Search Results (26)

As a rarefied metallic element, strontium (Sr) is susceptible to significant environmental radioactive contamination risks during industrial mining and refining processes. In this study, NaA molecular sieves were prepared by alkali excitation using synthetic powders, which were homogeneously blended with the polyacrylonitrile (PAN) matrix, and nanoscale TiO₂ reinforcing phases were introduced. Finally, composite separation membranes (TiO₂-NaA@PANMs) with stable adsorption properties were constructed by electrostatic spinning technology. The micro-morphology and interfacial properties were characterized by SEM, XRD, and FT-IR systems. The adsorption experiments demonstrated that the equilibrium adsorption capacity of the system for Sr²⁺ reached 55.00 mg/g at the optimized pH = 6.0, and the theoretical saturated adsorption capacity at 298 K was 80.89 mg/g. The isothermal process conformed to the Langmuir’s model of monomolecular layer adsorption, and the kinetic behavior followed the quasi-secondary kinetic equation. Following three cycles of regeneration by elution with a 0.3 mol/L sodium citrate solution, the membrane material exhibited 81.60% Sr²⁺ removal efficacy. The composite membrane passages exhibited remarkable potential for utilization in engineering applications involving the treatment of complex nuclear wastewater. Full article

Enhancing the photocatalytic efficiency of oxide materials under Vis light remains a significant challenge within the scientific community. Natural zeolite–metal oxide composites exhibit enhanced properties, especially due to the zeolite’s large active surface area, which facilitates the incorporation of metal oxide nanoparticles into its structure, thereby significantly increasing photocatalytic efficiency. The present study presents the synthesis of Na-zeolite-decorated black-TiO₂ by the impregnation method, in order to improve the structural characteristics to absorb into visible light. The experimental protocol involves two main steps: first, the synthesis of black-TiO₂ and white-TiO₂ nanocrystals using the sol-gel method, and second, the preparation of hybrid materials, consisting of Na-zeolite decorated with black-TiO₂ and white-TiO₂, through impregnation followed by thermal treatment. The morpho-structural and optical properties of the as-synthesized materials were investigated using XRD, SEM/EDX, FTIR, and DRUV-VIS analysis. The characterization results indicated that natural zeolite has a good thermal stabilization, the lamellar texture of natural zeolite and spherical form of anatase-TiO₂ materials being highlighted by SEM. In the case of Na-zeolite-decorated black-TiO₂, the adsorption edge is slightly shifted to the visible range, while Na-zeolite-decorated white-TiO₂ absorbs only in the ultraviolet region. The above results showed that these hybrid materials are adequate for application in photocatalytic processes. Full article

The combination of TiO₂ with zeolites has emerged as a transformative strategy to enhance photocatalytic performance for environmental applications. The combination of zeolites’ regular pore structure, high surface area, and adsorption capacity with the photocatalytic properties of TiO₂ allows synergistic effects, significantly improving the removal of organic pollutants and hazardous substances from water. This review provides a comprehensive analysis of TiO₂–zeolite composites, focusing on their synthesis, structural characteristics, and photocatalytic mechanisms. Advances in the characterization of material and computational analysis are applied to explain the relationship between structure and catalytic activity. Environmental applications such as water purification and renewable energy production are critically evaluated, highlighting their potential for addressing pressing global challenges. The review also addresses key challenges, including material stability, scalability of synthesis methods, and cost-effectiveness, while presenting future perspectives for the development and application of TiO₂–zeolite composites in sustainable catalysis. Full article

To synthesize high-quality TS-1 zeolites with enhanced catalytic performance for 1-hexene epoxidation is highly attractive for meeting the increased need for sustainable chemistry. Herein, we report that a series of framework Ti-enriched TS-1 zeolites with high crystallinity can be effectively synthesized by the hydrothermal crystallization of a composite precursor composed of diol-based polymer (containing titanium and silicon) and tetrapropylammonium bromide (TPABr). The pre-addition of a certain amount of TPABr into the polymer-based precursor plays a very positive role in maintaining the high crystallinity and framework Ti incorporation rate of TS-1 zeolites under the premise that a relatively low concentration of tetrapropylammonium hydroxide (TPAOH) template is adopted in the following hydrothermal crystallization process. The condition-optimized TS-1 zeolite with a smaller particle size (300–500 nm) shows excellent catalytic activity, selectivity, and recyclability for the epoxidation of 1-hexene with H₂O₂ as an oxidant, which can achieve a 75.4% conversion of 1-hexene and a 99% selectivity of epoxide at a reaction temperature of 60 °C, which is much better than the TS-1 zeolites reported in the previous literature. The relatively small particle size of the resultant TS-1 crystals may enhance the accessibility of the catalytically active framework Ti species to reagents, and the absence of non-framework Ti species, like anatase TiO₂, and low polymerized six-coordinated Ti species could effectively inhibit the ineffective decomposition of H₂O₂ and the occurrence of side reactions, leading to an improvement in the catalytic efficiency for the epoxidation of 1-hexente with H₂O₂. Full article

In the present work, a TiO₂/zeolite photocatalyst was synthesized by dispersing TiO₂ nanoparticles obtained through the sol-gel method onto the surface of natural zeolite derived from ignimbrite residue. The zeolite was obtained from an ignimbrite rubble treatment collected from a quarry in Arequipa City, Peru. The research focused on the effect of zeolite on the TiO₂ nanoparticles. The synthesized photocatalysts were characterized using various techniques, including field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDS), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and Brunauer–Emmett–Teller surface area analysis (BET). The results revealed that the TiO₂/zeolite samples displayed high crystallinity, with TiO₂ being present in three phases and zeolite being present in the analcime phase. Furthermore, these samples exhibited a band gap of 3.14 eV and a high surface area compared to that of bare TiO₂. Finally, the photocatalytic activity of the TiO₂/zeolite composite obtained was evaluated toward the decomposition of 10 ppm and 20 ppm of methyl orange (MO) dye. The TiO₂/zeolite samples demonstrated improved photocatalytic activity compared to that of pristine TiO₂ under the same experimental conditions. This enhancement is primarily attributed to the increased specific surface area of the TiO₂/zeolite samples, making them promising materials for future efficient and sustainable photocatalytic applications. Full article

Sulfamethoxazole (SMX) is a common antibiotic that is considered an emerging pollutant of water bodies, as it is toxic for various aquatic species. TiO₂-based photocatalysis is a promising method for SMX degradation in water. In this work, TiO₂/zeolite (Z-45 loaded with TiO₂ labeled as TZ and ZSM-5 loaded with TiO₂ labeled as TZSM) composites were prepared by mechanical mixing and liquid impregnation methods, and the photocatalytic performance of these composites (200 mg·L⁻¹) was investigated toward the degradation of SMX (30 mg·L⁻¹) in water under UV light (365 nm). The pseudo-first-order reaction rate constant of the TZSM1450 composite was 0.501 min⁻¹, which was 2.08 times higher than that of TiO₂ (k = 0.241 min⁻¹). Complete SMX degradation was observed in 10 min using the UV/TZSM1450 system. The mineralization ability in terms of total organic carbon (TOC) removal was also assessed for all of the prepared composites. The results showed that 65% and 67% of SMX could be mineralized within 120 min of photocatalytic reaction by TZSM2600 and TZSM1450, respectively. The presence of ${\mathrm{Cl}}^{-}$ and ${\mathrm{CO}}_3^{2-}$ anions inhibited the degradation of SMX, while the presence of ${\mathrm{NO}}_3^{-}$ had almost no effect on the degradation efficiency of the UV/TZSM1450 system. The electrical energy per order estimated for the prepared composites was in the range of 68.53–946.48 kWh m⁻³ order⁻¹. The results obtained revealed that the TZSM1450 composite shows promising potential as a photocatalyst for both the degradation and mineralization of SMX. Full article

An anatase phase of the TiO₂-H-beta (THB) zeolite composite photocatalyst is used for the photocatalytic degradation of caffeine, a persistent organic pollutant (POP). It is synthesized by a simple two-step sol-gel method. Phase formation, morphology, bandgap, and photocatalytic properties were analyzed using powder X-ray diffraction, scanning electron microscopy, and UV-Vis diffuse reflectance spectroscopy, respectively. The THB and the anatase TiO₂ samples were then tested for the photocatalytic activity of the degradation of caffeine. Photocatalytic studies reveal that the as-prepared THB composite showed excellent activity for the degradation of 10 ppm caffeine solution. The chemical oxygen demand (COD) analysis found caffeine to have degraded with an efficiency of 96%. Scavenging experiments indicated that the hydroxide radical played an important role in the degradation of caffeine. The results highlight the role of the H-beta zeolite as an effective support to TiO₂ and improved the photocatalytic activity. The study demonstrates that the THB composite could be effectively applied for the photocatalytic degradation of other POPs largely present in active pharmaceutical ingredients. Full article

The aim of this work was to develop hybrid TiO₂/ZIF-8 photocatalysts and test their activity for the removal of agricultural pollutants in water. The hybrid photocatalysts were prepared by an innovative method involving hydrothermal synthesis at 150 °C using a mechanochemically synthesized zeolitic imidazolate framework (ZIF-8) and titanium tetraisopropoxide as a titanium dioxide (TiO₂) precursor. Three composite photocatalysts with different mass fractions of titanium dioxide (5, 50, and 95 wt%) were synthesized and characterized, and their adsorption and photocatalytic properties investigated for the removal of imidacloprid. The equilibrium adsorption test showed that ZIF-8 is a good adsorbent and can adsorb 65% of the model component under the working conditions used in this work, while the hybrid photocatalysts can adsorb 1–3% of the model component. It is assumed that the adsorption is hindered by the TiO₂ layer on the surface of ZIF-8, which blocks the interactions of ZIF-8 and imidacloprid. A significant decrease in band gap energies (3.1–3.6 eV) was observed for the hybrid TiO₂/ZIF-8 photocatalysts compared to the values obtained with ZIF-8 (5 eV), depending on the mass fractions of TiO₂. The highest removal efficiency of imidacloprid was achieved with the hybrid photocatalysts containing 5 wt% TiO₂. Full article

The extensive production of coal fly ash by coal combustion is an issue of concern due to its environmental impact. TiO₂-zeolite composites were synthesized, at low cost, using recycled coal fly ash from a local thermoelectric power plant to produce the zeolite using the hydrothermal method. TiO₂ was loaded by means of the impregnation method using ethanol and titanium isopropoxide between 8.7 and 49.45 wt% TiO₂. The samples were characterized by X-ray diffraction, Raman, electron spin resonance, high-resolution transmission electron microscopy, N₂ adsorption-desorption, doppler broadening of annihilation radiation, and diffuse reflectance techniques, and the photocatalytic activity of the composites was evaluated according to the degradation of methyl orange under UV light. The results show that TiO₂ crystallizes in the anatase phase with a Ti³⁺ oxidation state, without post-treatment. TiO₂ particles were located within the pores of the substrate and on its surface, increasing the surface area of the composites in comparison with that of the substrates. Samples with TiO₂ at 8.7 and 25 wt% immobilized on hydroxysodalite show the highest degradation of methyl orange among all studied materials, including the commercial TiO₂ Degussa P25 under UV light. Full article

Zeolitic imidazolate framework-8 (ZIF-8) was doped with a rare-earth metal, Eu, using a solvent synthesis method evenly on the surface of a mixed-crystal TiO₂(Mc-TiO₂) structure in order to produce a core–shell structure composite ZIF-8(Eu)@Mc-TiO₂ adsorption photocatalyst with good adsorption and photocatalytic properties. The characterisation of ZIF-8(Eu)@Mc-TiO₂ was performed via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller analysis (BET) and ultraviolet–visible light differential reflectance spectroscopy (UV-DRs). The results indicated that Eu-doped ZIF-8 was formed evenly on the Mc-TiO₂ surface, a core–shell structure formed and the light-response range was enhanced greatly. The ZIF-8(Eu)@Mc-TiO₂ for basic fuchsin was investigated to validate its photocatalytic performance. The effect of the Eu doping amount, basic fuchsin concentration and photocatalyst dosage on the photocatalytic efficiency were investigated. The results revealed that, when 5%-Eu-doped ZIF-8(Eu)@Mc-TiO₂ (20 mg) was combined with 30 mg/L basic fuchsin (100 mL) under UV irradiation for 1 h, the photocatalytic efficiency could reach 99%. Further, it exhibited a good recycling performance. Thus, it shows certain advantages in its degradation rate and repeatability compared with previously reported materials. All of these factors suggested that, in an aqueous medium, ZIF-8(Eu)@Mc-TiO₂ is an eco-friendly, sustainable and efficient material for the photocatalytic degradation of basic fuchsin. Full article

HZSM-5 (MFI type) of composition (H_x)[Al³⁺_xSi_12−xO₂₄] × wH₂O and nanocomposites NA/HZSM-5, NA:M/HZSM-5 (NA—nanoscale anatase; M = V, Ni, Ag) with Si/Al = 12, 25, 40, 300 (sp.gr. Pnma or P2₁/n; z = 8), as well as zeolites [(Ti⁴⁺_xSi_12−xO₂₄] × wH₂O (TS) with Si/Ti = 47, 53, 73.5 (sp.gr. Pnma) were studied by XRPD, XAS, FTIR-spectroscopy, BET, XPS, SEM, EDX, TPD, UV–VIS-spectroscopy, UV–DRS, and chemiluminescence methods. The results obtained together with photocatalytic, adsorption, antimicrobial, catalytic properties were analyzed using crystallochemical concepts and literature data. It was shown that NA or NA:M introduction into HZSM-5 leads, respectively, to the photodegradation of MeO dye in the UV region or difenoconazole in the visible range, and contributes to the appearance in the dark of adsorption (almost complete extraction of P(V), As(V), and Se(V) from aquatic environment) and bacteriostatic properties in respect to Staphylococcus epidermidis, Bacillus antracoides, and Escherichia coli for NA:Ag/HZSM-5(40, 300). The presence of titanium ions in NA nanoparticles on the HZSM-5 surface improves the catalytic activity in ethanol and propane (the best performance for NA/HZSM-5(25) and NA/HZSM-5(40), respectively) conversion. Determination of the composition (surface and bulk) and structure (statistical and local) of TS zeolites together with the found correlations made it possible to propose new catalysts in the reactions of propane, ethanol, and allyl chloride conversion. Full article

Immobilization of photocatalysts in porous materials is an approach to significantly minimize the hazards of manipulation and recovery of nanoparticles. Inorganic materials, such as zeolites, are proposed as promising materials for photocatalyst immobilization mainly due to their photochemical stability. In this work, a green synthesis method is proposed to combine TiO₂-based photocatalysts with commercial ZY zeolite. Moreover, a preliminary analysis of their performance as photocatalysts for the abatement of organic pollutants in waters was performed. Our results show that the physical mixture of TiO₂ and zeolite maintains photocatalytic activity. Meanwhile, composites fabricated by doping TiO₂–zeolite Y materials with silver and palladium nanoparticles do not contribute to improving the photocatalytic activity beyond that of TiO₂. Full article

Adsorption is an effective method of removing harmful pollutants from air and water. In the present study, zeolites prepared by sol-gel method from two Ecuadorian clays were combined with precursor clays and the ZnTiO₃/TiO₂ semiconductor for adsorbing methylene blue (MB) as a water contaminant. The synthesized compounds were characterized using powder X-ray diffraction, X-ray fluorescence, scanning electron microscopy, energy dispersive X-ray, and surface area measurement. These compounds were combined to form cylindrical extrudates of 0.2 cm (diameter) and 1.0 cm (length). The adsorption characteristics of the composites were measured using batch sorption studies as a function of pH, initial concentration, and contact time. The pseudo-second-order model and the Langmuir isotherm model were better suited to the adsorption process. The equilibrium state was achieved around 180 min of adsorption, and a pH of 7 was established as the optimal operating condition. The maximum adsorption values of the dye were obtained with the composites derived from G-Clay, whose average adsorption capacity was 46.36 mg g⁻¹, in contrast with composites derived from R-Clay, whose average adsorption value was 36.24 mg g⁻¹. The results reflect that synthesized composites could be used potentially for the removal of cationic dye from wastewater. Full article

Detailed mineralogical and geochemical characteristics of typical surface sediments and hydrothermal deposits collected from the ultraslow-spreading Southwest Indian Ridge (SWIR) were studied by high-resolution XRD, SEM-EDS, XRF, and ICP-MS. The SWIR marine samples can be generally classified into two main categories: surface sediment (biogenic, volcanic) and hydrothermal-derived deposit; moreover, the surface sediment can be further classified into metalliferous and non-metalliferous based on the metalliferous sediment index (MSI). The chemical composition of biogenic sediment (mainly biogenic calcite) was characterized by elevated contents of Ca, Ba, Rb, Sr, Th, and light rare earth elements (LREE), while volcanic sediment (mainly volcanogenic debris) was relatively enriched in Mn, Mg, Al, Si, Ni, Cr, and high field strength elements (HFSEs). By contrast, the hydrothermal-derived deposit (mainly pyrite-marcasite, chalcopyrite-isocubanite, and low-temperature cherts) contained significantly higher contents of Fe, Cu, Zn, Pb, Mn, Co, Mo, Ag, and U. In addition, the metalliferous surface sediment contained a higher content of Cu, Mn, Fe, Co, Mo, Ba, and As. Compared with their different host (source) rock, the basalt-hosted marine sediments contained higher contents of Ti–Al–Zr–Sc–Hf and/or Mo–Ba–Ag; In contrast, the peridotite-hosted marine sediments were typically characterized by elevated concentrations of Mg–Cu–Ni–Cr and/or Co–Sn–Au. The differences in element enrichment and mineral composition between these sediment types were closely related to their sedimentary environments (e.g., near/far away from the vent sites) and inherited from their host (source) rock. Together with combinations of certain characteristic elements (such as Al–Fe–Mn and Si–Al–Mg), relict hydrothermal products, and diagnostic mineral tracers (e.g., nontronite, SiO_2(bio), olivine, serpentine, talc, sepiolite, pyroxene, zeolite, etc.), it would be more effective to differentiate the host rock of deep-sea sediments and to detect a possible hydrothermal input. Full article