CO2 Adsorption by Modified Palm Shell Activated Carbon (PSAC) Via Chemical and Physical Activation and Metal Impregnation

The aim of this study was to verify the ability of nickel-impregnated palm shell activated carbon (PSAC) for CO₂ adsorption and compare its performance with the chemically and physically activated PSAC. Sodium hydroxide and CO₂ were used as activating agents for chemical and physical activation, respectively. Nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) was used as a precursor for metal impregnation. The effect of different chemical loadings (NaOH: 20–50 wt%), metal impregnation (Ni(NO₃)₂·6H₂O: 16–28 wt%), and heat treatment time (1–4 h) was studied as parameters. Adsorption capacity was calculated using breakthrough graphs. The effect of humidity on CO₂ adsorption and desorption of CO₂ was also investigated in this study. The results revealed that chemically modified PSAC yields the highest adsorption capacity (48.2 mg/g) compared to other methods of activation. Interestingly, it was found that the adsorption capacity of nickel-impregnated PSAC was similar to other types of metal-impregnated activated carbon. Humidity gave a negative effect on CO₂ adsorption. In summary, results showed that chemical activation is an efficient technique to modify PSAC for CO₂ adsorption.     

Porous properties of activated carbon produced from Eucalyptus and Wattle wood by carbon dioxide activation

This work focused on the preparation of activated carbon from eucalyptus and wattle wood by physical activation with CO₂. The preparation process consisted of carbonization of the wood samples under the flow of N₂ at 400°C and 60 min followed by activating the derived chars with CO₂. The activation temperature was varied from 600 to 900°C and activation time from 60 to 300 min, giving char burn-off in the range of 20/2-83%. The effect of CO₂ concentration during activation was also studied. The porous properties of the resultant activated carbons were characterized based on the analysis of N2 adsorption isotherms at −196°C. Experimental results showed that surface area, micropore volume and total pore volume of the activated carbon increased with the increase in activation time and temperature with temperature exerting the larger effect. The activated carbons produced from eucalyptus and wattle wood had the BET surface area ranging from 460 to 1,490 m²/g and 430 to 1,030 m²/g, respectively. The optimum activation conditions that gave the maximum in surface area and total pore volume occurred at 900°C and 60 min for eucalyptus and 800°C and 300 min for wattle wood. Under the conditions tested, the obtained activated carbons were dominated with micropore structure (∼80% of total pore volume).     

Preparation of Activated Carbons from Tobacco Stems by Potassium Hydroxide Activation and Phosphine Adsorption

Activated carbon preparation from tobacco stems by KOH activation at different activation temperatures and KOH/char mass ratios were investigated in this study. The effects of preparation parameters on activated carbon pore structure, morphometrics, microcrystallinities, and surface functional groups were characterized by N₂ adsorption, SEM, XRD, and FTIR technologies, respectively. The optimum preparation condition of activated carbon was activation temperature of 850°C, and KOH/char mass ratio of 2. Under this condition, the BET surface area of 2215 m²/g, and the pore volume of 1.343 cm³/g can be obtained. Prepared activated carbon showed clearly honeycomb holes, and a predominated amorphous structure. With increase of activation temperature and KOH/char mass ratio, decrease of surface oxygen functional group, and aromatization of the carbon structure was found. The activated carbon was subject to PH₃ purification, and the maximum PH₃ adsorption capacity of 253 mg/g can be realized based on well prepared KOH-AC with modification of 2.5% Cu. It seems that the activated carbon produced from chemical activation of tobacco stem would be an effective and alternative adsorbent for PH₃ adsorption because of its high surface area, adsorption capacity, and low cost.     

Preparation and Phosphine Adsorption of Activated Carbon Prepared from Walnut Shells by KOH Chemical Activation

Walnut-shell activated carbons (WSACs) with high surface area and predominant micropore development were prepared by KOH chemical activation. The effects of carbonization temperature, activation temperature, and ratio of KOH to chars on the pore development of WSACs and PH₃ adsorption performance of the modified walnut-shell activated carbons (MWSACs) were studied. Criteria for determining the optimum preparation conditions were pore development of WSACs and PH₃ breakthrough adsorption capacity of MWSAC adsorbents. The result shows that the optimum preparation conditions are a carbonization temperature of 700°C, an activation temperature of 700°C, and a mass ratio of 3. The BET surface area and the micropore volume of the optimal WASC are 1636m²/g and 0.641cm³/g, respectively. The micropore volume percentage of WSAC plays an important role in PH₃ adsorption when there is a slight difference in BET surface areas. High-surface-area WSACs with predominant micropores are suitable for PH₃ adsorption removal. The MWSAC adsorbent owns the biggest PH₃ breakthrough adsorption capacity (284.12mg/g) due to the biggest specific surface area, total pore volume, and micropore volume percentage. The MWSAC adsorbent will be a potential adsorbent for PH₃ adsorption removal from yellow phosphorus tail gas.     

A Procedure for the Development of a Low-Cost Treatment Technology of Raw Biogas for Application in a Gas Engine. A Case of Sizing a Carbon Dioxide Removal Unit

A test laboratory (lab) for carbon dioxide (CO₂) adsorption from raw biogas onto a novel adsorbent was used to size a CO₂ removal unit in the development of a low-cost biogas treatment technology. The novel adsorbent was made out of clay and burnt maize cob particles, impregnated with hot natural alkaline solution of pH 10 ± 0.5, degassed, and then activated at a temperature of 250°C, thereby making it low cost. The activated absorbents were spherical balls of average diameter 17 mm, density 410 kg/m³, and surface area 128 m²/g, and contained exchangeable ions due to the presence of clay and increased pore sizes due to impregnation, degassing, and activation. The effect of pressure drops on CO₂ removal, the breakthrough curve, and the absorption isotherm were studied. As a result, reduced pressure drops enhanced CO₂ removal and 102 Pa/m was the suitable pressure drop; pressure drops less than 102 Pa/m were impractical because the biogas did not exit. The breakthrough curve was in typical s-shape and thus satisfied its use for determining the adsorption rate constant (k₁) to be 0.001952 l/mg s and the maximum percent of CO₂ removal to be 87.8% at 102 Pa/m pressure drop and temperatures ranging from 20 to 28°C. The isotherm was found to closely conform to the definition of the Freundlich equation with the Freundlich coefficient of 0.01809 (l/g)ⁿ, where n = 1.37 at the same temperature range. Therefore, the determined k₁ and fitted Freundlich isotherm can be used to size the CO₂ adsorption unit under these conditions.     

Preparation and Characterization of Activated Carbon from Eucalyptus Sawdust I. Activated by NaOH

Eucalyptus sawdust was used as a precursor to prepare activated carbon using NaOH as a chemical activation agent. The effect of preparation conditions on the characteristics of the produced activated carbon used as an adsorbent was investigated. The performance of the activated carbon was characterized by N₂ adsorption–desorption isotherms, Brunauer–Emmett–Teller equation, Barett–Joyner–Halenda equation, scanning electron microscopy and Fourier transform infrared analysis. When the eucalyptus sawdust mass was 30.00 g, with particle sizes between 0.25 and 0.42 mm, and the sawdust was heated and charred before activation by NaOH, the optimized conditions for the preparation of activated carbon was found to be as follows: mass ratio of NaOH to eucalyptus sawdust, 1:2; activation time, 30 min; and activation temperature, 700 °C. The Iodine number and BET surface area of the produced activated carbon was 899 and 1.12 × 10³ m² g^?1, respectively, with a 13.3 % yield. Activated carbon exhibits adsorption isotherms of type IV. The total pore volume, micropore volume and average pore diameter were recorded as 0.636, 0.160 cm³ g^?1 and 2.27 nm, respectively. The pore structure of the activated carbon is mainly mesoporous. Carbonyl and hydroxyl groups may also exist on the activated carbon surface.     

Utilization of Crofton weed for preparation of activated carbon by microwave induced CO2 activation

Crofton weed was converted into a high-quality activated carbon (CWAC) via microwave-induced CO₂ physical activation. The operational variables including activation temperature, activation duration and CO₂ flow rate on the adsorption capability and activated carbon yield were identified. Additionally the surface characteristics of CWAC were characterized by nitrogen adsorption isotherms, FTIR and SEM. The operating variables were optimized utilizing the response surface methodology and were identified to be an activation temperature of 980 °C, an activation duration of 90 min and a CO₂ flow rate of 300 ml/min with a iodine adsorption capacity of 972 mg/g and yield of 18.03%. The key parameters that characterize quality of the porous carbon such as the BET surface area, total pore volume and average pore diameter were estimated to be 1036 m²/g, 0.71 ml/g and 2.75 nm, respectively. The findings strongly support the feasibility of microwave heating for preparation of high surface area porous carbon from Crofton weed via CO₂ activation.     

Synthesis of High Surface Area MgAl2O4 Nanopowder as Adsorbent for Leather Dye Removal

Abstract

MgAl₂O₄ nanopowder has been prepared by alkoxides hydrolysis with further calcination at temperature of 700°C. The adsorption of a leather dye, Direct Black 38, onto this material was investigated. The sample was characterized by X-ray-diffraction (XRD), N₂ adsorption–desorption isotherm and Fourier transform infrared spectroscopy. The results showed that sample present a pure phase, and the average nanocrystal size of 8 nm, the BET surface area is about 206.5 m² · g^?1 and total pore volume is about 1.44 cm³ · g^?1. Adsorption kinetics data were modeled by film and pore diffusion model. The experimental isotherm was described by the Langmuir model. MgAl₂O₄ nanopowder presented a great removal efficiency of leather dye by adsorption process, with a maximum adsorption capacity of 833 mg of dye per gram of adsorbent.     

Performance as electrode of electrical double layer capacitor of activated carbon prepared from bamboo using guanidine phosphate and CO<Subscript>2</Subscript> activation

The electrochemical performances of an electrical double layer capacitor were investigated regarding the activated carbon prepared from bamboo by a new approach, that is, the combination of delignification, addition of guanidine phosphate, and CO₂ activation. In this study, a 1 M H₂SO₄ aqueous solution was used as the electrolyte of the capacitor. The physical properties, such as the BET specific surface area of the carbon material, depend on the preparation conditions of the activated carbon. A TEM image indicated that the addition of guanidine phosphate did not facilitate the graphitization and did not prevent activation by CO₂. The apparent reaction equation for the CO₂ activation was first-order, which is reasonable for physical activation. The electrochemical performances of the carbon material depended on the preparation conditions of the carbon material, such as the heat treatment temperature, amount of added guanidine phosphate, and CO₂ activation time. The sample prepared under the following conditions (the amount of added guanidine phosphate: 9 wt%, the heat treatment temperature: 800 °C, CO₂ activation time: 3 h) had the highest performance (153 F g^?1 at 1000 mA g^?1) because the sample had the highest BET specific surface area (2001 m² g^?1).     

Carbonization and CO<Subscript>2</Subscript> activation of scrap tires: Optimization of specific surface area by the Taguchi method

This research demonstrates the production of activated carbon from scrap tires via physical activation with carbon dioxide. A newly constructed apparatus was utilized for uninterrupted carbonization and activation processes. Taguchi experimental design (L16) was applied to conduct the experiments at different levels by altering six operating parameters. Carbonization temperature (550–700 °C), activation temperature (800–950 °C), process duration (30–120 min), CO₂ flow rate (400 and 600 cc/min) and heating rate (5 and 10 °C/min) were the variables examined in this study. The effect of parameters on the specific surface area (SSA) of activated carbon was studied, and the influential parameters were identified employing analysis of variance (ANOVA). The optimum conditions for maximum SSA were: carbonization temperature=650 °C, carbonization time=60 min, heating rate=5 °C/min, activation temperature= 900 °C, activation time=60 min and CO₂ flow rate=400 cc/min. The most effective parameter was activation temperature with an estimated impact of 49%. The activated carbon produced under optimum conditions was characterized by pore and surface structure analysis, iodine adsorption test, ash content, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The process yield for optimized activated carbon was 13.2% with the following properties: specific surface area=437 m²/g, total pore volume=0.353 cc/g, iodine number=404.7 mg/g and ash content=13.9% along with an amorphous structure and a lot of oxygen functional groups. These properties are comparable to those of commercial activated carbons.     

Application of Full Factorial Design for Removal of Polycyclic Aromatic Dye from Aqueous Solution Using 4A Zeolite: Adsorption Isotherms,Thermodynamic and Kinetic Studies

In this study, removal of the cationic dye acridine orange (AO) from aqueous solution using 4A zeolite was studied. The adsorption experiments were performed using batch system, and full factorial design was employed for investigating the condition of removal efficiency of dye. The four most important operating variables were the initial pH of the solution, the concentration of dye, the contact time, and the temperature. The 18 experiments were required to investigate the effect of variables on removal of the dye. The results were statistically analyzed to define important experimental variables and their levels using the analysis of variance (ANOVA). A regression model that considers the significant main and interaction effects was suggested and fitted the experimental data very well. Model predictions were found to be in good agreement (R² = 99.99%, adjusted R² = 99.86%) with experimental data. The optimized conditions for dye removal were at initial pH 3.0, 20.0 mg L^?1 dye, temperature 298.0 K and 80.0 min adsorption time. The experimental data were analyzed by the Langmuir, Freundlich, Temkin and Sips adsorption models. The maximum predicted adsorption capacities for AO was obtained as 29.851 mg g^?1. The adsorption thermodynamic parameters, namely ΔH°_ads, ΔG°_ads and ΔS°_ads, were determined. Furthermore, the kinetic of AO adsorption on the 4A zeolite was analyzed using pseudo-first- and second-order kinetic models and the results showed that the removal was mainly a pseudo-second-order process.     

Production and characterization of activated carbon derived from brewer’s yeast

Activated carbon (AC) was produced from brewer’s yeast with K₂CO₃ activation. The effects of K₂CO₃/yeast ratio and activation temperature on the yield and adsorption properties of the AC were investigated. The results indicate that the optimum conditions were as follows: ratio of K₂CO₃/yeast=2 and activation temperature 800 °C. The AC produced under the optimum conditions has BET surface area of 1,603 m²/g, pore volume of 1.43 cm²/g and average pore diameter of 3.5 nm. Adsorption of phenol onto the AC was determined by batch test at solution pH of 7. The effects of contact time and initial phenol concentration were investigated. The adsorption process was found to follow pseudo-second-order kinetics. The rate of phenol adsorption onto the AC produced was rapid with the adsorption equilibrium reached within 5 min. The experimental data fitted well with the Langmuir isotherm model. The maximum phenol uptake by the AC was estimated to be 513.5 mg/g.     

Preparation of activated carbon from olive mill solid residue

A process was developed for producing high quality activated carbon from Algerian mill waste. The solid olive mill residue was carbonized at 800 °C and physically activated with CO₂, air or steam. An optimum activation temperature of about 850 °C was determined for all the activation agents used. Steam appeared to be the most efficient activator as compared with air and CO₂. An optimal activation time of about 2 h was then determined with steam as the optimum activation agent. The porous structure of the activated carbon was characterized by nitrogen adsorption at −196 °C, and in all cases the surface areas, calculated by DR and BET methods, confirmed the production of a material with good microstructural characteristics and specific surfaces exceeding 1500 m² g⁻¹ for the carbon prepared by steam activation. Phenol adsorption isotherms gave the adsorption properties and the adsorption capacity of about 11.24 mg of phenol per gram of the activated carbon produced. The kinetics of the phenol adsorption onto the porous material was evaluated by means of two models: the external resistance model and the linear model. The second model appeared to constitute a more appropriate fit for the experimental data. © 2000 Society of Chemical Industry     

Activated carbon from cherry stones by chemical activation: Influence of the impregnation method on porous structure

Cherry stones are utilized as a precursor for the preparation of activated carbons by chemical activation with phosphoric acid (H₃PO₄). The activation process typically consists of successive impregnation, carbonization, and washing stages. Here, several impregnation variables are comprehensively studied, including H₃PO₄ concentration, number of soaking steps, H₃PO₄ recycling, washing of the impregnated material, and previous semi-carbonization. The choice of a suitable impregnation methodology opens up additional possibilities for the preparation of a wide variety of activated carbons with high yields and tailored porous structures. Microporous activated carbons with specific surface areas of ～800 m² g^?1 are produced, in which > 60% of the total pore volume is due to micropores. High surface areas of ～1500 m² g^?1 can be also developed, with micropore volumes being a 26% of the total pore volume. Interestingly, using the same amount of H₃PO₄, either carbons with surface areas of 791 and 337 m² g^?1 or only one carbon with a surface area of 640 m² g^?1 can be prepared. The pore volumes range very widely between 0.07–0.55, 0.01–0.90, and 0.09–0.79 cm³ g^?1 for micropores, mesopores, and macropores, respectively.     

Preparation,modification and industrial application of activated carbon from almond shell

Almond shell was used to prepare activated carbon using physical activation method, consisted of carbon dioxide (CO₂) gasification. The effects of the preparation variables which were activation temperature, activation time and carbon dioxide flow rate on the adsorption capacity of iodine and methylene blue solution were investigated. The optimal activated carbon was obtained by these conditions as follows: 800 °C activation temperature, 100 cm³/min carbon dioxide flow rate and 120 min activation time. The characterization of carbon materials is performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ¹³C (CP/MAS and MAS) solid-state NMR, nitrogen adsorption (BET) and Boehm's titration method. For an industrial application, the optimal activated carbon was ammoxidated to improve its adsorption capacity toward total organic carbon from Tunisian industrial phosphoric acid. The influence of experimental parameters such as specific consumption, initial concentration, contact time, agitation speed and temperature on TOC removal was studied.     

Nanoporous rice husk derived carbon for gas storage and high performance electrochemical energy storage

We report on the gas storage behaviour and electrochemical charge storage properties of high surface area activated nanoporous carbon obtained from rice husk through low temperature chemical activation approach. Rice husk derived porous carbon (RHDPC) exhibits varying porous characteristics upon activation at different temperatures and we observed high gas uptake and efficient energy storage properties for nanoporous carbon materials activated even at a moderate activation temperature of 500 °C. Various experimental techniques including Fourier transform-infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy and pore size analyser are employed to characterise the samples. Detailed studies on gas adsorption behaviour of CO₂, H₂ and CH₄ on RHDPCs have been performed at different temperatures using a volumetric gas analyser. High adsorption capacities of ~9.4 mmol g^?1 (298 K, 20 bar), 1.8 wt% (77 K, 10 bar) and ~5 mmol g^?1 (298 K, 40 bar) were obtained respectively for CO₂, H₂ and CH₄, superior to many other carbon based physical adsorbents reported so far. In addition, these nanoporous carbon materials exhibit good electrochemical performance as supercapacitor electrodes and a maximum specific capacitance of 112 F g^?1 has been obtained using aqueous 1 M Na₂SO₄ as electrolyte. Our studies thus demonstrate that nanoporous carbon with high porosity and surface area, obtained through an efficient approach, can act as effective materials for gas storage and electrochemical energy storage applications.     

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.     

Coal based magnetic activated carbon as a high performance adsorbent for methylene blue

Coal based magnetic activated carbons (MACs) were prepared by using the two-stage carbonization and activation of coal in the presence of Fe₂O₃ as the magnetic source. Compared with the single-stage carbonization and activation, the two-stage temperature method was found to be efficient for the preparation of MACs with the high specific surface area and good magnetic properties in a lower alkali/carbon ratio. The as-synthesized MACs at optimized conditions exhibited specific surface areas of up to 2075 m²/g and optimal saturation magnetization of as high as 15.02 emu/g. Moreover, as an adsorbent, the efficiency of removing methylene blue (MB) from aqueous solutions is excellent. Based on MB adsorption behaviors at various conditions, including initial dye concentration, contact time and temperature, MACs prepared at optimized conditions exhibited a maximum equilibrium MB adsorption capacity of 871 mg/g. The data of adsorption kinetics and isotherms could be well fitted by using the pseudo-second-order equation and the Freundlich model. Importantly, MACs can be separated and recovered easily by applying a magnetic field. Therefore, the coal-based magnetic activated carbons might be a promising candidate of high efficiency, low cost for removal of organic dyes.     

Process optimization of K2C2O4-activated carbon from kenaf core using Box–Behnken design

Potassium oxalate was evaluated as a new activating agent for preparation of kenaf core-based activated carbons. The preparation conditions were optimized through Box–Behnken design (BBD) to maximize I₂ and methylene blue (MB) adsorption values. Two quadratic models were developed to correlate the preparation variables namely activation temperature, impregnation ratio and activation time for both responses. The activated carbon produced at the optimum combination of process parameters showed 1161 mg/g and 330 mg/g of I₂ and MB uptakes, which were in excellent agreement with the predicted values from the models. Porosity parameters and scanning electron microscopy were used to investigate the obtained optimal sample. The results reveal that K₂C₂O₄ could be recommended as a promising effective activating agent for producing activated carbons from kenaf core with high surface area and potentially desirable dye removal capacity.     

Porous structure and adsorptive properties of pineapple peel based activated carbons prepared via microwave assisted KOH and K2CO3 activation

The present research explores the feasibility of microwave irradiation for preparation of high surface area activated carbon from pineapple peel (PPAC), an agricultural effluent emitted from the food can processing industries via KOH and K₂CO₃ activation. The activation process was performed at the microwave power of 600 W and irradiation time of 6 min. The equilibrium behavior of PPAC was investigated by performing batch adsorption experiments using methylene blue as adsorbate. Nonlinear adsorption isotherm models, Langmuir, Freundlich and Temkin were used to simulate the equilibrium data. KOH activated sample demonstrated a better development of pore structure, with the BET surface area, total pore volume and average pore size of 1006 m²/g, 0.59 m³/g and 23.44 Å, respectively, while the monolayer adsorption capacity of methylene blue was determined to be 462.10 mg/g. The findings support the potential use of microwave assisted KOH and K₂CO₃ activation as a promising activation technique.