Adsorption of CO<Subscript>2</Subscript> by iron-exchanged heteropolyacid Fe<Subscript>1.5</Subscript>PMo<Subscript>12</Subscript>O<Subscript>40</Subscript> supported on mesoporous cellular foams

Novel low-temperature swing adsorbents that preferably adsorb CO₂ were synthesized by varying loading of heteropolyacid Fe_1.5PMo₁₂O₄₀ (Fe–PMA) supporting on mesoporous cellular foams (MCFs) by wetting impregnation. The synthesized materials were characterized by various physicochemical, thermal and spectral techniques and the CO₂ adsorption capacity of the materials were evaluated. Solid adsorbents showed a significantly high adsorption capacity toward CO₂ due to the chemisorptions of CO₂. The CO₂ adsorption capacities of the materials decreased as the temperature increased. The results showed that the adsorption capacity reached a level of 81.8 mg CO₂/g-adsorbent at 25 °C for the 20 wt% Fe–PMA–MCFs. These results indicated that the iron (Fe²⁺) complexes acted as efficient catalysts for the separation of CO₂. The as-synthesized adsorbents were selective, thermally stable, long-lived, and could be recycled at a temperature of 110 °C.     

Polysulfone membranes containing ethylene glycol monomers: synthesis,characterization, and CO<Subscript>2</Subscript>/CH<Subscript>4</Subscript> separation

Copolymers based on glassy and rubbery units have been developed to take advantage of both domains to enhance solubility and diffusivity. In this study, a series of gas separation membranes from polysulfone (PSF) containing ethylene glycol were synthesized via nucleophilic substitution polycondensation. The structures of copolymers were characterized by nuclear magnetic resonance spectra, Fourier transform infrared spectra, and thermal gravity analysis. The permeability and selectivity of the membranes were studied at different temperatures of 25–55 °C and pressures of 0.5–1.5 atm using single gases CO₂ and CH₄. Gas permeation measurements showed that copolymers with different contents of poly(ethylene glycol) exhibited different separation performances. For example, the membrane from PSF-PEG2000-20 containing 20 wt% poly(ethylene glycol) showed better performance in terms of ideal selectivity over the other seven copolymer membranes. The highest ideal CO₂/CH₄ selectivity was 43.0 with CO₂ permeability of 6.4 Barrer at 1.5 atm and 25 °C.     

Influence of Calcination Temperature on Activity and Selectivity of Ni–CeO<Subscript>2</Subscript> and Ni–Ce<Subscript>0.8</Subscript>Zr<Subscript>0.2</Subscript>O<Subscript>2</Subscript> Catalysts for CO<Subscript>2</Subscript> Methanation

Herein, we studied the influence of calcination temperature (500–800 °C) of Ni/CeO₂ and Ni/Ce_0.8Zr_0.2O₂ catalysts on the specific surface area, pore volume, crystalline size, lattice parameter, chemical bonding and oxidation states, nickel dispersion and CH₄/CO production rate in CO₂ methanation. In general, the catalytic performance revealed that Zr doping catalysts could increase the CH₄ production rate. Combined with the production rate and the characterizations results, we found that the combination of nickel dispersion, peak area of CO₂–TPD and O_II/(O_II + O_I)) play the critical role in increasing the CH₄ production rate. It is well to be mentioned that the CO production rate is strongly influenced by the nickel dispersion. Furthermore, the in-situ DRIFTS confirmed that the CO originates from the decomposition of H-assisted formate species.     

Electrochemical synthesis,characterization and application of a microstructure Cu<Subscript>3</Subscript>(BTC)<Subscript>2</Subscript> metal organic framework for CO<Subscript>2</Subscript> and CH<Subscript>4</Subscript> separation

The electrochemical route is a promising and environmentally friendly technique for fabrication of metal organic frameworks (MOFs) due to mild synthesis condition, short time for crystal growth and ease of scale up. A microstructure Cu₃(BTC)₂ MOF was synthesized through electrochemical path and successfully employed for CO₂ and CH₄ adsorption. Characterization and structural investigation of the MOF was carried out by XRD, FE-SEM, TGA, FTIR and BET analyses. The highest amount of carbon dioxide and methane sorption was 26.89 and 6.63 wt%, respectively, at 298 K. The heat of adsorption for CO₂ decreased monotonically, while an opposite trend was observed for CH₄. The results also revealed that the selectivity of the developed MOF towards CO₂ over CH₄ enhanced with increase of pressure and composition of carbon dioxide component as predicted by the ideal adsorption solution theory (IAST). The regeneration of as-synthesized MOF was also studied in six consecutive cycles and no considerable reduction in CO₂ adsorption capacity was observed.     

The promotional effect of K on the catalytic activity of Ni/MgAl<Subscript>2</Subscript>O<Subscript>4</Subscript> for the combined H<Subscript>2</Subscript>O and CO<Subscript>2</Subscript> reforming of coke oven gas for syngas production

A K-promoted 10Ni-(x)K/MgAl₂O₄ catalyst was investigated for the combined H₂O and CO₂ reforming (CSCR) of coke oven gas (COG) for syngas production. The 10Ni-(x)K/MgAl₂O₄ catalyst was prepared by co-impregnation, and the K content was varied from 0 to 5 wt%. The BET, XRD, H₂-chemisorption, H₂-TPR, and CO₂-TPD were performed for determining the physicochemical properties of prepared catalysts. Except under the condition of a K/Ni=0.1 (wt%/wt%), the Ni crystal size and dispersion decreased with increasing K/Ni. The coke resistance of the catalyst was investigated under conditions of CH₄: CO₂: H₂: CO:N₂=1 : 1 : 2 : 0.3 : 0.3, 800 °C, 5 atm. The coke formation on the used catalyst was examined by SEM and TG analysis. As compared to the 10Ni/MgAl₂O₄ catalyst, the Kpromoted catalyst exhibited superior activity and coke resistance, attributed to its strong interaction with Ni and support, and the improved CO₂ adsorption characteristic. The 10Ni-1K/MgAl₂O₄ catalyst exhibited optimum activity and coke resistance with only 1wt% of K.     

Photoreduction of CO<Subscript>2</Subscript> into CH<Subscript>4</Subscript> using Bi<Subscript>2</Subscript>S<Subscript>3</Subscript>-TiO<Subscript>2</Subscript> double-layered dense films

Nano-sized bismuth sulfide (Bi₂S₃) and titanium dioxide (TiO₂) with the orthorhombic and anatase tetragonal structures, respectively, were synthesized for application as catalysts for the reduction of carbon dioxide (CO₂) to methane (CH₄). Four double-layered dense films were fabricated with different coating sequences—TiO₂ (bottom layer)/Bi₂S₃ (top layer), Bi₂S₃/TiO₂, TiO₂/Bi₂S₃: TiO₂ (1 : 1) mix, and Bi₂S₃: TiO₂ (1 : 1) mix/Bi₂S₃: TiO₂ (1 : 1) mix—and applied to the photoreduction of CO₂ to CH₄; the catalytic activity of the fabricated films was compared to that of the pure TiO₂/TiO₂ and Bi₂S₃/Bi₂S₃ doubled-layered films. The TiO₂/Bi₂S₃ double-layered film exhibited superior photocatalytic behavior, and higher CH₄ production was obtained with the TiO₂/Bi₂S₃ double-layered film than with the other films. A model of the mechanism underlying the enhanced photoactivity of the TiO₂/Bi₂S₃ double-layered film was proposed, and it was attributed in effective charge separation.     

Ni-Co bimetallic catalyst for CH<Subscript>4</Subscript> reforming with CO<Subscript>2</Subscript>

A co-precipitation method was employed to prepare Ni/Al₂O₃-ZrO₂, Co/Al₂ O₃-ZrO₂ and Ni-Co/Al₂O₃-ZrO₂ catalysts. Their properties were characterized by N₂ adsorption (BET), thermogravimetric analysis (TGA), temperature-programmed reduction (TPR), temperature-programmed desorption (CO₂-TPD), and temperature-programmed surface reaction (CH₄-TPSR and CO₂-TPSR). Ni-Co/Al₂O₃-ZrO₂ bimetallic catalyst has good performance in the reduction of active components Ni, Co and CO₂ adsorption. Compared with mono-metallic catalyst, bimetallic catalyst could provide more active sites and CO₂ adsorption sites (C + CO₂ = 2CO) for the methane-reforming reaction, and a more appropriate force formed between active components and composite support (SMSI) for the catalytic reaction. According to the CH₄-CO₂-TPSR, there were 80.9% and 81.5% higher CH₄ and CO₂ conversion over Ni-Co/Al₂O₃-ZrO₂ catalyst, and its better resistance to carbon deposition, less than 0.5% of coke after 4 h reaction, was found by TGA. The high activity and excellent anti-coking of the Ni-Co/Al₂O₃-ZrO₂ catalyst were closely related to the synergy between Ni and Co active metal, the strong metal-support interaction and the use of composite support.     

CO and CO<Subscript>2</Subscript> Methanation Over Ni/SiC and Ni/SiO<Subscript>2</Subscript> Catalysts

Ni/SiC and Ni/SiO₂ catalysts prepared by both wet impregnation (WI) and deposition–precipitation (DP) methods were compared for CO and CO₂ methanation. The prepared catalysts were characterized using N₂ physisorption, temperature-programmed reduction with H₂ (H₂-TPR), H₂ chemisorption, pulsed CO₂ chemisorption, temperature-programmed desorption of CO₂ (CO₂-TPD), transmission electron microscopy, and X-ray diffraction. H₂-TPR analysis revealed that the catalysts prepared by DP exhibit stronger interaction between the nickel oxides and support than those prepared by WI. The former catalysts exhibit higher Ni dispersions than the latter. The catalytic activities for both reactions over Ni/SiC and Ni/SiO₂ catalysts prepared by WI increase on increasing the Ni content from 10 to 20 wt%. The Ni/SiC catalyst prepared by DP shows higher catalytic activity for CO and CO₂ methanation than that of the Ni/SiC catalyst prepared by WI. Furthermore, it exhibits the highest catalytic activity for CO methanation among the tested catalysts. The high Ni dispersion achieved by the DP method and the high thermal conductivity enabled by SiC are beneficial for both CO and CO₂ methanation.     

Sorption studies of CO<Subscript>2</Subscript>, CH<Subscript>4</Subscript>, N<Subscript>2</Subscript>, CO,O<Subscript>2</Subscript> and Ar on nanoporous aluminum terephthalate [MIL-53(Al)]

Aluminum terephthalate, MIL-53(Al), metal–organic framework synthesized hydrothermally and purified by solvent extraction method was used as an adsorbent for gas adsorption studies. The synthesized MIL-53(Al) was characterized by powder X-Ray diffraction analysis, surface area measurement using N₂ adsorption–desorption at 77 K, FTIR spectroscopy and thermo gravimetric analysis. Adsorption isotherms of CO₂, CH₄, CO, N₂, O₂ and Ar were measured at 288 and 303 K. The absolute adsorption capacity was found in the order CO₂>CH₄>CO>N₂>Ar>O₂. Henry’s constants, heat of adsorption in the low pressure region and adsorption selectivities for the adsorbate gases were calculated from their adsorption isotherms. The high selectivity and low heat of adsorption for CO₂ suggests that MIL-53(Al) is a potential adsorbent material for the separation of CO₂ from gas mixtures. The high selectivity for CH₄ over O₂ and its low heat of adsorption suggests that MIL-53(Al) could also be a compatible adsorbent for the separation of methane from methane–oxygen gas mixtures.     

Separation characteristics of tetrapropylammoniumbromide templating silica/alumina composite membrane in CO<Subscript>2</Subscript>/N<Subscript>2</Subscript>, CO<Subscript>2</Subscript>/H<Subscript>2</Subscript> and CH<Subscript>4</Subscript>/H<Subscript>2</Subscript> systems

Nanoporous silica membrane without any pinholes and cracks was synthesized by organic templating method. The tetrapropylammoniumbromide (TPABr)-templating silica sols were coated on tubular alumina composite support ( γ-Al₂O₃/ α-Al₂O₃ composite) by dip coating and then heat-treated at 550 °C. By using the prepared TPABr templating silica/alumina composite membrane, adsorption and membrane transport experiments were performed on the CO₂/N₂, CO₂/H₂ and CH₄/H₂ systems. Adsorption and permeation by using single gas and binary mixtures were measured in order to examine the transport mechanism in the membrane. In the single gas systems, adsorption characteristics on the α-Al₂O₃ support and nanoporous unsupport (TPABr templating SiO₂/ γ-Al₂O₃ composite layer without α-Al₂O₃ support) were investigated at 20–40 °C conditions and 0.0–1.0 atm pressure range. The experimental adsorption equilibrium was well fitted with Langmuir or/and Langmuir-Freundlich isotherm models. The α-Al₂O₃ support had a little adsorption capacity compared to the unsupport which had relatively larger adsorption capacity for CO₂ and CH₄. While the adsorption rates in the unsupport showed in the order of H₂> CO₂> N₂> CH₄ at low pressure range, the permeate flux in the membrane was in the order of H₂≫N₂> CH₄> CO₂. Separation properties of the unsupport could be confirmed by the separation experiments of adsorbable/non-adsorbable mixed gases, such as CO₂/H₂ and CH₄/H₂ systems. Although light and non-adsorbable molecules, such as H₂, showed the highest permeation in the single gas permeate experiments, heavier and strongly adsorbable molecules, such as CO₂ and CH₄, showed a higher separation factor (CO₂/H₂=5-7, CH₄/H₂=4-9). These results might be caused by the surface diffusion or/and blocking effects of adsorbed molecules in the unsupport. And these results could be explained by surface diffusion. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

Preparation of amine-modified SiO<Subscript>2</Subscript> aerogel from rice husk ash for CO<Subscript>2</Subscript> adsorption

Amine-modified SiO₂ aerogel was prepared using 3-(aminopropyl)triethoxysilane (APTES) as the modification agent and rice husk ash as silicon source, its CO₂ adsorption performance was investigated. The amine-modified SiO₂ aerogel remains porous, the specific surface area is 654.24 m²/g, the pore volume is 2.72 cm³/g and the pore diameter is 12.38 nm. The amine-modified aerogel, whose N content is up to 3.02 mmol/g, can stay stable below the temperature of 300 °C. In the static adsorption experiment, amine-modified SiO₂ aerogel (AMSA) showed the highest CO₂ adsorption capacity of 52.40 cm³/g. A simulation was promoted to distinguish the adsorption between the physical process and chemical process. It is observed that the chemical adsorption mainly occurs at the beginning, while the physical adsorption affects the entire adsorption process. Meanwhile, AMSA also exhibits excellent CO₂ adsorption–desorption performance. The CO₂ adsorption capacity dropped less than 10 % after ten times of adsorption–desorption cycles. As a result, AMSA with rice husk ash as raw material is a promising CO₂ sorbent with high adsorption capacity and stable recycle performance and will have a broad application prospect for exhaust emission in higher temperature.     

CO oxidation from syngas (CO and H<Subscript>2</Subscript>) using nanoporous Pt/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst

The concept of “waste-to-wealth” is spreading awareness to prevent global warming and recycle the restrictive resources. To contribute towards sustainable development, hydrogen energy is obtained from syngas (CO and H₂) generated from waste gasification, followed by CO oxidation and CO₂ removal. In H₂ generation, it is key to produce more purified H₂ from syngas using heterogeneous catalysts. In this respect, we prepared Pt/Al₂O₃ catalyst with nanoporous structure using precipitation method, and compared its catalytic activity with commercial alumina (Degussa). Based on the results of XRD and TEM, it was found that metal particles did not aggregate on the alumina surface and showed high dispersion. Optimum condition for CO conversion was 1.5 wt% Pt loaded on Al₂O₃ support, and pure hydrogen was obtained after removal of CO₂ gas.     

Evaluating the ability of separation and adsorption of SO<Subscript>2</Subscript> by nano-CuO-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> in high concentrations and moderate temperatures

Nano CuO-Fe₂O₃/TiO₂ adsorbents were made with different compositions of metal oxides using precipitation- desorption method. The adsorbents were applied for adsorption of SO₂ at high concentrations ranging from 10,000 to 30,000 ppm and temperatures between 523 and 627 K. Adsorption experiments were applied for adsorbents in a laboratory fixed bed adsorption column. The adsorption capacity was measured by calculating the area under the adsorption curve using the integral method. The results showed that temperature is the most affecting factor on the adsorption capacity. The highest adsorption capacity was obtained by using 17, 8 and 75 wt% of CuO, Fe₂O₃ and nano TiO₂, respectively. Characteristics of the best sorbent were determined by using Fe-SEM, XRD and nitrogen adsorption-desorption analyses.     

Preparation of TiO<Subscript>2</Subscript> incorporated polyacrylonitrile electrospun nanofibers for adsorption of heavy metal ions

This paper describes the adsorption of lead and cadmium ions from an aqueous solution using a composite of titanium dioxide (TiO₂)-incorporated polyacrylonitrile (PAN) electrospun nanofibers. Adsorption capacities and the mechanical response of the PAN/TiO₂ composite electrospun nanofibers are investigated at different weight percentages of TiO₂ (0.5, 1.0, 2.0, and 5.0 wt.%). The adsorption capacities of the composite PAN/TiO₂ (2.0 and 5.0 wt.%) for Pb(II) and Cd(II) are remarkably increased by approximately 114 and 47%, respectively, compared to those of pure PAN electrospun nanofibers. Moreover, the adsorption of Pb(II) and Cd(II) by PAN/TiO₂ nanofibers reaches an equilibrium within 60 min, and the process can be described using the nonlinear pseudo-second-order kinetic model. The adsorption isotherm study can be represented by the Langmuir model, which suggests the homogeneous distribution of monolayer adsorptive sites on the composite nanofiber surface. Furthermore, the ultimate tensile strength and ductility of all nanofiber membranes are measured through a uniaxial tension test. Mechanical tests reveal a reduction in the tensile strength of the PAN/TiO₂ composite nanofibers with increase in TiO₂ amount due to the possible formation of agglomerates and voids in the nanofiber structure.     

Adsorption of CO<Subscript>2</Subscript> and CO on H-zeolites with different framework topologies and chemical compositions and a correlation to probing protonic sites using NH<Subscript>3</Subscript> adsorption

Adsorption of CO₂ and CO at 25 °C has been conducted using commercially-available (Y, ZSM-5) and laboratory-synthesized (SSZ-13, SAPO-34) H-zeolites with different framework topologies and chemical compositions, and their textual and surface properties have been characterized by N₂ sorption and NH₃ adsorption techniques. All the zeolites were microporous, although ZSM-5 and SSZ-13 apparently showed a mesoporous sorption behavior due to the interparticle spaces. The zeolites had Si/Al values in the order of SSZ-13 (16.44) > ZSM-5 (16.08) ? Y (2.82) ? SAPO-34 (0.19). Regardless, high CO₂ adsorption capacity was obtained for SSZ-13 and SAPO-34 with a CHA framework. The FAU zeolite Y with the highest micropore volume showed less CO₂ adsorption than the CHA zeolites and the MFI-type ZSM-5 yielded the poorest performance. Probing acid sites in the H-form zeolites using NH₃ disclosed that these all contain both weak and strong acid sites with significant dependence of their strengths and amounts on the topology. The acid strength of the weak acid sites in the CHA zeolites was the weakest, which might allow a stronger interaction with CO₂. The H-zeolites gave CO₂/CO selectivity factors that were in the range of 4.61–11.0, depending on the framework topology.     

A Novel Process for Renewable Methane Production: Combining Direct Air Capture by K<Subscript>2</Subscript>CO<Subscript>3</Subscript>/Alumina Sorbent with CO<Subscript>2</Subscript> Methanation over Ru/Alumina Catalyst

CO₂ methanation over supported ruthenium catalysts is considered to be a promising process for carbon capture and utilization and power-to-gas technologies. In this work 4% Ru/Al₂O₃ catalyst was synthesized by impregnation of the support with an aqueous solution of Ru(OH)Cl₃, followed by liquid phase reduction using NaBH₄ and gas phase activation using the stoichiometric mixture of CO₂ and H₂ (1:4). Kinetics of CO₂ methanation reaction over the Ru/Al₂O₃ catalyst was studied in a perfectly mixed reactor at temperatures from 200 to 300 °C. The results showed that dependence of the specific activity of the catalyst on temperature followed the Arrhenius law. CO₂ conversion to methane was shown to depend on temperature, water vapor pressure and CO₂:H₂ ratio in the gas mixture. The Ru/Al₂O₃ catalyst was later tested together with the K₂CO₃/Al₂O₃ composite sorbent in the novel direct air capture/methanation process, which combined in one reactor consecutive steps of CO₂ adsorption from the air at room temperature and CO₂ desorption/methanation in H₂ flow at 300 or 350 °C. It was demonstrated that the amount of desorbed CO₂ was practically the same for both temperatures used, while the total conversion of carbon dioxide to methane was 94.2–94.6% at 300 °C and 96.1–96.5% at 350 °C.     

Highly efficient photocatalytic degradation of methylene blue using carbonaceous WO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> composites

Recent improvements in the performance of photocatalysts made it possible to tackle pollution through environment friendly methods. This study investigates the modification of the photocatalytic activity of TiO₂ by employing WO₃ and conductive polymers, namely, polyaniline (Pani) and polypyrrole (Ppy). Basing on our previous improvement of TiO₂ using a conductive polymer and activated carbon (AC), this study determines the activated carbon forms of TiO₂. The prepared composites are characterized using X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared, thermogravimetric analysis, Brunauer–Emmet–Teller, and UV–Vis spectroscopy. The specific surface area of the mesoporous composites is as follows: WO₃/TiO₂·AC (Pani) > WO₃/TiO₂·AC (Ppy) > WO₃/TiO₂·Pani > WO₃/TiO₂·Ppy (127 > 98 > 68 > 44 m² g^?1), which exhibited a similar trend to the photocatalytic performances (100 > 95 > 91 > 72 % conversion rate). This result could be attributed to higher porosity, surge of charge separation, and photo-responding range extension induced by the synergistic effect of WO₃, conducting polymers, and TiO₂ in the samples.     

Oxychlorination of methane over FeO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/CeO<Subscript>2</Subscript> catalysts

Methane activation through oxychlorination is in the spotlight due to the relatively mild reaction conditions at atmospheric pressure and in the temperature range of 450–550 °C. Although CO₂ is known to exhibit good activity for methane oxychlorination, significant amounts of by-products such as CO₂, CO and carbon deposits are produced during the reaction over CO₂. We investigated the effect of iron in FeO_x/CO₂ catalysts on methane oxychlorination. FeO_x/CO₂ with 3 wt% iron shows the maximum yield at 510 °C with 23% conversion of methane and 65% selectivity of chloromethane. XRD and H₂ TPR results indicate that iron-cerium solid solution was formed, resulting in the production of more easily reduced cerium oxide and the suppression of catalysts sintering during the reaction. Furthermore, the selectivity of by-products decreased more significantly over FeO_x/CO₂ than cerium oxide, which can be attributed to the facilitation of HCl oxidation arising from the enhanced reducibility of the former sample.     

The influence of the acidic scouring treatment on the wastewater treatment of TiO<Subscript>2</Subscript> loaded activated carbon electrode

Activated carbon (AC) electrodes were loaded with TiO₂ by using sol–gel method after a pretreatment process, the effect of the acidic pretreatment of the TiO₂ loaded electrode on its deionization efficiency of the wastewater containing NaCl solutions was studied; the physical, chemical and electrochemical properties of the electrode were characterized. The physical and chemical properties of the activated carbon before and after loaded with TiO₂ nanoparticles are characterized by using scanning electron microscopy, energy dispersion spectrum analyzer, Brunauer–Emmett–Teller gas adsorption method, thermal gravimetric analysis, Fourier transform infrared spectroscopy respectively. Electrochemical properties were characterized by employing electrochemical workstation and electrical adsorption deionization test. It was found that both the specific capacitance and the ions removal efficiency of the activated carbon loaded with TiO₂ had an increase of 16.4 and 49.8 % respectively in comparison with original activated carbon electrode. It was believed that this is due to the presence of crystal anatase TiO₂ nanoparticles (the mass content of titanium element in the TiO₂/AC complex is about 24.91 %) on the surface and pores in the activated carbon; while Ti–O–C bonds was found on the surface of the activated carbon, its surface wetting properties was significantly improved. However, it was also noticed that and the specific surface area of the activated carbon was decreased from 680.5 to 523.35 m² g^?1. This might lead to the decrease of the physical adsorption properties of the activated carbon electrodes, but its Electrical double-layer capacitance increases, electrical adsorption efficiency was improved.     

A comparative study of CO<Subscript>2</Subscript> and CH<Subscript>4</Subscript> adsorption using activated carbon prepared from pine cone by phosphoric acid activation

Adsorption of pure carbon dioxide and methane was examined on activated carbon prepared from pine cone by chemical activation with H₃PO₄ to determine the potential for the separation of CO₂ from CH₄. The prepared adsorbent was characterized by N₂ adsorption-desorption, elemental analysis, FTIR, SEM and TEM. The equilibrium adsorption of CO₂ and CH₄ on AC was determined at 298, 308 and 318 K and pressure range of 1–16 bar. The experimental data of both gases were analyzed using Langmuir and Freundlich models. For CO₂, the Langmuir isotherm presented a perfect fit, whereas the isotherm of CH₄ was well described by Freundlich model. The selectivity of CO₂ over CH₄ by AC (CO₂: CH₄=50: 50, 298K, 5 bar), predicted by ideal adsorbed solution theory (IAST) model, was achieved at 1.68. These data demonstrated that pine cone-based AC prepared in this study can be successfully used in separation of CO₂ from CH₄.