Cytotoxicity and Genotoxicity Effects of a Magnetic Zeolite Composite in Daphnia magna (Straus, 1820).

Zeolite type 5A combined with the magnetic properties of maghemite nanoparticles facilitate the rapid absorption of heavy metals, which makes them an interesting proposal for the remediation of water contaminated with lead and arsenic. However, the physicochemical analysis related to concentration and size for the use of this magnetic zeolite composite (MZ0) in water bodies and the possible toxicological effects on aquatic fauna has not yet been carried out. The main objective of the research work is to determine lethal concentrations that cause damage to Daphnia magna based on LC50 tests, morphology, reproductive rate, and quantification of the expression of three genes closely involved in the morphological development of vital structures (Glass, NinaE, Pph13). To achieve this objective, populations of neonates and young individuals were used, and results showed that the LC50 for neonates was 11,314 mg L-1, while for young individuals, it was 0.0310 mg L-1. Damage to morphological development was evidenced by a decrease in eye size in neonates, an increase in eye size in young individuals, variations in the size of the caudal spine for both age groups, and slight increases in the heart size, body, and antenna for both age groups. The reproductive rate of neonates was not affected by the lower concentrations of MZ0, while in young individuals, the reproductive rate decreased by more than 50% from the minimum exposure concentration of MZ0. And for both ages, Glass gene expression levels decreased as the MZ0 concentration increased. Also, the MZ0 evidenced its affinity for the exoskeleton of D. magna, which was observed using both light microscopy and electron microscopy. It is concluded that MZ0 did not generate significant damage in the mortality, morphology, reproductive rate, or gene expression in D. magna at lower concentrations, demonstrating the importance of evaluating the possible impacts on different life stages of the cladoceran.

Biomass Valorization through Catalytic Pyrolysis Using Metal-Impregnated Natural Zeolites: From Waste to Resources.

Catalytic biomass pyrolysis is one of the most promising routes for obtaining bio-sustainable products that replace petroleum derivatives. This study evaluates the production of aromatic compounds (benzene, toluene, and xylene (BTX)) from the catalytic pyrolysis of lignocellulosic biomass (Pinus radiata (PR) and Eucalyptus globulus (EG)). Chilean natural zeolite (NZ) was used as a catalyst for pyrolysis reactions, which was modified by double ion exchange (H2NZ) and transition metals impregnation (Cu5H2NZ and Ni5H2NZ). The catalysts were characterized by nitrogen adsorption, X-ray diffraction (XRD), ammonium programmed desorption (TPD-NH3), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). Analytical pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) allowed us to study the influence of natural and modified zeolite catalysts on BTX production. XRD analysis confirmed the presence of metal oxides (CuO and NiO) in the zeolite framework, and SEM-EDS confirmed successful metal impregnation (6.20% for Cu5H2NZ and 6.97% for Ni5H2NZ). Py-GC/MS revealed a reduction in oxygenated compounds such as esters, ketones, and phenols, along with an increase in aromatic compounds in PR from 2.92% w/w (without catalyst) to 20.89% w/w with Ni5H2NZ at a biomass/catalyst ratio of 1/5, and in EG from 2.69% w/w (without catalyst) to 30.53% w/w with Ni5H2NZ at a biomass/catalyst ratio of 1/2.5. These increases can be attributed to acidic sites within the catalyst pores or on their surface, facilitating deoxygenation reactions such as dehydration, decarboxylation, decarbonylation, aldol condensation, and aromatization. Overall, this study demonstrated that the catalytic biomass pyrolysis process using Chilean natural zeolite modified with double ion exchange and impregnated with transition metals (Cu and Ni) could be highly advantageous for achieving significant conversion of oxygenated compounds into hydrocarbons and, consequently, improving the quality of the condensed pyrolysis vapors.

Hierarchical Y Zeolite-Based Catalysts for VGO Cracking: Impact of Carbonaceous Species on Catalyst Acidity and Specific Surface Area.

The performance of catalysts prepared from hierarchical Y zeolites has been studied during the conversion of vacuum gas oil (VGO) into higher-value products. Two different catalysts have been studied: CatY.0.00 was obtained from the standard zeolite (Y-0.00-M: without alkaline treatment) and CatY.0.20 was prepared from the desilicated zeolite (Y-0-20-M: treated with 0.20 M NaOH). The cracking tests were carried out in a microactivity test (MAT) unit with a fixed-bed reactor at 550 °C in the 20-50 s reaction time range, with a catalyst mass of 3 g and a mass flow rate of VGO of 2.0 g/min. The products obtained were grouped according to their boiling point range in dry gas (DG), liquefied petroleum gas (LPG), naphtha, and coke. The results showed a greater conversion and selectivity to gasoline with the CatY.0.20 catalyst, along with improved quality (RON) of the C5-C12 cut. Conversely, the CatY.0.00 catalyst (obtained from the Y-0.00-M zeolite) showed greater selectivity to gases (DG and LPG), attributable to the electronic confinement effect within the microporous channels of the zeolite. The nature of coke has been studied using different analysis techniques and the impact on the catalysts by comparing the properties of the fresh and deactivated catalysts. The coke deposited on the catalyst surfaces was responsible for the loss of activity; however, the CatY.0.20 catalyst showed greater resistance to deactivation by coke, despite showing the highest selectivity. Given that the reaction occurs in the acid sites of the zeolite and not in the matrix, the increased degree of mesoporosity of the zeolite in the CatY.0.20 catalyst facilitated the outward diffusion of products from the zeolitic channels to the matrix, thereby preserving greater activity.

Aluminosilicate and zeolitic materials synthesis using alum sludge from water treatment plants: Challenges and perspectives.

Alum sludge (AS) is a by-product generated from drinking water treatment and produced in large amounts around the world. Its chemical composition makes this waste an emerging alternative source of silicon and aluminum for aluminosilicates or zeolite material production, which can add value to residues and contribute to the circular economy process on a global scale. In this sense, and considering the scarcity of information about AS, this review shows data collection about AS in different countries, including generation, chemical composition, and disposal information. The reuse of AS is discussed based on circular economy and the environmental gains derived from such approaches are highlighted, including the possibility of utilization with other residues (e.g., ash, bioproducts, etc). Moreover, this review shows and discusses the benefits and challenges of AS reuse in the synthesis process and how it can be a sustainable raw material for aluminosilicates and zeolite synthesis. The most common conditions (conventional or non-conventional) in zeolite synthesis from AS are mentioned and advantages, limitations and trends are discussed. The discussions and data presented can improve the AS management and reuse legislations, which certainly will collaborate with sustainable AS use and circular economy processes.

Interplay Between Ni and Brønsted and Lewis Acid Sites in the Hydrodesulfurization of Dibenzothiophene.

Ni-MoS2/γ-Al2O3 catalysts are commonly used in hydrotreating to enhance fossil fuel quality. The extensive research on these catalysts reveals a gap in understanding the role of Ni, often underestimated as an inactive sulfide phase or just a MoS2 promoter. In this work, we focused on analyzing whether well-dispersed supported nickel nanoparticles can be active in the hydrodesulfurization of dibenzothiophene. We dispersed Ni by Strong Electrostatic Adsorption (SEA) method across four supports with different types of acidity: silica (~ neutral acidity), γ-Al2O3 (Lewis acidity), H+-Y zeolite, and microporous-mesoporous H+-Y zeolite (both with Brønsted-Lewis acidity). Our findings reveal that Ni is indeed active in dibenzothiophene hydrodesulfurization, even with alumina and silica as supports, although their catalytic activity declines abruptly in the first hours. Contrastingly, the acid nature of zeolites imparts sustained stability and performance, attributed to robust metal-support interactions. The efficacy of the SEA method and the added mesoporosity in zeolites further amplify catalytic efficiency. Overall, we demonstrate that Ni nanoparticles may perform as a hydrogenating metal in the same manner as noble metals such as Pt and Pd perform in hydrodesulfurization. We discuss some of the probable reasons for such performance and remark on the role of Ni in hydrotreatment.

Biocidal effects of organometallic materials supported on ZSM-5 Zeolite: Influence of the physicochemical and surface properties.

Antifouling coatings containing biocidal agents can be used to prevent the accumulation of biotic deposits on submerged surfaces; however, several commercial biocides can negatively affect the ecosystem. In this study, various formulations of a potential biocide product comprising copper nanoparticles and capsaicin supported on zeolite ZSM-5 were analyzed to determine the influence of the concentration of each component. The incorporation of copper was evidenced by scanning electron microscopy and energy dispersive spectroscopy. Similarly, Fourier-transform infrared spectroscopy confirmed that capsaicin was supported on the zeolite surface. The presence of capsaicin on the external zeolite surface significantly reduced the surface area of the zeolite. Finally, bacterial growth inhibition analysis showed that copper nanoparticles inhibited the growth of strains Idiomarina loihiensis UCO25, Pseudoalteromonas sp. UCO92, and Halomonas boliviensis UCO24 while the organic component acted as a reinforcing biocide.

Effect of Ecuadorian natural zeolite on the performance of anaerobic digestion of swine waste in semicontinuous regime.

This study explores the potential of zeolite as an amendment to mitigate ammonium inhibition in the anaerobic digestion of swine waste. Two 50 L reactors, one with and one without zeolite amendment were operated at an OLR of 3.0 g VS L-1d-1 for 130 days, and fed with swine waste from a full-scale pig farm. Under these conditions, zeolite doses of 4 g L-1 allowed total ammonia nitrogen (TAN) concentrations to be kept below 1000 mgNH3-N L-1. The zeolite-amended reactor not only showed an average increase of 8% in methane production under stable conditions but also exhibited 34% reduction in H2S concentrations in the biogas, compared to the reactor without zeolite. The community of archaea originating from the inoculum was conserved in the reactor with zeolite amendment, particularly the acetoclastic methanogens of the genus Methanosaeta. On the other hand, in the reactor without zeolite addition, the microbial community went from being dominated by the acetoclastic methanogen Methanosaeta to having a high relative abundance of hydrogenotrophic methanogens. The zeolite addition also favoured the reactor stability, prevented foaming, and produced an enriched natural zeolite with N, P and K. However, additional studies on the potential of enriched zeolite as a fertilizer are required, which could make the use of zeolite in Anaerobic Digestion of swine waste not only energetically favourable but also economically feasible.

Sustainable Zeolite-Silver Nanocomposites via Green Methods for Water Contaminant Mitigation and Modeling Approaches.

This study explores cutting-edge and sustainable green methodologies and technologies for the synthesis of functional nanomaterials, with a specific focus on the removal of water contaminants and the application of kinetic adsorption models. Our research adopts a conscientious approach to environmental stewardship by synergistically employing eco-friendly silver nanoparticles, synthesized using Justicia spicigera extract as a biogenic reducing agent, in conjunction with Mexican zeolite to enhance contaminant remediation, particularly targeting Cu2+ ions. Structural analysis, utilizing X-ray diffraction (XRD) and high-resolution scanning and transmission electron microscopy (TEM and SEM), yields crucial insights into nanocomposite structure and morphology. Rigorous linear and non-linear kinetic models, encompassing pseudo-first order, pseudo-second order, Freundlich, and Langmuir, are employed to elucidate the kinetics and equilibrium behaviors of adsorption. The results underscore the remarkable efficiency of the Zeolite-Ag composite in Cu2+ ion removal, surpassing traditional materials and achieving an impressive adsorption rate of 98% for Cu. Furthermore, the Zeolite-Ag composite exhibits maximum adsorption times of 480 min. In the computational analysis, an initial mechanism for Cu2+ adsorption on zeolites is identified. The process involves rapid adsorption onto the surface of the Zeolite-Ag NP composite, followed by a gradual diffusion of ions into the cavities within the zeolite structure. Upon reaching equilibrium, a substantial reduction in copper ion concentration in the solution signifies successful removal. This research represents a noteworthy stride in sustainable contaminant removal, aligning with eco-friendly practices and supporting the potential integration of this technology into environmental applications. Consequently, it presents a promising solution for eco-conscious contaminant remediation, emphasizing the utilization of green methodologies and sustainable technologies in the development of functional nanomaterials.

Microwave-Assisted Synthesis of Zeolite A from Metakaolinite for CO2 Adsorption.

The global demand for energy and industrial growth has generated an exponential use of fossil fuels in recent years. It is well known that carbon dioxide (CO2) is mainly produced, but not only from fuels, which has a negative impact on the environment, such as the increasing emission of greenhouse gases. Thus, thinking about reducing this problem, this study analyzes microwave irradiation as an alternative to conventional heating to optimize zeolite A synthesis conditions for CO2 capture. Synthesis reaction parameters such as different temperatures (60-150 °C) and different time durations (1-6 h) were evaluated. The CO2 adsorption capacity was evaluated by CO2 adsorption-desorption isotherms at 25 °C and atmospheric pressure. The results showed that the synthesis of zeolite A by microwave irradiation was successfully obtained from natural kaolinite (via metakaolinization), reducing both temperature and time. Adsorption isotherms show that the most promising adsorbent for CO2 capture is a zeolite synthesized at 100 °C for 4 h, which reached an adsorption capacity of 2.2 mmol/g.

Adsorption and Photodegradation of Lanasol Yellow 4G in Aqueous Solution by Natural Zeolite Treated by CO2-Laser Radiation.

Natural zeolite is a widely used material with excellent environmental cleaning performance, especially in water and wastewater treatment. Natural zeolite (Zini) calcined by CO2-laser radiation (ZL) was tested as a catalyst for the photodegradation and the adsorption of industrial azo dye Lanasol Yellow 4G (LY4G) in water. Morphology, chemical structure, and surface composition of Zini and ZL were analyzed by XRD, SEM, EDS, and XPS. UV/Visible spectrophotometry was used to evaluate the photocatalytic activity of Zini and ZL. The photocatalytic activity of the studied zeolites was associated with the presence of Fe oxides in their composition. Laser-treated natural zeolite showed higher efficiency as a photocatalyst compared to untreated natural zeolite.

Zeolite Nanoparticles Loaded with 2-Methoxystradiol as a Novel Drug Delivery System for the Prostate Cancer Therapy.

The estrogen metabolite 2-methoxyestradiol (2ME) is a promissory anticancer drug mainly because of its pro-apoptotic properties in cancer cells. However, the therapeutic use of 2ME has been hampered due to its low solubility and bioavailability. Thus, it is necessary to find new ways of administration for 2ME. Zeolites are inorganic aluminosilicates with a porous structure and are considered good adsorbents and sieves in the pharmaceutical field. Here, mordenite-type zeolite nanoparticles were loaded with 2ME to assess its efficiency as a delivery system for prostate cancer treatment. The 2ME-loaded zeolite nanoparticles showed an irregular morphology with a mean hydrodynamic diameter of 250.9 ± 11.4 nm, polydispersity index of 0.36 ± 0.04, and a net negative surface charge of -34 ± 1.73 meV. Spectroscopy with UV-vis and Attenuated Total Reflectance Infrared Fourier-Transform was used to elucidate the interaction between the 2ME molecules and the zeolite framework showing the formation of a 2ME-zeolite conjugate in the nanocomposite. The studies of adsorption and liberation determined that zeolite nanoparticles incorporated 40% of 2ME while the liberation of 2ME reached 90% at pH 7.4 after 7 days. The 2ME-loaded zeolite nanoparticles also decreased the viability and increased the mRNA of the 2ME-target gene F-spondin, encoded by SPON1, in the human prostate cancer cell line LNCaP. Finally, the 2ME-loaded nanoparticles also decreased the viability of primary cultures from mouse prostate cancer. These results show the development of 2ME-loaded zeolite nanoparticles with physicochemical and biological properties compatible with anticancer activity on the human prostate and highlight that zeolite nanoparticles can be a good carrier system for 2ME.

Reducing toxic element leaching in mine tailings with natural zeolite clinoptilolite.

The use of natural zeolite clinoptilolite to reduce the leaching rate of potentially toxic elements such as Cd, Pb, and Mn in soil from mine tailings was studied. Soil from the surroundings of the mine El Bote in Zacatecas, Mexico, was analyzed, and the zeolite was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and nitrogen physisorption. An ammonium-exchange method for the zeolite was employed. Leaching experiments using packed columns with polluted soil and zeolite mixtures were carried out and the effect of the pH of the carrier solutions was studied. Incorporation of zeolite in the soil achieved a beneficial increase in pH, from 5.03 to 6.95. The concentration of Cd and Mn was reduced when zeolite was present in the column and the ammonium-modified zeolite with ammonia also enhanced the concentration reduction of metallic species in leachates in a range of 28 to 68%. The first-order model best fits the experimental data, suggesting that the leaching rate is controlled by concentration difference between the liquid and the soil matrix. These results demonstrate the potential for using natural zeolite clinoptilolite to reduce the leaching rate of potentially toxic elements in soil from mine tailings.

Natural Ecuadorian zeolite: An effective ammonia adsorbent to enhance methane production from swine waste.

Anaerobic digestion (AD) of swine waste allows obtaining renewable energy, biofertilizer and the reduction of environmental impacts. However, the low C:N ratio of pig manure generates high concentrations of ammonia nitrogen in the digestion process, reducing methane production. Zeolite is an effective ammonia adsorbent; thus, in this research the ammonia adsorption capacity of natural Ecuadorian zeolite was studied under different operating conditions. Subsequently, its effect on methane production from swine waste was evaluated using three doses of zeolite, 1.0, 4.0 and 8.0 g, in 1 L batch bioreactors. The results showed that the Ecuadorian natural zeolite has an adsorption capacity of around 19 mgNH3-N gZ-1 when using ammonium chloride solution and, an adsorption capacity between 37 and 65 mgNH3-N gZ-1 using swine waste. On the other hand, the addition of zeolite had a significant effect on methane production (p < 0.01). The zeolite doses that provided the highest methane production were 4.0 and 8.0 g L-1, which led to values of 0.375 and 0.365 Nm3CH4 kgVS-1, compared to the values of 0.350 and 0.343 Nm3CH4 kgVS-1 that were obtained for the treatments without addition of zeolite and using a dose of 1.0 g L-1, respectively. Addition of natural Ecuadorian zeolite meant not only a significant increase on methane production in the AD of swine waste, but also a better quality of the biogas with higher percentages of methane and lower concentrations of H2S.

Handleable TiO2-coated zeolitic material for photodecomposition of caffeine boosted by urine matrix.

The photocatalytic decomposition of caffeine under UV-light irradiation was observed for the first time in a matrix of synthetic urine using granules of hydrogenated and iron-exchanged natural zeolite, coated with two loadings of TiO2. A natural clinoptilolite-mordenite blend was used to prepare photocatalytic adsorbents coated with TiO2 nanoparticles. The performance of the obtained materials was tested in the photodegradation of caffeine, a water contaminant of emerging concern. The photocatalytic activity was better in the urine matrix, due to the formation of surface complexes on the TiO2 coating, cation exchange performed by the zeolite support, and use of the carrier electrons in the reduction of ions, affecting recombination of the electrons and holes during photocatalysis. The composite granules maintained photocatalytic activity for at least four cycles, with more than 50% of caffeine removal in the synthetic urine matrix.

A comprehensive study of product distributions and coke deposition during catalytic cracking of vacuum gas oil over hierarchical zeolites.

In this study, zeolites (Z) were used as catalysts in the cracking of a Colombian vacuum gas oil (VGO), with a focus on product distribution and coke deposition. The catalytic tests were carried out in a MAT-type reactor under typical conditions. The zeolites were subjected to alkaline treatment with NaOH at concentrations ranging from 0.05 to 0.4 mol/L, resulting in the creation of several samples (Z-0.05, Z-0.10, Z-0.20, Z-0.30 and Z-0.40) that were then hydrothermally stabilized (Z-0.05-M, Z-0.10-M, Z-0.20-M, Z-0.30-M and Z-0.40-M) to increase mesoporosity and reduced crystallinity. The increase in mesoporosity was accompanied by an improvement in acidity. Despite Z-0.30-M having higher acidity, Z-0.00-M and Z-0.10-M exhibited the highest activity due to their high crystallinity and microporosity, yielding the highest gas yields. Gasoline was the main product, with maximum yields exceeding 30%. Z-0.20-M produced more aromatic and olefin compounds than the others, resulting in higher quality gasoline. Coke formation followed the trend: Z-0.00-M < Z-0.10-M < Z-0.20-M < Z-0.30-M. The higher intracrystalline mesoporosity in the zeolites favored the formation of a more condensed coke.

Zeolites as Ingredients of Medicinal Products.

Development of new medicinal products for particular therapeutic treatment or for better manipulations with better quality and less side effects are possible as a result of advanced inorganic and organic materials application, among which zeolites, due to their properties and versatility, have been gaining attention. This paper is an overview of the development in the use of zeolite materials and their composites and modifications as medicinal products for several purposes such as active agents, carriers, for topical treatments, oral formulations, anticancer, the composition of theragnostic systems, vaccines, parenteral dosage forms, tissue engineering, etc. The objective of this review is to explore the main properties of zeolites and associate them with their drug interaction, mainly addressing the advances and studies related to the use of zeolites for different types of treatments due to their zeolite characteristics such as molecule storage capacity, physical and chemical stability, cation exchange capacity, and possibility of functionalization. The use of computational tools to predict the drug-zeolite interaction is also explored. As conclusion was possible to realize the possibilities and versatility of zeolite applications as being able to act in several aspects of medicinal products.

Study of Electric and Magnetic Properties of Iron-Modified MFI Zeolite Prepared by a Mechanochemical Method.

Zeolites are materials of undeniable importance for science and technology. Since the properties of zeolites can be tuned after the inclusion of additional chemical species into the zeolitic framework, it is necessary to study the nature of zeolites after modification with transition metals to understand the new properties that were obtained, and with this information, novel applications can be proposed. This paper reports a solvent-free approach for the rapid synthesis of zeolites modified with iron and/or iron oxide particles. The samples were characterized, and their electrical and magnetic properties were investigated.

Organic-Free Synthesis of Finned Mordenite Zeolite.

Mordenite is a well-known zeolite widely used for industrial processes. However, its pore architecture can be inconvenient due to diffusional issues. A study of the synthesis parameters from an organic-free dense gel was carried out to control the crystal morphology, which resulted in finned mordenite zeolite particles. The obtained materials were characterized by XRD, FTIR, 29Si and 27Al MAS-NMR, elemental analysis, nitrogen physisorption, SEM, and TEM. We found that careful manipulation of the hydrothermal parameters directly affected the sizes and morphologies of the crystallites and particles, as well as the textural properties of the final products. Additionally, it was found that mordenite could exhibit a fin morphology with additional mesoporosity, which is a promising means to reduce the diffusional problems of one-dimensional-channel zeolites.

The effect of the acid pretreatment temperature of natural diatomaceous earth on the Si/Al ratio of ZSM-5 zeolite

La tierra de diatomea boliviana es una fuente de silicio potencialmente más económica en comparación a los reactivos de alta pureza comúnmente utilizados para la síntesis de zeolitas. Dada su composición compleja es necesario realizarle un pretratamiento ácido con el fin de reducir las impurezas y regular el contenido de aluminio. En este artículo se realizaron múltiples experimentos durante la etapa de pretratamiento ácido. La temperatura del pretratamiento ácido fue modificada en un rango entre 50 y 155 °C esto con el fin de determinar su efecto en la relación Si/Al final. Los resultados mostraron que la relación Si/Al puede ser modulada en un rango entre 6,2 y 38,1. Posteriormente, se obtuvieron zeolitas a partir de la tierra de diatomea modificada. Las zeolitas obtenidas presentaron una relación Si/Al entre 9,6 y 40,2. Se aplicaron distintas técnicas de caracterización para la determinación de las propiedades. El grado de cristalinidad y el área superficial específica están directamente relacionadas con la relación Si/Al. Los sitios ácidos están conformados por ácidos fuertes de tipo Brönsted y ácidos fuertes y débiles de tipo Lewis. Para la zeolita con menor relación Si/Al se determinó una elevada acidez total (>0,51 molNH3/Kgzeolita), mientras que para la zeolita con mayor relación Si/Al la acidez total se redujo considerablemente (<0,38 molNH3/Kgzeolita).

Bolivian diatomaceous earth is a potentially lower cost silica source than conventional high purity reagents used in zeolite synthesis. Due to its complex composition, it is necessary to pre-treat it with sulfuric acid in order to reduce impurities and regulate the aluminum content. In the present work several experiments were carried out with natural Bolivian diatomaceous earth in the pre-treatment stage. In order to determine the effect on the final Si/Al ratio, the temperature of the acid pre-treatment was varied between 50 to 155 °C. The results show that the Si/Al ratio can be modulated from 6.2 up to 38.1. These treated diatomaceous earth samples were used to synthetise ZSM-5 zeolite. The obtained ZSM-5 zeolites have a Si/Al ratio in the following range: 9.6 to 40.2. XRD, NH3-TPD and Nitrogen Physisorption techniques were used to characterise the properties of the obtained zeolites. The degree of crystallisation and the specific surface area are directly related to the Si/Al ratio, resulting in high values at high Si/Al ratios. The acid sites are composed of strong Brönsted acid sites and, strong and weak Lewis acid sites. For the zeolite with a low Si/Al ratio a high total acidity was found (>0.51 molNH3/Kgzeolite), while at high Si/Al ratios the total acidity is reduced (<0.38 molNH3/Kgzeolite).

A terra diatomácea boliviana é uma fonte potencialmente mais barata de silício em comparação com os reagentes de alta pureza comumente usados para a síntese de zeólitas. Dada a sua composição complexa, é necessário realizar um pré-tratamento ácido para reduzir as impurezas e regular o teor de alumínio. No presente trabalho, vários experimentos foram realizados durante a etapa de pré-tratamento ácido. A temperatura do pré-tratamento ácido foi modificada em uma faixa entre 50 e 155 °C para determinar seu efeito na relação Si/Al final. Os resultados mostram que a razão Si/Al pode ser modulada em uma faixa entre 6,2 e 38,1. Posteriormente, as zeólitas foram obtidas a partir de terra diatomácea modificada. As zeólitas obtidas possuem uma razão Si/Al entre 9,6 e 40,2. Diferentes técnicas de caracterização foram aplicadas para determinar as propriedades. O grau de cristalinidade e a área superficial específica estão diretamente relacionados com a razão Si/Al. Os sítios ácidos são compostos por ácidos fortes do tipo Brönsted e ácidos fortes e fracos do tipo Lewis. Para a zeólita com menor relação Si/Al, foi determinada uma alta acidez total (>0,51 molNH3/Kgzeólita), enquanto para a zeólita com maior relação Si/Al, a acidez total foi consideravelmente reduzida (<0,38 molNH3/Kgzeolita).

Technical and economic aspects of a sequential MF + NF + zeolite system treating landfill leachate.

This work explores the techno-economic aspects of landfill leachate treatment by an integrated scheme composed of microfiltration (MF), nanofiltration (NF), and zeolite application for carbon and nitrogen removal. In bench-scale experiments, MF and NF were investigated, and zeolite batch tests were carried out to determine optimum conditions. A preliminary economic analysis is presented for a 200 m3 d-1 full-scale treatment facility based on the data obtained from experimental tests and literature surveys. The maximum removals of 92%, 94%, and 79% for chemical oxygen demand (COD), absorbance at 254 nm, and ammonium nitrogen (NH4+-N) were achieved in bench experiments, respectively. It was possible to reach the local discharge standard for COD (200 mg L-1), but it was not possible to reach the Brazilian disposal requirement for NH4+-N (20 mg L-1). The total cost of the integrated MF + NF + zeolite system was estimated at 19.89 US$m-3. In this study, the costs of the zeolite application account for around 70% of the total costs of the integrated scheme. Membrane process integration was an adequate strategy for removing organic compounds at low operating costs; However, further NH4+-N depuration is needed to meet discharge requirements.