Zeolite Y Research Articles

Catalytic synthesis of niacin from 3-methyl-pyridine and 30%H2O2 by Cu-based zeolite

Niacin is well known not only as vitamin B3 but also as an important chemical, and has wide applications in the fields of food, farming, medicine, pharmaceuticals, and industry. With the rapid development of human society, the requirement for niacin has been increasing constantly worldwide. Meanwhile, development of green routes to produce niacin under mild conditions has become particularly urgent to substitute the conventional reaction process with the consideration of energy conservation and emission reduction. Among various synthesis routes of niacin, selective oxidation of 3-methyl-pyridine and hydrogen peroxide (H2O2) in the liquid phase has become the focus of research due to its distinct advantages, such as mild reaction conditions, environmentally friendly reaction processes, and so on. Herein, zeolite-based catalysts have been first applied in the liquid phase synthesis of niacin from 3-methyl-pyridine and 30%H2O2 under mild reaction conditions. In addition, Cu-based 13X zeolite is found to show the highest catalytic performance, and optimal catalytic reaction systems have been established. This work provides a green and optional route for the synthesis of niacin.

Adsorption-absorption technique for effective CO2 capture

ABSTRACT This paper presents a study on the removal of CO2 gas from gas mixture (CO2/N2) of 14% CO2 using adsorption onto zeolite 13X in a fluidized bed at 298 K and 1 atm pressure. The effects of static bed height (5–25 cm) and rate of flow of the gas mixture (6–14 L/min) on the breakthrough time were studied. The desorption of CO2 was performed by absorbing the adsorbed CO2 molecules using NaOH solution (0.1 M). The absorption process which was accompanied with chemical reaction achieved two objectives. The first was converting CO2 gas into a valuable substance (Na2CO3) which could be used in many industries. The second was the storage of CO2 gas in what was called a chemical carrier which could emit the gas when it was needed. The effect of static bed height (5–25 cm) on the absorption process in the fluidized bed was also studied. For the adsorption process, the results showed that the breakthrough time increased with decreasing the flow rate but with increasing the static bed height. In the desorption process, the total amount of absorbed CO2 molecules was 396 mg, achieving a recovery of 90.8% at 5 cm static bed height.

Process swing adsorption with selective purge gas recirculation (PSA-SPUR): Adsorption process technology optimised for separation of heavy component from a gas mixture and its design for CO2 capture through Equilibrium Theory analysis

PSA-SPUR (Pressure Swing Adsorption with Selective Purge Gas Recirculation) has been developed aimed at separating the most strongly adsorbing component from a gas mixture at high product purity and recovery. The innovative strategy for designing a Pressure Swing Adsorption system features recycling its purge gas stream exiting the column and mixing it back into the feed. This operation enriches the mixed feed with an elevated fraction of the heavy component during the adsorption step, thus enhancing the PSA’s performance greatly. Reusing the purge gas helps significantly increase the product recovery compared to conventional methods where purge gas is simply discarded or taken as a low-quality product. For theoretical analysis of a PSA-SPUR system, a bespoke Equilibrium Theory model was developed and solved successfully, providing valuable insights into the performance of the PSA-SPUR system designed for capturing CO2 from a flue gas. The study revealed that there exists an optimum extent of purging that maximises the heavy component mole fraction in the mixed feed, leading to the best possible feed throughput of the adsorption system. Furthermore, the effects of the desorption pressure and feed composition on the PSA-SPUR system’s performance were investigated. The results indicate that the CO2 capture PSA-SPUR system using commercial zeolite 13X has excellent potential to achieve very high product purity and recovery, being allowed to operate at moderate vacuum pressures without having to compress the flue gas feed, even when the gas feed contains less than 10 mol% CO2.

Preparation and Characterization of Materials for Low- to Intermediate-Temperature CO2 Adsorption

Global carbon dioxide emissions are rising and the use of fossil fuels in several sectors are the leading causes. As global population and economies continue to grow significantly, the most practical method of lowering such emissions is to capture CO2. Although other technologies are more developed, adsorption is very promising and has attracted much attention. To ensure this technology’s success, it is essential to have suitable CO2 adsorbent materials. In this work, several new hydrotalcites (HTs) with different initial concentrations of ion precursors were prepared for the first time by the co-precipitation method—it was possible to verify that the ion concentrations influence the characteristics of the materials. The prepared HTs were characterized by thermogravimetric analysis (TG), X-Ray diffraction (XRD), surface area measurements and temperature-programmed desorption of CO2 (TPD-CO2) to relate their CO2 capture capacity to their physicochemical properties; the CO2 adsorption equilibrium isotherms were determined at 35 and 300 °C for the prepared samples, as well as for some commercial materials: magnesium oxide, calcium oxide, aluminium oxide and Zeolite 13X. After determining which materials present the best CO2 adsorption capacity, these were submitted to adsorption-desorption cycles to study their stability. The main objective of the work was to prepare and study different CO2 adsorbents for processes that are carried out at low and intermediate temperatures. From the experimental results, it was possible to conclude that the Zeolite 13X showed the best capacity at 35 °C, 3.38 mmol·g−1 (@ pCO2 = 1 bar), and a prepared calcined HT (c-HT2) was the best at 300 °C, 0.97 mmol·g−1 (@ pCO2 = 1 bar). Moreover, it seems there is an optimum initial concentration of the ions’ solutions for the tested HTs, which depends on the final application—c-HT1 showed a better capacity at 35 °C and c-HT2 at 300 °C. From the adsorption-desorption cycles—performed at 35 and 300 °C with the best materials using a magnetic suspension microbalance at 1 bar of CO2 partial pressure —, a working cyclic capacity of 2.69 mmol∙g−1 was achieved by the Zeolite at 35 °C; in turn, c-HT2 showed a working cyclic capacity of 0.79 mmol∙g−1 at 300 °C.

Application of aluminosilicate residue-based zeolite from lithium extraction in water treatment

In a previous study, the Na-P1 type zeolites were synthesized from aluminosilicate residues using an efficient and cost-effective process, exhibiting an excellent adsorption capacity for Ca2+ in comparison to commercial zeolites 13X and A. Building upon this, the current study evaluates their performance for the adsorption of various elements, including Ca2+, Mg2+, and NH4+. The objective was to evaluate the performance of the Na-P1 type zeolites for the adsorption of various elements, including Ca2+, Mg2+, and rare earth elements, with a particular emphasis on the adsorption kinetics and water hardness removal in comparison to commercial zeolite A. The results demonstrated that the Na-P1 zeolite exhibited a satisfactory sorption capacity for Ca2+ and NH4+ ions (66 mg/g), while displaying a relatively lower effectiveness for the sorption of Mg2+ ions (5.6 mg/g). The Langmuir model is particularly well suited to the sorption of Ca2+, while the Freundlich model is more appropriate for Mg2+. Both models demonstrated satisfactory representation of NH₄ ⁺ sorption. Moreover, the pseudo-second-order kinetic model provides an excellent description of the Ca2⁺ and Mg2⁺ sorption processes, while both models effectively describe the NH₄⁺ adsorption kinetics. Additionally, Na-P1 zeolite was observed to effectively reduce water hardness from 322 to 63 mg CaCO₃/L at temperatures of 10, 20, and 38 °C, and to 18 mg/L at 58 °C. These findings suggest that Na-P1 zeolite has promising potential for applications as a water softening agent. Regarding metals and rare earths, the Na-P1 zeolite demonstrated noteworthy sorption efficiencies for Cd2+ (138 mg/g), Ce3+ (209 mg/g), Cr3+ (56.2 mg/g), and Cu2+ (60.5 mg/g). However, it demonstrated lower sorption efficiencies for Co2+, Mn2+, Ni2+ and Dy3+ (below 16 mg/g). The findings illustrate that Na-P1 zeolites are effective for the adsorption of diverse elements, offering a promising avenue for the sustainable transformation of industrial waste into valuable materials for environmental applications.

Exploring the promotion effect of low MnCoOx doping for low-temperature NH3-SCR of 13X zeolite synthesized from coal fly ash

Using fly ash rich in SiO2 and Al2O3 to prepare heterogeneous zeolite catalysts is an efficacious pathway for the resource development of solid waste. Herein, 13X zeolite with a rich specific surface area was synthesized from fly ash, and low amount of active components (Mn and Co) was added during the preparation of the 13X zeolite. Finally, a series of low-load xMnyCo/13X denitration catalysts were successfully prepared. The results show that the low supported 1Mn2Co/13X zeolite catalyst exhibits excellent selective catalytic performance, with higher than 80 % NO conversion and more than 90 % N2 selectivity during 150–350 ℃. It also demonstrates excellent resistance to both water and sulfur. Physicochemical characterization analysis indicated that a little Mn and Co were doped on the surface of 13X zeolite did not have a detailed crystal structure. The element Co doping increased the proportion of Mn3+, Mn4+ and Ov on 13X zeolite. The results of in situ DRIFTs demonstrated that the NH3-SCR reaction on the surface of 1Mn2Co/13X zeolite followed both the E-R and L-H mechanisms. Additionally, process simulation results further show that using 1Mn2Co/13X zeolite as an industrial denitration agent can reduce material costs by 64.0 % and operating costs by nearly 20 %.

Fabrication of yeast engineered porous 13X adsorbent layers for CO2 capture

This study investigates a novel environmentally friendly coating technique using yeast fermentation to obtain super porous Zeolite 13X adsorbent layers through freeze-drying technique for CO2 capture applications. Several mass ratios of sugar to yeast were used to control the porosity and pore sizes in the adsorbent layer. A unique peeling process was integrated to obtain foamy, hollow structures to have deeper layer accessibility of adsorbent for adsorption applications. These coated adsorbent layers were experimentally characterized as a function of the mass ratio of sugar to yeast and adsorbent solid fraction. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FT-IR) are used to analyze the coated layers. The void fraction for coated samples is found to vary between 0.48 and 0.56, making the samples applicable for adsorption applications. Adsorption performance experiments are performed to test the coated samples' performance compared to 13X powder. Due to their simplistic fabrication, cost-effectiveness, rapid pore formation, and high adsorption capacity, these porous 13X layers hold potential for large-scale fabrication and CO2 capture applications.

Modelling of a continuous sorption-enhanced methanation process in an adiabatic packed-bed reactor system

The present study investigates a sorption-enhanced methanation process and successive solid regeneration stages using a dual-function catalyst containing nickel as a catalyst and zeolite 13X for water removal. An adiabatic packed bed, modelled by a dynamical and heterogeneous model, has been considered, and a five-stage sequence describes the sorption-enhanced methanation and successive solid regeneration. First, methanation occurs with in-situ water removal; then, the catalyst drying using a pressure and temperature swing approach implemented by blowdown, purge, cooling, and pressurisation stages. In adiabatic operation, heat management is crucial; on the other hand, the heat produced can be efficiently used to dry the zeolite. Process intensification is pursued by addressing the effect of gas inlet temperature, pressure, and GHSV on system performance. Achieving an average purity of 99 % of the methane for pressures greater than 2 bar is possible for long-time operation, with productivity averaging 0.8 mol/(kgads min) at the highest gas hourly space velocity investigated.

Solar-driven calcination of clays for sustainable zeolite production: CO2 capture performance at ambient conditions

This study presents the environmentally sustainable synthesis of zeolites from solar-calcined kaolin and halloysite, emphasizing their application in CO2 capture due to their distinctive porous structures and chemical attributes. Expanding upon prior research that utilized solar energy for kaolin calcination, we now explore halloysite as an alternative clay mineral for zeolite production and CO2 capture. Employing a solar simulator, halloysite was calcined at temperatures ranging from 700 to 1000 °C, resulting in the synthesis of zeolites 4A and 13X via hydrothermal methods. The synthesized zeolites were characterized using X-ray diffraction (XRD), low angle XRD (LA-XRD), transmission electron microscopy (TEM), and field-emission scanning electron microscopy (FE-SEM), and Brunauer–Emmett–Teller (BET) surface area measurements. Notably, the presence of Al-Si spinel, which crystallizes at elevated solar calcination temperatures, persisted within the zeolite 13X matrix, inducing a secondary mesoporous phase. The observed hysteresis in 13X samples, rather than confirming the mesoporous character of zeolite 13X, indicates a tandem effect of mesoporous Al-Si spinel with microporous zeolite 13X, exemplifying systems known as micro/mesoporous zeolitic composites (MZCs). The correlation obtained between the interplanar distances calculated from LA-XRD and pore size distributions acquired from the BJH desorption branches highlights LA-XRD as an alternative analysis method for assessing mesoporosity. While the microporosity of Al-Si spinel possessing 13X samples positively correlates with CO2 capture performance, mesoporosity appears to have minimal impact. Among the zeolites synthesized using solar energy, zeolite 4A (LTA) demonstrates superior CO2 capture capability, achieving an adsorption capacity of 2.15 mmol/g at 25 °C and 1 bar. This study highlights the potential of solar energy in producing eco-friendly zeolites from kaolin and halloysite for improved CO2 capture, advancing sustainable environmental solutions.

Optimization of carbon dioxide adsorption from industrial flue gas using zeolite 13X: A simulation study with Aspen Adsorption and response surface methodology

One of the best ways to prevent further warming of the planet and reduce pollutants is to remove or adsorb and recover carbon dioxide gas from the exit of cement factory exhaust. So far, several methods have been proposed for this; In this research, zeolite 13X adsorbent is used considering the operational conditions. To remove CO2 gas from the desired gas mixture, an adsorption operation unit with a column filled with zeolite 13X adsorbent was simulated in Aspen Adsorption V14 software. Changes in parameters such as temperature, and pressure and their effects on adsorption rate, adsorbent saturation time, and output heat rate were investigated to achieve higher system efficiency and optimal operating conditions. The adsorption unit was optimized by RSM to achieve maximum CO2 adsorption. Temperature and mole fraction of CO2 were identified as key influencing factors determining the adsorption performance of zeolite 13X for CO2 adsorption. It was found that the system should be operated at a temperature of 28.07 °C and a pressure of 1.202 bar to achieve maximum adsorption. Finally, 2.784 mol% CO2 gas was captured by the said process in optimal operating conditions. Further analysis revealed higher temperatures slightly decrease CO2 adsorption capacity, while increasing pressure enhances it. Conversely, elevated flow rates reduce breakthrough time, indicating a trade-off between adsorption capacity and capture efficiency.

Systematic screening and evaluation for an optimal adsorbent in a facade-integrated adsorption-based solar cooling system for high-rise buildings

Solar-powered adsorption chillers are a climate-friendly solution for building cooling, but costs and space requirements limit their widespread adoption. Recently developed adsorption cooling facade systems (ACFS) save installation space and further reduce CO2 emissions. The performance of ACFS depends on the implemented adsorbent. To achieve low costs and high performance of ACFS, this study systematically screened and scored adsorbents using the analytic hierarchy process (AHP) method, focusing on price, stability, driving temperature and adsorption capacity. This method narrowed down 293 adsorbents to top 10 scored adsorbents including 4 silica gels, 4 active carbons and 2 molecular sieves. The adsorbent-specific performance is evaluated by numerical simulation, revealing silica gel Type A++, Type 2560, Siogel and molecular sieve AQSOA-FAM-Z02 have peak adsorber temperatures 1.5–9.3 °C lower and increase solar cooling efficiency (SCE) by 25–27 % compared to reference adsorbent Zeolite 13X. A sensitivity analysis of the Dubinin-Astakhov equation shows increasing E and decreasing V leads to an only minor adsorber temperature decrease and minor system efficiency increase. Lower temperatures and higher capacity cannot guarantee better system performance. This underscores that improving system performance cannot be achieved solely through adsorbent optimization but requires system optimization in parallel.

Study and characterization of zeolites for the removal of artificial radionuclides in wastewater samples from nuclear power plants

4A, 13X, phillipsite and chabazite zeolites have been characterized regarding their capacity to remove Cs+ and Co2+ ions from aqueous solutions. The aim is to simulate the decontamination process of radioactive wastewater, originating from the former Garigliano nuclear plant in Italy, which is contaminated with 137Cs and 60Co. The four zeolites, in powder state, have been tested with solutions containing cesium nitrate and cobalt nitrate hexahydrate, in both individual and combined configurations, at different solid/liquid ratios. The Cs+ and Co2+ concentrations have been monitored over time by inductively coupled plasma (ICP) spectrometry. The results demonstrate the high efficacy of 13X zeolite providing almost 100 % of removal of both elements in a relatively short time (20–30 min). These findings are the basis for the kinetic characterization of the zeolite using radioactive solutions and, hence, for the setup of an in-situ pre-pilot plant to carry out tests with contaminated wastewater at the Garigliano facility. 13X zeolite presents a promising alternative for decommissioning radioactive wastewater.

Performance study of an electrified temperature vacuum swing adsorption cycle for post combustion carbon capture

The performance of a fully electrified temperature vacuum swing adsorption (E-TVSA) carbon capture process is investigated and compared with the performance of a VSA cycle as the reference case. A five-step process including (I) adsorption, (II) co-current heating, (III) counter-current evacuation, (IV) counter-current pressurizing, and (V) co-current closed loop cooling steps was devised and simulated. The adsorption time, electric heating power, and evacuation pressure were chosen as the independent variables for evaluating their impact on key performing indicators (KPI) of purity, recovery, productivity and energy consumption. In total 2717 cases were simulated to the cyclic steady state condition to provide 44 contours of the KPIs. From these contours it can be concluded that in E-TVSA carbon capture using 13X zeolite, a temperature rise of almost 50 degrees is necessary during the heating step, and the evacuation step should be continued to reach a pressure between 2.5 and 3 kPa. Under these conditions, a recovery and purity of more than 98 % were achieved with a production rate above 1.1 kg CO2/kg ads day and a specific energy consumption of 1.74 MJ/kg CO2 (0.61 MJ/kg CO2 for evacuation and 1.13 MJ/kg CO2 for heating). When comparing E-TVSA and VSA, it is noteworthy that the production rate and specific energy consumption of E-TVSA are in the same order as that of VSA. However, E-TVSA surpasses VSA in terms of purity and recovery rates. Further analysis of the transformation efficiency from electricity to heat revealed the transformation efficiency must be at least 50 % to keep the energy consumption below 3 MJ/kg CO2.

High potency of application on an open direct-contact thermal storage using humid air

To reuse low-temperature wasted heat as a thermal resource for high temperature, a direct-contact adsorption thermal storage was focused using humid air and zeolite 13X particles as the working fluid and adsorbent, respectively. Only a few previous studies have chosen the working fluid in gaseous form because it is unavailable for latent heat in generating heat sources. Recovering waste heat in humid air to generate hotter steam is unique and becomes an originality of our present work. The time required to regenerate zeolite particles and the maximum temperature of the generated steam were investigated assuming a warm-up device for a vehicle. The time required to regenerate zeolite was investigated by changing the dew point, temperature, and superficial velocity of the inlet humid air. It was mainly affected by the temperature of the inlet air. The absorbent was regenerated within 30 min when the humid air preheated to 200 °C was supplied. On the other hand, the maximum steam temperature was investigated by changing the superficial velocity and temperature of saturated inlet humid air. As one of the significant and novel finding in this work, the steam of >200 °C was obtained as a high-temperature heat source even with saturated humid air unavailable latent heat. Moreover, as theoretical knowledge, it was revealed that the maximum temperature of the heat source can be estimated by the relationship between the heat balance on the packed bed and adsorption equilibrium.

Unveiling Ru(bpy)3 2+-Encapsulated Zeolite Y as Photocatalyst: Harnessing Photocatalytic Singlet Oxygen Generation for Mustard Gas Simulant Detoxification.

This study explores the encapsulation of Ru(bpy)3 2+ within Zeolite Y (ZY) to improve photocatalytic singlet oxygen generation for the degradation of a mustard gas simulant, namely 2-chloroethyl ethyl sulfide (CEES). Mustard gas simulants are known to disrupt several biological processes; thus, their effective degradation is essential. Zeolite Y, with its hierarchical structure and adjustable Si/Al ratios, is an ideal host for Ru(bpy)3 2+, significantly improving its photocatalytic efficiency and stability. It is demonstrated through XRD and spectroscopic analyses that encapsulated Ru(bpy)3 2+ maintains its structural and photophysical properties, which are essential for generating singlet oxygen. Ru(bpy)3(1.0) loaded ZY(15) (where 1.0 and 15 represent the encapsulated amount of Ru(bpy)3 2+ and Si/Al ratio, respectively) outperforms other investigated photocatalytic systems in the oxidation of CEES, demonstrating high conversion rates and selectivity toward nontoxic sulfoxide products. Immobilization of Ru(bpy)3 2+-encapsulated zeolite Y onto cotton fabric results in effective degradation of CEES. The experimental results, validated by theoretical calculations, indicate an improved oxygen affinity and accessibility in zeolites with higher Si/Al ratios. This study advances the design of photocatalytic materials for environmental and defense applications, providing sustainable solutions for hazardous chemical degradation.

Exploring enhanced CO2 separation from blast furnace gas: A multicolumn vacuum swing adsorption approach with process design and experimental assessment

Excessive emissions of carbon dioxide (CO2) are a major driver of global warming. Blast furnace gas (BFG) represents a major source of CO2 emissions in the steel industry, accounting for approximately 30 % CO2 emissions among the industry sectors. Hence, effective CO2 capture from BFG is imperative. This study presents an approach utilizing the vacuum swing adsorption (VSA) technology to capture CO2 from BFG. A 6-column VSA rig was designed and constructed to separate CO2 from a simulated BFG (CO2/N2 = 20 %/80 %) using zeolite 13X as adsorbents. The VSA process involved steps of adsorption, desorption, heavy product purge, light product re-pressurization, and pressure equalization. Five different process modes, i.e., 1-column and 3-step, 2-column and 6-step, 2-column and 8-step, 3-column and 9-step, and 4-column and 16-step configurations, were implemented to evaluate the influence of various process design factors on the separation performance. Additionally, a 6-column and 36-step process was devised to conduct a parametric study of VSA cycles by varying the adsorption duration and desorption pressure. Results revealed the pivotal role of heavy product purge and pressure equalization on the separation performance. The six-column process achieved a CO2 purity and recovery of 94 % and 82 %, respectively, with a energy consumption of 0.76 GJ/tonCO2 when employing a desorption step duration of 240 s and pressure of 8 kPa. In addition, a method of process optimization based on the bed capacity ratio, C, was introduced in this study, which provides a dimensionless quantity of the utilization of the adsorption column. Moreover, capturing CO2 from BFG through the VSA cycle not only enhances its heating value but also yields substantial advantages in terms of mitigating CO2 emissions.

Analysis of catalytic sites in FeY zeolite prepared by sono-assisted exchange of iron (II) ions

In the refining industry, Y-type faujasite (FAU) plays an irreplaceable role, being widely used to convert crude oil into more valuable products such as gasoline. However, the demand for fuels and chemicals stimulates the search for alternatives, showing the applications of FAU beyond producing value-added chemicals from petroleum-based derivatives. These alternative applications are further enhanced from active sites that emerge in zeolites when iron is incorporated by a sonochemical treatment. Given that ultrasonic irradiation promotes mass transfer, uniform coverage of active sites is expected to produce more efficient catalysts. Likewise, Fe-zeolites catalyze a wide range of reactions in mild conditions, linked to the research of bio-refinery, biomimicry and environmental remediation. This work explores the potential of a Fe-Y zeolite prepared by a sono-assisted ion exchange method in different applications: biomass conversion (lactose hydrolysis), enzyme mimetic materials (partial oxidation of benzene to phenol) and transformation of renewable energy (photodegradation of nitrobenzene and rhodamine B). The modification of FAU was performed at different sonication times 5, 15, 30 and 120 min and characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), N2 adsorption-desorption isotherms, magnetic and non-magnetic thermogravimetric analysis (MTGA and TGA), zeta potential (ζ), Fourier-transformed Infrared (ATR-FTIR), and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS). Finding that the modification of zeolite Y with Fe species enhances its activity for the tested applications, owing their catalytic activity primarily to α-Fe (II) sites. Presenting the sono-assisted ion exchange method as an alternative for introducing Fe species and enhancing the catalytic activity of zeolites.

Techno-Economic Analysis of Ethylene Adsorptive Separation Using Zeolite 13X in Oxidative Coupling of Methane Integrated Process

Techno-Economic Analysis of Ethylene Adsorptive Separation Using Zeolite 13X in Oxidative Coupling of Methane Integrated Process

Anchoring highly dispersed FeCo/C nanoparticles within zeolite 13X to promote 1O2 generation in the degradation of tetracycline hydrochloride

This paper reports the preparation of a FeCo/C@13X catalyst derived from FeCo/ZIF using Na-13X molecular sieves as substrates through the ion-exchange method, followed by in situ FeCo/ZIF growth and a carbonization step. Compared with FeCo/ZIF@13X and Co/C@13X, FeCo/C@13X exhibited an improved peroxymonosulfate (PMS) activation effect owing to the well-dispersed FeCo sites embedded in the carbon@13X matrix, as confirmed by high-resolution transmission electron microscopy, Fourier transform infrared spectra and X-ray diffraction. The cobalt loading in the FeCo/C@13X catalysts was up to 15.32 wt% as determined by ICP-OES. FeCo/C@13X, prepared by the introduction of organic Fe and calcining FeCo/ZIF@13X, exhibited good reusability and stability, viz. 92 % degradation efficiency after five cycles compared to 84 % of Co/C@13X and 79 % of FeCo/ZIF@13X. The FeCo/C@13X/PMS system was highly stable over a wide pH range and showed excellent tolerance for background substances in aqueous environments because of non-radical-dominated degradation. Quenching experiments and electron paramagnetic resonance analysis demonstrated that singlet oxygen (1O2) primarily facilitated the tetracycline hydrochloride (TCH) removal during the FeCo/C@13X catalytic process. The electron transfer and free radicals (SO4∙−, ∙OH, and O2∙−) were engaged in the TCH degradation. Through electrochemical measurements and in situ Raman spectroscopy, electrons were rapidly transferred from FeCo/C@13X to PMS, consuming HSO5− to generate metastable active species (FeCo/C@13X-PMS* complexes), which can efficiently accelerate the cycling of Fe3+/Co3+ to Fe2+/Co2+ and enhance 1O2 production. This study provides a suitable method for designing heterogeneous Fenton-like catalysts with high and stable catalytic performances for the continuous production of 1O2.

3D-printed zeolite 13X gyroid monolith adsorbents for CO2 capture

Self-standing 3D-printed gyroid monoliths of zeolite 13X were fabricated for the first time for carbon dioxide adsorption. Gyroid sheet-based triply periodic minimal surface (TPMS) lattices provide high surface area per unit volume, smooth surfaces with no discontinuities, and low pressure drop compared to powder and beads, which are essential in gas adsorption. A photopolymer resin and zeolite 13X powder slurry was 3D-printed by digital light processing followed by debinding to remove the polymer and sintering to diffuse and consolidate the zeolite 13X particles. The sintered adsorbents were mechanically stable, and structural and morphological analyses revealed the interconnected nature of the gyroid cells permitting CO2 molecules to easily diffuse into the printed structure, thus ensuring sufficient adsorbent/adsorbate contact. The gyroid zeolite monoliths reached an equilibrium adsorption capacity of 3.5 mmol g−1 in 77 min at 25 °C and 1 bar, whereas the beads and powder required 96 and 100 min, respectively, while after 20 pressure swing adsorption (PSA) cycles, the zeolite monolith showed sustainable performance compared to the powder. The CO2/N2 selectivity ranged from 328 (at 50 mbar) to 51 (at 1 bar) at 25 °C for the zeolite monolith, whereas the powder exhibited selectivity values in the range of 294 (at 50 mbar) to 33 (at 1 bar). Dynamic breakthrough experiments using CO2/N2 mixtures confirmed the fast kinetics and separation performance of the monoliths, while the pressure drop was also significantly lower than the powder and the beads. The novel topology of the developed self-standing gyroid zeolite monoliths eliminate the need for structuring of powdered adsorbents and exhibit competitive performance, enhanced kinetics and cyclability, and reduced pressure drop toward large-scale carbon capture application.