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Adsorption capacities of CH4, CO2, CO, N2 and H2 on NaY zeolite were measured at 298 K, 318 K, 338 K and 358 K with pressure ranged from 0 to 10 bar. The order of adsorption capacity was CO2 ≫ CH4 > CO > N2 ≫ H2. The experiment data were fitted by the Langmuir, Toth and Sips equations. The fitting relativity of above models were also compared. More...
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The recently developed thermodynamic Langmuir isotherm model is used to estimate the isosteric heat of adsorption for pure component adsorption. Specifically, pure component adsorption isotherms at different temperatures are first correlated with the thermodynamic Langmuir isotherm model. Then the pure component isosteric heat of adsorption is calc...
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... LTA could increase its CO 2 adsorption capacity following ion-exchange with Ca, while the natural zeolite clinoptilolite could perform better at higher adsorption temperatures, a property that was attributed to its Fe 2+ ion content inside the zeolitic framework. Typical commercially available zeolites that have been employed for CO 2 adsorption/separation include ZSM-5, Y (NaY), X (NaX), A (NaA), and other synthetic or natural zeolites [18][19][20][21][22][23]. In general, commercial zeolites are also quite effective for CO 2 adsorption (for example, 190 mg g −1 CO 2 adsorption capacity was achieved using a commercial 13X type zeolite at 30 • C and 1 bar in Ref. [21]), and they are often employed for comparison purposes in works dealing with laboratory synthetized zeolites [19,22] or in works dealing with modelling of CO 2 adsorption processes [21,23,24]. ...
... The application of theoretical modelling in such adsorption processes is quite important for parameter optimization, and various theoretical models have been previously employed [20,[24][25][26][27]. For example, Karka et al. [26] prepared polyethylenimine-modifed zeolite 13x and tested it for CO 2 capture while also performing kinetic studies. ...
... The CO 2 adsorption kinetics could best be described by the Avrami's fractional order and the dual kinetic model, while intraparticle diffusion was the rate limiting step. Feng et al. [20] modelled the adsorption isotherms of various gases (CO 2 , CH 4 , CO, N 2 , and H 2 ) over a NaY zeolite via the Langmuir, Toth, and Sips equations, while the isosteric heats of adsorption were also calculated via the Clausius-Clapeyron equation. The Toth model was found to be the best fit for CO 2 adsorption, while CO 2 demonstrated the highest heat of adsorption when compared to the other gases. ...
The present work studies the adsorption of CO2 using a zeolitic industrial molecular sieve (IMS) with a high surface area. The effect of the CO2 feed concentration and the adsorption temperature in conjunction with multiple adsorption–desorption cycles was experimentally investigated. To assess the validity of the experimental results, theoretical calculations based on well-established equations were employed and the values of equilibrium, kinetic, and thermodynamic parameters are presented. Three additional column kinetic models were applied to the data obtained experimentally, in order to predict the breakthrough curves and thus facilitate process design. Results showed a negative correlation between temperature and adsorption capacity, indicating that physical adsorption takes place. Theoretical calculations revealed that the Langmuir isotherm, the Bangham kinetic model (i.e., pore diffusion is the rate-determining step), and the Thomas and Yoon–Nelson models were suitable to describe the CO2 adsorption process by the IMS. The IMS adsorbent material maintained its high CO2 adsorption capacity (>200 mg g−1) after multiple adsorption–desorption cycles, showing excellent regenerability and requiring only a mild desorption treatment (200 °C for 15 min) for regeneration.
... Further, the syngas with a high concentration of hydrogen generated using oxy-steam gasification of mixed agro-residue pellets (ARP) can be separated downstream for hydrogen production. Swing adsorption technologies are widely applied for this purpose due to their simplicity, low energy consumption [33,34] at a small scale (output < 500 tons per day) [35], and applicability over a wide range of temperatures, pressures, and mixture compositions [4]. Most of the adsorptive separations reported in the literature are performed with the feed gas available at the exit of the fossil SMR-water gas shift (WGS) process, which primarily contains hydrogen (~75 vol%) and has carbon dioxide (20-25 vol%) as the major impurity. ...
The present work reports on the characterization of mixed agro-residue pellets and their subsequent use for
syngas generation in a laboratory-scale downdraft gasifier utilizing the mixture of oxygen and steam as the
gasifying agent (equivalence ratio/steam to biomass ratio: 0.21/2.15). Pure hydrogen is realized in a vacuum
pressure swing adsorption system using zeolite 13X adsorbent. Regarding pellets, the high ash content (11.46 ±
0.38 wt%) and the presence of inorganic elements (potassium, silicon, calcium) dictate gasification process level
interventions. The key requirement established experimentally is maintaining the reactor temperature under
900 ◦C for a clinker-free operation. This prerequisite, accomplished through an optimized char-ash extraction
rate, enables the consistent production of hydrogen-rich (42.2 ± 0.9 vol%) syngas with a lower heating value of
8.3 ± 0.2 MJ/Nm3 at a gross cold gas efficiency of 78.9%. The cyclic separation system operates at a pressure
ratio of 7.5 and continually generates pure hydrogen with minimal contaminants. The oxy-steam gasification of
high ash feedstock in a near-ambient fixed-bed reactor and its integration to a low-pressure swing adsorption
system for practical multi-specie syngas separation with quality assessment of the produced hydrogen are the
main novelty features.
... Several separation technologies, including cryogenic distillation, membranes, absorption, and adsorption, are available. Out of these methods, the latter works on a simple principle, is flexible [17], has low energy consumption [18], is applicable over a wide range of temperatures and pressures [19,20], and is therefore adopted for multi-component gas separation. ...
... Vacuum/pressure swing adsorption (V/ PSA) processes are commonly applied for bulk separation due to their higher productivity, longer adsorbent life, and easy operation. The literature reports the generation of high-purity H 2 , with most of the studies detailing the use of fossil SMR-WGS process stream containing (mol%) H 2 (~75), CO (0-5), CO 2 (15)(16)(17)(18)(19)(20), CH 4 (3)(4)(5), and N 2 (0-3), and utilize either a PSA or a VPSA process for separation which exploits the available high pressure (13-34 bar-abs) of the syngas during adsorption step and desorbs the pre-adsorbed impurities by exposing the columns to ambient or vacuum (0.1-0.9 bar-abs) [21][22][23][24][25]. Additionally, the use of high H 2 -content (83-99 mol%) feeds [1,[26][27][28], coal gas [29], and coke oven gas [30] has also been discussed. The reviewed studies report experimental and/or simulation results, employ various adsorbent types (activated carbons, zeolites, and metal organic frameworks), involve 1 to 10 adsorbers, and primarily use a simulated-dry feed gas mixture. ...
The current work reports on the performance characterization of a VPSA system developed in-house for ISO-quality green hydrogen generation using commercially available zeolite 13X from two practical multi-specie feed streams generated from near-ambient oxy-steam and air gasification of casuarina wood chips. The breakthrough dynamics in a packed column, and the effect of extrinsic and intrinsic decision variables on the separation performance under a cyclic steady state are analyzed. Adsorption pressure and feed flow rate are noted as the most significant influencing factors. The assessment indicates the prevalence of bed thermal gradients and establishes N2 as a limiting gas impurity and CO2 desorption as a rate-determining step. Additionally, Pareto curves signifying the process capability to produce hydrogen of different grades are generated. The average recovery range achieved using syngas feed for obtaining purity >98 mol% (ISO grade A and above) at the lab-scale is noted to be 40.7–74.4%, which is analogous to published literature for fossil streams. Adopting the optimal parameters from the prototype studies and a precise gas contaminant analysis, the technology is practically demonstrated at the pilot scale (feed: 100 Nm3/h) for the continuous generation of fuel cell compliant hydrogen (fuel index ≥ 99.97) and a successful operation at an average recovery of 68.4 ± 3.5% is realized.
... Adsorption of ciprofloxacin and tetracycline has been carried out with several natural and synthetic adsorbents. These adsorbents include activated carbon (Worch 2012), polymeric materials (Olasupo et al. 2022) and polymer nanocomposite (Naushad et al. 2019), zeolite (Feng et al. 2020), silica (Zhang et al. 2017), graphene oxide (Khan et al. 2017) and carbon nanotubes (Spaolonzi et al. 2022). However, these materials are prohibitively expensive and unsuitable for water treatment, especially in developing countries which has necessitated the need for investigation into low-cost, readily available and environmentally friendly materials that can serve as adsorbents for the removal of these contaminants. ...
The use of water containing antibiotics can result in adverse effects on humans and other living organisms. Therefore, it is essential to remove them from water. Adsorption is a promising method for their efficient removal since it is inexpensive and effective. In this study, the efficiency of an adsorbent prepared from kaolinite clay, coconut husk and stearic acid (SMC) for the removal of ciprofloxacin and tetracycline from aqueous solution was investigated. In batch adsorption, 99% of both ciprofloxacin and tetracycline were removed in 120 min at a pH of 6; SMC dose of 0.05 g; and initial concentration of 40 mg/L. Experimental data best fit the Brouers–Sotolongo isotherm with maximum adsorption capacities of 88.1 mg/g and 93.4 mg/g for ciprofloxacin and tetracycline, respectively. Kinetic data fitted best the fractal kinetics (R2 = 0.995) and the intraparticle diffusion (R2 = 0.970) models for ciprofloxacin and tetracycline adsorption, respectively. The results demonstrate that adsorption occurred via more than one interaction on active sites with different energies, while intraparticle diffusion played a significant role in the adsorption. The regeneration studies performed on SMC revealed that at the beginning of the third cycle of adsorption–desorption, the adsorbent maintained 97% efficiency. This shows that SMC is easily regenerated and can be reused multiple times while maintaining a high adsorption capacity. SMC which is prepared from readily available, low-cost materials is a highly sustainable alternative adsorbent for the effective removal of ciprofloxacin and tetracycline from wastewater.
... In the MPTA theory, the adsorbate inside the pores is considered a real fluid subjected to an external adsorption potential ( i ) of attractive nature emitted from the adsorbent surface, [22] which magnitude decreases as the distance from the surface ( z ) increases. The equilibrium criterium between the bulk phase and a respective position in the adsorbed segregated phase region is given by [13]: ...
... From Fig. 1 it can be verified favorable type I isotherms [28] for all components in both materials, which are [22] generally found for these molecules in other adsorbents, such as NaA zeolite [29] and activated carbons [30]. Adsorbed amounts are greater for H 2 S > CO 2 > CH 4 > N 2 , and this is directly related to adsorbate polarizabilities, which according to NIST Standard Reference Database 101 and Olney et al. [31] are 3631, 2507, 2448 and 1710 Å 3 for H 2 S, CO 2 , CH 4 and N 2 , respectively. ...
In natural gas sweetening processes, expensive technologies are usually applied, where adsorption can be a viable and economic alternative. In this sense, the usage of adsorption for natural gas sweetening depends on adsorbent potentiality. Thus, in this work, the potential usage of FAU NaX and NaY for natural gas sweetening at high-pressure (4 MPa) and ambient temperature (298 K) by adsorption processes was investigated by simulations using a validated Multicomponent Potential Theory of Adsorption coupled to Dubinin–Radushkevitch–Astakhov model (MPTA-DRA). Pure component adsorption data for H2S, CO2, CH4 and N2 show favorable isotherms on both materials and the correlation using MPTA-DRA model is in good agreement with experimental results. The simulation of multicomponent sour natural gas adsorption indicates that almost none CH4 and N2 are adsorbed in conditions studied and that CO2 and H2S compete for adsorption sites on both NaX and NaY. Partition coefficients of H2S are higher than CO2 and increase from 18.90 to 43.30, for NaX, and from 4.04 to 27.39, for NaY, as CO2 molar fraction in bulk phase decreases. The selectivity of H2S over CO2 follows a different trend, decreasing from 27.16 to 20.14 for NaX and remaining somewhat constant around 4 for NaY. These results suggest higher selectivity for NaX when a lower CO2 molar gas fraction is present. Meanwhile, for NaY, the CO2 molar fraction does not influence the H2S/CO2 selectivity. Therefore, simulations indicate that FAU NaX and NaY have good potential for natural gas sweetening at 4 MPa and 298 K.
... Equilibrium adsorption capacity Q e was calculated using a mass balance equation (Eq. (1)), described detailedly in published papers [20,21]. ...
Copper/graphene nanosheets composites (CGCs) were adopted as multi-gas adsorbents to remove two harmful gases (i.e., ammonia and sulfur dioxide) in the atmospheric environment, respectively. Methods such as N2 adsorption/desorption, scanning electron microscopy, and X-ray diffraction were selected to fully characterize CGCs. Under laboratory conditions, the adsorption isotherms of NH3 and SO2 onto CGCs at three different temperatures (298.15 K, 308.15 K, and 318.15 K) and different pressures (0∼1.8 bar) were quantitatively tested. A multilayer model with saturation (M5) was adopted as the best suitable model to explore the adsorption mechanism for SO2-CGCs and NH3-CGCs adsorption systems from a molecular level. The numerical simulation results demonstrated that the adsorption of NH3 by CGCs is a multi-anchorage process and a pure parallel adsorption position (298.15 K), a multi-linking process and a mixed adsorption orientation (308.15 K and 318.15 K). In contrast, SO2-CGCs adsorption system at 298.15 K, 308.15 K, and 318.15 K, there will be a multi-molecule process and a pure non-parallel adsorption position. Overall, from statistical physical, thermodynamic and SED analyses, the adsorption mechanism of SO2 and NH3 on CGCs, which was mainly governed by the density of receptor sites (Dm), was a spontaneous exothermic reversible adsorption process driven by physical interaction forces for which van der Waals interactions were responsible, while the high temperature is detrimental to the occurrence of high adsorption capacity.
... Small-pore zeolites are known effective adsorbents with a high adsorption capacity at high pressures and low temperatures of CO2 and CH4. Examples of these are, in addition to LTA [5,6], NaY [7], MOF-74 [8], RHO [9], CHA [10,11], HEU, and 13X [12,13] zeolites, which present values ranging from 0.15 to 5.5 mmol/g in the temperature range of 273-373 K. However, these values are mainly for synthetic zeolites that involve additional energy and environmental cost to obtain. ...
This paper describes the isosteric enthalpy through narrow pores at low levels of coverage through adsorption of CO2, CH4, and H2 on pores in natural chabazite exchanged with aqueous solutions of Na+, Mg2+, and Ca2+ salts at different concentrations, and with variable time and temperature of treatment. Experimental data of CO2, CH4, and H2 adsorption were treated by the Freundlich and Langmuir equations. Complementarily, the degree of interaction of these gases with these zeolites was evaluated by the evolution of isosteric enthalpy of adsorption. The exchange with Mg2+ and Na+ favors an increase in the adsorption capacity for CO2. while that of Ca2+ and Mg2+ favor adsorption through to H2 and CH4. These cations occupy sites in strategic positions S4 and S4’, which are located in the channels and nanocavities of these zeolites. The presence of Ca2+ and Mg2+ at S4 and S4′ sites causes increased adsorption into the nanocavities and on the external area of the ion-exchanged zeolites. Depending on the conditions of the exchange treatment, Ca2+ and Mg2+, and Na+ were found to be most favorable, well distributed, and accessible for CO2, CH4, and H2 adsorption.
... According to the principle of gas separation, the adsorption and desorption behavior of adsorbate-adsorbent pairs is closely related to the separation performance. Therefore, most efforts in PSA technology have focused on the use of adsorbents with high selectivity (material science), and the design/operation of efficient processes (engineering) [7]. Fabian et al. conducted a CO 2 -PSA warm gas separation technology with a ZnO sorbent for IGCC power plants, wherein the cost of electricity would reach up to 127.2 $/MWh within one year [8]. ...
The pressure swing adsorption (PSA) process has been considered a promising method for gas separation and purification. However, experimental methods are time-consuming, and it is difficult to obtain the detailed changes in variables in the PSA process. This review focuses on the numerical research developed to realize the modelling, optimization and control of the cyclic PSA process. A complete one-dimensional mathematical model, including adsorption bed, auxiliary devices, boundary conditions and performance indicators, is summarized as a general modelling approach. Key simplified assumptions and special treatments for energy balance are discussed for model reliability. Numerical optimization models and control strategies are reviewed for the PSA process as well. Relevant attention is given to the combination of deep-learning technology with artificial-intelligence-based optimization algorithms and advanced control strategies. Challenges to further improvements in the adsorbent database establishment, multiscale computational mass transfer model, large-scale PSA facility design, numerical computations and algorithm robustness are identified.
... This process consumes more energy that surpasses the energy released during the adsorption reaction. When the range of ΔH θ lies between 40 and 400 kJ/mol, the nature of adsorption is defined as chemisorption (Feng et al. 2020). Hence, the type of adsorption involved in the CV removal study is chemisorption (ΔH θ = 57.7714 ...
A novel fabrication of magnetite (Fe3O4) nanochains, surface functionalized with glutathione (GSH), has been attempted through a basic wet reduction method, coalesced with oxidative etching for the removal of crystal violet (CV) and phenol red (PR) from an aqueous solution. The structural and functional characterizations of GSH@Fe3O4 MNPs were performed using SEM-EDX, DLS, XRD, and FTIR. The nanochain-structured adsorbent was found to have an average size of 24 ± 1.29 nm and a zeta potential value of − 6.44 mV. The batch experiments showed that GSH@Fe3O4 MNPs have a brilliant removal efficiency of 97% and 79% for CV and PR dyes, respectively, within a period of 60 min. The influence of different operational parameters like adsorbent dosage, pH, temperature, reaction time, and initial dye concentration on the removal behaviour of the adsorbent was studied in detail. The adsorbate-adsorbent reaction was tested over isotherm models, and the reaction fitted well for Langmuir isotherm with an excellent qmax value of 1619.5 mg/g and 1316.16 mg/g for CV and PR dye, respectively. The experimental results were also validated using different reaction kinetics, and it was found that the pseudo-first-order model fits well for PR dye adsorption (R² = 0.91), while adsorption of CV dye was in best agreement with the pseudo-second-order kinetic model (R² = 0.98). Thermodynamic studies revealed that the adsorption reaction was spontaneous and endothermic in nature. Furthermore, GSH@Fe3O4 MNPs can be reused effectively up to 5 cycles of dye removal. Major mechanisms involved in the adsorption reaction were expected to be electrostatic attraction, hydrogen bonding, and π-interactions. The efficiency of GSH@Fe3O4 MNPs in real water samples suggested that it has a high potential for dye removal from complex aqueous systems and could be used as an effective alternative for remediation of dyes contaminated water.
... Q st of both CO 2 and CH 4 for all samples were analyzed (Fig. S4). CH 4 Q st shows almost constant values with ~16 kJ mol − 1 for all samples except for Ti-CHA, which is very similar to reported values for NaY (~15 kJ mol − 1 ) [47] and siliceous CHA (16.8 kJ mol − 1 ) [48,49] zeolites. In contrast, CH 4 Q st for Ti-CHA gradually increases from 10 to 15 kJ mol − 1 as the pressure increases, due to a weaker interaction between CH 4 and Ti-CHA. ...
Chemically and structurally flexible zeolites that adapt to coordinate extra-framework cations show a rich variety of gas adsorption behavior. Zeolite framework composition can be tuned to optimize pore geometry and host-guest interaction to improve selectivity. Herein, we report the study on the influence of zeolite framework nature on the separation of CO2/CH4, for CHA system containing variable isomorphously substituted heteroelements (none, B, Al, Ga, and Ti). Their performance has been evaluated by single-component isotherms and the overall separation ability was found to be related to both the geometry of 8-ring pore apertures in CHA and interaction between zeolite host and guest molecules, as revealed by Rietveld refinement of PXRD after dehydration and variable-pressure FTIR spectroscopy. Nearly isotropic geometry of the 8-ring pore opening in Al-CHA (3.84 × 3.89 Å) was obtained, while Ga-CHA exhibits the largest distortion (3.76 × 3.93 Å). Despite the smallest ionic radius of B, both the pore size of 8-ring (3.76 × 3.86 Å) as well as the unit cell volume are the smallest amongst the studied materials. Due to the combination of both the textural and the chemical factors, the maximum CO2 capacity and separation selectivity over CH4 follows the order Al-CHA > Ga-CHA > B-CHA ≈ Si-CHA > Ti-CHA. These observations suggest that tuning the framework composition of zeolite can strongly influence the separation of small molecules such as CO2 and CH4.
