Fe-modified Zeolite Research Articles

Size-selective trapping and photocatalytic degradation of PFOA in Fe-modified zeolite frameworks

Removal and destruction of perfluorooctanoic acid (PFOA) are challenging due to its extreme persistence and dilute concentrations. This study investigated dual-function adsorptive-photocatalytic zeolite materials to selectively adsorb and degrade PFOA via tuning pore structures and doping transition metals. It is found that the pore opening is critical in the size-selective trapping of PFOA, while the iron doped zeolites present excellent adsorption of PFOA (>80 mg g−1) combining hydrophobic and electrostatic interactions. The formation of PFOA-iron complexes has reduced bond dissociation energy of C−F, calculated from density functional theory, for favorable stepwise defluorination (over 60% defluorination in 4 hours) by superoxide radicals and ligand-to-metal charge transfer. This mechanistic investigation extends the potential of the concentrate-and-degrade concept to remove PFOA selectively and effectively from contaminated water.

Catalyst for lactose hydrolysis based on zeolite Y modified with Fe species by ultrasound treatment

Research has focused on biomass as a sustainable energy source, driving biomass valorization to convert carbohydrates. The price of lactose has dropped below the production cost, urging exploration for diverse applications, such as conversion into value-added compounds. Zeolites, especially Y zeolite, enhance hexose conversion when modified with metals. Fe-modified zeolites show promise, with controlled Si/Al ratios impacting acidity and selectivity. The recent challenges remain in active site comprehension, catalyst tunability, and reaction optimization. Therefore, this study explores the selective hydrolysis of lactose, limiting undesired side-product formation catalyzed through a sono-assisted modified zeolite Y with Fe. The obtained series of Fe-modified zeolite Y were evaluated for the hydrolysis of lactose in a screening experiment. The samples with the higher potential were further used to optimize reaction conditions by a response surface methodology (RSM). This revealed that the samples prepared at high pH generated more impurities and that higher temperatures and lactose concentrations favored hydrolysis. Despite their apparent similarities, the selected Fe-modified zeolite Y samples (Fe5Y and FeYII) highlight distinct catalytic behaviors and active sites. Employing UV-Vis spectroscopy, FTIR spectroscopy, and magnetic thermal gravimetric analysis (MTGA), various Fe active sites were detected, including α-Fe(II), FeOx nanoparticles, and iron oxides. These active sites give insight into the mechanisms involved with temperature and time, which play critical roles—evidencing the potential of sono-assisted iron modification of zeolite Y to achieve selective lactose hydrolysis. These findings contribute to understanding metal-zeolite composites as bifunctional catalysts and their application in sustainable processes. Furthermore, this research highlights the complexity of catalytic reactions of modified zeolites and their potential for fine-tuning active sites for various applications, particularly lactose hydrolysis. Such advancements hold the promise of propelling the field of sustainable energy and catalysis towards a more efficient and environmentally friendly future.

Controlling Diels-Alder reactions in catalytic pyrolysis of sawdust and polypropylene by coupling CO2 atmosphere and Fe-modified zeolite for enhanced light aromatics production

Producing value-added light aromatics (BTEX) from solid waste streams holds excellent promise for resource recovery. Here we present a thermochemical conversion approach that enhanced BTEX production by coupling CO2 atmosphere and Fe-modified HZSM-5 zeolite to facilitate the Diels-Alder reactions in catalytic pyrolysis of sawdust and polypropylene. The Diels-Alder reactions between sawdust-derived furans and polypropylene-derived olefins could be controlled by tuning CO2 concentration and Fe loading amount. Sufficient CO2 (≥50%) with moderate Fe loading (10 wt%) were observed to produce more BTEX and fewer heavy fractions (C9+aromatics). To deepen the mechanistic understanding, quantification of polycyclic aromatic hydrocarbons (PAHs) and catalyst coke was further conducted. The co-use of CO2 atmosphere and Fe modification suppressed the appearance of low-, medium-, and high-membered ring PAHs by over 40%, decreased pyrolysis oil toxicity from 42.1 to 12.8 μg/goil TEQ, and transformed coke from "hard" to "soft". Based on the characterization of CO2 adsorption behavior, it was deduced that the introduced CO2 was activated by loaded Fe and reacted in situ with H2 generated during aromatization to expedite H-transfer. Meanwhile, BTEX recondensation was prevented through the Boudouard reactions of CO2 and water-gas reactions between the resulting water and carbon deposits. These synergistically enhanced the production of BTEX and suppressed the formation of heavy species, including PAHs and catalyst coke.

Exploration of Fe speciation preference for aerobic methane oxidation by using isotopic Fe-modified zeolites

Methane-oxidizing bacteria (MOB) dominate the natural consumption of fugitive methane (CH4), which is largely produced by methanogens in aerobic-anaerobic habitats. Although the influence of iron (Fe) on MOB activities has been examined, the underlying mechanism in terms of the preference remains to be clarified, the key to which may be the extracellular uptake of Fe during CH4 oxidation. In this study, isotopic ferric chloride was used to treat stable raw zeolites (Fe-Z) through a pyrolytic procedure (Fe-Z600). All samples were allowed to develop for 52 d, and the CH4 oxidation rate and contents of Fe and extracellular polymers (EPS) in different MOB periods were determined. The cumulative oxidation mass of CH4 in Fe-Z600 was two times that in Fe-Z, and the abundance of Methylocystis in Fe-Z600 was 21% higher. More uniformly dispersed α-Fe2O3 nanoparticles were formed during the pyrolysis of Fe-Z600, which accelerated the extracellular migration and stimulated MOB growth. In addition, Fe-Z600 presented the strongest extracellular polysaccharides (ECPs) inhibition; the total amount of ECPs was about 53.9% lower than that of the Raw group. Simultaneously, Fe was more likely to be stored in loosely bound EPS (LB-EPS), with a maximum cumulative amount of 38% during the stable period of CH4 oxidation in Fe-Z600, decreasing LB-EPS and tightly bound EPS by 47.4% and 75.4%, respectively. The presented findings can provide guidance for alleviating EPS blockage in long-term activities of MOB to ensure their efficient and durable CH4 oxidation.

Zeolite-supported biofilms as inoculants for the treatment of MCPA-polluted soil and sand by bioaugmentation: A microcosm study

In this study, the effectiveness of bioaugmentation approach using zeolite supported biofilms as inoculants was evaluated in microcosm experiments. For this, selected MCPA-degrading microbial consortium was grown as biofilm on natural and Fe-modified zeolite grains (0.2–1.25 mm in size) and the obtained biocomposites (4 × 1010 cells/g of biocomposite) were amended to soil or sand microcosms (130 g biocomposites/m2; 4 × 107 cells/g of dry weight soil or sand) supplemented with herbicide MCPA (2-methyl-4-chlorophenoxyacetic acid, 0.166 mg/kg dw soil or 0.309 mg/kg of dw sand, respectively). The major part of the identified bacterial sequences (51–59 %) in both biocomposites was attributed to the bacterial genera related to biodegradation of pesticides, including phenoxy-herbicides (Cupriavidus, Novosphingobium, Pseudomonas, Rhodococcus, Sphingobium, Sphingopyxis). The present study showed that the MCPA biodegradation ability of the studied biocomposites was very close to each other and characterised with similar kinetics: biodegradation of 80 % MCPA within 2 days in soil and 5 days in sand. Thus, the zeolite-supported biofilms could be effective inoculants for pesticide biodegradation at polluted agricultural sites. The biocomposites can be effectively used not only for treatment of soil but also sand, however its activity may change with variation of the matrix. Surface modifications of a given support material is an interesting approach to select different microbial communities, which can provide significant advantages according to the site to be treated.

Mitigating toxicity of acetamiprid removal techniques – Fe modified zeolites in focus

All remediation pathways in aqueous solutions come down to three dominant ones - physical, chemical, and combinations thereof. Materials proposed for adsorption and oxidative degradation can induce positive or negative effects on cells compared to the pollutants themselves. Present research deals with the effects different methods for pesticide remediation have and how they impact cytotoxicity. With this particular intention, Fe-modified zeolites (obtained via citrate/oxalate complexes) of three zeotypes (MFI, BEA and FAU) were prepared and tested as adsorbents and Fenton catalysts for the removal of the acetamiprid pesticide. The materials are characterized by AFM, FTIR spectroscopy and ICP-OES. A different effect of the zeolite framework and modification route was found among the samples, which leads to pronounced adsorption (FAU), efficient Fenton degradation (MFI) or synergistic effect of both mechanisms (BEA). The cytotoxic effects of acetamiprid in the presence of zeolites, in pristine and modified forms, were tested on the MRC-5 human fibroblast cell line. A complete survey of the toxicity effect behind different pesticide removal methods is presented. Since neither adsorption nor catalytic degradation is the best option for pesticide removal, the focus is shifted to a combination of these methods, which proved to be optimal for pesticide toxicity reduction.

Conversion of cellulose to glucose and further transformation into fuels over solid acid catalysts: A mini review

The abundant of cellulose biomass resources and the projected global market escalations for allied chemicals and fuels inferred that large-scale valorization would benefit the global energy and chemical industries. In line with this strategy, the paper carefully reviewed and examined resourceful literature on the potentials of solid acids for cellulose-to-glucose reaction and the transformation into fuels/chemicals. It initially evaluated the cellulose to glucose path by considering ionic liquids as the media for hydrolysis. The influence of employing sulfonated mesoporous carbon systems was adequately explored. In addition to critical analysis of the cellulose to sugar alcohols, the paper also analyzed the role of Fe-modified zeolites for glucose upgrading. It simultaneously discussed the parameters necessary for process upgrade and addressing catalyst-stability challenges. We have also provided new directions for further investigations in line with the findings established.

Controlling Diels-Alder Reactions in Catalytic Pyrolysis of Sawdust and Polypropylene by Coupling Co2 Atmosphere and Fe-Modified Zeolite for Enhanced Light Aromatics Production

Controlling Diels-Alder Reactions in Catalytic Pyrolysis of Sawdust and Polypropylene by Coupling Co2 Atmosphere and Fe-Modified Zeolite for Enhanced Light Aromatics Production

Adsorption and catalytic degradation of Tartrazine in aqueous medium by a Fe-modified zeolite

Azo dyes, as Tartrazine (T), are one of the rawest materials in food, pharmaceutical and textile industries. Many dyes are difficult to degrade due to their complex structure and xenobiotic properties. Although adsorption is considered an effective, efficient, and economic method for water purification, degradation of organic pollutant like synthetic dyes by using advanced oxidation processes (AOPs), as Fenton process, has become increasingly significant during last decades. However, as Fenton process requires ferrous salt for the oxidation reaction to take place, the iron sludge formed after the reaction, has to be removed before discharging. A novel composite material, which is referred to as iron-loaded natural zeolite (NZ-A-Fe), was used for the removal of Tartrazine (T) from water through the combined adsorption and heterogeneous catalysis. Since the adsorption step determines the rate in heterogeneous catalytic processes, its study becomes necessary for understanding the degradation mechanism. The suitability of Langmuir and Freundlich isotherms to the equilibrium data was investigated in the solid-liquid system. The equilibrium adsorption capacity (qe) increases with the increase of the initial concentration of T. The pseudo-second-order model can well describe the adsorption process of T on NZ-A-Fe, where k2 = 0.246 g(mg.min)−1is the rate constant for adsorption process. Degradation kinetics can be described using the classical pseudo-first order. Tartrazine degradation was high between 90 and 95% for [H2O2] /[T] = 37 for [T] = 10 mg/L. The novelty of this work is the simultaneous adsorption and Fenton degradation using a supported catalyst NZ-A-Fe that facilitates the design of filters for wastewater treatment.

A developed hybrid fixed-bed bioreactor with Fe-modified zeolite to enhance and sustain biohydrogen production

In this study, we describe the development of a hybrid bioreactor with integrated chlorinated polyethylene (CPE) fixed-bed and zeolite as a microorganism nutrition carrier (MNC), aiming at enhancing and sustaining biohydrogen production during the anaerobic digestion (AD) process. In the batch test, the hybrid bioreactor achieved a maximum biohydrogen production of 646.3 mL/L. Accordingly, the hybrid bioreactor significantly enhanced biohydrogen production and maintained a stable performance for 50 days of semi-continuous operation. This result should be attributed to the CPE providing roughness surface and high porosity for microorganism immobilization, resulting in the enhancement of microbial quantity, confirmed by our scanning electron microscope and immobilized biomass analyses. Moreover, the element ratio significantly decreased, indicating that zeolite could provide metal cations for stimulating microbial bioactivity and growth, as well as contributing to superior biohydrogen productivity during the 50-day operation. In order to further enhance and sustain long-term biohydrogen production, raw zeolite was modified with iron. The hybrid-Fe bioreactor (CPE with Fe-modified zeolite) operated mainly following the acetate pathway and exhibited higher sustainability in improving biohydrogen production with a peak value of 1893.0 mL/L during a 72-day-lasting operation. The synergistic mechanism of the Fe-modified zeolite and CPE fixed-bed revealed that it could effectively induce favorable pathways and contribute to the synthesis of essential enzymes, micronutrient supplementation, electoral conductivity, and microbial immobilization for biohydrogen production. Therefore, a hybrid-Fe bioreactor could provide a unique alternative for the enhancement of hydrogen production for practical applications.

Fe-Modified Zeolite BETA as an Active Catalyst for Intramolecular Prins Cyclization of Citronellal

Prins intramolecular cyclization of citronellal giving desired product isopulegol was performed using different modified zeolites BETA (Si/Al ratio 25, 38 and 75 modified with iron or zinc of 1, 5 or 10 wt.% by wet impregnation method). In case of materials BETA Si/Al 38 and 75 led material impregnation with metal to increase of material catalytic activity (accompanied with increase of amount of weak acid sites detected using temperature programmed desorption). Material BETA 38 with loading 1 wt.% of Fe provided 97% citronellal conversion and 94% selectivity of isopulegol formation (90 °C, toluene, 24 h).

Removal of Heavy Metals from Polluted Solutions by Zeolitic Adsorbents: a Review

The usage of zeolites in wastewater treatment has been extended in the two recent decades. This review investigates recent developments on the zeolite usage in the removal of heavy metals from polluted solutions. Various databases were used to search, evaluate, combine and analyze. The number of specific publications based on keywords linked with zeolite usage used in searching engines was more than 1000. However, about 200 publications passed the criteria set. The synthesis methodology for the production of zeolitic adsorbents, the modification of natural zeolites and their effect on the removal of heavy metals are described. Furthermore, the capacity of adsorbents to remediate polluted solutions and identify optimum conditions are reported and compared. The maximum adsorption capacity among heavy metals was for Pb(II) for all types of zeolite adsorbents (27.70 mg/g for chloride-modified zeolite, 113 mg/g for Fe-modified zeolite, 653 mg/g for surfactant modified zeolite, 808 mg/g for synthesized zeolites and 909.09 mg/g for nanozeolite). Cr(IV), Cu(II), Ni(II), Zn(II) and Co(II) were other heavy metals having good adsorption capacities on synthesized zeolites. According to the literature review, the adsorption of heavy metals by synthesized and nanozeolites is the most efficient.

Consequence of replacing nitrogen with carbon dioxide as atmosphere on suppressing the formation of polycyclic aromatic hydrocarbons in catalytic pyrolysis of sawdust

This study evaluates the effect of replacement of N2 with CO2 as atmosphere in catalytic pyrolysis of waste lignocellulosics with acidic and metal-modified zeolites, respectively, on the 16 EPA priority pollutant polycyclic aromatic hydrocarbons (PAHs) in bio-oils. By coupling solid phase extraction pretreatment with single ion monitoring detection, it is found that the replacement alleviates PAHs in bio-oil concerning synchronously abating the 16 PAHs with low, medium and high molecular weights, and the benzo[a]pyrene equivalent toxicity of bio-oil decreases. Meanwhile, CO2 decreases the content of small oxygenates, e.g. furans, ketones, acids, and increases phenolics and aromatics affording more stable and valuable bio-oils. Moreover, CO2 enhances carbon conversion efficiency, especially in combination with Fe-modified zeolite, which presents a synergistic effect. This study indicates the practical application of CO2 as an atmosphere in catalytic pyrolysis to improve the bio-oil quality by suppressing PAHs formation and adjusting compound constituent.

Solvent-induced selectivity in α-pinene oxide isomerization catalyzed by Fe-modified zeolite beta

α-Pinene oxide rearrangement to important product—trans-carveol and campholenic aldehyde in the presence of zeolite beta modified by various amount of iron (0.625–20 wt%) was studied. The amount of iron influenced initial reaction rate and time for 50% conversion. The initial reaction rate decreased with decreasing amount of iron therefore with decreasing acidity. On the other side, the highest conversion achieved after 180 min was in the case of material modified by 5 wt% of iron. The selectivity was only slightly influenced by the iron amount, but very important was the influence of used solvent on product distribution. Large variety of solvents was used in this reaction (toluene, acetonitrile, 1,4-dioxane, acetone, N,N-dimethylformamide, N,N- dimethylacetamide, dimethyl sulfoxide). Using strongly basic polar solvents (e.g., dimethyl sulfoxide) the main product in the reaction mixture was trans-carveol and using low-basic solvents (e.g. toluene) it was campholenic aldehyde. It was shown that the product distribution may be induced by used solvent.

Perillyl alcohol preparation from β-pinene oxide using Fe-modified zeolite beta

Iron-modified zeolites beta with different loading of iron (0–10 wt.% of iron) were used for the preparation of perillyl alcohol from β-pinene oxide. The prepared catalysts were characterized by XRD, XRF, UV/Vis and TPD of pyridine to determine their structural properties and acidity. The influence of iron loading, solvent type (DMSO and DMF) and presence of strong Bronsted acid (nitric acid) on the reaction course was evaluated. The highest selectivity to perillyl alcohol was obtained using catalyst with 1.25 wt.% of iron. This catalyst was not the most acidic, but the interaction of iron sites in the catalyst with strong basic polar solvent was supposed to influence positively the conversion. With an increasing amount of iron in zeolite beta, the selectivity together with conversion decreased. The type of the solvent was the most important parameter in the studied reaction—using DMSO, a significantly higher conversion in the same time and selectivity was observed compared to the reaction using DMF. The presence of nitric acid in the reaction mixture positively influenced both conversion and selectivity. The synergy between iron-modified zeolite beta, nitric acid and DMSO led to high selectivity (up to 65%) to perillyl alcohol. No iron leaching was observed during the reaction.

Direct activation of CH4 to oxygenates and unsaturated hydrocarbons using N2O on Fe-modified zeolites

Direct activation of CH4 to oxygenates and unsaturated light hydrocarbons was investigated using Fe-modified ZSM-5 and Ferrierite (FER) for a partial oxidation of CH4 with N2O oxidant. The amount of active α-oxygen sites and number of Bronsted acid sites on the Fe-modified zeolites were well correlated with CH4 conversion rate and product distributions. The amount of α-oxygen sites was largely changed according to preparation method such as wet impregnation or ion-exchange of iron precursor and types of zeolites. A large number of Bronsted acid sites and α-oxygen sites on the Fe-modified FER revealed a higher oxygenate formation such as methanol and dimethyl ether (DME) with COx, and a larger number of strong acid sites on Fe-modified ZSM-5 was also responsible for a higher selectivity to light hydrocarbons by a successive dehydration of oxygenates formed. The different catalytic performances were verified through proper measurements of the amount and type of acidic sites as well as the α-oxygen sites measured by N2O pulse chemisorption. The Fe-modified FER prepared by impregnation method possessed a larger amount of α-oxygen sites due to abundant Bronsted acid sites, which was responsible for a higher rate of CH4 conversion to oxygenates with the help of N2O decomposition on the α-oxygen sites originated from iron oxide nanoparticles.

Functional Gradient Adsorbents Processed with Biogenic Components for Ecologically Benign Water Purification

The topic of this paper is to review some results of laboratory examinations of mostly volcanic aluminosilicates (clinoptilolite-rich tuffs, tephra, stilbite, alginite, montmorillonite, perlite product vapex) deposited in Slovak and some Chinese repositories, which were achieved during scientific cooperation. The overview is limited and highlights only those results which concern Pb(II), Al(III), PO4 3- and Sb species removal from aqueous solutions and also compares other pollutants such as nitrate, sulphate, azodyes and cefazoline using the above adsorbents. The paper reports several synthesis routes, by which naturally available minerals or even waste products (furnace slag), occur in both cooperating countries in vast quantities and have been combined with specific biogenic components (like surfactant, alginate and xanthan gum) in order to prepare novel functional gradient adsorbents suitable for economically and ecologically viable water decontamination. Additionally, Fe-modified zeolite and the German commercial product GEH as well as the Czech Nanofer 25S in the form of stabilized aqueous suspension of Fe(0) were used in the experiments to compare the adsorption efficiency of the above materials. Keywords: Adsorption, alginite, aluminum, antimony, chinese slag, clinoptilolite-rich tuff, efficiency, isotherms, iron oxihydroxide modified zeolite, kinetics, lead, phosphate, pollutants removal, stilbite, tephra, xanthan gum.

Synthesis and characterization of Fe-modified zeolite for spin conversion of hydrogen at cryogenic temperature

Fe-modified zeolite was prepared by ion-exchange of zeolite with ferric chloride and calcination, for effective spin conversion of ortho- to-para-hydrogen. Studies carried out using BET, SEM, EDS, and VSM techniques. Results indicated that spin conversion rate showed great dependence on magnetic properties of the composite according to calcination temperature change. For lower sintering temperatures, the samples showed more paramagnetic behavior. As sintering temperature increased, ferromagnetic state increase, while paramagnetic states decreased. The highest spin conversion was observed at paramagnetic state, comparing with ferromagnetic, at lower calcination temperature. Moreover, Fe-modified zeolite showed a superior hydrodynamic property such as the pressure drop ratio of composite to a commercial iron oxide. These composites can be applied in more efficient hydrogen liquefaction processes.

H- and Fe-modified zeolite beta catalysts for preparation of trans-carveol from α-pinene oxide

The isomerisation of α-pinene oxide has been intensively investigated for selective preparation of campholenic aldehyde, a compound used in the synthesis of fragrances. Selective preparation of another product of α-pinene oxide rearrangement, trans-carveol, still remains a challenging task. Trans-carveol is a highly valuable compound used in perfume bases, food flavour compositions and as an active pharmaceutical substance in chemoprevention of mammary carcinogenesis.In the present work zeolite beta with different SiO2/Al2O3 molar ratios was modified by iron, characterised and tested per se and in the modified form for trans-carveol preparation from α-pinene oxide. The isomerisation reaction was carried out in a polar basic solvent N,N-dimethylacetamide at 140°C. The activities and selectivities of the catalysts were correlated with their acid properties and with the iron content.

Removal of Heavy Metals from Aqueous Solution Using Natural and Fe(III) Oxyhydroxide Clinoptilolite

AbstractThe increasing levels of industrial wastewater released to the environment present a serious threat to human health, living resources, and ecological systems. Fe-modified zeolites were developed and tested for removal of Cu2+ and Zn2+ from contaminated water. The surfaces of the naturally occurring zeolite, clinoptilolite, were modified with Fe(III) oxyhydroxides using three different methods, denoted I, II, and III (FeCli1, FeCli2, and FeNaCli1, respectively). The oxyhydroxides were prepared in Method I using 0.1 M FeCl3·6H2O in an acetate buffer (pH = 3.6); in Method II, using 10ai] FeCl3·6H2O solution in 0.1 M KOH (pH = 10); and Method III was the same as Method I except the clinoptilolite was pretreated with NaCl. Newly synthesized materials from these three methods were then tested for their ability to enhance the sorption capacity for Cu and Zn compared to the natural sample (Cli). Powder X-ray diffraction measurements and the chemical composition of these modified samples confirmed that clinoptilolite maintained its structure while amorphous Fe3+ species were synthesized. The specific surface area (BET method) of both the natural and modified clinoptilolite increased by 2 and 7.5 times for Methods I and II, respectively. Scanning electron microscopy and energy dispersive X-ray spectroscopy revealed that CaO was formed during Method I (FeClii). Throughout the adsorption process, the hydrolysis of CaO and the release of OH− caused the precipitation of Cu and Zn hydroxide, which made the determination of the sorption capacity of FeClii impossible. This phenomenon was avoided in Method III (FeNaClii) because of the absence of exchangeable Ca2+. The adsorption experiments with Method II resulted in double-enchanced adsoprtion capacity. Laboratory batch experiments revealed that the sorption capacities increased in the following order: Cli < FeCli2 < FeNaCli1, for Cu: 0.121 mmol/g < 0.251 mmol/g < 0.403 mmol/g and for Zn: 0.128 mmol/g < 0.234 mmol/g < 0.381 mmol/g.