Local and Average Structural Changes in Zeolite A upon Ion Exchange

Titania-zeolite composite for tetracycline photocatalytic degradation under visible light: A comparison between doping and ion exchange

In this study, TiO2 supported over embryonic Beta zeolite (BEA) was prepared for the photocatalytic degradation of Tetracycline (TC) antibiotic under visible light. The immobilization of sol-gel TiO2 over the zeolite increased its surface area from 33 (m2/g) to 226 (m2/g) and enhanced its adsorption efficiency from 8 % to 18 %. In order to expand the photocatalytic activity of TiO2 towards the visible light region (i.e. λ > 380 nm), two different metal sensitization techniques with Iron ions from aqueous solution of FeCl3 were explored. In the ion-exchange method, the substitutional cations within the TiO2/BEA structure were exchanged with Fe3+. Whereas, in the doping technique, solgel TiO2 was doped with Fe3+ during its synthesis and before its immobilization over Zeolite. Four different samples with 20, 40, 60, and 100 % w/w of TiO2/BEA ratio were prepared. After testing the various ion-exchanged photocatalysts under blue and white lights, only Fe-60%TiO2/BEA showed better activity compared to pure TiO2 under white light at TC initial concentration, C o = 20 ppm. For the doped immobilized Titania with 60 wt% TiO2/BEA, three different doped photocatalysts were prepared with 3 %, 7 %, and 10 % per mole Fe/TiO2. All the Fe-doped TiO2/BEA photocatalysts showed better activity compared to pure TiO2 under white light. Under solar irradiations, the 3 % Fe-doped TiO2/BEA was able to degrade all TC within 120 min, while Fe-60%TiO2/BEA needed 200 min, and TiO2 needed more than 300 min. This enhanced performance was a result of both increased surface area due to immobilization over BEA as well as iron doping by Fe3+ that simultaneously increased the visible light absorption of TiO2 and minimized the charge carrier recombination effect.

Zeolite/Polymer Composites Prepared by Photopolymerization: Effect of Compensation Cations on Opacity and Gas Adsorption Applications

The fabrication of structured zeolite adsorbents through photopolymerization-based 3D printing which offers a solution to the limitations of conventional shaping techniques has been demonstrated but many parameters still need to be optimized. In this study, we studied the influence of zeolite compensation cations on the photopolymerization and the composite's properties. Modified zeolites (LTA 4 A and FAU 13X exchanged with K+ , Li+ , Sr2+ , Ca2+ or Mg2+ ) were incorporated in PEGDA with BDMK as photoinitiator, and the formulation was cured under mild conditions (LED@405 nm, room temperature, under air). Our results indicate that the nature of zeolite compensation cations affects the colorimetric properties of polymer/zeolite composites: a better translucency parameter results in higher depth of cure. After calcination at 650 °C and complete removal of PEGDA, pure zeolitic monoliths were tested for adsorption of gas molecules of interest (carbon dioxide, dichlorobenzene and water). Structured 4 A and 13X monoliths obtained by 3D printing exhibit comparable adsorption capacity to commercial beads prepared from the same zeolites. This study enhances our understanding of the photopolymerization process involved in the production of polymer/zeolite composites. These composites are used in the fabrication of zeolitic objects through 3D printing, offering potential solutions to various environmental and dental challenges.

Thermal-Driven Formation of Silver Clusters Inside Na/Li FAUY Zeolites for Formaldehyde Detection

In this research, the LiY zeolite was firstly synthesized by using NaY as the parent zeolite; thereafter, the LiYAg and NaYAg zeolites created for formaldehyde gas detection were prepared with further Ag⁺-Li⁺/Na⁺ exchange and a mild thermal treatment at 300 °C to promote the formation of luminescent Ag CLs. The spectra experimental results indicated that Ag CLs showed stronger and blue-shifted emissions in LiYAg compared with in NaYAg, and the emission intensity of Ag CLs in both zeolites monotonously decreased when exposed to increasing formaldehyde gas content. Moreover, the linear dependence of the Ag CLs' emission intensity variation on formaldehyde content indicated a reliable method for fast and sensitive formaldehyde detection. According to the XPS, UV-vis absorption, and N₂ adsorption-desorption isotherm studies, the formaldehyde-gas-induced luminescence quenching of Ag CLs is due to the formation of Ag₂O and Ag NPs, in which the higher content of Ag⁺/Ag⁰ redox couples in LiYAg and larger surface area of NaYAg benefit the precise detection of formaldehyde gas in low- and high-content ranges, respectively. Furthermore, the blue-shifted peak position and widened FWHM of Ag CLs can also be used for the indication of formaldehyde gas and the detection limit of NaYAg and LiYAg, which both meet with the standards of the WHO and OSHA.

Development of a novel silver ions-nanosilver complementary composite as antimicrobial additive for powder coating

Applying silver into coatings has become a prevalent method in fabricating antimicrobial surfaces. However, the concerns about durability always exist and limit its applications. Here, a highly inhibitory, active, durable, and easy-to-use silver ions-nanosilver antimicrobial additive for powder coatings was fabricated in this study. Silver nanoparticles were chemically bonded to the Ag, Cu, and Zn-ternary ion-exchanged zeolite by α -lipoic acid, which was then encapsulated by hydrophilic polymers. The fabricated silver ions and silver nanoparticles (Ag+-AgNPs) complementary structure provides a synergistic effect. Ag+ is the main antimicrobial agent, while AgNPs act as a supplementary reservoir of Ag+. As well, the formed thin layer of silver nanoparticles and hydrophilic film prolongs the release of active Ag+ from zeolite, and Ag+ facilitates the activation of AgNPs. The results show that this additive indicates excellent antimicrobial activity to E. coli, S. aureus, P. aeruginosa, and C. albicans, and that the coatings with the additive exhibit over 99.99% reduction rate for the tested bacteria and fungi. The coating film is able to maintain over 99% antimicrobial reduction even after 1200 repeated solution wipings, or over 30 wash cycles of artificial sweat solution, indicating high durability. Furthermore, the yellowness of the coating is not evident (Δb < 2) despite the high loading of silver, and the silver nanoparticles have little impact on gloss, haze, and distinctness of the coating film image.

Zeolite-Polymer Composite Materials as Water Scavenger

The influence of the charge compensating cation nature (Na+, Mg2+) on the water adsorption properties of LTA-type zeolites used as filler in composite materials (zeolite/polymers) was investigated. Large scale cation exchanges were performed on zeolite powder at 80 °C for 2 h using 1 M magnesium chloride (MgCl2) aqueous solutions. XRF, ICP, and EDX analyses indicate a successful cationic exchange process without the modification of the zeolite structure as shown by XRD and solid-state NMR analyses. Composite materials (granulates and molded parts) were manufactured using to extrusion and injection processes. In the case of MgA zeolite, nitrogen adsorption-desorption experiments allowed us to measure a microporous volume, unlike NaA zeolite, which is non-porous to nitrogen probe molecule. SEM and EDX analyses highlighted the homogeneous distribution of zeolite crystals into the polymer matrix. Water adsorption capacities confirmed that the trends observed in the zeolite powder samples are preserved after dragging zeolites into composite formulations. Granulates and molded parts composite samples containing the magnesium exchanged zeolite showed an increase of their water adsorption capacity up to +27% in comparison to composite samples containing the non-exchanged zeolite. The MgA composite is more promising for water decontamination applications due to its higher water adsorption properties than the NaA composite.

Structural characterizations of fly ash-based geopolymer after adsorption of various metal ions

Geopolymer, an amorphous substance, has been viewed as good adsorbent or catalyst and attracted much attentions from all over the world. In order to achieve the better applications of geopolymer in these fields, a deep understanding of the microstructure of geopolymer would be strongly required. In the present study, geopolymer was synthesized from coal fly ash, and the structural analysis of geopolymer after adsorption of various metal ions (Li⁺, Cs⁺, Sr²⁺ and Co²⁺) was studied using XRD, SEM-EDX, FTIR, UV-VIS DRS, TG-DTA as well as surface area and pore distribution analysis. Pair distribution function preferably illustrated that geopolymer was successfully prepared from calcined fly ash. Geopolymer possesses different affinities towards various metal ions. After exchanging with other metal ions, the main structure of geopolymer was maintained. Metal ions with a large radius would have greater effect on the existing state and amount of water molecules in geopolymer. Moreover, the specific surface area of geopolymer after exchanging with metal ions decreased as a function of the radius of them. The spectra corresponding to d-d transitions indicated that the Co²⁺ could be incorporated into the deformed six-member rings or eight-membered rings. It could be deduced that the sites for ion exchange could be different rings or even cavities distributed on the surface layer of geopolymer. Furthermore, the rings distributed in the geopolymer structure were predominant in the 6-, 8-, 10- or even 12-member rings to maintain the structure stability and charge balance with the cations.

Synthesis and Characterization of Magnetic Fe3O4/Zeolite NaA Nanocomposite for the Adsorption Removal of Methylene Blue Potential in Wastewater Treatment

In this research, the magnetic Fe3O4/zeolite NaA nanocomposite (Fe3O4/ZA), Fe3O4 nanoparticles, and zeolite NaA have been synthesized by facile hydrothermal methods for adsorption removal of methylene blue from aqueous solution. The as-synthesized Fe3O4/ZA nanocomposite was characterized by X-ray diffraction (XRD), MicroRaman analysis, Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray fluorescence (XRF), N2 adsorption isotherms (BET), and UV-VIS analysis. The results show that with a small weight loading of Fe3O4, the ∼3.3% Fe3O4/ZA sample exhibits a high adsorption capacity (∼40.36 mg·g−1) and removal efficiency (∼96.8%) compared to that of the zeolite NaA (∼32.99 mg·g−1 and 79.11%, respectively). Interestingly, the removal efficiency and the adsorption capacity increase rapidly with the increase of adsorption time (10–60 minutes) and Fe3O4 loading (∼3.3–9.3% wt.) in the Fe3O4/ZA composition. The adsorption mechanism of MB molecules of the Fe3O4/ZA can be addressed at the combination of the interaction between active sites on the surfaces and edges of the invert spinel ferrite Fe3O4 nanoparticles and zeolite NaA with MB molecules. Our approach provides a simple, efficient, and scalable synthesis process that render practical applications of the magnetic Fe3O4/ZA nanocomposite as a lower-cost adsorbent for wastewater treatment.

Simultaneous removal of ammonium ions and sulfamethoxazole by ozone regenerated high silica zeolites

Continuous development of industry and civilization has led to changes in composition, texture and toxicity of waste water due to the wide range of pollutants being present. Considering that the conventional wastewater treatment methods are insufficient for removing micropollutants and nutrients to a high level, other, alternative, treatment methods should be used to polish wastewater treatment plant effluents. In this study we developed an alternative, polishing concept for removal of ammonium and micropollutants that could potentially be incorporated in existing wastewater treatment plants. We demonstrated a method to use high silica MOR zeolite granules as an adsorbent for simultaneous removal of the micropollutant sulfamethoxazole (SMX) and ammonium (NH₄⁺) ions from aqueous solutions. At an initial NH₄⁺ concentration of 10 mg/L the high silica zeolite mordenite (MOR) granules removed 0.42 mg/g of NH₄⁺, similar to the removal obtained by commonly used natural zeolite Zeolita (0.44 mg/g). However, at higher NH₄⁺ concentrations the Zeolita performed better. In addition, the Langmuir isotherm model showed a higher maximum adsorption capacity of Zeolita (q_max, 4.08 mg/g), which was about two times higher than that of MOR (2.11). The adsorption capacity of MOR towards SMX, at both low (2 µg/L) and high (50 mg/L) initial concentrations, was high and even increased in the presence of NH₄⁺ ions. The used adsorbent could be regenerated with ozone and reused in consecutive adsorption-regeneration cycles with marginal decrease in the total adsorption capacity.

Effect of mono- and divalent extra-framework cations on the structure and accessibility of porosity in chabazite zeolites

The differences in valence and size between extra-framework cations exert a significant effect on the nitrogen sorption ability in the synthesised chabazite zeolites (K-CHA, Cs-CHA, Ca-CHA, Ba-CHA, Sr-CHA and Zn-CHA).

Synthesis of FAU-Type Zeolite Membranes with Antimicrobial Activity

In this study, a layer of a pure and dense phase of FAU-type zeolite was synthesized directly on the surface of α-Al₂O₃ plane macroporous support. Before hydrothermal synthesis, a step of cleaning of the support by an anionic detergent was performed, a roughness surface is created, allowing the anchoring of the zeolite nuclei and then their growth, favoring in this sense the formation of a homogeneous zeolite layer. The obtained membranes were fully characterized using X-ray diffraction analysis (XRD), nitrogen sorption, scanning electron microscopy (SEM), and mercury porosimetry. After 24 h of thermal treatment at 75 °C, a homogeneous zeolite layer composed of bipyramidal crystals of FAU-type zeolite is obtained with a thickness of about 2.5 µm. No obvious defects or cracks can be observed. It was found that the increase in heating temperature could lead to the appearance of an impurity phase, GIS-type zeolite. Then the ideal zeolite membrane was exchanged with Ag⁺ or Zn²⁺ cations to studies their antimicrobial properties. Zeolites membranes exchanged with Ag⁺ showed an agar-diffusive bactericidal activity against gram negative Escherichia coli (E. coli) bacteria. Zn²⁺ exchanged zeolite membrane presented a bacteriostatic activity that is less diffusive in agar. As expected, non-exchanged zeolite membrane (in its Na⁺ form) have no effect on bacterial activity. This process is particularly interesting for the synthesis of a good quality FAU-type zeolite membranes with antimicrobial properties.

Influence of the Compensating Cation Nature on the Water Adsorption Properties of Zeolites

The influence of the compensating cation (Na⁺, Li⁺, Mg²⁺) nature on the water adsorption properties of LTA and FAU-type zeolites was investigated. Cation exchanges were performed at 80 °C for 2 h using 1 M aqueous solutions of lithium chloride (LiCl) or magnesium chloride (MgCl₂). XRF and ICP-OES analyses indicate that the cation exchange yields reach values between 59 to 89% depending on the number of exchange cycles and the nature of the zeolite and cation, while both zeolites structures are preserved during the process, as shown by XRD and solid state NMR analyses. Nitrogen adsorption-desorption experiments indicate a higher available microporous volume when sodium cations are replaced by smaller monovalent lithium cations or by divalent magnesium cations because twice less cations are needed compared to monovalent cations. Up to 15% of gain in the available microporous volume is obtained for FAU-type zeolites exchanged with magnesium cation. This improvement facilitates the adsorption of water with an increase in the water uptake up to 30% for the LTA and FAU type zeolites exchanged with magnesium. These exchanged zeolites are promising for uses in water decontamination because a smaller amount is needed to trap the same amount of water compared to their sodium counterparts.

Curcumin-loaded zeolite as anticancer drug carrier: effect of curcumin adsorption on zeolite structure

In this work we used a combination of different techniques to investigate the adsorption properties of curcumin by zeolite type A for potential use as an anticancer drug carrier. Curcumin is a natural water-insoluble drug that has attracted great attention in recent years due to its potential anticancer effect in suppressing many types of cancers, while showing a synergistic antitumor effect with other anticancer agents. However, curcumin is poorly soluble in aqueous solutions leading to the application of high drug dosage in oral formulations. Zeolites, inorganic crystalline aluminosilicates with porous structure on the nano- and micro-scale and high internal surface area, can be useful as pharmaceutical carrier systems to encapsulate drugs with intrinsic low aqueous solubility and improve their dissolution. Here, we explore the use of zeolite type A for encapsulation of curcumin, and we investigate its surface properties and morphology, before and after loading of the anticancer agent, using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and UV-vis spectroscopy. Results are used to assess the loading efficiency of zeolite type A towards curcumin and its structural stability after loading.