained in simulated wastewater as synthetic raw materials, combined with commonly used silicon sources and aluminum sources as synthetic raw material, through exploring different reaction conditions such as reaction temperature, reaction time, and alkali addition, the hydrothermal synthesis of pollucite was finally successfully realized. Then the influence of different reaction conditions on synthesis and cesium removal efficiency was investigated, and its growth mechanism was also analyzed. Finally, it was realized that pollucite was successfully synthesized under 150°C hydrothermal conditions using common chemical reagents as raw materials, which further promoted pollucite application in the safe disposal of radioactive cesium.

Crystalline hybrid organic–inorganic alumino-silicates

Various type of zeolites has been produced based on kaolinite and this study likewise utilized kaolin clay as raw material to synthesis zeolite A. Kaolin was in inactive state, therefore it was transformed to metakaolin through dehydroxylation at 800 °C for 4 h. The metakaolin as a source of silica and alumina was then utilized in the synthesis of zeolite A. After hydrothermal synthesis, the zeolite A was exchanged with different concentration of zinc nitrate solution. Zinc content in ion-exchanged zeolite A, ZnA was determined through AAS to calculate the ion exchange capacity. Higher concentration of zinc nitrate had higher zinc content and higher ion exchange capacity. Zeolite A and zinc-exchanged zeolite A were characterized under SEM, XRD and FTIR. Finally, zeolite A and zinc-exchanged zeolite A was used to investigate the antimicrobial properties against gram-negative bacteria, Escherichia coli and gram-positive bacteria Staphylococcus aureus. There was no antimicrobial activity for zeolite A yet zinc-ion–exchanged zeolite A showed inhibition zones around the samples for both the microorganisms.

Kaolin is a cheap and abundant source of silica and alumina, which may be used as precursors for the production of zeolites, molecular sieves with pores in the nanometer scale. Brazil, one the largest producers of kaolin, generates tons of kaolin waste in the paper coating process. That waste may be used to synthesize zeolite A and hydroxysodalite, greater added value materials with a wide range of applications. In this work, Zeolite A and hydroxysodalite were synthesized from kaolin waste of processing industries for paper coating. Kaolin was calcined to dehydroxylate kaolinite and obtain metakaolin, an amorphous material with Si/Al ratio equal to 1, being suitable for production of zeolite A and hydroxysodalite. Zeolites were synthesized under static hydrothermal conditions by reacting metakaolin with NaOH solutions of different concentrations. The zeolitic products were characterized by means of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The results showed that the higher the NaOH concentration in the reaction medium, the higher the proportion of hydroxysodalite in the zeolitic samples.

Isomerization of 1-butene over SAPO-11 catalysts synthesized by varying synthesis time and silica sources

The mineral sillimanite and zircon recovered from beach sand were considered as the sources of alumina, silica, and zirconia for the synthesis of fused zirconia mullite ( MUZ ). The mullite phase appears as a primary phase up to the zirconia percentages of 20, whereas it appears as a secondary phase in the higher percentages of zirconia (>20) in the MUZ composites. The thermal plasma provides higher temperature up to 2100°C to favor the transformation of monoclinic phases of zirconia to tetragonal/cubic zirconia for which a mixture of monoclinic, tetragonal, and cubic zirconia is observed in the X ‐ray diffraction pattern. The electron probe microstructure analysis reveals the presence of glass phase ( SiO 2 ) in the lower (5%) and higher (>15%) percentage of zirconia composites. A variation in the optical band gap (2.06–2.63 eV) and enhancement in the hardness are observed with the increasing concentration of zirconia in the MUZ composites.

Synthesis of geopolymer from industrial wastes

Seed-assisted synthesis of ZSM-48 zeolite with low SiO2/Al2O3 ratio for n-hexadecane hydroisomerization

This study presents a sustainable synthesis route for mordenite zeolite (MOR) using rice husk ash (RHA) as the silica source and waste porcelain (WP) as the aluminum source, with tetraethylammonium hydroxide (TEAOH) employed as the organic structure-directing agent (OSDA). Zeolites were synthesized with controlled Si/Al molar ratios (10, 20, and 30) to assess how framework composition influences their structural, textural, and preliminar adsorption properties. The materials were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), nitrogen physisorption (BET), thermogravimetric analysis (TGA), temperature-programmed desorption of ammonia (NH3-TPD) and cation exchange capacity (CEC). Increasing the Si/Al ratio (SAR) resulted in higher surface area, enhanced pore development, and improved thermal stability. The synthesized zeolites were then exploratorily evaluated for the removal of Pb2+, Cu2+, and Cd2+ ions under controlled pH conditions (4 and 8) at initial metal concentrations of 1–5 mg L−1, simulating textile effluents. The highest adsorption efficiencies were observed at pH 8 and for the sample with SAR = 10, particularly for Pb2+, followed by Cu2+ and Cd2+. This behavior is attributed to the greater density of framework negative charges and increased effective accessibility of acid sites in the more aluminum-rich material. Conversely, the SAR = 30 sample exhibited higher surface area and microporosity but lower affinity for metal cations, highlighting the role of framework composition in governing adsorption selectivity. Overall, the findings indicate the technical feasibility and environmental relevance of converting industrial and agro-industrial residues into zeolitic materials with promising performance for heavy-metal removal from aqueous systems. This approach promotes waste valorization while supporting the development of cleaner and potentially cost-effective water-treatment technologies.