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.     

The performance of two adsorption ice making test units using activated carbon and a carbon composite as adsorbents

The available adsorption working pairs applied to adsorption refrigeration system, which utilize activated carbon as adsorbent, are mainly activated carbon-methanol, activated carbon-ammonia, and composite adsorbent-ammonia. The adsorption properties and refrigeration application of these three types of adsorption working pairs are investigated. For the physical adsorbents, consolidated activated carbon showed best heat transfer performance, and activated carbon-methanol showed the best adsorption property because of the large refrigerant amount that can be adsorbed. For the composite adsorbents, the consolidated composite adsorbent with mass ratio of 4:1 between CaCl₂ and activated carbon, showed the highest cooling density when compared to the granular composite adsorbent and to the merely chemical adsorbent. The physical adsorption icemaker that employs consolidated activated carbon-methanol as working pair had the optimum coefficient of refrigeration performance (COP), volume cooling power density (SCP_v) and specific cooling power per kilogram adsorbent (SCP) of 0.125, 9.25 kW/m³ and 32.6 W/kg, respectively. The composite adsorption system that employs the consolidated composite adsorbent had a maximum COP, SCP_v and SCP of 0.35, 52.68 kW/m³ and 493.2 W/kg, respectively, for ice making mode. These results are improved by 1.8, 4.7 and 14 times, respectively, when compared to the results of the physical adsorption icemaker.     

Pore structures of multi-walled carbon nanotubes activated by air, CO2 and KOH

Multi-walled carbon nanotubes (MWNTs) synthesized by the catalytic decomposition of benzene were activated by KOH, CO₂ or air. The adsorption isotherms of the activated MWNTs were analyzed and their pore size distributions were obtained. The results showed that the specific surface areas of the MWNTs activated by KOH, CO₂ and air were increased to 785 m²/g, 429 m²/g and 270 m²/g, respectively. The MWNTs activated by KOH were rich in micropores and mesopores, especially high mesopores having volumes up to 1.04 cm³/g. The CO₂-activated MWNTs also had many micropores while the air-activated MWNTs had a much smaller micropore volume. The morphologies of the activated MWNTs were examined by transmission electron microscopy and high resolution transmission electron microscopy, and the activation mechanisms were discussed.     

Activated carbon from cherry stones

Fruit stones constitute a significant waste disposal problem for the fruit-processing industry. High-quality activated carbon can be produced from waste cherry stones: the activated carbon is low in impurities and has an adsorption capacity that compares favorably with commercial activated carbons. Activation at 800°C in steam for 2–3 hours, following initial carbonization, produces an activated carbon in about 10% yield (by weight) of the initial cherry stone. The activated carbons produced have surface areas (CO₂ adsorption) as high as 1200 m²/g and CCl₄ numbers of 70–80. Activation in carbon dioxide requires higher temperatures (900°C) and gives a carbon of slightly lower activity. Carbon from the hull, or hard outer portion of the fruit stone, provides essentially all of the adsorption capacity; the inner kernel does not form a microporous material. The hull structure is dominated by 0.4-micron pores which facilitate access to internal microporosity. This structure requires that the carbon be ground to less than 75 micron particles to achieve reasonable adsorption rates.     

HEMP-derived activated carbon fibers by chemical activation with phosphoric acid

Activated carbon fibers were prepared by chemical activation of hemp fibers with phosphoric acid at different carbonization temperatures and impregnation ratios. Surface properties of the activated carbons fibers were significantly influenced by the activation temperature and the impregnation ratio. An increase of either of these parameters produced a high development of the porous structure of the fibers. Activated carbon fibers with apparent surface area of 1350 m²/g and mesopore volume of 1.25 cm³/g were obtained at 550 °C with an impregnation ratio of 3. The activated carbon fibers presented a high oxidation resistance, due to the presence of phosphorus compounds on the carbon surface. The oxidation resistance results suggest that C-O-PO₃ and mainly C-PO₃ and C-P groups act as a physical barrier, blocking the active carbon sites for the oxidation reaction.     

Development of polymer derived carbon coated monolith for liquid adsorption application by response surface methodology

The preparation of polymer derived activated carbon coated monolith is reported. The response surface methodology based on Box–Behnken design is used to find the optimal condition for synthesis of mesoporous carbon. The dominant parameters identified are the carbonization temperature, concentration, and molecular weight of pore former agent. Typical values for BET surface area are 341 m²/g _carbon and 20 m²/g _{supported carbon} with pores size distribution in the range of 4–400 nm. The highest pore volume obtained is 182.77 mm³/g _{supported carbon}.     

Study on the preparation of activated carbon for direct carbon fuel cell with oak sawdust

Direct carbon fuel cell (DCFC) is a device, which converts chemical energy of carbon into electrical energy through electrochemical oxidisation directly and its performance enormously depends on the characteristics of the fuel used. In this study, oak sawdust is used to prepare the activated carbon for the DCFC, with K₂CO₃ as the activating agent. Nickel catalyst is applied to improve the electrical conductivity, while HNO₃ treatment is used for the purpose of surface modification and ash removal. The performance of the prepared activated carbon in DCFC is evaluated in a self‐built DCFC anode apparatus. The results show that the BET surface area of activated carbon reaches 1240 m²/g under the following conditions: activation temperature, 1173 K; activation time, 2 h; and impregnation ratio, 1. Electrical conductivity is well improved through the nickel catalyst while the amount of surface oxygen functional groups is increased and ash content is decreased through the HNO₃ treatment. When used as the fuel in the DCFC anode, the self‐made activated carbon exhibits predominant performance among all tested carbon fuels, including graphite, activated carbon fibre, etc. © 2011 Canadian Society for Chemical Engineering     

Activated carbon nanotubes-supported catalyst in fuel cells

The electrochemical property of platinum loaded on activated carbon nanotubes (Pt/ACNTs) was investigated by cyclic voltammograms (CVs) recorded in H₂SO₄ and H₂SO₄/CH₃OH aqueous solutions, respectively. Compared to 0.0046 A/cm² of Pt-loaded on pristine carbon nanotubes (Pt/CNTs) with a S_BET of 164 m²/g and 0.0042 A/cm² of conventional carbon black (Pt/C, Vulcan XC-72) with a S_BET of ∼250 m²/g, a better electrochemical activity (a high current density of 0.0070 A/cm² for weak-H₂ adsorption/desorption) of the Pt/ACNTs with high specific surface area (S_BET) of 830-960 m²/g was obtained. Furthermore, the highest current density of 0.079 A/cm² at 0.65 V in anodic sweep was observed during the methanol oxidation. On the basis of Pt size, utility ratio, and electro-active specific surface area (EAS), the Pt/ACNTs with a high Pt-loading of 50 wt.% exhibited the best electrochemical activity. The present ACNTs may be an excellent support material for electrochemical catalyst in proton exchange membrane and direct methanol fuel cells.     

RF oxygen plasma treatment of activated carbon electrodes for electrochemical capacitors

Activated carbon modified by Radio Frequency (RF) plasma at different power levels, times and volume flow rates of oxygen was prepared for activated carbon electrodes. Electrochemical characterization of different activated carbon electrodes was carried out using cyclic voltammetry (CV) with different electrolytes at a concentration of 0.1 M. A maximum capacitance of 38.9 F g⁻¹ was obtained in a 0.1 M H₂SO₄ solution for the activated carbon (precursor material: coconut shell made in Japan) with plasma treatment conditions: power = 300 W, time = 3 min, and volume flow rates of oxygen = 45 sccm (standard cubic centimeter per minute). In addition, specific surface areas/pore-size distributions, functional groups, and surface morphologies of activated carbon with/without plasma treatment were examined by gas adsorption meter, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM), respectively.     

Preparation and characterization of activated carbon spheres from polystyrene sulphonate beads by steam and carbon dioxide activation

The polymeric precursor polystyrene sulphonate beads were used to produce activated carbon spheres (ACSs). ACSs were prepared by carbonization of polymeric precursor at 800°C followed by activation of resultant char with steam and carbon dioxide activation processes. The resulting ACSs were characterized for N₂ adsorption, Raman spectrometry, and scanning electron microscope (SEM). The adsorption properties such as, BET surface area (S_BET), pore volume (V_pore), and micropore volume (V_micro) of ACSs produced at different gasification time and temperature with steam and carbon dioxide activation were investigated in this study. It is found that porosity of ACSs produced from steam and carbon dioxide activation increases with increasing activation time. The results exhibited that ACSs produced from above carbon dioxide activation have shown high S_BET and V_pore 1266 m²/g and 1.13 cm³/g respectively compared to ACSs from steam activation S_BET 949 m²/g and V_pore 0.98 cm³/g, respectively. SEM study revealed that ACSs produced from carbon dioxide activation have exhibited a smooth surface and better microstructure as compared to ACSs from steam activation process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterisation of activated nanoporous carbon for supercapacitor electrode materials

Commercial nanoporous carbon RP-20 was activated with water vapor in the temperature range from 950 °C to 1150 °C. The XRD analysis was carried out on nanoporous carbon powder samples to investigate the structural changes (graphitisation) in modified carbon that occurred at activation temperatures T ? 1150 °C. The first-order Raman spectra showed the absorption peak at 1582 cm⁻¹ and the disorder (D) peak at 1350 cm⁻¹. The low-temperature N₂ adsorption experiments were performed at −196 °C and a specific surface area up to 2240 m²g⁻¹ for carbon activated at T = 1050 °C was measured. The cell capacitance for two electrode activated nanoporous carbon system advanced up to 60 F g⁻¹ giving the specific capacitance ∼240 F g⁻¹ to one electrode nanoporous carbon ∣1.2 M (C₂H₅)₃CH₃NBF₄ + acetonitrile solution interface. A very wide region of ideal polarisability for two electrode system (∼3.2 V) was achieved. The low frequency limiting specific capacitance very weakly increases with the rise of specific area explained by the mass transfer limitations in the nanoporous carbon electrodes. The electrochemical characteristics obtained show that some of these materials under discussion can be used for compilation of high energy density and power density non-aqueous electrolyte supercapacitors with higher power densities than aqueous supercapacitors.     

Spherical microporous/mesoporous activated carbon from pulping black liquor

BACKGROUND: A simple and effective method with environmental and economic benefits has been developed to produce spherical lignin and spheroidal microporous/mesoporous activated carbon from pulping black liquor. RESULTS: Spherical lignin with regular size of about 100 nm was obtained at 90 °C after 8 h treatment at pH 2. Pyrolysis of spherical lignin was impregnated with H₃PO₄ producing spheroidal microporous/mesoporous activated carbon with high apparent Brunauer–Emmett–Teller (BET) surface area of 1972 m² g^?1 and high carbon content of 68.0 wt% at 700 °C with impregnation ratio of 1:7. CONCLUSION: The process was inexpensive, sustainable, environment‐friendly and suitable for large‐scale production. Copyright © 2011 Society of Chemical Industry     

Reuse of carwash water with a cellulose acetate ultrafiltration membrane aided by flocculation and activated carbon treatments

A reuse system for carwash water with a cellulose acetate (CA), hollow-fiber-type ultrafiltration membrane with the aid of flocculation and activated carbon treatments was proposed. The multi-blended flocculating agent containing bentonite, Al₂(SO₄)₃, sodium alginic acid and a cationic polyacrylamide showed higher removals of COD and turbidity for carwash wastewater compared with Al₂(SO₄)₃ or a water-soluble polymer individually. The effect of pure water permeability of the membrane on permeation flux in pretreated carwash wastewater by this agent was examined using three kinds of CA membranes whose molecular weight cut-offs were 150,000 Dalton. Permeation flux showed a higher value in the case of the membrane with higher pure water permeability. Practical scale experiments with a membrane area of 32 m² and 48 m² were conducted under a membrane pressure of 20 kPa. When carwash wastewater was pretreated with 50 mg/L of this multi-blended flocculating agent, permeation flux through the CA membrane with pure water permeability of 0.78 m³/(m²/h) at 100 kPa showed 1.0 m³/(m²/d) for more than 6 months. The COD, BOD and extract by n-hexane values of reuse water were 3.7-15.7 mg/L, 2.5-14.0 mg/L and below 0.5 mg/L, respectively.     

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).     

A new type of poly(vinyl alcohol)/nitrocellulose/granular activated carbon/KNO3 composite bead used as a biofilter material

A new type of poly(vinyl alcohol)/nitrocellulose/granular activated carbon/KNO₃ composite bead was prepared and shown to be suitable for use as a filter material in the biofiltration process. This composite bead was a porous spherical particle with a diameter of 2.4–6.0 mm and a density of 1.125 g/cm³. The amount of water-soluble nitrogen dissolved out of this composite bead was 145.5 mg N/g dry composite bead. The biochemical kinetic behaviors of n-butyl acetate in a spherical poly(vinyl alcohol) (PVA)/nitrocellulose (NC)/granular activated carbon (GAC)/KNO₃ composite bead biofilter (NC biofilter) and a spherical PVA/peat/GAC/KNO₃ composite bead biofilter (peat biofilter) were investigated. The values of the half-saturation constant K _s for the NC biofilter and the peat biofilter were 33.55 and 35.54 ppm, respectively. The values of the maximum reaction rate V _m for the NC biofilter and the peat biofilter were 23.83 and 22.46 ppm/s, respectively. Diffusion-limited zero-order kinetics were regarded as the most adequate biochemical reaction model for the two biofilters. The microbial growth rates and biochemical reaction rates for the two biofilters were inhibited at higher inlet concentrations. The biochemical kinetic behaviors of the two biofilters were similar. The maximum elimination capacities of the NC biofilter and the peat biofilter were 170.72 and 174.51 g C/h m³ bed volume, respectively. The PVA/nitrocellulose/GAC/KNO₃ composite bead made it easier for the microbes to adjust to their new environment and secrete exocellular enzymes to break down the substrate.     

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]     

Effects of chemical modification of petroleum cokes on the properties of the resulting activated carbon

Activated carbons have been prepared from petroleum cokes by the combination of a chemical treatment with HClO₄ or H₂O₂ and a chemical activation with KOH at a constant KOH/coke ratio of 3/1. The influence of different chemical treatments on the properties of the activated carbon precursors and final carbons activated with KOH was invested by using XRD, FTIR, and BET techniques. XRD results indicated that the value of interplanar distance d₀₀₂ increased by chemical treatment and the disappearance of the peak corresponding to 0 0 2 faces correlated to high specific surface area. FTIR studies showed that chemical modification promoted the formation of surface oxygen functionalities. Significant effects on BET surface area, pore texture and iodine adsorption capacity were evidenced. The results show that chemical modification prior to activation dramatically increased the BET surface area and total pore volume of the resulting activated carbon. Modified petroleum coke based activated carbon with chemical activation had higher specific surface area (2336 m²/g) and better iodine adsorption value (1998 mg/g).     

A comparison of physical activation of carbon xerogels with carbon dioxide with chemical activation using hydroxides

Carbon xerogels synthesized with a fixed resorcinol/sodium carbonate molar ratio (R/C) were physically activated using CO₂. The effect of activation temperature and activation time on the final properties of the activated carbon xerogels was evaluated. The specific surface area increases from ∼600 m² g⁻¹ to 2000 m² g⁻¹ and more by increasing the temperature and duration of the activation step. A comparison between physical activation with CO₂ and chemical activation with hydroxides was also performed: it was found that both processes produce an increase of the micropore volume and specific surface area without altering the mesoporosity developed during the synthesis. However, chemical activation can lead to the development of the narrow microporosity mainly whereas, in physical activation, the widening of the narrow micropores takes place whatever the process conditions.     

Removal of dibenzothiophenes in kerosene by adsorption on rice husk activated carbon

The capacity of rice husk activated carbon (RHAC) to adsorb refractory sulfur compounds of dibenzothiophenes (DBTs) from commercial kerosene was evaluated in terms of their textural and chemical characteristics. Rice husk activated at 850 °C for 1 h showed an acceptable adsorption capacity for DBTs, despite a much lower specific surface area (473 m²/g) and total pore volume (0.267 cm³/g), when compared to micro-porous activated carbon fiber with a large specific surface area (2336 m²/g) and total pore volume (1.052 cm³/g). The volumes of ultramicropores acting as DBTs adsorption sites, and of mesopores leading DBTs into the ultramicropores were closely related to the DBTs adsorption capacity of the RHACs.     

In situ nitrogen enriched carbon for carbon dioxide capture

In situ nitrogen enriched carbon was synthesized from locally available low cost soybean as the proteinaceous source. The material was synthesized by chemical activation using zinc chloride followed by physical activation using CO₂. The surface area of synthesized nitrogen enriched carbon was found to be 811 m²/g which is comparable with commercially available activated carbon. The nitrogen enriched carbon was having a breakthrough adsorption capacity of 23 mg/g at 120 °C which was almost three times higher in comparison with the commercially available activated carbon for a gas mixture comprising 15% CO₂ balanced with helium. This high adsorption capacity was attributed to the presence of nitrogen group within the carbon matrix, which was estimated to be about 0.64% as determined using the Kjeldahl’s method. The presence of different nitrogen containing groups assisting the adsorption of CO₂ in the synthesized sample was also confirmed by infrared analysis. For checking the consistent performance of the synthesized carbon, multi-cycle adsorption-desorption studies were carried out at 30 and 75 °C in binary mixture of CO₂/N₂.