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An activated carbon (AC) with a specific surface area of 700 m 2  g −1 was prepared by KOH activation of tyre pyrolysis char (TPC) and tested to remove Bisphenol A (BPA) from aqueous solutions. BPA adsorption on this AC was evaluated by studying both the adsorption isotherms at three different temperatures and the decrease of BPA concentration with time, in order to determine the thermodynamic and the kinetic parameters, respectively. The results were compared with those obtained with pristine TPC and with a multipurpose commercial activated carbon (CAC) recommended for BPA adsorption. The present KOH-activated TPC showed a great potential to adsorb BPA with a monolayer capacity as high as 123 mg g −1 , higher than that of the CAC used as a reference. BPA adsorption equilibrium data were fitted using different isotherm models with two or three parameters, and the best fitting models were those of Langmuir and Radke-Prausnitz. BPA adsorption was an exothermic process, and the adsorption capacity decreased with increasing temperature. The adsorption kinetics of BPA was adequately described by a pseudo-second order model. [ABSTRACT FROM AUTHOR]

12 activated carbons (ACs) were prepared by KOH activation using hydrochars as precursors. These hydrochars were prepared by hydrothermal carbonisation (HTC) of sucrose solutions at concentrations ranging from 0.2 to 1.6 mol L −1 . The KOH to hydrochar weight ratio ( W ) was varied from 1 to 5, and the activation temperature was set to 1023 K. ACs texture was assessed by nitrogen and carbon dioxide adsorption at 77 and 273 K, respectively; pore size distribution was calculated by using both isotherms and the SAIEUS© software. ACs with surface areas between 790 and 2240 m 2 g −1 were obtained. Hydrogen excess adsorption was determined at 298 K and pressures up to 10 MPa in a volumetric device, and the isosteric heat of adsorption ( Q st ) was calculated for four ACs, using hydrogen isotherms obtained at 278, 298 and 308 K. Potassium intercalation between graphitic planes was assumed to account for the high Q st values, 7–8 kJ mol −1 . Hydrogen uptake at 2 MPa was compared with hydrogen adsorption data of 38 other ACs reported in the open literature. Hydrogen adsorption fundamentally depends on micropore volume and preliminary HTC did not enhance hydrogen storage although it could be a good strategy for doping carbon with heteroelements. [ABSTRACT FROM AUTHOR]

Tyre pyrolysis char (TPC), produced when manufacturing pyrolysis oil from waste tyre, was used as raw material to prepare activated carbons (ACs) by KOH activation. KOH to TPC weight ratios ( W ) between 0.5 and 6, and activation temperatures from 600 to 800 °C, were used. An increase in W resulted in a more efficient development of surface area, microporosity and mesoporosity. Thus, ACs derived from TPC (TPC-ACs) with specific surface areas up to 814 m 2 g −1 were obtained. TPC, TPC-ACs and a commercial AC (CAC) were tested for removing Tetracycline (TC) in aqueous phase, and systematic adsorption studies, including equilibrium, kinetics and thermodynamic aspects, were performed. Kinetics was well described by the pseudo-first order model for TPC, and by a pseudo second-order kinetic model for ACs. TC adsorption equilibrium data were also fitted by different isotherm models: Langmuir, Freundlich, Sips, Dubinin–Radushkevich, Dubinin–Astokov, Temkin, Redlich–Peterson, Radke–Prausnitz and Toth. The thermodynamic study confirmed that TC adsorption onto TPC-ACs is a spontaneous process. TC adsorption data obtained in the present study were compared with those reported in the literature, and differences were explained in terms of textural properties and surface functionalities. TPC-ACs had similar performances to those of commercial ACs, and might significantly improve the economic balance of the production of pyrolysis oil from waste tyres. [ABSTRACT FROM AUTHOR]

Abstract: Three activated carbons (ACs) having apparent surface areas ranging from 2450 to 3200 m2/g were doped with Pd nanoparticles at different levels within the range 1.3–10.0 wt.%. Excess hydrogen storage capacities were measured at 77 and 298 K at pressures up to 8 MPa. We show that hydrogen storage at 298 K depends on Pd content at pressures up to 2–3 MPa, below which the stored amount is low (<0.2 wt.%). At higher pressures, the micropore volume controls H2 storage capacity. At 77 K, Pd doping has a negative effect on hydrogen storage whatever the pressure considered. From N2 adsorption at 77 K, TPR, XRD, TEM, and H2 chemisorption studies, we concluded that: (i) Pd particles remained mainly decorating the outer surface of the ACs; (ii) increasing Pd content produced an increase of the metal particle size; (iii) ACs with higher surface area produced smaller metallic nanoparticles at a given Pd content. [Copyright &y& Elsevier]

Abstract: We measured hydrogen storage on five well-known commercial carbon materials (CCMs) and we compared their performances to those obtained on our lab-made activated carbons (ACs). H2 uptake of our lab-made ACs was always higher than that of CCMs of similar SBET , our best AC reached 6 wt.% H2 excess adsorption at 77 K and 4 MPa. We calculated the contribution of four ranges of pores (<0.5 nm; 0.5–0.7 nm, 0.7–2 nm and >2 nm) to the H2 excess adsorption for the 14 carbon materials considered in this study. We clearly demonstrated that: (i) the superiority in H2 excess adsorption of lab-made ACs over the CCMs is related to their pore size distribution; (ii) H2 uptakes higher than 3 wt.% are due to pores with diameter wider than 0.7 nm. [Copyright &y& Elsevier]

Abstract: We studied the effect of physically and/or chemically deashing rice straw (RS) on the adsorption capacity of their derived activated carbons (ACs) produced by chemical activation with H3PO4. Surface area and pore volumes were determined by nitrogen adsorption at 77 K. Methylene blue adsorption isotherms onto ACs were carried out, and we applied Langmuir and Freundlich models to fit the adsorption data. We showed that preliminary deashing does not bring significant improvement to the resultant ACs’ properties. ACs prepared by H3PO4 activation of raw and deashed RS have intermediate performances between those of ACs prepared by 1- and 2-step KOH activation, but are much cheaper to produce. [Copyright &y& Elsevier]

Abstract: A high area pre-concentrator based on microporous activated carbon with different activation conditions is presented. The adsorbing layer was deposited on a self-heated planar substrate using the air-brushing technique. By coupling the preconcentrator to a mass spectrometer (MS), we measured the benzene desorption over time, when a temperature pulse is applied to the heater. The effect of activation conditions on the adsorption capacity of the selected carbons is discussed. The highest adsorption capacity was exhibited by the material having the lowest activating agent per precursor weight ratio. [Copyright &y& Elsevier]

Abstract: Ferric chloride forced hydrolysis is shown to be a good method for increasing the iron content of activated carbons (ACs). Iron content increased linearly with hydrolysis time, and ACs with iron content as high as 9.4wt.% at 24h hydrolysis time could be prepared. The increase in iron content did not produce any modification in the textural parameters determined by nitrogen adsorption at 77K. Iron-based nanoparticles, homogeneous in size and well-dispersed in the carbon matrix, were obtained. Nanoparticles forming iron (hydr)oxide agglomerates at the outer surface of the carbon grains at hydrolysis times higher than 6h were also produced. The AC obtained after 6h of ferric chloride forced hydrolysis removed 94% of the arsenic present in a groundwater from the State of Chihuahua (Mexico), whereas the commercial AC used as precursor allowed the removal of only 14%. The lower performance in arsenic removal observed for AC prepared using long forced hydrolysis time (24h) is probably due to the existence of iron (hydr)oxides nanoparticles agglomerates, which once hydrated could prevent diffusion of arsenate (HAsO4 −) towards the inner surface of the AC grain. [Copyright &y& Elsevier]

Arsenic removal from natural well water from the state of Chihuahua (Mexico) is investigated by adsorption using a commercial activated carbon (AC). The latter is used as such, or after oxidation by several chemicals in aqueous solution: nitric acid, hydrogen peroxide, and ammonium persulphate. Raw and oxidised activated carbons are fully characterised (elementary analysis, surface chemistry, pore texture parameters, pHZC, and TEM observation). Adsorption of As is measured in the aforementioned water, containing ca. 300ppb of arsenic: removal of As is poor with the raw AC, and only the most oxidised carbons exhibit higher performances. By contrast, iron-doped ACs are much more efficient for that purpose, though their As uptake strongly depends on their preparation conditions: a number of samples were synthesised by impregnation of raw and oxidised ACs with HCl aqueous solutions of either FeCl3 or FeCl2 at various concentrations and various pH. It is shown that iron(II) chloride is better for obtaining high iron contents in the resultant ACs (up to 8.34wt.%), leading to high As uptake, close to 0.036mg As/g C. In these conditions, 100% of the As initially present in the natural well water is removed, as soon as the Fe content of the adsorbent is higher than 2wt.%. [Copyright &y& Elsevier]

Abstract: Adsorption of phenol in aqueous phase onto activated carbons (ACs) having different textural and surface properties has been considered. Six types of ACs were used: three were commercial, and three were obtained from Kraft lignin chemically activated with sodium hydroxide, potassium hydroxide or ortho-phosphoric acid. The apparent surface areas of the commercial ACs varied from 620 to 1320m2/g, while ACs made from lignin presented surface areas as high as 1300m2/g and 2900m2/g when prepared with H3PO4 and alkaline hydroxides, respectively; moreover, the highest proportion of microporosity was found for ACs derived from lignin. A kinetic study was carried out, showing that the phenol adsorption data may be correctly adjusted, for all the ACs tested, by an equation corresponding to a pseudo second-order chemical reaction. Freundlich, Langmuir and Tempkin equations were tested for modelling the adsorption isotherms at equilibrium, and it was concluded that Langmuir model fitted adequately the experimental data. However, Tempkin model fitted even better the adsorption data obtained with ACs derived from lignin activated with alkaline hydroxides, which are characterized by the highest number of surface groups. Remarkably high phenol adsorption capacities were found for the ACs prepared by activation of Kraft lignin with NaOH and KOH: 238 and 213mg/g of AC, respectively. Finally, the adsorption of phenol was found to depend not only on the micropore volume, but also on the total amount of carbonyl and basic groups and on the ratio of acid to basic groups. [Copyright &y& Elsevier]

Since air quality is a major public health concern, especially in urban areas, the use of alternative fuels for vehicular applications has been strongly encouraged. Of these fuels, hydrogen is the only one that can produce zero emission through fuel cells. However, the storage of such a very light and highly combustible gas has yet to be solved. Only adsorption storage is discussed in the present paper. It should be recalled that no material has been capable of meeting the recommended targets to date. Recent progresses in preparing suitable carbon structures for hydrogen storage are described, and new routes for characterising and correspondingly improving the micropore texture are explored. [ABSTRACT FROM AUTHOR]

Abstract: Activated carbons were prepared by activation of Kraft lignin with ortho-phosphoric acid at various temperatures (400–650°C), weight ratios of ortho-phosphoric acid to lignin (P/L=0.7–1.75) and impregnation times (1–48h). The resulting carbons were characterised by elemental analysis, N2 adsorption at 77K and SEM. The results indicate that the pyrolysis of lignin impregnated with ortho-phosphoric acid produces essentially microporous carbons, with a percentage of the total micropore volume approximately constant (80%), whatever the carbonisation temperature. The fraction of ultramicropores decreases with increasing temperature whereas that of supermicropores reaches a maximum at 600°C. The maximum surface area (1305m2/g) and pore volume (0.67cm3/g) are reached at 600°C, while pyrolysis of acid-impregnated lignin at temperatures higher than 600°C produces a significant reduction of both pore volume and BET surface area due to: (i) the shrinkage of the material caused by the degradation of the phosphate and polyphosphate bridges and (ii) the oxidation of the carbon caused by the loss of the protecting P2O5. Increasing the P/L ratio increases the carbon yield and involves changes in the total volume of pores, the pore size distribution and the BET surface area. There exists an optimum P/L ratio which probably depends on the activation temperature, an excess of ortho-phosphoric acid beyond this optimum value reducing the surface area and the pore volume of the resultant activated carbon. Increasing the impregnation time, the surface area and the pore volume are lowered, and such an effect is more severe at higher activation temperatures. [Copyright &y& Elsevier]

In this article, we present a mathematical model that describes the calcination and sintering of calcium-based sorbents in furnace sorbent injection (FSI) conditions. We assumed that the sorbent decomposition follows a shrinking core model with a changing pore size distribution in every layer and we used a comprehensive mathematical model for sintering. Cylindrical and plate-like or slit pore geometries, usually associated with carbonate- and hydroxide-derived sorbents, respectively, were adopted and compared. It was concluded that sorbents with cylindrical pores sinter to a greater extent than those with slit pores. The decomposition and sintering kinetics were determined for three calcium sorbents with different pore geometries in FSI conditions. The study revealed that the presence of CO2 and H2O in the reaction atmosphere affects the sintering parameters whereas the calcination parameters remain constant. The model effectively correlated the experimental data and adequately predicted not only the evolution of the specific surface area but also the evolution of the pore size distribution of the sorbent over time. The most striking aspect of the research was that although our model calculated the total area by adding together the pore sizes in all the layers of the sorbent, the results were very similar to those of other sintering models. [Copyright &y& Elsevier]

Abstract: A high area planar pre-concentrator based on various microporous activated carbons of different origins, granularities and preparation conditions, is studied. The adsorbing layer of different thicknesses was deposited on a self-heated planar substrate using the air-brushing technique. By coupling the pre-concentrator to a mass spectrometer, the thermo-desorption of benzene induced by application of a heat pulse was monitored with time. The effects of adsorbent layer thickness, grain size, origin, and activation conditions on the adsorption capacity and pre-concentration of the device are examined and discussed. Suggestions are given for preparing a planar pre-concentrator presenting the highest performances for the detection of benzene present as traces in a carrier gas. [Copyright &y& Elsevier]

The problems of valorisation of particleboard wastes on one hand, and contamination of aqueous effluents by phenolic compounds on the other hand, are simultaneously considered in this work. Preparation of activated carbons from a two steps thermo-chemical process, formerly designed for generating combustible gases, is suggested. The resultant carbonaceous residue is activated with steam at 800°C. Depending on the preparation conditions, surface areas within the range 800–1300m2/g are obtained, close to that of a commercial activated carbon (CAC) specially designed for water treatment and used as a reference material. The present work shows that particleboard waste-derived activated carbons (WAC) are efficient adsorbents for the removal of phenol from aqueous solutions, with maximum measured capacities close to 500mg/g. However, most of times, the adsorption capacities are slightly lower than that of the commercial material in the same conditions, i.e., at equilibrium phenol concentrations below 300ppm. Given the extremely low cost of activated carbons prepared from particleboard waste, it should not be a problem to use it in somewhat higher amounts than what is required with a more expensive commercial material. Phenol adsorption isotherms at 298K were correctly fitted by various equations modelling type I and type II isotherms for CAC and WAC, respectively. Phenol adsorption isotherms of type II were justified by a 3-stages adsorption mechanism. [Copyright &y& Elsevier]

Abstract: During the last years, the use of gas pre-concentrators coupled to gas sensors became more important due to the difficulty of fabricating gas sensors with sensitivities in the range of tens of ppb (or lower). Among the different adsorbents used in pre-concentrators, carbons are the most usual, since they are very common materials in chemistry, and because their adsorption performances are very high. In the present work, a family of microporous activated carbons prepared from chemical activation of Kraft lignin was used as adsorbents, and compared with a commercial material. The carbonaceous adsorbents were sprinkled onto self-heated alumina substrates using a binding layer deposited by screen-printing. Their characterisation was performed by means of a GC–MS with a 6-way valve injection system. Concentration factors higher than 1000 for benzene have been achieved with some particular adsorbents. In the present work, the microporous activated carbons and Carbopack have been adhered over the self-heated surface of pre-concentrators. The performances obtained for all the microporous activated carbons are much higher than those obtained with the commercial carbon black Carbopack X, so these lab-made materials are very promising adsorbents for micro pre-concentrators, which could be used in conjunction with sensors in gas detection systems. [Copyright &y& Elsevier]

Abstract: Enzymatic membrane reactors were obtained from polymeric membranes and activated carbon, and used for oligosaccharide purification. The activated carbon was used to adsorb the enzyme, directly or via a metal ion as intermediate. We studied the adsorption capacity of two activated carbons (a commercial carbon and a home-made one) and the formation of the complex. In a second step, we studied the activity of the enzymes in batch experiments, and analyzed the synthesis and performance of the membrane reactors. Different kinds of enzymatic membrane reactors were obtained with immobilized solid enzymes. Our results show good agreement between the kinetics of the reactions and the velocity of the flux across the membrane, since both reaction and separation were properly achieved. We also determined optimum amounts of enzyme for obtaining the desired products with a low degree of polymerization and low concentrations of monomer. [Copyright &y& Elsevier]

The effect of heteroatoms on hydrogen adsorption properties of activated and hybrid carbon materials is critically described. For that purpose, olive stones were activated chemically with KOH, and subsequently washed or not, and oxidised with ozone or not. Olive stones were also activated physically with CO 2. A series of activated carbons prepared by chemical activation of sucrose was also investigated for comparison. As a result, many activated carbons with different pore-size distributions, surface areas, average micropore widths, oxygen contents and amounts of mineral matter could be compared. All were thoroughly characterised by adsorption of N 2 , CO 2 and H 2 O, elemental analysis, XPS, thermogravimetry, and adsorption of H 2 at different pressures. Many correlations between textural parameters, composition and adsorption properties could be evidenced, and were critically discussed. We show that the hydrogen uptake at 77 K is controlled by the following parameters, listed by decreasing order of importance: specific surface area, average micropore size, surface chemistry and shape of the pore size distribution. At room temperature (i.e., at 298 K), the adsorbed hydrogen uptake was in the range of 0.19–0.42 wt %; the presence of large amounts of alkali metals can further improve the hydrogen adsorption properties, but surface chemistry still has a major influence, especially through the acidic surface functions. Image 1 • Olive stones-based carbon materials with high surface area were prepared. • Comparison with other materials highlighted oxygen-promoted H 2 physisorption. • Carboxyl surface groups play an important role in oxygen-promoted H 2 physisorption. • A 26% increase of adsorbed hydrogen was attributed to acidic functions. • Residual carbonates and potassium play a marginal role in physisorption. [ABSTRACT FROM AUTHOR]

Hydrogen storage in activated carbons (ACs) has proven to be a realistic alternative to compression and liquefaction. Adsorption capacities up to 5.8 wt% have indeed been obtained. The amount of adsorbed hydrogen depends on the textural properties of ACs, such as specific surface area and total pore volume. The modified Dubinin-Astakhov (MDA) equation proved to be a good analytical tool for describing hydrogen adsorption in a wide range of pressures and temperatures and for several adsorbents. The parameters of this model have been found to be somehow related to the textural properties of the adsorbent. Thus, we applied this model to understand better hydrogen adsorption on ACs over a wide range of pressures in relation to the textural properties of the ACs. We applied the MDA equation to evaluate also the isosteric heat of hydrogen adsorption, which was found to be in the range of 5–9 kJ mol−1. We compared the results obtained by applying the MDA equation with those obtained by both the sorption isosteric method and the Sips equation. This allowed finding the temperature dependence of the isosteric heat of adsorption, as well as its variation with respect to the textural properties of the ACs. • The modified Dubinin-Astakhov (MDA) equation well described H 2 adsorption up to 15 MPa. • MDA parameters were related to the textural properties of activated carbons (ACs). • Isosteric heats of adsorption in the range 5–9 kJ mol−1 were found. • Adsorption entropy was higher for ACs having both narrow pores and high microporosity. • c p of the adsorbed phase varied from 10 to 18 J mol−1 K−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • Texture prevails over heteroatom content in CO 2 uptake within 1–25 bar and 273–323 K. • N-O-doping reduces textural properties but enhances CO 2 /N 2 selectivity up to 5 bar. • Heteroatom doping increases the isosteric heat of adsorption at low coverage. • Tap density is a key parameter affecting fixed-bed column breakthrough performance. This study shows the substantial impact of textural properties, with greater weight than N-doping, on CO 2 adsorption by carbon materials over a pressure range from 1 to 25 bar and a temperature range from 273 to 323 K. It also highlights the importance of providing volumetric CO 2 adsorption capacities when presenting newly developed materials. These results were obtained by exploring the influence of O- and N-doping on CO 2 uptake on 14 activated carbons (ACs) with distinct specific surface areas, from 1736 to 3200 m2/g, and micropore fractions from 37 to 96 %. Based on 3 commercial ACs, N content was maximized by hydrogen peroxide oxidation and urea treatment, reaching around 11 at.%. O-N-doping mainly impacted the largest pores, reducing material textural properties and thus CO 2 adsorption, although it improved CO 2 /N 2 selectivity, especially up to 5 bar and between 273 and 323 K. The contribution of heteroatoms to CO 2 uptake was particularly significant at low pressures and high temperatures, with threshold pressures increasing at higher temperatures. Breakthrough simulations were also carried out and the results demonstrate that, despite a lower specific surface area, the O-doped material exhibited longer breakthrough times than its commercial counterpart. This can be attributed to a balance between CO 2 adsorption capacity, governed by the textural properties, and tap density, i.e., adsorption capacity per unit volume. [ABSTRACT FROM AUTHOR]