Zeolite 4A Research Articles

Effective adsorption of zeolite/carbon composite molecular sieve synthesized from spent bleaching earth.

Spent bleaching earth (SBE) as anindustrious solid rubbish seriously causes the environmental pollution problem. The resourceful utilization of SBE has become increasingly important. In this work, silicon and carbon ingredients derived from SBE were coincidently employed to synthesize a 4A zeolite/carbon composite molecular sieve (4A/CMS). Therein, the graphite carbon components in the form of porous lamellar scattering among the interlayer, surface, and periphery of 4A zeolite promote the rate of mass transfer for the lipophilic gas, which can effectively improve the adsorption property for the volatile organic compounds. The obtained 4A/CMS has large specific surface area, hierarchical pore structure, satisfactory adsorption capacity, and regeneration performance, and its equilibrium adsorption capacity of p-xylene can achieve 209.57mg·g-1. The pseudo-first-order rate equation is appropriate for the adsorption kinetics. In the end, the formation mechanism of 4A/CMS was illuminated in detail. □ Spent bleaching earth (SBE) as anindustrious solid rubbish were utilized resourcefully. Silicon and carbon ingredients from SBE were coincidently employed to synthesize 4A/CMS. Graphitic carbon with hierarchical pore promoted the rate of mass transfer of organic gas. 4A/CMS exhibited excellent adsorption capacity and regeneration performance of p-xylene.

Aspen adsorption simulation for the effects of purge flow rate and vacuum pressure in vacuum pressure swing adsorption

Vacuum pressure swing adsorption (VPSA) process has received great attention for gas separation because it is a clean process with relatively low energy consumption and produces no waste. In order to optimize the VPSA process, a number of experiments must be performed to obtain an optimal set of operating parameters. To reduce a number of experiments, process simulation has been widely used to study the effects of the operating parameters. In this study, a mathematical model was constructed, and the simulation was performed using Aspen Adsorption. The model was first validated for the separation of carbon dioxide (CO2) from gas mixtures using zeolite 13X and zeolite 5A as the adsorbent material. Then, the model was employed to study the effects of purge flow rates and levels of vacuum pressure on the efficiency of the adsorbent regeneration. For both zeolite 13X and 5A, the purge flow rate of 20 SLPM resulted in a greater desorption of CO2 than the purge flow rate of 10 SLPM and 5 SLPM. Similarly, the vacuum pressure of 5 kPa resulted in a greater desorption of CO2 than the vacuum pressure of 10 kPa and 50 kPa. The results also showed that the regeneration of zeolite 5A was more difficult than zeolite 13X, despite the fact that the CO2 adsorption capacity of zeolite 5A was lower than that of zeolite 13X.

Chitosan Biocomposites for the Adsorption and Release of H2S.

The search for H2S donors has been increasing due to the multiple therapeutic effects of the gas. However, the use of nanoporous materials has not been investigated despite their potential. Zeolites and activated carbons are known as good gas adsorbents and their modification with chitosan may increase the material biocompatibility and simultaneously its release time in aqueous solution, thus making them good H2S donors. Herein, we modified with chitosan a series of A zeolites (3A, 4A and 5A) with different pore sizes and an activated carbon obtained from glycerin. The amount of H2S adsorbed was evaluated by a volumetric method and their release capacity in aqueous solution was measured. These studies aimed to verify which of the materials had appropriate H2S adsorption/release properties to be considered a potential H2S donor. Additionally, cytotoxicity assays using HeLa cells were performed. Considering the obtained results, the chitosan composite with the A zeolite with the larger pore opening was the most promising material to be used as a H2S donor so a further cytotoxicity assay using H2S loaded was conducted and no toxicity was observed.

Predicting carbon dioxide adsorption capacity on types 13X and 5A zeolites using artificial neural network modeling

Predicting carbon dioxide adsorption capacity on types 13X and 5A zeolites using artificial neural network modeling

Hybrid inorganic-organic membranes in the service of clean coal technologies

Clean coal technologies (CCT) are all technological solutions that are designed to increase the efficiency of coal combustion, processing and extraction. They are therefore, all the technologies that will help to reduce its environmental nuisance during the production and use of coal and can be introduced at various stages of coal application. Earlier was stated that none of the energy sources (natural gas, crude oil and renewable energy sources), their native resources, the used technologies and the sources of imports are not able to eliminate hard coal from the energy mix of Poland in the near future. That is why the authors began research to create a new clean-coal technology based on the hybrid inorganic-organic membranes, which can be used for elimination of harmful substances generated during coal combustion, especially CO2. This work concerns the study of the inorganic-organic hybrid membranes based on few modified polymer matrices and various inorganic fillers. It was found that incorporation of zeolite 4A into the polymer matrix had significantly changed the gas transport parameters (D, P, S and α). In turn, the mechanical (Rm and E) parameters have increased with the filler content. The application allows the initial selection of ingredients from which the final membrane will be created. The designed technology does not require high financial expenditures, and it is also highly universal. It can be used both in households, heating plants and, above all, in power plants.

Reduction of Lead and Antimony Ions from the Crystal Glass Wastewaters Utilising Adsorption

The presented research examined five adsorbents, i.e., zeolite 4A, a mixture of three zeolites (4A, 13X, and ZSM-5), natural zeolite (tuff), activated carbon, and peat, and their potential capability for removal of exceeded ions of lead (Pb), antimony (Sb), sulphates (SO42−), and fluorides (F−) from real wastewater generated in the crystal glass industry, which was previously treated in-situ by flocculation, with the aim to attain the statutory values for discharge into watercourses or possible recycling. The screening experiment evidenced that the tuff was the most suitable adsorbent for the reduction of Pb (93.8%) and F− (98.1%). It also lowered wastewater’s pH sufficiently from 9.6 to 7.8, although it was less appropriate for the reduction of Sb (66.7%) as compared to activated carbon (96.7%) or peat (99.9%). By adjusting the pH of the initial wastewater to pH 5, its adsorption capacity even enlarged. Results from the tuff-filled column experiment revealed reduction of Pb up to 97%, Sb up to 80%, and F− up to 96%, depending on the velocity flow, and thus it could be used for post-treatment (and recycling) of wastewaters from the crystal glass industry. Moreover, the system showed an explicit buffering capacity, but negligible reduction of the SO42−.

The efficiency of zeolites in water treatment for combating ammonia – An experimental study on Yamuna River water & treated sewage effluents

This study was meant to study the effectiveness of natural and synthetic zeolites in water treatment for combating ammonia nitrogen so that specific zeolites could be utilized at waterworks and sewage disposal works. In this study, three different zeolites were utilized in their pristine state, namely natural clinoptilolite, natural mordenite, and synthetic zeolites 4A. We examined the zeolites for their ammonia removal capacity. We performed experimental studies on synthetically prepared ammonia water, the Yamuna River water, and municipally treated sewage effluents by using Jar Test Apparatus at 100 RPM. Ammonia nitrogen content was determined by nesslerization standard method using a spectrophotometer. It has been observed that all zeolites are significantly effective in treating ammonia nitrogen in artificially prepared ammonia nitrogen water without having competing ions interference. However, because competing ions interfere in natural water, its use limits ammonium ions removal. Based on the present study outcomes, the authors have suggested replacing sand media from Rapid Sand Filters and Slow Sand Filters with Mordenite and Clinoptilolite at municipal water treatment utilities to combat low amounts of ammonium ions.

Cover Feature: Supported CuII Single‐Ion Catalyst for Total Carbon Utilization of C2 and C3 Biomass‐Based Platform Molecules in the N‐Formylation of Amines (Chem. Eur. J. 68/2021)

Upgrading biomass without waste: Scientists from Rostock and Lanzhou have, for the first time, succeeded in directly converting C2−C3 biomass molecules with amines and H2O2 to industrially important formamides by valorizing all carbon atoms of the substrates without producing undesired by-products. The reaction is catalyzed under very mild conditions by a 5A zeolite with active CuII single sites; .NHPh and .OOH radicals play a key role. More information can be found in the Full Paper by A. Brückner, F. Shi et al. (DOI: 10.1002/chem.202102300).

Synergistic removal of As(V) from aqueous solution by nanozero valent iron loaded with zeolite 5A synthesized from fly ash

Nanozero valent iron (NZVI) loaded on zeolite 5A can efficiently remove As(V) in water through the synergism of zeolite 5A and NZVI. In this study, zeolite 5A was first obtained by ion exchange using zeolite 4A synthesized from fly ash and CaCl2, and then NZVI-5A zeolite was synthesized by a reduction method to load NZVI on zeolite 5 A. NZVI-5A zeolite had a specific surface area of 238 m2/g. The As(V) removal capacity by NZVI-5A zeolite was 72.09 mg/g by the Langmuir model fitting, and the removal capacity was almost not affected by solution pH in the pH range of 4–12. As(V) was removed by the precipitation of Ca2+ in zeolite 5A with As(V), Ca2+ and NZVI with As(V), and the reduction and inner ball complex reaction of NZVI. The As(V) removal efficiency by NZVI-5A zeolite was almost unaffected by the coexistence of CO32-, SO42-, NO3- and Cl- but decreased with high concentrations of PO43- in solution. The NZVI-5A zeolite could efficiently remove metal ions coexisting with As(V) in solution. The As(V) removal efficiency by the NZVI-5A zeolite was 84.0% after 5 cycles, and the NZVI-5A zeolite could be separated from the solution with an external magnetic field.

Critical analysis of zeolite 4A synthesis through one-pot fusion hydrothermal treatment approach for class F fly ash

In this study, ‘‘One-pot fusion assisted hydrothermal synthesis’’ approach was employed to understand the nucleation and crystallization behaviour of the fusion product of Class F fly ash for zeolite 4A synthesis. Two sets of experiments were conducted by tailoring the control parameter of H 2 O/Na 2 O molar ratio (L/S) to investigate the nucleation and crystallization behaviour of zeolite 4A. The molar ratios of SiO 2 /Al 2 O 3 and Na 2 O/SiO 2 were tuned before alkali fusion by adding different amounts of Al(OH) 3 to the fly ash along with the alkali agent, Na 2 CO 3 . Under the conditions of 12h aging at 47 °C and 7h crystallization at 90 °C, the sample with high L/S ratio (3.1 Na 2 O: 2.2 SiO 2 : 1.0 Al 2 O 3 : 79.2 H 2 O) yielded pure phase of Zeolite 4A with 94% relative crystallinity, while the sample with low L/S ratio (3.1 Na 2 O: 2.2 SiO 2 : 1.0 Al 2 O 3 : 42.2 H 2 O) resulted in the highest sodalite impurity. In general, the alkalinity level was observed to be the most dominant factor among all synthesis parameters. Nevertheless, low L/S ratio led to rapid crystallization in just 2.5h at 75 °C. Because of the dependency on the alkalinity level, the dissolution of low-carnegieite (LC) was determined as the decisive factor in the formation of zeolite 4A from the fusion product. The total time of hydrothermal treatment and aging temperature were the other main factors. The crystal growth of zeolite 4A was more sensitive to changes induced by crystallization time and temperature at high L/S ratio. Relative crystallinity of zeolite 4A varied in an expanded range in terms of crystallization time (36%–86%) and temperature (25%–73%) at high L/S ratio. • The control parameter L/S ratio led to sharp differences in crystallization behaviour. • Dissolution of low-carnegieite was decisive on the %crystallinity of zeolite 4A. • Alkalinity level strongly influenced dissolution of low carnegieite. • Alkalinity level was the major factor on the nucleation and crystallization. • Faster dissolution of low-carnegieite resulted in formation of sodalite.

Nitrogen Gas Adsorption Filter (NgAF) to enhance producer gas quality

Biomass gasification is a thermochemical conversion process of solid biomass into a gaseous fuel called producer gas that can be used to generate power and electricity. The producer gas consists of around 47% of Nitrogen (N2), 24% Carbon Monoxide (CO), 16% Carbon Dioxide (CO2), 12% Hydrogen (H2), and 1% Methane (CH4). However, Nitrogen (N2) content in the producer gas reduces its heating values as N2 acts as a diluent because of the low calorific value (LCV) of gas. This study aims to design a Nitrogen gas filter for capturing nitrogen gas from producer gas to increase the heating value of producer gas as fuel in combustion. The method to increase the heating value of producer gas will increase the number of combustible gases or reduce the composition of non-combustible gases in producer gas. The use of material name zeolite with its microporous structures able to adsorb nitrogen molecules and act as catalysts to chemical reactions. Zeolites 5A have a small pore highly efficient to adsorb nitrogen gas because pore diameter is relatively similar to the size of nitrogen molecules. The quality of the producer gas depends on the design and operating parameters of the zeolite catalyst. Nitrogen Gas Adsorption Filter is a new method that has to be designed to improve the previous producer gas quality. Nitrogen Gas Adsorption Filter consists of a cylindrical shape body packed with crushed zeolites 5A. When this method of adsorption process is applied, the heating value of the producer gas is increased by observing the quantity of blue flame colour produced by NgAF.

Adsorption mechanisms investigation of methylene blue on the (0 0 1) zeolite 4A surface in aqueous medium by computational approach and molecular dynamics

The cationic methylene blue (CMB) and its protonated forms have been studied by computational tools to predict their adsorption behavior on zeolite 4A. The interaction nature has been exhaustively studied in terms of energy gap (ΔEg), global reactivity descriptors, Fukui functions, adsorption energy, density of states and natural bond orbital analysis. It was found that the protonated CMB (N36N35) molecule is less stable, more electrophilic and very reactive. The highest contribution to the lowering of the stabilization energy (E2) for all systems was mainly due to the intramolecular charge transfer from the lone pair of the nitrogen atoms as a donor orbital to π* as an acceptor orbital. DFT calculations revealed that N36 and N35 site of CMB was faced with a lower energy gap (ΔEg) and chemical hardness (ɳ) as well as a higher electron accepting power compared to other sites. Monte Carlo molecular modeling simulation (MCMM) confirmed the predominant of electrostatic interactions and p-p electron coupling. The studied compounds prefer to have configurations that facilitate p-p interaction, which is evident from the parallel orientation of CMB with zeolite surface. The dynamic parameters show that the adsorption of methylene blue is exothermic and spontaneous chemisorption.

Supported CuII Single-Ion Catalyst for Total Carbon Utilization of C2 and C3 Biomass-Based Platform Molecules in the N-Formylation of Amines.

The shift from fossil carbon sources to renewable ones is vital for developing sustainable chemical processes to produce valuable chemicals. In this work, value‐added formamides were synthesized in good yields by the reaction of amines with C2 and C3 biomass‐based platform molecules such as glycolic acid, 1,3‐dihydroxyacetone and glyceraldehyde. These feedstocks were selectively converted by catalysts based on Cu‐containing zeolite 5A through the in situ formation of carbonyl‐containing intermediates. To the best of our knowledge, this is the first example in which all the carbon atoms in biomass‐based feedstocks could be amidated to produce formamide. Combined catalyst characterization results revealed preferably single CuII sites on the surface of Cu/5A, some of which form small clusters, but without direct linking via oxygen bridges. By combining the results of electron paramagnetic resonance (EPR) spin‐trapping, operando attenuated total reflection (ATR) IR spectroscopy and control experiments, it was found that the formation of formamides might involve a HCOOH‐like intermediate and .NHPh radicals, in which the selective formation of .OOH radicals might play a key role.

Biogas upgrading to fuel grade methane using pressure swing adsorption: Parametric sensitivity analysis on an industrial scale

Biogas upgrading to fuel-grade methane employing PSA technology is examined using a one-dimensional binary mixture comprising of CH4 and CO2, heat and mass balance model through Aspen Adsorption TM version 10 and Aspen Hysys simulation. Comparison between the experimental data over a bed of silica gel and the simulated results reveal that the methane and carbon dioxide breakthrough curves and temperature responses at various positions along the adsorption bed is in a good agreement. The effects of design parameters such as feed flowrate, adsorption step duration, axial dispersion coefficient, and bed dimensions at an industrial scale on methane purity and recovery are analyzed. Aside from silica gel, five more adsorbents including CMS-3 k, zeolite-NAUSY, Zeolite KZ10-04, porous polymeric beads and zeolite 5A were employed and their process performances were evaluated. CMS-3 K records the highest biomethane purity and recovery of 97.165% and 86.2%, respectively which meets the biogas quality standards. The developed model has great competence for making prediction of biogas upgrading performance of PSA cycle with impressive ability to manage the effect of heat generated on adsorption properties.

Catalytic ozonation for the removal of reactive black 5 (RB-5) dye using zeolites modified with CuMn2O4/gC3N4 in a synergic electro flocculation-catalytic ozonation process.

This study aims to investigate the decolourization efficiency of reactive black 5 (RB-5) dye by using CuMn2O4/gC3N4 coated zeolites (zeolite 4A) for the first time in a hybrid electro-flocculation-catalytic ozonation process. A comparison between various treatment options such as electro-flocculation, electro-flocculation in the presence of a catalyst, and catalytic ozonation in combination with electro-flocculation was explored. Moreover, the effect of different factors such as pH, time, catalyst dose, ozone dose, radical scavenger, and voltage has been studied in each treatment option mentioned earlier. The results indicated that the best treatment option was found to be catalytic ozonation in combination with electro-flocculation with removal efficiency (RE) of 90.31% at pH 10 after 30 min of the treatment process. The hydroxyl radical scavenger effect indicated that the synergistic catalytic process follows a radical mechanism. It is therefore concluded that CuMn2O4/gC3N4-zeolite catalysts in synergic electro-flocculation-catalytic ozonation process may be effectively used for the treatment of textile wastewaters.

Impact of Xylose on Dynamics of Water Diffusion in Mesoporous Zeolites Measured by NMR.

Zeolites are known to be effective catalysts in biomass converting processes. Understanding the mesoporous structure and dynamics within it during such reactions is important in effectively utilizing them. Nuclear magnetic resonance (NMR) T2 relaxation and diffusion measurements, using a high-power radio frequency probe, are shown to characterize the dynamics of water in mesoporous commercially made 5A zeolite beads before and after the introduction of xylose. Xylose is the starting point in the dehydration into furfural. The results indicate xylose slightly enhances rotational mobility while it decreases translational motion through altering the permeability, K, throughout the porous structure. The measurements show xylose inhibits pure water from relocating into larger pores within the zeolite beads where it eventually is expelled from the bead itself.

Zeolite 4A supported CdS/g-C3N4 type-II heterojunction: A novel visible-light-active ternary nanocomposite for potential photocatalytic degradation of cefoperazone

The CdS/g-C3N4 heterojunction photocatalyst supported on 4A zeolite was successfully synthesized using a simple chemical precipitation method. The physicochemical characteristics of the as-prepared ternary composite were assessed using X-Ray diffraction (XRD), field emission- scanning electron microscopy (FE-SEM), energy dispersive X-Ray (EDX), transmission electron microscopy (TEM), N2 adsorption–desorption, differential reflectance spectroscopy (UV–Vis-DRS), and photoluminescence (PL) techniques. The results confirmed the successful synthesis of the CdS/g-C3N4/4AZ nanocomposite and introduction of the CdS and g-C3N4 on the substrate of 4A zeolite. Cefoperazone (CFP) antibiotic was tested as the model pollutant to assess the photocatalytic performance of the synthesized nanocomposite under visible light irradiation. The response surface methodology (RSM) and artificial neural network (ANN) showed desirable reasonability for the prediction of the CFP degradation efficiency. More than 93% of CFP with a concentration of 17 mg L-1 degraded in the presence of the 0.4 g L-1 of the catalyst at pH of 9 after 80 min treatment time (RSM-based optimization results). The pH of the solution, irradiation time, catalyst dosage, and the initial concentration of the CFP affected degradation efficiency with a percentage impact of 37, 29, 19, and 15 %, respectively (ANN-based modeling results). The addition of 1 mM of isopropanol, benzoquinone, and sodium oxalate reduced the CFP degradation efficiency from 93.23% to 85.18, 41.16, and 32.47%, respectively, proving the decisive role of the °O2– and h+ in the photodegradation process. The kinetic studies indicated the following of the process from the Langmuir-Hinshelwood’s pseudo-first-order model (kapp = 3.71 × 10-2 min−1). The structure of the identified by-products using GC-MS analysis confirmed that CFP mainly decomposed through the cleavage of C-S, C-N, and N-N bonds. Moreover, the formation of the aliphatic compounds and carboxylic acids as by-products confirmed nearly complete mineralization of the CFP to non-toxic products.

TGA investigation of water and ethanol adsorption over LTA zeolites

In absolute ethanol production, LTA zeolites (3A and 4A) are industrially used because of their selectivity and affinity to water. Despite the numerous studies performed on these materials, a lack of data is encountered, particularly at the gaseous phase. This study contributes to the understanding and elucidation of the behavior of water and ethanol adsorbed separately over 3A, 4A and 5A zeolites. Using TGA measurements in dynamic mode, this study focuses on the investigation of temperature effect (T = 20–45 °C) on the adsorption kinetics of water and ethanol. The comparison of the adsorption properties of the three zeolites shows a particular behavior of the 3A, which is characterized by both the higher water uptake and the specific affinity reflected by the initial adsorption rate and the diffusion coefficient. Based on some previous studies, which point out that ethanol may be adsorbed on 3A, this investigation shows the role of water traces in the “ethanol” uptake. The comparison of the water and ethanol kinetics at various temperatures leads to estimate the optimal selectivity temperature. On the other hand, the modeling study using four kinetic models highlights the good fitting of pseudo‒first order from which the adsorption activation energies are deduced.

Physicochemical characterization of encapsulated sulfides in zeolite 4A

Sulfides encapsulated in zeolite 4A have been known to be stabilized by protection of the inorganic framework in spite of the possibility that they could be decomposed and eventually released into environment. This study focused on their release properties along with identification of the chemical species and location. At an optimized treatment condition, zeolite 4A encapsulated sulfides to be the total sulfur content up to a weight % of 10.61. Major encapsulated sulfides were identified to be S62− in α-cage and S3•− in β-cage, respectively. Extraction with deionized water revealed that 77% of the encapsulated sulfides was rapidly released within 3 days while the rest was gradually and completely released within 3 weeks. It was suggested in zeolite 4A that S62− in α-cage was released rapidly whereas S3•− in β-cage slowly. This release behavior of encapsulated sulfides provides a new strategy to explore their potentials for advanced applications.

Saturation loadings on 5A zeolite above and below the critical conditions: monatomic species data evaluation and modeling

Saturation loadings on 5A zeolite above and below the critical conditions: monatomic species data evaluation and modeling