Pure Zeolite Research Articles

Synthesis of novel antibacterial nanocomposite CuO/Ag-modified zeolite for removal of MB dye

Novel CuO/Ag nanocomposites added zeolite (CAZ) were successfully fabricated, and their effectiveness as an antibacterial on S. aureus and MB removal was evaluated. EDX, XRD, and FTIR confirm the presence of the elemental compositions of CAZ. Friable CuO nanorods (10–70 nm in diameter) existed on the surface of the zeolite. Pure zeolite had a higher band gap (5.433 eV) and lower MB removal efficiency than CAZ. The adsorption method by CAZ was more effective at removing MB than photodegradation. 0.10 CAZ had the highest removal effectiveness (~ 99%) and adsorption capacity (~ 70.4 mg g−1) of MB. The inhibitory zone diameter for 0.005 CAZ against S. aureus was 20 mm, while 0.01 CAZ had a diameter of 17 mm. Azithromycin, ceftriaxone, and erythromycin antibiotics demonstrated lower or no efficacy against S. aureus than CAZ. Significant antibacterial activities and wastewater treatment were achieved by CAZ. The combination of photodegradation and adsorption enhanced pollutant removal. It will be interesting to study further the optimal molar ratio for MB removal (0.10 CAZ) in future investigations.

Tuning crystallization for controlled morphology of Zeolite A by an eco-friendly sonochemical precursor-less method

This study describes the sustainable synthesis of zeolite 4A from industrial solid residues without the addition of chemical precursors, as well as the optimization of its structural and morphological control using a central composite design. High-modulus silicate and aluminate are extracted from fly ash and red mud by low-temperature alkali fusion (350 °C) followed by ultrasonication. The transformation of colloidal aluminosilicate sol into a stable crystal of zeolite 4A by the hydrothermal method was studied to observe morphological changes and hypothesize a crystal growth mechanism. A total of 20 experiments were conducted to optimize high-quality truncated edge cubic zeolite 4A formation. A pure zeolite 4A (85% of crystallinity, 79.825 m2/g of specific surface area, uniform pore size distribution of 3.69 nm) is obtained under the optimized conditions of FA/RM extract = 1.02, crystallization temperature = 90 °C, crystallization time = 10.25hrs. The surface morphology of zeolite 4A appears in three distinct forms: sharp edge cube when FA/RM extract is greater than 1.02 (Run 19), truncated edge cube when FA/RM extract is equal to 1.02 (Run 2), and rounded edge cube when FA/RM extract is less than 1.02 (Run 18). Based on the ANOVA and desirability function results, we can infer that our anticipated model is a fit and the desired goal of maximum crystallinity was achieved with 95% confidence. The optimized zeolite 4A shows a higher hardness removal capacity of Ca2+(184.6 Ca2+mg/g in just 15 min) and Mg2+ (253.94 mg Mg2+/g in 5 h) for moderately hard pond water than commercial one. The kinetic and thermodynamic study reveals a better fit for the pseudo 2nd order kinetic model with a faster exchange rate of Ca2+(1.5 × 10−2 g.mg−1. min−1) than Mg2+ (7.4 × 10−5 g mg−1. min−1) and cation exchange is a spontaneous endothermic process.

Development of a selective nanoporous Na-zeolite X from Moroccan coal fly ash for anionic dye adsorption and removal

ABSTRACT The hydrothermal treatment of Moroccan coal fly ash (CFA) in a basic medium leads to the selective formation of Na-X zeolite. By fusion with sodium hydroxide in the presence of CFA, the particles are transformed into sodium silicate and sodium aluminate, from which hydrothermal reaction favourably results in the production of a pure Na-X zeolite. A good crystallinity of Na-X zeolite was attained at NaOH:fly ash ratio of 1.2. Their high surface area and pore characteristics make the Na-X zeolite useful for the removal of the model anionic dye RY145 from water. The adsorption efficiency of the synthesised Na-X zeolite was evaluated and compared to raw CFA. Dye adsorption is more significant at acid pH, suggesting that the zeolite surface is positively charged. Kinetic and isotherm models applied to fit the experimental data reveal that the adsorption process is physisorption. It results that zeolite X is an efficient adsorbent for the extraction of dyes.

CO2-Induced Gate-Opening Adsorption on a Chabazite/Phillipsite Composite Zeolite Transformed from a Faujasite Zeolite Using Organic Structure-Directing Agent-Free Steam-Assisted Conversion.

Organic structure-directing agent-free steam-assisted conversion and Cs+ ion exchange were used to transform the faujasite (FAU)-type zeolite to the Cs+-type chabazite/phillipsite (CHA/PHI) composite zeolite. Compared with the pure PHI-type zeolite, the Cs+-type CHA/PHI zeolite showed gate-opening CO2 adsorption behavior and good thermal stability. In situ powder X-ray diffraction (PXRD) of the CO2 adsorption was measured to elucidate the mechanism for the gate-opening adsorption on the CHA/PHI zeolite. The Na+-type CHA/PHI zeolite did not show such adsorption behavior, and the PXRD pattern of the Na+-type CHA/PHI zeolite did not change with increasing CO2 partial pressure, which suggests that this unique adsorption behavior was caused by the PHI framework transition or Cs+ ions moving in both the CHA and PHI frameworks. Furthermore, in situ Fourier-transform infrared spectra of CO2 adsorption and CO2 breakthrough measurement on the Cs+-type CHA/PHI zeolite suggest that the CHA and PHI frameworks in the CHA/PHI zeolite shared eight-membered-ring windows and that CO2 molecules could easily diffuse from a CHA cage to a PHI framework. The ideal adsorbed solution theory was used to calculate the CO2/N2 separation selectivity for the Cs+-type CHA/PHI zeolite. At 298 and 318 K, the Cs+-type CHA/PHI composite zeolite showed a high CO2/N2 separation coefficient of >10,000 compared with other zeolites with high CO2 adsorption capacity. Furthermore, the CO2 working capacity was calculated for the Cs+-type CHA/PHI zeolite in both the pressure- and temperature-swing processes, and the results showed that the CHA/PHI composite zeolite could selectively separate CO2 from the CO2/N2 gas mixtures released from power generation plants operating using these processes.

Synthesis of zeolites Na-A, Na-X, and analcime from crushed stone waste and their applications in heavy metal removal in aqueous media

Crushed stone waste produced by the stone crushing in the production of aggregate for the construction industry is currently discharged in large stockpiles that facilitate the dispersion of the particles by wind currents and rainwater. Such dispersion leads to environmental issues due to suspended particles in the air and natural bodies of water, as well as dust deposited on vegetation, soil, and urban settlements neighboring the quarry. To upgrade these solids to the status of feedstock for the synthesis of materials, this work developed a conversion process for the crushed stone waste into pure zeolites Na-A, Na-X, and analcime. The high concentration of silicon in this waste encouraged this application. Mild synthesis conditions were established from the analysis of the effect of the SiO2/Al2O3 mass ratio and the crystallization temperature and time on the type of produced zeolite. Zeolites Na-X showed BET surface areas between 552 and 620 m2/g. Pb2+ and Cd2+ removal from aqueous solutions by zeolites Na-A and Na-X was investigated at different pHs through adsorption isotherms. The adsorption capacities were 555.6 and 454.5 mg Pb2+/g zeolite for zeolites Na-A and Na-X, respectively. 158.7 and 113.6 mg Cd2+/g zeolite were the corresponding capacities in the case of Cd2+.

Synthesis of NaP Zeolite Based on Bauxite Red Mud Using Hydrothermal Method on Mole Ratio of SiO2/Al2O3 Variations

Red mud is a bauxite industrial waste of reddish-brown mud with high alkalinity. Red mud has relatively high silica and alumina content, so it can be utilized as a raw material in the synthesis of zeolite. This study aims to synthesize high-purity NaP zeolite from red mud at various SiO2/Al2O3 mole ratios. The synthesis begins with neutralizing the red mud, followed by decomposition using the alkaline fusion method at a ratio of red mud:NaOH = 1:1 (w/w). The filtrate produced by the alkaline fusion was adjusted to the mole ratio of SiO2/Al2O3 = 2.0; 2.5; 3.0; and 4.0, respectively, by adding sodium silicate, followed by a hydrothermal process using an autoclave at 120oC for 16 hours. The synthesized zeolites were characterized using XRD and FTIR spectrophotometry. The XRD results showed that the zeolite produced in all variations of the SiO2/Al2O3 mole ratio studied was a type of high-purity NaP with no other zeolite crystalline phases found as impurities. The structure formed is tetragonal with a degree of crystallinity of 74.54%; 76.47%; 78.94%; 75.64%, and crystal size 80.2286; 54.3437; 37.7099 and 40.1226 nm for zeolite with SiO2/Al2O3 mole ratio 2.0; 2.5; 3.0; and 4.0, respectively. Based on the results of the study, pure NaP zeolite can be synthesized from red mud material using the hydrothermal method at the ratio of moles SiO2/Al2O3 = 2.0 – 4.0.

Catalytic Hydrogenation of Anthracene on Binary (Bimetallic) Composite Catalysts

The catalytic activity of the binary composite catalysts of Fe2O3-CoO/CaA and Fe2O3-CoO/ZSM-5 was studied. They were obtained by impregnation of CaA and ZSM-5 zeolites with aqueous solutions of sulfates of iron (FeSO4·7H2O) and cobalt (CoSO4·7H2O). The total metal content was no more than 5%. Then, oxidizing burning at 720 °C for 60 min was performed to produce the metal oxides. It was found that the obtained Fe-Co/CaA catalyst contains iron and cobalt as CoFe2O4 compound, and the Fe-Co/ZSM-5 catalyst includes CoFe2O4 and CoFe. The phase composition of the obtained catalysts was detected by the X-ray diffraction analysis. The surface morphology was investigated by the electron microscopy. The elemental composition of the obtained catalysts was determined by energy dispersive spectroscopy with mapping and inductively coupled plasma atomic emission spectroscopy. The atomic absorption analysis by the IR-spectroscopy showed the shifts of absorption bands in the infrared spectra of the pure zeolites and with added Fe and Co. The catalytic hydrogenation of anthracene was performed to determine the catalytic properties of the obtained catalysts. It is one of the most common model compounds applied to investigate the efficiency of catalytic systems. The result of hydrogenation found that conversion of anthracene at 400 °C, initial pressure of 6 MPa and duration of 60 min using the Fe-Co/CaA catalytic system equaled to ~87%. However, hydrogenation products equaled to ~84%. Anthracene conversion using the Fe-Co/ZSM-5 catalytic system and the same conditions was ~91%; among them, hydrogenated derivatives were ~71%. The proposed method is characterized by its simple execution. The obtained catalysts are be slightly inferior to platinum and rhodium catalysts in the catalytic activity.

Structure-property relationship of zeolite-Y/cubic ZnS nanohybrid material and its utilization for gaseous phase mercury removal

Zinc acetate dihydrate and thiourea based metal sulfide was synthesized and used to develop zeolite-ZnS (ZY-ZnS) nanohybrid material by using sonication process, solvothermal method and heat treatment process. The sulfur atom in thiourea is involved in formation of metal sulfide and ethylene glycol was used as solvents in the solvothermal method. The structure of the nanohybrid material was analyzed by Raman spectroscopy, FTIR, XRD and XPS. Raman spectra confirmed the presence of 4, 6- membered rings of zeolite and polar modes A1 and E1 and nonpolar mode E2 of ZnS nanoparticles. The morphology of the nanohybrid material was analyzed by TEM and SEM analysis. The uniform distribution of ZnS in the zeolite matrix was observed in TEM and SEM morphology. The spherical aggregates ZnS crystals size between 100 and 200 nm were observed. Cubical morphology was observed in pure zeolite samples in the range of 400 nm−500 nm. The X-ray photoelectron spectroscopy analysis was used to confirm the metal-sulfide species in the hybrid material. Mercury adsorption (elemental (Hg°)) in the vapor phase follows both pseudo-first-order and pseudo-second-order kinetic models. Kinetic study shows that the mercury adsorption on the zeolite-ZnS nanohybrid adsorbent was mostly regulated by the chemisorption. Vapor phase mercury adsorption capacity of zeolite-Y (ZY) and zeolite-ZnS (ZY-ZnS), is 2295 and 3461 µg/g at 180 °C, respectively. In ZY and ZY-ZnS the intraparticle diffusion rates were 86.1 and 141.2 μg/gmin-1/2, respectively. The higher intraparticle diffusion rate observed in ZY-ZnS confirm the uniformly decorated ZnS nano particles in ZY-ZnS nanohybrid material.

Synthesis of zeolite A and zeolite X from electrolytic manganese residue, its characterization and performance for the removal of Cd2+ from wastewater

Electrolytic manganese residue (EMR) can cause serious environmental and biological hazards. In order to solve the problem, zeolite A (EMRZA) and zeolite X (EMRZX) were synthesized by EMR. The pure phase zeolites were synthesized by alkaline melting and hydrothermal two-step process, which had high crystallinity and excellent crystal control. And the optimum conditions for synthesis of zeolite were investigated: NaOH-EMR mass ratio = 1.2, L/S = 10, hydrothermal temperature = 90 °C, and hydrothermal time = 6 h. Then, EMRZA and EMRZX showed excellent adsorption of Cd2+. When T = 25 °C, time = 120 min, pH = 6, C0 = 518 mg·L−1, and quantity of absorbent = 1.5 g·L−1, the adsorption capacities of EMRZA and EMRZX reached 314.2 and 289.5 mg·g−1, respectively. In addition, after three repeated adsorption–desorption cycles, EMRZA and EMRZX retained 80% and 74% of the initial zeolites removal rates, respectively. Moreover, adsorption results followed quasi-second-order kinetics and monolayer adsorption, which was regulated by a combination of chemisorption and intra-particle diffusion mechanisms. The adsorption mechanism was ions exchange between Cd2+ and Na+. In summary, it has been confirmed that EMRZA and EMRZX can be reused as highly efficient adsorbents to treat Cd2+-contaminated wastewater.

Synthesis of magnetic NaY zeolite for plasma proteomics application

Magnetically modified NaY zeolite has shown advantages in high-throughput and large-scale clinical plasma proteomic studies. In this study, magnetic NaY zeolite was prepared via an improved method, "layer by layer adhesion", using epoxy adhesive. The morphology, structure, and magnetic properties of magnetic NaY zeolite were characterized and tested by scanning electron microscope (SEM), fourier transform infrared spectrometer (FT-IR), X-ray diffractometer (XRD), and vibrating sample magnetometer (VSM), and using sodium dodecyl sulfonate-polyacrylamide gelelectrophoresis (SDS-PAGE) and liquid chromatography-tandem mass spectrometry (LC-MS) for plasma proteomics studies. The results showed that NaY zeolite was coated on the surface of Fe3O4 by epoxy adhesive, and such coating did not affect the surface properties of the magnetic zeolite. The saturation magnetization of magnetic NaY zeolite was measured as 9.964 emu g−1. Approximately 2929 proteins could be identified from plasma protein corona formed on magnetic NaY zeolite, reaching 97.6 % of the identification number of pure NaY zeolite. Furthermore, compared with NaY zeolite, the solid-liquid separation processes of magnetic zeolite during plasma proteomics studies were significantly reduced from half an hour to few minutes. Due to excellent plasma protein adsorption performance and rapid magnetic separation property, magnetic NaY zeolite is expected to become a powerful tool for the large-scale adsorption of low-abundant plasma proteins and high-throughput proteomic studies.

Zeolite membrane separators for fire-safe Li-ion batteries – Effects of crystal shape and membrane pore structure

The state-of-the-art lithium-ion batteries (LIB) use carbonate-based liquid electrolytes and polymeric separators which pose safety issues including fire-hazard. The use of fire-retarding salt-concentrated electrolytes can address the safety issues of LIBs, but these electrolytes have high viscosity and low wettability with polymeric separators making it difficult to fabricate high performance LIBs with the electrolytes. Here we report development of zeolite membrane separators with tailored pore structure and surface chemistry for preparation of fire-safe LIBs using salt-concentrated electrolytes. The zeolite membrane separators are made of zeolite particles with a specific zeolite structure, Si/Al ratio, and different particle shapes, coated on cathode by a scalable blade coating method. Intermediate pore, pure silica MFI-type zeolite (silicalite) was selected as the fire-proof material for membrane separators which also offer high wettability for the fire-retarding salt-concentrated electrolyte of lithium bis(fluorosulfonyl)imide (LiFSI) in tri-methyl phosphate solvent (TMP) solvent. Two silicalite membrane separators of similar pore size but different porosity and tortuosity were coated on cathode (LiNi0.5Mn0.3Co0.2O2 or NMC) using plate-shaped silicalite particles of low aspect ratio (LAR) and high aspect ratio (HAR). Both zeolite separators show significantly better wettability for the LiFSI/TMP electrolyte than the commercial polypropylene (PP) separator allowing fabrication of high-performance NMC/LiFSI-TMP/graphite cells with the non-combustible silicalite separator. The new fire-safe zeolite-membrane-based LIBs with the fire-retarding electrolyte exhibit excellent charge and discharge characteristics and cycle performance (similar to the state-of-the-art, but fire-unsafe LIBs with LiPF6-carbonate electrolyte and polymer separator). The membrane separators made of HAR plate-shaped zeolite showing low interparticle porosity and high tortuosity perform better than the membrane made of LAR zeolite particles, due to a more uniform lithium-ion flux from both interparticle pores and intraparticle zeolitic pores at the separator/anode interface.

Pure silica Beta zeolite supported copper species for efficient hydrogenolysis of glycerol to 1,2-propanediol

Catalytic conversion of glycerol to 1,2-propanediol is an important issue for sustainable production of fine chemicals and biodiesel. Here it is found that pure silica Beta zeolite supported copper species via hydrothermal treatment (Cu/Si-Beta-HT) are highly efficient for hydrogenolysis of glycerol to 1,2-propanediol, achieving 96.0% conversion and more than 99.9% selectivity after reaction at 240 °C for 3 h. TEM images and N2O titration experiments confirm the high dispersion of Cu nanoparticles in the catalyst. In addition, pyridine-adsorption FT-IR spectra and NH3-TPD profiles suggest the presence of copper species as Lewis acidic sites in the catalyst. The hydrogenolysis of glycerol to 1,2-propanediol mainly includes the dehydration of glycerol to acetol and hydrogenation of acetol into 1,2-propanediol, which are catalyzed by copper cations and Cu nanoparticles, respectively. In situ FT-IR spectra and kinetic studies suggest that the dehydration rate is slower than the hydrogenation rate, and the dehydration is a key step for the hydrogenolysis of glycerol to 1,2-propanediol.

Zeolite Y-supported carbon-doped TiO2 nanocomposites: Efficient solar photocatalysts for the purification of medicinal wastewater

The existence of antibiotics in aquatic streams destroys water quality and thereby poses serious ecological hitches. Photocatalysis involving nanosemiconductors is an environmentally benign technique for the mineralization of antibiotics. Herein, we prepared a new visible light-sensitive photocatalyst, zeolite Y-supported carbon-doped TiO2 nanocomposite (zeolite Y-c-TiO2), for the elimination of cefazolin antibiotic in wastewater systems. The structural and optical properties of the synthesized nanocomposites were investigated by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller surface area analysis (BET) as well as diffuse reflectance spectroscopy (UV-DRS) and photoluminescence spectroscopy (PL). The UV-Vis absorbance spectrum of zeolite Y-c-TiO2 exhibited a red shift towards longer wavelength with an increase in visible light absorption as compared to pure TiO2 nanoparticles and zeolite Y-supported TiO2 nanocomposites (zeolite Y-TiO2). Accordingly, the photocatalytic action of the zeolite Y-c-TiO2 for the degradation of methylene blue was evaluated under solar simulator, and it turned out to be highly efficient (100%) mineralization as compared to TiO2-nanoparticles (42%) and zeolite Y-TiO2 (62%) after 70 min irradiation for a 50mg L-1 methylene blue solution. Radical scavenging experiments revealed the involvement of hydroxyl radicals, superoxide radicals, and photogenerated holes in the degradation process. Consequently, zeolite Y-c-TiO2 was applied for the photocatalytic degradation of the cefazolin antibiotic in water, and complete degradation of cefazolin (50 mg L-1) was observed within 6 h of solar light irradiation on zeolite Y-c-TiO2. The degradation pathway of cefazolin was proposed by considering various intermediates detected via LC-MS analysis. The study points to the significant potential of zeolite Y-c-TiO2 photocatalyst for the purification of medicinal wastewater under sunlight.

Hybrid Organomineral Carriers for Therapeutic Proteins

—Drug delivery systems are developed to provide a necessary concentration and prolonged effect of the active substance in the organism. Orally administered protein preparations require a protection from the proteolysis in the gastrointestinal tract. Biocompatible hydrophilic polysaccharides in the composition of the matrix are especially promising, since they do not irritate the intestine and are gradually cleaved by specific glycosidases, releasing a therapeutic agent. The introduction of an insoluble porous mineral matrix into the composition of the carrier allows us to increase the concentration of the therapeutic agent in the matrix without a significant increase in the volume of the drug tablet form. In this work, a new original organomineral carrier was created based on heat-treated crushed clinoptilolite zeolite in combination with natural polysaccharides of red algae (agar–agar, agarose, and carrageenan). Granular and finely dispersed clinoptilolites in the composition of the matrix are loaded with a promising therapeutic agent (Bacillus pumilus ribonuclease (binase)), which shows a selective cytotoxicity to tumor cells. It was established that both granular and finely dispersed zeolites in a complex with polysaccharides retain the protein better as compared with pure zeolites and provide a gradual complete release of the enzyme in 18 h; at the same time, binase retains a catalytic activity and causes apoptosis in up to 23.8% of the population of HuTu80 human duodenal adenocarcinoma cells. Data obtained substantiate the prospects of designing dosage forms based on the studied organomineral carriers.

Interzeolite transformation from H+-type FAU zeolite into pure CHA zeolite via OSDA/seeds-free and steam-assisted conversion process

Pure CHA zeolite was transformed from FAU zeolite via organic structure-directing agent (OSDA)/seeds-free steam-assisted conversion (SAC). CHA zeolite was transformed using H+-type FAU zeolite with a low Si/Al ratio (Si/Al = 2.8) and a small amount of potassium hydroxide (KOH) and H2O. The Si/Al ratio of the CHA zeolite of the final product was the same as that of FAU-type zeolite as raw material because OH− ions derived from KOH reacted with H+ ions in FAU zeolite. Then, Si constituting FAU zeolite was little dissolved in a small amount of the basic solvent during the interzeolite transformation process. In general, in the interzeolite transformation process, the Si/Al ratio of the final product is lower than that of zeolite as raw material due to the dissolution of Si in the framework in the basic solvent. However, the interzeolite transformation process in this study can reduce the dissolving Si ratio using H+-type FAU zeolite. In addition, the PHI framework with low CO2 adsorption capacity arose with CHA zeolite transformed from Na+-type FAU zeolite via OSDA-free interzeolite SAC in a previous study. However, in this study, the PHI framework did not arise in OSDA-free steam-assisted interzeolite transformation process due to the use of H+-type FAU zeolite. Furthermore, the second particle morphology of CHA zeolite transformed from H+-type FAU zeolite was spherical, which has not been seen in CHA zeolite particles synthesized in previous reports. Finally, the CO2 adsorption capacity and performance of FAU and CHA zeolites were measured. CHA zeolite showed higher CO2 adsorption capacity than H+-type FAU zeolite as the starting material and high CO2 loadings at low CO2 equilibrium pressure. This study investigated that the synthesis condition, chemical properties, and CO2 adsorption performance of CHA zeolite transformed from H+-type FAU zeolite via the OSDA/seeds-free steam-assisted interzeolite transformation process.

Pure Silica with Ordered Silanols for Propylene/Propane Adsorptive Separation Unraveled by Three-Dimensional Electron Diffraction.

Adsorptive separation of propylene (C3H6) from propane (C3H8), which could deal with energy-intensive cryogenic distillation technologies, remains challenging due to their similar physiochemical properties. Herein, we present a pure silica zeolite with ordered silanols (OSs), whose crystallographic structure was unraveled by the advanced three-dimensional electron diffraction (3D ED), displaying the highly efficient separation of propylene from propane under ambient conditions. The 3D ED technique enables us to investigate its 8-ring pore opening transformation from the round one to the elliptical one during the removal of organic structure-directing agents. Such unique elliptical 8-ring pore openings can exclude larger-size propane and only adsorb propylene. Its C3H6/C3H8 separation performance is also confirmed by column breakthrough experiments, showing a high dynamic adsorption capacity of 53.36 cm3 g-1 for C3H6 but negligible C3H8 under ambient conditions. The dynamic capacity for C3H6 is superior to that of the well-known pure silica DDR-type zeolite (31.07 cm3 g-1). The density functional theory calculation demonstrates that the adsorbed propylene is distributed in the heart-shaped cavity and has a weak interaction with the OSs.

Advanced high-iron coal fly ash zeolites for low-carbon emission catalytic combustion of VOCs

Coal fly ash zeolites (CFAZs) with increased iron oxide content were prepared by double-stage alkaline conversion of high-iron lignite coal ash. Catalysts were modified by applying radiofrequency plasma treatment with trifluoromethane (RF CHF3) to increase their surface activity. Textural, compositional, and structural characterization of the parent and plasma-modified zeolites were performed by N2-physisorption, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FT-IR) spectroscopy. Oxidation state and coordination of iron species were studied by Mössbauer spectroscopy, UV-Vis spectroscopy and temperature-programmed reduction method (TPR). Acidic properties were investigated by FT-IR spectroscopy of adsorbed pyridine. The initial and plasma-modified samples were studied under toluene oxidation, where toluene was used as a model VOC. The plasma-modified iron-enriched zeolite was found to exhibit high catalytic activity for VOC oxidation, reaching a 98% toluene conversion rate at 500 °C. Despite some structural degradation effects, the plasma-treated catalysts outperformed the untreated ones in catalytic activity. Furthermore, CO2 adsorption capacity of the plasma-modified zeolite was investigated under dynamic conditions. Although plasma-treated iron-enriched zeolite showed relatively low specific surface area (194 m2/g), high dynamic carbon capture capacity of 3.8 mmol/g was measured. It significantly exceeded the capacity of CFAZs with higher specific surface area, not to mention the pure zeolite phase.

Metakaolin-based geopolymer – Zeolite NaA composites as CO2 adsorbents

In this work, three metakaolin-based geopolymer matrices were prepared, varying the molar ratio Si:Al (2.0 or 1.2) and the type of cation (sodium or potassium). Starting from these matrices, geopolymer-zeolite composites were synthesized and consolidated (80 °C), incorporating a commercial sodium-based zeolite, Na4A, with the aim of producing post combustion CO2 adsorbents, since the presence of Na4A crystalline phase is desirable due to its known remarkable CO2 adsorption capacity.The sodium-based geopolymer matrix with Si:Al = 1.2 allowed the in situ nucleation of the zeolite NaA, therefore this matrix was added with different amount of synthetic zeolite Na4A to verify the total conversion of the matrix into zeolite NaA, in view of an alternative low-cost synthesis method to obtain zeolite NaA as a “solid” in a complex form.The composites were deeply characterized and lastly tested for CO2 adsorption. The geopolymer matrices act as binders allowing the shaping of zeolite and producing functional composites with mutable chemical composition, microstructure and porosity according to the starting composition. The sodium-based geopolymer zeolite composite was the best performing in term of CO2 adsorption capacity being 1.0 mmol g−1 at 0.1 bar, nearly equivalent to synthetic zeolite Na4A (1.2 mmol g−1) and close to pure zeolite Na13X (1.4 mmol g−1), the current benchmark material for carbon capture application.

Hybrid Organomineral Carriers for Therapeutic Proteins

Drug delivery systems are designed to provide the necessary concentration and prolonged effect of the active substance in the body. Orally administered protein preparations require protection from proteolysis in the gastrointestinal tract. Biocompatible hydrophilic polysaccharides in the matrix are especially promising, since they do not irritate the intestines and are gradually cleaved by specific glycosidases, releasing the therapeutic agent. The introduction of an insoluble porous mineral matrix into composition of carrier makes it possible to increase the concentration of therapeutic in matrix without a significant increase in the volume of drug tablet form. In this work, a new original organic mineral carrier based on heat-treated crushed clinoptiolite zeolite in combination with natural polysaccharides from red seaweeds – agar-agar, agarose, and carrageenan was created. Granular and finely dispersed clinoptiolites in the matrix are loaded with a promising therapeutic agent, Bacillus pumilus ribonuclease (binase), which exhibits selective cytotoxicity to tumor cells. It has been established that both granular and finely dispersed zeolites in combination with polysaccharides retain protein better than pure zeolites and provide a gradual complete release of enzyme in 18 hours. At the same time, the enzyme retains its catalytic activity and induces apoptosis up to 23.8% cells of the human duodenal adenocarcinoma HuTu80. The data obtained substantiate the prospects of dosage forms based on the used organomineral carriers designing.

Catalytic Reduction of p-Nitrophenol on MnO2/Zeolite -13X Prepared with Lawsonia inermis Extract as a Stabilizing and Capping Agent

p-nitrophenol (pNP) is a highly toxic organic compound and is considered carcinogenic and mutagenic. It is a very stable compound with high resistance to chemical or biological degradation. As a result, the elimination of this pollutant has been very challenging for many researchers. Catalytic reduction is one of the most promising techniques, if a suitable catalyst is developed. Thus, this work aims to prepare an eco-friendly catalyst via a simple and low-cost route and apply it for the conversion of the toxic p-nitrophenol (pNP) into a non-toxic p-aminophenol (pAP) that is widely used in industry. Manganese oxide was prepared in an environmentally friendly manner with the aid of Lawsonia inermis (henna) extract as a stabilizing and capping agent and loaded on the surface of 13X molecular sieve zeolite. The UV-Vis spectrum, EDS, and XRD patterns confirmed the formation of the pure MnO2 loaded on the zeolite crystalline network. The TGA analysis showed that the samples prepared by loading MnO2 on zeolite (Mn2Z, Mn3Z, and Mn4Z) lost more mass than pure MnO2 (Mn) or zeolite (Z), which is mainly moisture adsorbed on the surface. This indicates a better dispersion of MnO2 on the surface of zeolite compared to pure MnO2, and thus a higher number of active adsorption sites. SEM images and EDS confirmed the dispersion of the MnO2 on the surface of the zeolite. Results showed a very fast reduction rate, following the order Mn2Z > Mn3Z > Mn4Z > Mn > Z. With sample Mn2Z, 96% reduction of pNP was achieved in 9 min and 100% in 30 min. For Mn3Z, Mn4Z, and Mn, 98% reduction was achieved in 20 min and 100% in 30 min. Zeolite was the slowest, with only a 40% reduction in 30 min. Increasing the amount of zeolite in the synthesis mixture resulted in lower reduction efficiency. The kinetic study indicated that the reduction of p-nitrophenol on the surface of the prepared nanocomposite follows the pseudo-first-order model. The results show that the proposed nanocomposite is very effective and very promising to be commercially applied in water treatment, due to its low cost, simple synthesis procedure, and reusability.