CO2 adsorption on carbonaceous materials obtained from forestry and urban waste materials: A comparative study (original) (raw)
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Journal of co2 utilization, 2021
In this study, activated carbon (AC) based adsorbents were synthesized from biomass-derived hydro-char (HC) through modified hydrothermal carbonization (HTC) process coupled with H 3 PO4 (PA), ZnCl2, (ZnCl), and KOH thermochemical activation with a specific impregnation ratio of 1:3 (HC/activating agent) at 600 • C. The prepared ACs were characterized through CHN-S analyser, XRD, SEM/EDS, BET, TGA, and FTIR analysis. The modification in textural and surface morphology has been observed. Thermochemical activation results in surface modification of AC samples with a higher specific (S BET) surface area having a range of 650− 1225 m2 /g, large microporous volume (V μD-A , V μD-R) up to 0.624 and 0.642 cm3 /g with 68-90 % micro-porosity. The CO2 adsorption capacity was examined through a high-pressure gas sorption analyser at a pressure of 0− 16 bar and temperature of 15 • C, 30 • C, and 45 • C. At 15 • C of temperature, AC-PA showed the adsorption capacity of 130 and 958 mg/g, while AC-ZnCl exhibited 160 and 836 mg/g of adsorption at 1 and 16 bar of pressure respectively. Whereas AC-KOH exhibited a notable CO2 adsorption capacity of 198 and 1560 mg/g at 1 and 16 bar of pressure (15 • C). Furthermore, experimental equilibrium data of CO2 adsorption were analysed by applying Freundlich, Langmuir, Redlich-Peterson, Sips, and Toth isotherm models and validate these models by calculating the regression coefficient (R2), and standard deviation Δq (%). Finally, the thermodynamics parameters (ΔH • , ΔS • , ΔG • , and ΔH Isosteric) were evaluated and concluded that the adsorption of CO2 (adsorbate) on adsorbent is spontaneous and exothermic.
CO2 adsorption onto synthetic activated carbon: Kinetic, thermodynamic and regeneration studies
Separation and Purification Technology, 2013
An activated carbon for CO 2 adsorption from flue gas was synthesized using an industrial by-product (coal tar pitch) and furfural. The produced activated carbon possesses a well-developed pore structure and an alkaline character, as testified by the presence of different oxygen containing functional groups on the carbon surface. Adsorption tests have been carried out in lab-scale fixed-bed column, at different temperatures and CO 2 concentrations, in order to investigate both kinetic and thermodynamic aspects. Moreover, regeneration studies have been conducted in order to verify the possibility of activated carbon reutilization, to determine its CO 2 adsorption capacity within consecutive cycles of adsorption-desorption and to assess the optimal operating conditions for CO 2 recovery by desorption. It was established that the synthesized activated carbon has a good CO 2 adsorption capacity, likely related to its surface area and composition, as well as to the intrinsic nature of the solid. Adsorption rate increases with CO 2 concentration and temperature, even if an increase in temperature significantly reduces the adsorption capacity. Experimental results confirmed that CO 2 adsorption is a reversible process and that desorption temperature is the main controlling parameter. It was demonstrated that the regenerated carbon can be used in consecutive adsorption-desorption cycles without any significant loss in its CO 2 adsorption capacity. Finally, the most suitable operating set parameters for CO 2 recovery has been defined.
Post-combustion CO2 adsorption on activated carbons with different textural properties
Microporous and Mesoporous Materials, 2014
Fixed bed CO 2 adsorption tests were carried out in model flue-gas streams onto two commercial activated carbons, namely Filtrasorb 400 and Nuchar RGC30, at 303 K, 323 K and 353 K. Thermodynamic adsorption results highlighted that the presence of a narrower micropore size distribution with a prevailing contribution of very small pore diameters, observed for Filtrasorb 400, is a key factor in determining a higher CO 2 capture capacity, mostly at low temperature. These experimental evidences were also corroborated by the higher value of the isosteric heat derived for Filtrasorb 400, testifying stronger interactions with CO 2 molecules with respect to Nuchar RGC30. Dynamic adsorption results on the investigated sorbents highlighted the important role played by both a greater contribution of mesopores and the presence of wider micropores for Nuchar RGC30 in establishing faster capture kinetics with respect to Filtrasorb 400, in particular at 303 K. Furthermore, the modeling analysis of 15% CO 2 breakthrough curves allowed identifying intraparticle diffusion as the rate-determining step of the process.
Adsorption of CO2 on KOH activated carbon adsorbents: Effect of different mass ratios
Journal of Environmental Management, 2019
Nitrogen and oxygen enriched carbons were prepared by the cost-effective synthesis route of carbonization of polyacrylonitrile (PAN) and subsequent KOH activation for CO 2 capture. The effect of four impregnation mass ratios (KOH: PAN = 1-4) and activation temperatures (600-900°C) on the synthesized carbon adsorbent properties was explored by different analyses. The X-ray photoelectron spectroscopy (XPS) revealed the existence of basic nitrogen and oxygen functionalities on the adsorbent's surface which increases the adsorption rate for CO 2 by providing its basic sites. By increasing mass ratio (KOH:PAN) from 1:1 to 3:1, the surface area increased from 1152.4 to 1884.2 m 2 g −1 and the dynamic CO 2 adsorption capacity also increased from 2.1 to 2.5 mmol g −1 respectively, at 30°C (approximately ten times the adsorption capacity of untreated PAN, 0.22 mmol g −1). Physisorption and exothermic nature of the process were confirmed by the decrease in the adsorption capacity of the adsorbents with the increase in adsorption temperature. Moreover, good cyclic stability and regenerability over 5 adsorption-desorption cycles were obtained for the adsorbents. The fractional order kinetic and Temkin isotherm models fitted best with the adsorption data. A heterogeneous interaction between CO 2 and the surface of adsorbents was suggested by the isosteric heat of adsorption values. Combined with the simple method for the preparation of activated carbon adsorbents, efficient CO 2 adsorption and excellent regeneration make it appropriate adsorbents for post-combustion CO 2 capture.
Chemical Engineering Journal, 2014
Activated carbon was prepared from eucalyptus wood with H 3 PO 4 and modified by NH 3 . AC surface chemistry and micropore structure improved by ammonia modification. AC modified by ammonia showed enhanced CO 2 loading relative to the untreated AC. Incorporation of nitrogen group in ACs increased their adsorption capacities. Adsorption isotherm, kinetic and thermodynamics of ammonia-treated AC were studied. a b s t r a c t Eucalyptus wood was used to produce activated carbon by chemical activation with H 3 PO 4 as an adsorbent for adsorption of CO 2 . It was subjected to thermal treatment with the ammonia solution at 400 and 800°C in order to improve CO 2 capture. The textural and surface characteristics of the prepared activated carbons were determined from the analysis of N 2 adsorption isotherms, elemental analysis, Fourier Transform Infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), acid-base Boehm titration and X-ray photoelectron spectroscopy (XPS). The results show that the modification of activated carbon at high temperature enhanced BET surface area and micropore volume. The results indicate that the physical parameters such as surface area, lower pore diameter, and larger micropore volume of carbon samples show influence on the adsorbed amount of CO 2 . The adsorption behavior of CO 2 onto carbon samples was experimentally evaluated by volumetric method at temperatures ranging from 288 to 348 K and pressure range of 0-16 bar. The CO 2 adsorption capacity achieved by modified carbon was 3.22 mmol/g at 1 bar and 303 K which became more than the virgin carbon (2.9 mmol/g). The equilibrium CO 2 adsorption data were fitted by Langmuir and Freundlich isotherms models. The thermodynamic parameters were investigated and indicated that the adsorption process was spontaneous and exothermic in nature and physisorption was the dominant mechanism for CO 2 adsorption.
Adsorption of CO2 on Activated Carbons Prepared by Chemical Activation with Cupric Nitrate
ACS Omega, 2020
Activated carbons were prepared from a lignocellulosic material, African palm shells (Elaeis guineensis), by chemical impregnation of the precursor with solutions of 1−7% w/v Cu(NO 3) 2 at five different concentrations. These were carbonized in a carbon dioxide atmosphere at 1073 K to obtain different carbons. Their textural properties were characterized by nitrogen and carbon dioxide adsorption isotherms in order to evaluate the pore-size distribution. The immersion enthalpies of the activated carbons in benzene, dichloromethane, and water were determined. The CO 2 adsorption capacities of the materials at 273 K under low-pressure conditions were also determined. Chemical characterization was performed by mass spectrometry, Fourier transform infrared spectroscopy, and temperature-programmed reduction. With this method of preparation under the concentrations described, activated micro−mesoporous carbons were obtained, with the formation of highly mesoporous solids that favored the process of diffusion of molecules of CO 2 into the material. Here, we show that activated carbons were obtained with different textural characteristics: surface Brunauer−Emmett−Teller areas varied between 473 and 1361 m 2 g −1 and micropore volume between 0.18 and 0.51 cm 3 g −1. The activated carbon with the highest values of textural parameters was ACCu5-1073. Micro− mesoporous solids were obtained with the methodology used. This is important as it may help the entry of CO 2 molecules into the pores. The adsorption of CO 2 in the materials prepared presented values between 103 and 217 mg CO 2 g −1 ; the values of volume of narrow microporosity obtained were between 0.16 and 0.45 cm 3 g −1. The solid with the greatest capacity for adsorption of CO 2 and volume of narrow microporosity was ACCu3-1073. The use of these solids is of importance for future practical and industrial applications. The adsorption kinetic of CO 2 in the activated carbons prepared with metallic salt of copper is in good accordance with the intraparticle diffusion model, for which diffusion is the rate-limiting step. The adsorption of CO 2 in the prepared activated carbons is favorable from the energy and kinetic point of view, as these accompanied by the presence of wide micro−mesoporosity favor the entry of CO 2 into the micropores.
Carbon Dioxide Adsorption Isotherms on Activated Carbons
Journal of Chemical & Engineering Data, 2011
This paper presents adsorption isotherm data of CO 2 onto two different types of highly porous activated carbons (ACs) for temperatures ranging from (À18 to 80)°C and pressures up to 10 MPa. The assorted adsorbents are activated carbon fiber (ACF) of type A-20 and activated carbon powder of type Maxsorb III. Adsorption isotherm data have been obtained using a volumetric technique and fitted to the DubininÀAstakhov (DÀA), T oth, Langmuir, and modified DÀA equations. The latter considers the pseudosaturation pressure of CO 2 that plays an important role for supercritical gas adsorption, and the pseudosaturation pressure was determined from the experimental data. The T oth and modified DÀA isotherms correlate with the experimental data within 5 % root-mean-square deviation (rmsd) and present a better fitting than that of the Langmuir and the DÀA equations. The isosteric heat of adsorption data were derived from the T oth and modified DÀA isotherm equations and the correlation proposed by Chakraborty et al., and the average heat of adsorption values were found to be comparable. These data are essential for designing CO 2 -based adsorption cooling, refrigeration, and gas storage systems.
Increase the Microporosity and CO2 Adsorption of a Commercial Activated Carbon
Applied Mechanics and Materials, 2015
Microporous carbons prepared from commercial activated carbon WG12 by KOH and/or ZnCl 2 treatment were examined as adsorbents for CO 2 capture. The micropore volume and specific surface area of the resulting carbons varied from 0.52 cm3/g (1374 m 2 /g) to 0.70 cm3/g (1800 m 2 /g), respectively. The obtained microporous carbon materials showed high CO 2 adsorption capacities at 40 bar pressure reaching 16.4 mmol/g.
Surface modification of activated carbons for CO2 capture
Applied Surface Science, 2008
The reduction of anthropogenic CO 2 emissions to address the consequences of climate change is a matter of concern for all developed countries. In the short term, one of the most viable options for reducing carbon emissions is to capture and store CO 2 at large stationary sources. Adsorption with solid sorbents is one of the most promising options.
CO2 and CH4 Adsorption Behavior of Biomass Based Activated Carbons
The aim of the present study is to provide new insights into the CO2 and CH4 adsorption using a set of biomass-based activated carbons obtained by physical and chemical activation of olive-stones. The adsorption behavior is analyzed by means of pure gas adsorption isotherms up to 3.2 MPa at two temperatures (303.15 and 323.15 K).The influence of the activation method on the adsorption uptake is studied in terms of both textural properties and surface chemistry. For three activated carbons the CO2 adsorption was more important than that of CH4. The chemically activation resulted in higher BET surface area and micropore volume that lead to higher adsorption for both CO2 and CH4. For methane the presence of mesopores seems to facilitate the access of the gas molecules into the micropores while for carbon dioxide, the presence of oxygen groups enhanced the adsorption capacity.