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).     

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.     

Porous carbonaceous materials from hydrothermal carbonization and KOH activation of corn stover for highly efficient CO2 capture

Sustainable biomass-derived carbon materials were produced by hydrothermal carbonization of corn stover that was followed by chemical activation with KOH. The prepared carbon materials were used for CO₂ adsorption and had a CO₂ uptake of 7.14?mmol/g at a pressure of 1?bar and at 0°C that was much higher than CO₂ uptake by activated carbon that was prepared from direct activation of corn stover (2.78?mmol/g). The porous corn stover-derived carbonaceous material had high surface area (2442?m²/g) and large pore volume (1.55?cm³/g). Product yields obtained by the activation of hydrothermally carbonized corn stover were significantly higher than those obtained by the direct activation of corn stover (36–75?vs. 8%). The prepared corn stover-derived porous carbon had a high CO₂/N₂ selectivity of 15.5 and exhibited constant CO₂ uptake for five successive reuse cycles. The hydrothermal carbonization step plays an important role for producing porous carbons from biomass that have high and specific adsorption properties.     

Synthesis of carbon molecular sieves from palm shell by carbon vapor deposition

A series of experiments were conducted to produce carbon molecular sieves (CMS) through carbon deposition from a locally available palm shell of Tenera type for separating gaseous mixtures. The process involves three stages; carbonization, physical activation with steam, and carbon deposition by using benzene cracking technique. Carbonization of the dried palm shells was occurred at 900°C for duration of 1 h followed by steam activation at 830°C for 30–420 min to obtain activated carbons with different degree of burn-offs. The highest micropore volume of activated carbon obtained at 53.2% burn-off was used as a precursor for CMS production. Subsequent carbon deposition of the activated sample at temperature range from 600 to 900°C for 30 min has resulted in a series of CMSs with different selectivities of CO₂/CH₄ and O₂/N₂. The kinetic adsorption isotherm of CO₂, CH₄, O₂ and N₂ at room temperature also presented in this work.     

Production and adsorption characteristics of MAXSORB: High-surface-area active carbon

High-surface-area (over 3000 m² g⁻¹) active carbon has been developed with an extremely large adsorption capacity. Various kinds of petroleum coke were mixed with an excess amount of KOH and dehydrated at 400°C, followed by activation at 600–900°C in an inert atmosphere. The remaining KOH was removed by washing with water after the activation. Pore analysis indicated that this active carbon has a large portion of mesopores (1.0–1.5 ml g⁻¹) with radii between 10 and 20 Å, whereas micropores are as numerous as in conventional steam activated carbon (0.5 ml g⁻¹). Since considerable amounts of K₂CO₃ and hydrogen were formed, the majority of the carbon consumption was due to the transformation of K₂O into K₂CO₃ by CO₂. Potassium metal was also formed from the hydroxide by dehydration and reduction by hydrogen or carbon. Reversible adsorption of gasoline vapour, and isotherms of methylene blue and iodine in solution were obtained. Regardless of the kind of adsorbent tested, the adsorption capacity increased proportionally to the BET surface area. The fact that the surface area exceeds the geometric maximum was explained by introducing the concept of associated adsorption. This product is now commercially available from our company under the brand name of MAXSORB.     

Preparation and characterization of chars and activated carbons from Saskatchewan lignite

Saskatchewan lignite was used as a precursor to prepare carbonaceous adsorbents for use as SO₂ adsorbent from flue gases. The lignite was carbonized producing char in a fixed bed microreactor system at different temperatures from 350 to 550 ^°C in nitrogen atmosphere. The chars obtained at 475 ^°C for 120 min exhibited the highest micropore surface area (136 m²/g) and volume (0.062 cm³/g) and the smallest median pore diameter (∼ 0.7 nm). Carbon dioxide and steam were used as activating agents. Activation of char at optimum conditions of 650–675 ^°C for 15 min with carbon dioxide and steam resulted in a further increase in micropore surface area (220 and 186 m²/g for CO₂ and steam, respectively) and volume (0.090 and 0.085 cm³/g for CO₂ and steam, respectively). The yield of char was 64 wt.%, while the yields of activated carbon were 60 and 57 wt.% for CO₂ and steam activation, respectively; all based on the mass of original lignite.     

Preparation and characterization of mesoporous activated carbon from waste tires

Activated carbons were produced from waste tires and their characteristics were investigated. Rubber separated from waste tires was first carbonized at 500 °C in N₂ atmosphere. Next, the obtained chars were activated with steam at 850 °C. As a result, fairly mesoporous activated carbons with mesopore volumes and BET surface areas up to 1.09 cm³/g and 737 m²/g, respectively, were obtained. To further improve the porous properties of the activated carbons, the char was treated with 1 M HCl at room temperature for 1 day prior to steam activation. This treatment increased mesopore volumes and BET surface areas of the activated carbons up to 1.62 cm³/g and 1119 m²/g, respectively. Furthermore, adsorption characteristics of phenol and a dye, Black 5, on the activated carbon prepared via acid treatment were compared with those of a commercial activated carbon in the liquid phase. Although the prepared carbon had a larger micropore volume than the commercial carbon, it showed a slightly lower phenol adsorption capacity. On the other hand, the prepared carbon showed an obviously larger dye adsorption capacity than the commercial carbon, because of its larger mesopore volume.     

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.     

Response Surface Modeling and Optimization of Remazol Brilliant Blue Reactive Dye Removal Using Periwinkle Shell-Based Activated Carbon

This work investigates both batch and optimization studies of adsorption of Remazol Brilliant Blue Reactive (RBBR) dye onto activated carbon prepared from periwinkle shells (PSAC). The effects of three preparation variables: CO₂ activation temperature, CO₂ activation time, and KOH: char impregnation ratio (IR) were studied using Response Surface Modeling (RSM). Based on the central composite design (CCD), a quadratic model and two-factor interaction models (2FI) were developed to correlate the three preparation variables to the two responses: RBBR dye removal and PSAC yield. The optimum conditions for preparing PSAC for adsorption of RBBR dye were found as follows: CO₂ activation temperature of 811°C, CO₂ activation time of 1.7 h and IR of 2.95, which resulted in 82.76% of RBBR dye removal and 35.83% of PSAC yield. Experimental results obtained agreed satisfactorily well with the model predictions. The activated carbon prepared under optimum conditions was mesoporous with BET surface area of 1894 m²/g, total pore volume of 1.107 cm³/g and average pore diameter of 2.32 nm. The surface morphology and functional groups of PSAC were respectively determined from the scanning electron microscopy (SEM) and Fourier transform infrared analysis (FTIR).     

CO2 sorption performance by aminosilane functionalized spheres prepared via co‐condensation and post‐synthesis methods

Amine functionalized silica microspheres were synthesised via a modified Stöber reaction for carbon dioxide (CO₂) adsorption. A number of adsorbents were synthesized by co‐condensation and post synthesis immobilization of amines on porous silica spheres. CO₂ adsorption studies were carried out on a fixed bed gas adsorption rig with online mass spectrometry. Amine co‐condensed silica spheres were found to adsorb up to 66 mg CO₂ g^?1 solid in a 0.15 atm CO₂ stream at 35°C. Simple post‐synthesis addition of aminopropyltriethoxysilane to amine co‐condensed silica was found to significantly increase the uptake of CO₂ to 211 mg CO₂ g^?1 under similar conditions, with CO₂ desorption commencing at temperatures as low as 60°C. The optimum temperature for adsorption was found to be 35°C. This work presents a CO₂ adsorbent prepared via a simple synthesis method, with a high CO₂ adsorption capacity and favorable CO₂ adsorption/desorption performance under simulated flue gas conditions. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2825–2832, 2016     

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.     

Combined processes of glycerol polymerization/carbonization/activation to produce efficient adsorbents for organic contaminants

BACKGROUND: Glycerol was used to produce efficient adsorbents with a high surface area for organic contaminants by a combined process based on polymerization, carbonization and activation. RESULTS: Glycerol and sulfuric acid catalyst at concentrations of 0, 0.5, 1, 2 and 5 mol% were heated to 150 °C to form polyglycerol, which was then decomposed at 580 °C and activated with CO₂ at 850 °C. The resulting activated carbons had a high specific area (1630 m²g^?1) and high adsorption capacity of methylene blue used as a model organic contaminant. This process was also used to produce a special composite adsorbent based on expanded vermiculite (EV) coated with activated carbon. These composites were produced by impregnation of EV with glycerol followed by polymerization, thermal decomposition and activation with CO₂ to produce up to 25 wt% carbon and a surface area of 835 m²g^?1. CONCLUSIONS: The carbon layer present in the EV composite/activated carbon (GVE4CA2) produces a remarkable increase in the methylene blue adsorption capacity of the expanded vermiculite and strongly decreases undesirable water absorption. Copyright © 2012 Society of Chemical Industry     

Characterization and application of activated carbon produced by H3PO4 and water vapor activation

Activated carbons have been prepared from woody biomass birch by using various activation procedures: a) treatment with phosphoric acid and pyrolysis at 600 °C in inert atmosphere, b) the same as in (a) followed by steam activation at the same temperature and c) treatment with phosphoric acid and direct pyrolysis in a stream of water vapor at 700 °C. The surface area and the porosity of the activated carbons were strongly dependent on the treatment after impregnation with H₃PO₄ (pyrolysis in inert atmosphere, steam pyrolysis or combination of both).Activated carbon, prepared by impregnation with phosphoric acid followed by steam pyrolysis (steam activation) had highly developed porous structure and the largest surface area among all prepared carbons (iodine number 1280 mg/g and BET surface area 1360 m²/g). The adsorption capacity of this sample for Hg(II) from aqueous solution was studied in varying treatment conditions: contact time, metal ion concentration and pH. The adsorption followed Langmuir isotherms and the adsorption capacity for Hg(II) at 293 K was 160 mg/g.     

Production of carbonaceous adsorbents by using novolac-resin and cottonseed

Mixtures of novolac resin with pressed cottonseed in different proportions after their curing as small cylinders, and also pressed cottonseed as powder were pyrolyzed until 1000°C. Some samples follow, as well as an activation process by steam between 700 and 950°C. The weight losses of the samples are much higher, up to 500°C, while small weight losses are observed over 800°C. The weight losses for the 100% pressed cottonseed during the carbonization are essentially higher than those of the specimens also containing novolac; indeed, for the total weight losses up to 1000°C an increasing linear dependence was found with increasing proportion of the cottonseed in its mixture with novolac. The shrinkage of the specimens also containing novolac follows in general a curve similar to that of the weight losses for the corresponding case. The specific surface areas of the carbonaceous materials produced show higher values with measuring by CO₂ than by N₂ due to the larger dimensions of the N₂ molecule as compared to the CO₂ molecule, so that N₂ areas are more sensitive to slight changes in aperture sizes of the porous materials produced. The specific surface areas of the materials that have also been activated indicate higher values in comparison with those without activation and also higher than activated carbon commercially available. The more increased and fine porous structure of the activated carbons as compared to those only pyrolyzed become also obvious from the corresponding photos obtained by the scanning electron microscope. These results are also in agreement with the discoloring ability of the produced adsorptive media for the methylene blue from aqueous solution, following the Freundlich equation for the adsorption.     

Activation of olive-seed waste residue using CO2 in a fluidized-bed reactor

Physical activation of olive-seed waste residue was carried out under N₂/CO₂ atmosphere in a fluidized-bed reactor system. The effects of activation temperature, activation time and particle size on both yield and quality of the prepared products were studied. The quality was measured in terms of iodine number and adsorptive capacity towards methylene blue dye. In general, it was found that higher activation temperature, longer activation time and smaller particle size produced a higher quality activated carbon. The products were compared to a commercial grade activated carbon prepared by steam activation process. Samples of 0.71–0.85 mm particle size activated at 900°C and activation time greater than 60 min were superior to the commercial carbon. Similar results were obtained for similar samples activated at 800°C and activation times greater than 60 min. A kinetic model was applied to the data. A first order reaction kinetics was found to fit the experimental data well. The value of the rate constant for activation was found to be 0.65 s⁻¹.     

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 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.     

Utilization of Raw and Activated Date Pits for the Removal of Phenol from Aqueous Solutions

Activated carbons prepared from date pits, an agricultural waste byproduct, have been examined for the adsorption of phenol from aqueous solutions. The activated carbons were prepared using a fluidized bed reactor in two steps; carbonization at 700 °C for 2 hours in N₂ atmosphere and activation at 900 °C in CO₂ atmosphere. The kinetic data were fitted to the models of intraparticle diffusion, pseudo‐second order, and Lagergren, and followed more closely the pseudo‐second‐order chemisorption model. The isotherm equilibrium data were well fitted by the Freundlich and Langmuir models. The maximum adsorption capacity of activated date pits per Langmuir model was 16 times higher than that of nonactivated date pits. The thermodynamic properties calculated revealed the endothermic nature of the adsorption process. The uptake of phenol increased with increasing initial phenol concentration from10 to 200 ppm and temperature from 25 to 55 °C, and decreased with increasing the solution pH from 4 to 12. The uptake of phenol was not affected by the presence of NaCl salt.     

Preparation and adsorption performances of mesopore-enriched bamboo activated carbon

Activated carbon with high specific surface area and considerable mesopores was prepared from bamboo scraps by phosphoric acid activation. The effect of activation conditions was studied. Under the conditions of impregnating bamboo with 80% H₃PO₄ at 80°C for 9 days and activation at 500°C for 4 h, the prepared activated carbon had the highest mesopore volume of 0.67 cm³/g, a specific surface area of 1567 m²/g, and the mesopore ratio reached 47.18%. The study on adsorption isotherms of CH₄, CO₂, N₂ and O₂ on the activated carbon were carried out at 298 K. The considerable difference in the adsorption capacity between CO₂ and the other gases was observed, which would be of interest for the adsorptive separation/purification of gaseous CO₂ from its mixtures, especially from mixtures with N₂ and/or O₂. __________ Translated from Journal of Functional Materials, 2008, 39(3): 420–423 [译自: 功能材料]     

The factors affecting the performance of activated carbon prepared from oil palm empty fruit bunches for adsorption of phenol

Powdered activated carbons (PACs) were produced from oil palm empty fruit bunches (EFB) by varying the operating parameters of temperatures, CO₂ gas flow rates and activation times using 2-level full factorial experimental design. The EFB samples were first carbonized for 30 min using nitrogen gas followed by physical activation using CO₂ to optimize best production conditions. The optimum conditions for PACs produced were investigated through adsorption tests on aqueous solution of phenol. The results of this study demonstrated that the activation temperature with the range of 800–900 °C had the most significant effect on the adsorption characteristics as well as the yield of the activated carbon produced. Based on the analysis of variance (ANOVA) and model equation developed, the optimum production conditions for the EFB PAC were found to be at the activation temperature of 900 °C with CO₂ gas flow rate of 0.1 L/min and activation time of 15 min. Characterization of PAC produced showed that the activation conditions would find good-quality adsorbent with the BTE surface area of 345.1 m²/g and well forming pores distribution.