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.     

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.     

Pecan shell-based granular activated carbon for treatment of chemical oxygen demand (COD) in municipal wastewater

The present investigation was undertaken to compare the adsorption efficiency of pecan shell-based granular activated carbon with the adsorption efficiency of the commercial carbon Filtrasorb 200 with respect to uptake of the organic components responsible for the chemical oxygen demand (COD) of municipal wastewater. Adsorption efficiencies for these two sets of carbons (experimental and commercial) were analyzed by the Freundlich adsorption model. The results indicate that steam-activated and acid-activated pecan shell-based carbons had higher adsorption for organic matter measured as COD, than carbon dioxide-activated pecan shell-based carbon or Filtrasorb 200 at all the carbon dosages used during the experiment. The higher adsorption may be related to surface area as the two carbons with the highest surface area also had the highest organic matter adsorption. These results show that granular activated carbons made from agricultural waste (pecan shells) can be used with greater effectiveness for organic matter removal from municipal wastewater than a coal-based commercial carbon.     

Preparation and characterization of activated carbon produced from rice straw by (NH4)2HPO4 activation

Effects of different pretreatment protocols in (NH(4))(2)HPO(4) activation of rice straw on porous activated carbon evolution were evaluated. The pore structure, morphology and surface chemistry of obtained activated carbons were investigated by nitrogen adsorption, scanning electron microscopy and Fourier transform infrared spectroscopy. It was found that pretreatment combining impregnation with (NH(4))(2)HPO(4) and preoxidation could significantly affect the physicochemical properties of prepared activated carbons. The apparent surface area and total pore volume as high as 1154 m(2)/g and 0.670 cm(3)/g were obtained respectively, when combined process of impregnation followed by preoxidation at 200°C and activation at 700°C was carried out. Meanwhile, the activated carbon yield and maximum methylene blue adsorption capacity up to 41.14% and 129.5 mg/g were achieved, respectively. The results exhibited that (NH(4))(2)HPO(4) could be an effective activating agent for producing activated carbons from rice straw.     

Characterization of mesoporous activated carbons prepared by pyrolysis of sewage sludge with pyrolusite

Activated carbons were prepared from sewage sludge by chemical activation. Pyrolusite was added as a catalyst during activation and carbonization. The influence of the mineral addition on the properties of the activated carbons produced was evaluated. The results show that activated carbons from pyrolusite-supplemented sewage sludge had up to a 75% higher BET surface area and up to a 66% increase in mesoporosity over ordinary sludge-based activated carbons. Batch adsorption experiments applying the prepared adsorbents to synthetic dye wastewater treatment yielded adsorption data well fitted to the Langmuir isotherm. The adsorbents from pyrolusite-supplemented sludges performed better in dye removal than those without mineral addition, with the carbon from pyrolusite-augmented sludge T2 presenting a significant increase in maximum adsorption capacity of 50 mg/g. The properties of the adsorbents were improved during pyrolusite-catalyzed pyrolysis via enhancement of mesopore production, thus the mesopore channels may provide fast mass transfer for large molecules like dyes.     

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.     

Adsorption of volatile organic compounds by pecan shell- and almond shell-based granular activated carbons

The objective of this research was to determine the effectiveness of using pecan and almond shell-based granular activated carbons (GACs) in the adsorption of volatile organic compounds (VOCs) of health concern and known toxic compounds (such as bromo-dichloromethane, benzene, carbon tetrachloride, 1,1,1-trichloromethane, chloroform, and 1,1-dichloromethane) compared to the adsorption efficiency of commercially used carbons (such as Filtrasorb 200, Calgon GRC-20, and Waterlinks 206C AW) in simulated test medium. The pecan shell-based GACs were activated using steam, carbon dioxide or phosphoric acid. An almond shell-based GAC was activated with phosphoric acid. Our results indicated that steam- or carbon dioxide-activated pecan shell carbons were superior in total VOC adsorption to phosphoric acid-activated pecan shell or almond shell carbons, inferring that the method of activation selected for the preparation of activated carbons affected the adsorption of VOCs and hence are factors to be considered in any adsorption process. The steam-activated, pecan shell carbon adsorbed more total VOCs than the other experimental carbons and had an adsorption profile similar to the two coconut shell-based commercial carbons, but had greater adsorption than the coal-based commercial carbon. All the carbons studied adsorbed benzene more effectively than the other organics. Pecan shell, steam-activated and acid-activated GACs showed higher adsorption of 1,1,1-trichloroethane than the other carbons studied. Multivariate analysis was conducted to group experimental carbons and commercial carbons based on their physical, chemical, and adsorptive properties. The results of the analysis conclude that steam-activated and acid-activated pecan shell carbons clustered together with coal-based and coconut shell-based commercial carbons, thus inferring that these experimental carbons could potentially be used as alternative sources for VOC adsorption in an aqueous environment.     

Adsorption of Cd(II) ions from aqueous solutions using activated carbon prepared from olive stone by ZnCl2 activation

This study is aimed to remove Cd(II) ions from aqueous solutions by adsorption. As adsorbent, activated carbon prepared from olive stone, an agricultural solid by-product was used. Different activating agent (ZnCl(2)) amounts and adsorbent particle size were studied to optimize adsorbent surface area. The adsorption experiments were conducted at different parameters such as, adsorbent dose, temperature, equilibrium time and pH. According to the experiments results, the equilibrium time, optimum pH, adsorbent dosage were found 60 min, pH > 6 and 1.0 g/50 ml respectively. The kinetic data supports pseudo-second order model and intra-particle model but shows very poor fit for pseudo-first order model. Adsorption isotherms were obtained from three different temperatures. These adsorption data were fitted with the Langmuir and Freundlich isotherms. In addition, the thermodynamic parameters, standard free energy (DeltaG(0)), standard enthalpy (DeltaH(0)), standard entropy (DeltaS(0)) of the adsorption process were calculated. To reveal the adsorptive characteristics of the produced active carbon, BET surface area measurements were made. Structural analysis was performed using SEM-EDS. The resulting activated carbons with 20% ZnCl(2) solution was the best sample of the produced activated carbons from olive stone with the specific surface area of 790.25 m(2)g(-1). The results show that the produced activated carbon from olive stone is an alternative low-cost adsorbent for removing Cd(II).     

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.     

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).     

Decolorization of sugar syrups using commercial and sugar beet pulp based activated carbons

Sugar syrup decolorization was studied using two commercial and eight beet pulp based activated carbons. In an attempt to relate decolorizing performances to other characteristics, surface areas, pore volumes, bulk densities and ash contents of the carbons in the powdered form; pH and electrical conductivities of their suspensions and their color adsorption properties from iodine and molasses solution were determined. The color removal capabilities of all carbons were measured at 1/100 (w/w) dosage, and isotherms were determined on better samples. The two commercial activated carbons showed different decolorization efficiencies; which could be related to their physical and chemical properties. The decolorization efficiency of beet pulp carbon prepared at 750 degrees C and activated for 5h using CO2 was much better than the others and close to the better one of the commercial activated carbons used. It is evident that beet pulp is an inexpensive potential precursor for activated carbons for use in sugar refining.     

Adsorption of Phenolic Compounds and Methylene Blue onto Activated Carbon Prepared from Date Fruit Pits

Activated carbon has been prepared from date fruit pits. The carbon, prepared at different burn‐off rates, showed a high uptake of methylene blue. At 92 % burn‐off (weight loss percent of the carbonized pits upon activation), methylene blue uptake was 590 mg/g. With this high capacity, the carbon was then used to study the adsorption of phenol, 2‐nitrophenol, 2,4‐dinitrophenol, and 2,4,6‐trinitrophenol. The prepared activated carbon showed an adsorption capacity better than that of many activated carbons in current use. The experimental adsorption data for the single components were regressed using both Langmuir and Freundlich isotherm models and the fit was generally satisfactory. The experimental adsorption data of the binary system phenol‐2‐nitrophenol were compared with the predicted results using two predictive models: the generalized Langmuir and the IAS models. The data were better represented by the IAS theory than the generalized Langmuir model even though the fit of the experimental data was not adequate.     

Freundlich adsorption isotherms of agricultural by-product-based powdered activated carbons in a geosmin-water system

The present study was designed to model the adsorption of geosmin from water under laboratory conditions using the Freundlich isotherm model. This model was used to compare the efficiency of sugarcane bagasse and pecan shell-based powdered activated carbon to the efficiency of a coal-based commercial activated carbon (Calgon Filtrasorb 400). When data were generated from Freundlich isotherms, Calgon Filtrasorb 400 had greater geosmin adsorption at all geosmin concentrations studied than the laboratory produced steam-activated pecan shell carbon, steam-activated bagasse carbon, and the CO2-activated pecan shell carbon. At geosmin concentrations < 0.07 microg/l for the phosphoric acid-activated pecan shell carbon and below 0.08 microg/l for a commercially produced steam-activated pecan shell carbon obtained from Scientific Carbons, these two carbons had a higher calculated geosmin adsorption than Filtrasorb 400. While the commercial carbon was more efficient than some laboratory prepared carbons at most geosmin concentrations, the results indicate that when the amount of geosmin was below the threshold level of human taste (about 0.10 microg/l), the phosphoric acid-activated pecan shell carbon and the Scientific Carbons sample were more efficient than Filtrasorb 400 at geosmin removal.     

Removal of color from biomethanated distillery spentwash by treatment with activated carbons

This work examined 19 carbon samples prepared by acid and thermal activation of various agro-residues viz. bagasse, bagasse flyash, sawdust, wood ash and rice husk ash for color removal from biomethanated distillery effluent. Phosphoric acid carbonized bagasse B (PH) showed the maximum color removal (50%). However, commercial activated carbons AC (ME) and AC (LB) showed better performance of over 80% color removal. Besides color removal, activated carbon treatment also showed reduction in chemical oxygen demand (COD), total organic carbon (TOC), phenol and total Kjeldahl nitrogen (TKN). The performance was related to the characteristics of the investigated samples. Further, adsorption isotherms for melanoidins, which is the primary coloring compound in distillery spentwash, followed the Langmuir isotherm implying monolayer adsorption.     

Physical and chemical properties of selected agricultural byproduct-based activated carbons and their ability to adsorb geosmin

The objectives of this study were to evaluate selected physical and chemical properties of agricultural byproduct-based activated carbons made from pecan shells and sugarcane bagasse, and compare those properties to a commercial coal-based activated carbon as well as to compare the adsorption efficiency of these carbons for geosmin. Comparison of the physical and chemical properties of pecan shell- and bagasse-based carbons to the commercial carbon, Calgon Filtrasorb 400, showed that pecan shell carbon, but not the bagasse carbon, compared favorably to Filtrasorb 400, especially in terms of surface area, bulk density, ash and attrition. A carbon dosage study done in a model system showed the amount of geosmin adsorbed to be greater for Filtrasorb 400 and the bagasse-based carbon at low carbon concentrations than for the pecan shell carbons, but geosmin adsorption was similar in all carbons at higher carbon dosages. Application of the Freundlich isotherm model to the adsorption data showed that carbons made by steam activation of pecan shells or sugarcane bagasse had geosmin adsorption characteristics most like those of the commercial carbon. In terms of physical, chemical and adsorptive properties, steam-activated pecan shell carbon most resembled the commercial carbon and has the potential to replace Filtrasorb 400 in applications involving removal of geosmin from aqueous environments.     

Purification of sugar beet vinasse - adsorption of polyphenolic and dark colored compounds on different commercial activated carbons

The adsorption on activated carbons of dark colored compounds contained in sugar beet vinasse was studied. Four commercial activated carbons with different properties (particle size, residual acidity and microporous properties) were respectively checked for efficiency at two temperature levels (25 °C and 40 °C) and at four pH levels (2, 3.5, 7, 10). The adsorption of organic molecules was determined by quantifying the amounts of total polyphenolic compounds and total organic carbon. The results showed that the adsorption capacity of dark colored compounds was enhanced by the decrease in both temperature and pH values of the solution. In this study, it is shown that this capacity depends on activated carbon characteristics which can be classified in the following order: particle size > residual acidity > microporous volume. Three models (Langmuir, Freundlich and Dubinin–Radushkevich) were tested from experimental data and compared. The Langmuir model provided the best correlation on all the activated carbons studied.     

Cometabolic bioregeneration of activated carbons loaded with 2-chlorophenol

Thermally and chemically activated carbons were used to investigate the extent of cometabolic bioregeneration in laboratory scale activated sludge reactors. Bioregeneration was determined and quantified by measuring the substrate and chloride concentrations, oxygen uptake rates, and deterioration in adsorption capacities. Activated carbons loaded with 2-chlorophenol could be partially bioregenerated in the presence of phenol as the growth substrate. The occurrence of exoenzymatic bioregeneration was also possible during cometabolic bioregeneration of thermally activated carbons. However, cometabolic bioregeneration of chemically activated carbons was much superior compared with thermally activated carbons. In cometabolic bioregeneration of activated carbons loaded with 2-chlorophenol, biodegradation, rather than desorption, was the rate-limiting step. Environmental Scanning Electron Microscopy analyses showed that groups of cocci-shaped phenol-oxidizers were attached to the outer surface or internal cavities of activated carbon as a fingerprint of bioregeneration.     

Enhanced adsorption of phenolic compounds, commonly encountered in olive mill wastewaters, on olive husk derived activated carbons

Olive husk was used for the preparation of activated carbon by chemical activation with KOH. The effects of carbonization and activation time on carbon properties were evaluated. The surface area of the produced carbons was measured by means of N(2) adsorption at 77K. The carbons with the highest surface area were further characterized by means of elemental analysis, particle size measurement, Boehm titration, zeta potential measurement, and temperature programmed desorption (TPD). Subsequently they were used for adsorption of a mixture of polyphenols consisting of caffeic acid, vanillin, vanillic acid, pi-hydroxybenzoic acid and gallic acid at two temperatures, and their adsorptive capacity was compared to a commercial carbon Acticarbon CX and found to be higher enough. The role of the porosity and surface groups are discussed in relation to the adsorption forces and the properties of the adsorbed substances. A thermodynamic interpretation of the results is also attempted.     

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.     

Activated carbons from flax shive and cotton gin waste as environmental adsorbents for the chlorinated hydrocarbon trichloroethylene

Agricultural by-products represent a considerable quantity of harvested commodity crops. The use of by-products as precursors for the production of widely used adsorbents, such as activated carbons, may impart a value-added component of the overall biomass harvested. Our objective in this paper is to show that flax shive and cotton gin waste can serve as a precursor for activated carbon that can be used for adsorption of trichloroethylene (TCE) from both the liquid and gas phases. Testing was conducted on carbon activated with phosphoric acid or steam. The results show that activated carbon made from flax shive performed better than select commercial activated carbons, especially at higher TCE concentrations. The activation method employed had little effect on TCE adsorption in gas or vapor phase studies but liquid phase studies suggested that steam activation is slightly better than phosphoric acid activation. As expected, the capacity for the activated carbons depended on the fluid phase equilibrium concentration. At a fluid concentration of 2 mg of TCE/L of fluid, the capacity of the steam activated carbon made from flax shive was similar at 64 and 80 mg TCE/g of carbon for the vapor and liquid phases, respectively. Preliminary cost estimates suggest that the production costs of such carbons are $1.50 to $8.90 per kg, depending on activation method and precursor material; steam activation was significantly less expensive than phosphoric acid activation.