Physicochemical properties of carbons prepared from pecan shell by phosphoric acid activation

Activated carbons were prepared from pecan shell by phosphoric acid activation. The pore structure and acidic surface groups of these carbons were characterized by nitrogen adsorption, Boehm titration and transmittance Fourier infrared spectroscopy (FTIR) techniques. The characterization results demonstrated that the development of pore structure was apparent at temperatures 250 degrees C, and reached 1130m(2)/g and 0.34cm(3)/g, respectively, at 500 degrees C. Impregnation ratio and soaking time at activation temperature also affected the pore development and pore size distribution of final carbon products. At an impregnation ratio of 1.5, activated carbon with BET surface area and micropore volume as high as 861m(2)/g and 0.289cm(3)/g was obtained at 400 degrees C. Microporous activated carbons were obtained in this study. Low impregnation ratio (less than 1.5) and activation temperature (less than 300 degrees C) are favorable to the formation of acidic surface functional groups, which consist of temperature-sensitive (unstable at high temperature) and temperature-insensitive (stable at high temperature) two parts. The disappearance of temperature-sensitive groups was significant at temperature 300 degrees C; while the temperature-insensitive groups are stable even at 500 degrees C. FTIR results showed that the temperature-insensitive part was mostly phosphorus-containing groups as well as some carbonyl-containing groups, while carbonyl-containing groups were the main contributor of temperature-sensitive part.     

Utilization of rice husks as a feedstock for preparation of activated carbon by microwave induced KOH and K2CO3 activation

Rice husk (RH), an abundant by-product of rice milling, was used for the preparation of activated carbon (RHAC) via KOH and K(2)CO(3) chemical activation. The activation process was performed at the microwave input power of 600 W for 7 min. RHACs were characterized by low temperature nitrogen adsorption/desorption, scanning electron microscopy and Fourier transform infrared spectroscopy. The adsorption behavior was examined using methylene blue as adsorbate. The K(2)CO(3)-activated sample showed higher yield and better pore structures and adsorption capacity development than the KOH-activated sample, with a BET surface area, total pore volume and monolayer adsorption capacity of 1165 m(2)/g, 0.78 cm(3)/g and 441.52 mg/g, respectively. The results revealed the feasibility of microwave heating for preparation of high surface area activated carbons from rice husks via K(2)CO(3) activation.     

Preparation of activated carbons from cattle-manure compost by zinc chloride activation

Dried cattle-manure compost was pyrolyzed by a one-step process to obtain activated carbon using chemical activation by zinc chloride. The influence of activation parameters such as ZnCl(2) to cattle-manure compost (ZnCl(2)/CMC) ratio, activation temperature and retention time on the final products was investigated. The resultant activated carbons were characterized by nitrogen adsorption-desorption isotherms at 77 K. The results showed that the surface area and pore volume of activated carbons, which were estimated by BET and t-plot methods, were achieved as high as 2170 m(2)/g and 1.70 cm(3)/g in their highest value, respectively. Thermogravimetric analysis (TGA) was carried out to monitor the pyrolysis process of cattle-manure compost (CMC) and ZnCl(2) impregnated one (ZnCl(2)/CMC). The capabilities of phenol adsorption were also examined for the CMC carbons prepared with various treatments.     

Effects of Heat Pretreatment During Impregnation on the Preparation of Activated Carbon from Chinese Fir Wood by Phosphoric Acid Activation

Activated carbons were prepared from Chinese fir wood by phosphoric acid activation. The effects of heat pretreatment from 80 to 180 °C during impregnation on the properties of fir wood and its activated carbons were discussed. The crystallinity index and surface chemistry of the pretreated fir wood were characterized by X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR). The porous texture of activated carbons was investigated by N₂ adsorption–desorption isotherms. The results showed that with increasing pretreatment temperature, the crystallinity of the pretreated samples decreased, which gave rise to a significant development of pores, especially micropores as high as 97.2 %. FT-IR results revealed that the carbonyl-containing and phosphorus-containing groups of the pretreated samples increased with increasing pretreatment temperature. For a temperature of 140 °C, the specific surface area, the total pore volume, and the micropore volume reached a maximum of 1603.0 m²/g, 0.792 cm³/g, and 0.770 cm³/g, respectively. However, a higher pretreatment temperature was not beneficial for activation. Thus, heat pretreatment during impregnation can be regarded as an excellent method for manufacturing phosphoric acid-activated carbon with a high micropore volume.     

Production and comparison of high surface area bamboo derived active carbons

High surface area activated carbons have been produced from the natural biomaterial bamboo, using phosphoric acid as the activating agent. The effects of phosphoric acid impregnation ratio, activation temperature, heating rate on the carbon surface area, porosity and mass yield are presented. Three of these bamboo derived active carbons, surface areas 1337, 1628 and 2123m(2)/g were assessed for their ability to adsorb Acid Red 18 dye from aqueous solution; these results were compared with three conventional adsorbents: activated carbon F400, bone char and peat. Isotherm data were analysed using Langmuir, Freundlich, Redlich-Peterson and Langmuir-Freundlich isotherms. Different isotherms provided the best fit correlations to the adsorption experimental data but the Langmuir-Freundlich equation provided the best overall correlation of data. The adsorption capacities of two of the selected bamboo derived carbons were much greater than the capacities of the other three adsorbents.     

Preparation and characterization of activated carbon from palm shell by chemical activation with K2CO3

Palm shell was used to prepare activated carbon using potassium carbonate (K2CO3) as activating agent. The influence of carbonization temperatures (600-1000 degrees C) and impregnation ratios (0.5-2.0) of the prepared activated carbon on the pore development and yield were investigated. Results showed that in all cases, increasing the carbonization temperature and impregnation ratio, the yield decreased, while the adsorption of CO2 increased, progressively. Specific surface area of activated carbon was maximum about 1170 m2/g at 800 degrees C with activation duration of 2 h and at an impregnation ratio of 1.0.     

Preparation and characterization of activated carbon from rice bran

A study on the preparation of rice bran-based activated carbon was conducted, with and without an acid treatment step prior the activation process. The influence of the activation time on the structure of the activated carbons was evaluated. The acid treatment had a significant positive influence on sorption properties. The rice bran-activated carbon presented a BET surface area of 652m(2)g(-1) and a pore volume of 0.137cm(3)g(-1), with mesopores predominance (ca. 55%). These experimental results indicated the potential use of rice bran as a precursor in the activated carbon preparation process, thus representing an economically promising material.     

Activated carbon from Eucalyptus camaldulensis Dehn bark using phosphoric acid activation

The powdered activated carbon prepared by phosphoric acid activation was significantly affected by the carbonization temperature and the weight ratio between raw material and phosphoric acid. With an activation time of 1h and an impregnation ratio of 1:1, the activated carbons with better adsorption capacity were obtained at 500 degrees C. A reduction in the adsorption capacity of the carbon product at higher acid content than this was observed, possibly due to the collapse of the micropore structure. The properties of the resulting activated carbon were: bulk density 0.251gcm(-3), ash content 4.88%, yield 26.2%, iodine adsorption 1043mgg(-1), methylene blue adsorption number 427mgg(-1), and BET surface area 1239m(2)g(-1).     

Activated carbons from waste biomass by sulfuric acid activation and their use on methylene blue adsorption

Preparation of the activated carbons from sunflower oil cake by sulphuric acid activation with different impregnation ratios was carried out. Laboratory prepared activated carbons were used as adsorbents for the removal of methylene blue (MB) from aqueous solutions. Liquid-phase adsorption experiments were conducted and the maximum adsorption capacity of each activated carbon was determined. The effects of various process parameters i.e., temperature, pH, initial methylene blue concentration, contact time on the adsorption capacity of each activated carbon were investigated. The kinetic models for MB adsorption onto the activated carbons were studied. Langmuir isotherm showed better fit than Freundlich isotherm for all activated carbon samples. The rates of adsorption were found to conform to the pseudo-second-order kinetics with good correlation. The separation factor (R(L)) revealed the favorable nature of the isotherm of the MB activated carbon system.     

Production of activated carbon from bagasse and rice husk by a single-stage chemical activation method at low retention times

The production of activated carbon from bagasse and rice husk by a single-stage chemical activation method in short retention times (30-60min) was examined in this study. The raw materials were subjected to a chemical pretreatment and were fed to the reactor in the form of a paste (75% moisture). Chemicals examined were ZnCl2, NaOH and H3PO4, for temperatures of 600, 700 and 800 degrees C. Of the three chemical reagents under evaluation only ZnCl2 produced activated carbons with high surface areas. BET surface areas for rice husk were up to 750m2/g for 1:1 ZnCl2:rice husk ratio. BET surface areas for bagasse were up to 674m2/g for 0.75:1 ZnCl2:bagasse ratio. Results were compared to regular two-stage physical activation methods.     

Activated carbon from olive kernels in a two-stage process: industrial improvement

Activated carbons have been prepared from olive kernels and their adsorptive characteristics were investigated. A two stage process of pyrolysis-activation has been tested in two scales: (a) laboratory scale pyrolysis and chemical activation with KOH and (b) pilot/bench scale pyrolysis and physical activation with H(2)O-CO(2). In the second case, olive kernels were first pyrolysed at 800 degrees C, during 45 min under an inert atmosphere in an industrial pyrolyser with a throughput of 1t/h (Compact Power Ltd., Bristol, UK). The resulting chars were subsequently activated with steam and carbon dioxide mixtures at 970 degrees C in a batch pilot monohearth reactor at NESA facility (Louvain-la Neuve, Belgium). The active carbons obtained from both scales were characterized by N(2) adsorption at 77 K, methyl-blue adsorption (MB adsorption) at room temperature and SEM analysis. Surface area and MB adsorption were found to increase with the degree of burn-off. The maximum BET surface area was found to be around 1000-1200 m(2)/g for active carbons produced at industrial scale with physical activation, and 3049 m(2)/g for active carbons produced at laboratory with KOH activation. The pores of the produced carbons were composed of micropores at the early stages of activation and both micropores and mesopores at the late stages. Methylene blue removal capacity appeared to be comparable to that of commercial carbons and even higher at high degrees of activation.     

Nanostructured synthetic carbons obtained by pyrolysis of spherical acrylonitrile/divinylbenzene copolymers

Novel carbon materials have been prepared by the carbonization of acrylonitrile (AN)/divinylbenzene (DVB) suspension porous copolymers having nominal crosslinking degrees in the range of 30-70% and obtained in the presence of various amounts of porogens. The carbons were obtained by pre-oxidation of AN/DVB copolymers at 250-350°C in air followed by pyrolysis at 850°C in an N(2) atmosphere. Both processes were carried out in one furnace and the resulting material needed no further activation. Resulting materials were characterized by XPS and low temperature nitrogen adsorption/desorption. It was found that maximum pyrolysis yield was ca. 50% depending on the oxidation conditions but almost independent of the crosslinking degree of the polymers. Porous structure of the carbons was characterized for the presence of micropores and macropores, when obtained from highly crosslinked polymers or polymers oxidized at 350°C and meso- and macropores in all other cases. The latter pores are prevailing in the structure of carbons obtained from less porous AN/DVB resins. Specific surface area (BET) of polymer derived carbons can vary between 440 m(2)/g and 250 m(2)/g depending on the amount of porogen used in the synthesis of the AN/DVB polymeric precursors.     

Adsorption of Neutral Red onto Mn-impregnated activated carbons prepared from Typha orientalis

Activated carbon was prepared from an inexpensive and renewable carbon source, Typha orientalis, by H(3)PO(4) activation and then impregnated with different Mn salts and tested for its Neutral Red (NR) adsorption capacities. The amount of Mn impregnated in the activated carbon was influenced by the anion species. Impregnation with Mn decreased the surface area, changed the pore size and crystal structure, and introduced more acidic functional groups such as carboxyl, lactone and phenol groups. The optimum adsorption performance for all the activated carbons was obtained at pH 3.7, Mn-Carbon dose of 0.100g/100ml solution and contact time 4.5h. The adsorption isotherms fit the Langmuir isotherm equation. The kinetic data followed the pseudo-second-order model. The thermodynamic parameters indicated that the processes were spontaneous and endothermic. According to these results, the prepared Mn modified activated carbons are promising adsorbents for the removal of Neutral Red from wastewater.     

Production of granular activated carbons from select agricultural by-products and evaluation of their physical,chemical and adsorption properties

Representative samples of soft, low density, group 1 (rice straw, rice hulls, sugarcane bagasse) and hard, high density, group 2 agricultural by-products (pecan shells) were converted into granular activated carbons (GACs). GACs were produced from group 1 and 2 materials by physical activation or from group 2 materials by chemical activation. Carbons were evaluated for their physical (hardness, bulk density), chemical (ash, conductivity, pH), surface (total surface area), and adsorption properties (molasses color removal, sugar decolorization) and compared with two commercial reference carbons. The results show that the type of by-product, binder, and activation method determine the properties of GACs. Regardless of the binder, sugarcane bagasse showed a better potential than rice straw or rice hulls as precursor of GACs with the desirable properties of a sugar decolorizing carbon. Pecan shells produced GACs that were closest to the reference carbons in terms of all the properties investigated.     

Optimization of microporous palm shell activated carbon production for flue gas desulphurization: experimental and statistical studies

Optimizing the production of microporous activated carbon from waste palm shell was done by applying experimental design methodology. The product, palm shell activated carbon was tested for removal of SO2 gas from flue gas. The activated carbon production was mathematically described as a function of parameters such as flow rate, activation time and activation temperature of carbonization. These parameters were modeled using response surface methodology. The experiments were carried out as a central composite design consisting of 32 experiments. Quadratic models were developed for surface area, total pore volume, and microporosity in term of micropore fraction. The models were used to obtain the optimum process condition for the production of microporous palm shell activated carbon useful for SO2 removal. The optimized palm shell activated carbon with surface area of 973 m(2)/g, total pore volume of 0.78 cc/g and micropore fraction of 70.5% showed an excellent agreement with the amount predicted by the statistical analysis. Palm shell activated carbon with higher surface area and microporosity fraction showed good adsorption affinity for SO2 removal.     

Generalized Mechanochemical Synthesis of Biomass‐Derived Sustainable Carbons for High Performance CO2 Storage

Novel mechanochemical activation generates biomass‐derived carbons with unprecedented CO₂ storage capacity due to higher porosity than analogous conventionally activated carbons but similar pore size. The mechanochemical activation, or so‐called compactivation, process involves compression, at 740 MPa, of mixtures of activating agent (KOH) and biomass hydrochar into pellets/disks prior to thermal activation. Despite the increase in surface area and pore volume of between 25% and 75% compared to conventionally activated carbons, virtually all of the porosity of the biomass (sawdust and lignin) derived mechanochemically activated carbons is from small micropores (5.8–6.5 Å), which results in a dramatic increase in CO₂ storage capacity at 25 °C and low pressure (≤1 bar). The ambient temperature CO₂ uptake for a carbon derived from sawdust at 600 °C and a KOH/carbon ratio of 2, rises from 1.3 to 2.0 mmol g^?1 at 0.15 bar, and from 4.3 to 5.8 mmol g^?1 at 1 bar, which is the highest ever reported for carbonaceous materials. The mechanochemically activated carbons have a superior CO₂ working capacity for pressure swing adsorption and vacuum swing adsorption processes and, due to a high packing density, they exhibit excellent volumetric CO₂ uptake that is higher than for any material reported to date.     

Activated carbon from char obtained from vacuum pyrolysis of teak sawdust: pore structure development and characterization

The preparation of activated carbon from vacuum pyrolysis char of teak sawdust was studied and the results are presented in this paper. The effects of process variables such as temperature and activation time on the pore structure of activated carbons were studied. The activated carbon prepared from char obtained by vacuum pyrolysis has higher surface area and pore volume than that from atmospheric pyrolysis char. The BET surface area and pore volume of activated carbon prepared from vacuum pyrolysis char were 1150 m2/g and 0.43 cm3/g, respectively.     

Lignin--from natural adsorbent to activated carbon: a review

The present review compiles the work done over the last few decades on the use of lignin and lignin-based chars and activated carbons as adsorbents for the removal of substances from water and focuses on the utilisation of lignin as adsorbent, its conversion to chars and activated carbons and the use of these materials as adsorbents. Moreover, the review also examines the textural and surface chemical properties of lignin-based activated carbons. The work so far carried out indicates that lignin is relatively non-reactive and probably the component of lignocellulosic precursors primarily responsible for the microporosity of activated carbons. Under appropriate conditions of activation it is possible to obtain materials with surface areas and pore volumes approaching 2000 m(2)g(-1) and 1cm(3)g(-1), respectively, and these materials have capacities for the aqueous phase adsorption of metallic pollutants that are comparable to those of commercial activated carbons. Relatively little work has so far been published and there is considerable scope for more detailed studies on the preparation, characterisation and adsorption applications of lignin-based activated carbons.     

Microwave-assisted preparation and adsorption performance of activated carbon from biodiesel industry solid reside: influence of operational parameters

Preparation of activated carbon has been attempted using KOH as activating agent by microwave heating from biodiesel industry solid residue, oil palm empty fruit bunch (EFBAC). The significance of chemical impregnation ratio (IR), microwave power and activation time on the properties of activated carbon were investigated. The optimum condition has been identified at the IR of 1.0, microwave power of 600 W and activation time of 7 min. EFBAC was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption isotherm. The surface chemistry was examined by zeta potential measurement, determination of surface acidity/basicity, while the adsorptive property was quantified using methylene blue as dye model compound. The optimum conditions resulted in activated carbon with a monolayer adsorption capacity of 395.30 mg/g and carbon yield of 73.78%, while the BET surface area and total pore volume were corresponding to 1372 m²/g and 0.76 cm³/g, respectively.     

Preparation of activated carbons from corn cob catalyzed by potassium salts and subsequent gasification with CO2

In the present study, granular activated carbons were prepared from agricultural waste corn cob by chemical activation with potassium salts and/or physical activation with CO2. Under the experimental conditions investigated, potassium hydroxide (KOH) and potassium carbonate (K2CO3) were effective activating agents for chemical activation during a ramping period of 10 degrees C/min and subsequent gasification (i.e., physical activation) at a soaking period of 800 degrees C. Large BET surface areas (>1,600 m2/g) of activated carbons were thus obtained by the combined activation. In addition, this study clearly showed that the porosity created in the acid-unwashed carbon products is substantially lower than that of acid-washed carbon products due to potassium salts left in the pore structure.