Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Applied Surface Science (v.252, #17)
Preface
by Eduardo M. Cuerda-Correa Guest Editor; Antonio MacÃas-GarcÃa Guest Editor; José Gañán-Gómez Guest Editor (pp. 5947-5947).
Carbon molecular sieves from PET for separations involving CH4, CO2, O2 and N2 by P.J.M. Carrott; I.P.P. Cansado; M.M.L. Ribeiro Carrott (pp. 5948-5952).
Carbon molecular sieves (CMS) have been made for the first time from PET textile fibres by carbonisation and pore mouth narrowing using CVD of benzene. The diffusion of O2, N2, CO2 and CH4 in these materials, and also in the commercial CMS Takeda 3A, was studied. It was found that the best PET based CMS was obtained after 10min CVD time and had adsorption capacities and rates of diffusion similar to those of the Takeda 3A.
Keywords: PACS; 51.10.+y; 67.70.+n; 68.43.JkCarbon molecular sieve; Methane; PET; CVD
Controlling the micropore size of activated carbons for the treatment of fuels and combustion gases by P.J.M. Carrott; P.A.M. Mourão; M.M.L. Ribeiro Carrott (pp. 5953-5956).
Exclusively microporous activated carbons have been prepared from cork by physical and chemical activation under different conditions. The results show that it is possible to control the pore size of the activated carbons and to obtain materials with narrow micropore size (≥0.69nm) and high micropore volume (≤0.64cm3g−1) equal to or better than the best activated carbon fibres. Higher micropore volumes are generally obtained by chemical activation at higher temperature using dry or potassium hydroxide impregnation. On the other hand, wet or carbonate impregnation, as well as high temperature, or physical activation with CO2 or H2O under appropriate conditions, favours low mean pore widths.
Keywords: PACS; 67.70; +; nCork; Activated carbon; Activated carbon fibre; Micropore size
Preparation of charcoal from cherry stones by Carlos J. Durán-Valle; Manuel Gómez-Corzo; Vicente Gómez-Serrano; José Pastor-Villegas; MarÃa L. Rojas-Cervantes (pp. 5957-5960).
Cherry stones (CS) are carbonised at 400–1000°C for 0–4h in N2 and the charcoals obtained are characterised to gain information about their chemical composition and porous texture, with a view to their use in the preparation of activated carbon. Depending on the heating conditions, the products obtained may possess a low ash content and a high fixed carbon content and are essentially microporous and macroporous solids.
Keywords: PACS; 61.43.G; 82.30.Lp; 68.35Cherry stones; Carbonisation; Chemicophysical characterisation
Preparation and textural characterisation of activated carbon from vine shoots ( Vitis vinifera) by H3PO4—Chemical activation by B. Corcho-Corral; M. Olivares-MarÃn; C. Fernández-González; V. Gómez-Serrano; A. MacÃas-GarcÃa (pp. 5961-5966).
An abundant and low-cost agricultural waste as vine shoots ( Vitis vinifera) (VS), which is generated by the annual pruning of vineyards, has been used as raw material in the preparation of powder activated carbon (AC) by the method of chemical activation with phosphoric acid. After size reduction, VS were impregnated for 2h with 60wt.% H3PO4 solution at room temperature, 50 and 85°C. The three impregnated products were carbonised at 400°C. The product impregnated at 50°C was heated either first at 150–250°C and then at 400°C or simply at 350–550°C in N2 atmosphere. The time of isothermal treatment after each dynamic heating was 2h. The carbons were texturally characterised by gas adsorption (N2, −196°C), mercury porosimetry, and density measurements. FT-IR spectroscopy was also applied. Better developments of surface area and microporosity are obtained when the impregnation of VS with the H3PO4 solution is effected at 50°C and for the products heated isothermally at 200 and 450°C. The mesopore volume is also usually higher for the products impregnated and heated at intermediate temperatures.
Keywords: PACS; 61.47.Gt; 68.43.−h; 81.05.Rm; 82.45.−JnActivated carbon; Vine shoots; Phosphoric acid activation
Preparation of activated carbon from cherry stones by chemical activation with ZnCl2 by M. Olivares-MarÃn; C. Fernández-González; A. MacÃas-GarcÃa; V. Gómez-Serrano (pp. 5967-5971).
Cherry stones (CS), an industrial product generated abundantly in the Valle del Jerte (Cáceres province, Spain), were used as precursor in the preparation of activated carbon by chemical activation with ZnCl2. The influence of process variables such as the carbonisation temperature and the ZnCl2:CS ratio (impregnation ratio) on textural and chemical-surface properties of the products obtained was studied. Such products were characterised texturally by adsorption of N2 at −196°C, mercury porosimetry and density measurements. Information on the surface functional groups and structures of the carbons was provided by FT-IR spectroscopy. Activated carbon with a high development of surface area and porosity is prepared. When using the 4:1 impregnation ratio, the specific surface area (BET) of the resultant carbon is as high as 1971m2g−1. The effect of the increase in the impregnation ratio on the porous structure of activated carbon is stronger than that of the rise in the carbonisation temperature, whereas the opposite applies to the effect on the surface functional groups and structures.
Keywords: PACS; 61.43.Gt; 68.43.−h; 81.05.Rm; 82.45.−JnCherry stones; ZnCl; 2; activation; Activated carbon; Characterisation
Study of the pore size distribution and fractal dimension of HNO3-treated activated carbons by A. MacÃas-GarcÃa; M.A. DÃaz-DÃez; E.M. Cuerda-Correa; M. Olivares-MarÃn; J. Gañan-Gómez (pp. 5972-5975).
In the present work, the effect of the oxidizing treatment with nitric acid on three activated carbon samples has been studied. The influence of the acid treatment on the surface groups of the different samples has been investigated by means of FT-IR spectroscopy. The pore size distributions of the different samples were determined by means of the HK and DFT methods. The HK method points out a moderate increment of the microporosity due to the action of the nitric acid, whereas the DFT method shows an increase in the microporosity range above 17Ã…. Finally, the values of the fractal dimension reveal that the treatment of the samples with nitric acid leads to chemical reactions of a limited extent.
Keywords: PACS; 61.43.Gt; 61.43.Hv; 68.47.−bActivated carbon; Pore size distribution; Oxidizing treatment; Fractal dimension
Preparation and characterization of activated carbons from impregnation pitch by ZnCl2 by J. Gañán-Gómez; A. MacÃas-GarcÃa; M.A. DÃaz-DÃez; C. González-GarcÃa; E. Sabio-Rey (pp. 5976-5979).
Using an impregnation pitch from bituminous coal tar (OP) supplied by Industrias QuÃmicas del Nalon Company as raw material, two phases (isotropic and anisotropic) have been obtained. The latter was used as precursor for the preparation of activated carbons. First, a chemical activation process was carried out with ZnCl2 as activating agent. The process was conducted at different concentrations and temperatures and by means of impregnation with solid zinc chloride. Optimal values were obtained for samples prepared by using a ZnCl2:pitch ratio equal to 3:1 (sample AZn3). Next, this sample was thermally treated at two different temperatures, i.e., 700 and 800°C. A lose of specific surface area, microporosity and mesoporosity was observed with respect to sample AZn3, such a lose being more remarkable as temperature increased. Moreover, impregnation of the anisotropic phase of the original pitch with an aqueous solution of ZnCl2 followed by thermal treatment resulted in a poorly developed surface area and porous texture, probably due to the presence of Zn complexes, which interfere with the activation process.
Keywords: Pitch; Activated carbon; Porosity; ZnCl; 2
Preparation of activated carbons from cherry stones by activation with potassium hydroxide by M. Olivares-MarÃn; C. Fernández-González; A. MacÃas-GarcÃa; V. Gómez-Serrano (pp. 5980-5983).
Using cherry stones, the preparation of activated carbon has been undertaken in the present study by chemical activation with potassium hydroxide. A series of KOH-activated products was prepared by varying the carbonisation temperature in the 400–900°C range. Such products were characterised texturally by gas adsorption (N2, −196°C), mercury porosimetry, and helium and mercury density measurements. FT-IR spectroscopy was also applied. The carbons prepared as a rule are microporous and macroporous solids. The degree of development of surface area and porosity increases with increasing carbonisation temperature. For the carbon heated at 900°C the specific surface area (BET) is 1624m2g−1, the micropore volume is 0.67cm3g−1, the mesopore volume is 0.28cm3g−1, and the macropore volume is 1.84cm3g−1.
Keywords: PACS; 61.43.Gt; 68.43.−h; 81.05.Rm; 81.05.Uw; 82.45.JnCherry stones; KOH activation; Activated carbon
Preparation of activated carbons previously treated with hydrogen peroxide: Study of their porous texture by M. López de Letona Sánchez; A. MacÃas-GarcÃa; M.A. DÃaz-DÃez; E.M. Cuerda-Correa; J. Gañán-Gómez; A. Nadal-Gisbert (pp. 5984-5987).
Cedar wood was used as raw material for the preparation of activated carbons by treatment with hydrogen peroxide of different concentrations. The samples were next carbonised and activated under CO2 atmosphere. The activated carbons were characterised by means of the adsorption isotherms of N2 at 77K, as well as by applying the Density Functional Theory (DFT) method and mercury porosimetry. The experimental results corresponding to the activated samples indicate a more remarkable porous development as a consequence of the treatment with hydrogen peroxide, probably due to the elimination of surface complexes produced during the activation step. The DFT diagrams point out that the activating treatment favours the development of medium and narrow-size micropores whereas the carbonisation process leads to the development of wide micropores of size close to that corresponding to mesopores.
Keywords: PACS; 61.43.Gt; 61.43.Hv; 68.47.-bActivated carbon; Hydrogen peroxide; Average pore size distribution
Air-activated carbons from almond tree pruning: Preparation and characterization by J. Gañán; J.F. González; C.M. González-GarcÃa; A. Ramiro; E. Sabio; S. Román (pp. 5988-5992).
In this work the results obtained in the preparation and characterization of carbons made from almond tree pruning by non-catalytic and catalytic gasification (using K and Co) with air are analyzed and discussed. The main aim was to obtain high quality activated carbons at the lowest possible cost. The variables studied have been the temperature (190–260°C) and the time (1–10h) in non-catalytic gasification and the influence of the catalyst type (K and Co, 1wt.% referred to cation, at 190°C and 1h) and the time (1–4h) in catalytic gasification with Co at 190°C. The air flow rate used in all the series was 167cm3min−1. In non-catalytic gasification the reaction normalized rate versus the conversion degree was maintained until a conversion value of 10% for the experiment made at 260°C since, at lower temperatures, this rate drops quickly for low conversion values. The N2 adsorption isotherms for the carbons of this series resemble type I, although there is an increase of N2 adsorbed volume at relatively high pressures. A temperature rise produced an increase of the carbon porosity and BET specific surface (116–469m2g−1). The activation time has a positive effect on the N2 volume adsorbed by the carbons. The isotherms shapes were similar to those previously commented. A concentration equal to 1wt.% was used to study the influence of the catalyst type. Under the studied experimental conditions, Co drives to a bigger porosity development than K, although with both catalysts a very similar pore size distribution is obtained. The activation time, in the gasifications catalyzed with Co, gives rise to a very important porosity development in the carbons. This produces a strong increase of the carbon specific surface area with very high values in the 4h experiment, in which a BET specific surface of 959m2g−1 was obtained.
Keywords: PACS; 81.05RmAir gasification; Activated carbon; Almond pruning; Textural properties
Carbon dioxide-activated carbons from almond tree pruning: Preparation and characterization by J. Gañán; J.F. González; C.M. González-GarcÃa; A. Ramiro; E. Sabio; S. Román (pp. 5993-5998).
Activated carbons were prepared from almond tree pruning by non-catalytic and catalytic gasification with carbon dioxide and their surface characteristics were investigated. In both series a two-stage activation procedure (pyrolysis at 800°C in nitrogen atmosphere, followed by carbon dioxide activation) was used for the production of activated samples. In non-catalytic gasification, the effect of the temperature (650–800°C for 1h) and the reaction time (1–12h at 650°C) on the surface characteristics of the prepared samples was investigated. Carbons were characterized by means of nitrogen adsorption isotherms at 77K. The textural parameters of the carbons present a linear relation with the conversion degree until a value of approximately 40%, when they come independent from both parameters studied. The highest surface area obtained for this series was 840m2g−1. In the catalytic gasification the effect of the addition of one catalyst (K and Co) and the gasification time (2–4h) on the surface and porosity development of the carbons was also studied. At the same conditions, Co leads to higher conversion values than K but this last gives a better porosity development.
Keywords: PACS; 81.05.RmPyrolysis; CO; 2; gasification; Activated carbon; Adsorption
Preparation of activated carbons from used tyres by gasification with steam and carbon dioxide by Juan F. González; José M. Encinar; Carmen M. González-GarcÃa; E. Sabio; A. Ramiro; José L. Canito; José Gañán (pp. 5999-6004).
Activated carbons were prepared from waste tyres by gasification with steam and carbon dioxide and their characteristics were investigated. A two-stage activation procedure (pyrolysis at 800°C in N2 atmosphere, followed by steam or carbon dioxide activation) was used for the production of activated samples. The effect of the activation temperature (750–900°C) and the activation time (1–3h) on the surface characteristics of the prepared carbon was investigated. Carbons produced to different degrees of burn-off were characterized by means of their nitrogen adsorption isotherms at 77K. In both sets of experiments, the mesopore, micropore volume, and BET surface area increased almost linearly with the degree of activation. For burn-off values lower than 53%, the steam activation produced carbons with a narrower and more extensive microporosity and higher BET and external surface area than the carbon dioxide activation. As the activation proceeds (burn-off>53%), a strong development of the mesoporosity in the carbons was observed and the micropores size distribution revealed broader micropores, that is, a more heterogeneous distribution.
Keywords: PACS; 81.05.RmWaste tyres; Activated carbon; Activation; Porosity
Demineralisation of semi-anthracite char with molten salts/HCl by M. Alfaro-DomÃnguez; F.J. Higes-Rolando; M.L. Rojas-Cervantes; V. Gómez-Serrano (pp. 6005-6008).
The effects of chemical heat treatments of a semi-anthracite char (AC) on textural properties and reactivity in air of the material are investigated. The starting char was first treated with a mixture of LiCl/KCl or LiCl/KCl/CaO at 743, 873 or 1173K and the products obtained were then washed thoroughly with distilled water. A small fraction of these samples were treated with 10−3M HCl solution. Valuable information on textural modifications produced in the material was derived from the adsorption isotherms for CO2 at 273K. The reactivity tests were carried out at 808, 823 and 823K. The microporosity developed and the reactivity in air increased in the partially demineralised products. The former effect was stronger for the LiCl/KCl/CaO-treated samples and the latter for a larger number of the LiCl/KCl-treated samples.
Keywords: PACS; 81.05.Rm; 81.40.−zSemi-anthracite char; Demineralisation; Molten salts; Textural properties; Air reactivity
Demineralisation of a semianthracite char with molten salts/HCl by M. Alfaro-DomÃnguez; F. Sánchez Bajo (pp. 6009-6012).
The effects of chemical heat treatments of a semianthracite char (AC) on the composition of the mineral fraction of the material are investigated. The starting char was first treated with a mixture of LiCl/KCl or LiCl/KCl/CaO at 743, 873 or 1173K and the products obtained were then washed thoroughly with distilled water. A small fraction of these samples were treated with 10−3M HCl solution. The composition changes were studied by X-ray diffraction. The predominant mineral components initially present in the starting char are quartz, mullite, muscovite and/or kaolinite and oldhamite. The treatments of AC resulted in significant changes in the mineral fraction of the material, in particular when LiCl/KCl/CaO was used. In this case, spurrite, γ-calcium orthosilicate and gehlenite were formed, which were eliminated by treatment with 10−3M HCl solution.
Keywords: PACS; 61.10.−i; 61.66.FnSemianthracite char; Demineralisation; Molten salts; X-ray diffraction
Determination of optical properties in nanostructured thin films using the Swanepoel method by J. Sánchez-González; A. DÃaz-Parralejo; A.L. Ortiz; F. Guiberteau (pp. 6013-6017).
We present the methodological framework of the Swanepoel method for the spectrophotometric determination of optical properties in thin films using transmittance data. As an illustrative case study, we determined the refractive index, thickness, absorption index, and extinction coefficient of a nanostructured 3mol% Y2O3-doped ZrO2 (yttria stabilized zirconia, 3YSZ) thin film prepared by the sol–gel method and deposited by dipping onto a soda-lime glass substrate. In addition, using the absorption index obtained with the Swanepoel method, we calculated the optical band gap of the film. The refractive index was found to increase, then decrease, and finally stabilize with increasing wavelength of the radiation, while the absorption index and extinction coefficient decreased monotonically to zero. These trends are explained in terms of the location of the absorption bands. We also deduced that this 3YSZ thin film has a direct optical band gap of 4.6eV. All these results compared well with those given in the literature for similar thin films. This suggests that the Swanepoel method has an important role to play in the optical characterization of ceramic thin films.
Keywords: PACS; 68.55.Jk; 81.05.Je; 81.20.Fw; 78.20.CiThin films; Zirconia; Sol–gel; Optical properties
Effect of ion nitriding on the crystal structure of 3mol% Y2O3-doped ZrO2 thin-films prepared by the sol–gel method by A.L. Ortiz; A. DÃaz-Parralejo; O. Borrero-López; F. Guiberteau (pp. 6018-6021).
We investigated the effect of ion nitriding on the crystal structure of 3mol% Y2O3-doped ZrO2 (3YSZ) thin-films prepared by the sol–gel method. For this purpose, we used X-ray diffractometry to determine the crystalline phases, the lattice parameters, the crystal sizes, and the lattice microstrains, and glow discharge–optical emission spectroscopy to obtain the depth profiles of the elemental chemical composition. We found that nitrogen atoms substitute oxygen atoms in the 3YSZ crystal, thus leading to the formation of unsaturated-substitutional solid solutions with reduced lattice parameters and Zr0.94Y0.06O1.72N0.17 stoichiometric formula. We also found that ion nitriding does not affect the grain size, but does generate lattice microstrains due to the increase in point defects in the crystalline lattice.
Keywords: PACS; 68.55.Jk; 68.55.L; 81.20.Fw; 61.10.Nz; 61.66.FnZirconia thin-films; Ion nitriding; Sol–gel; X-ray diffractometry; Crystal structure
Interactions of xanthines with activated carbon by R. Navarrete Casas; A. GarcÃa Rodriguez; F. Rey Bueno; A. EspÃnola Lara; C. Valenzuela Calahorro; A. Navarrete Guijosa (pp. 6022-6025).
Because of their pharmaceutical and industrial applications, we have studied the adsorption of xanthine derivates (caffeine and theophylline) by activated carbon. To this end, we examined kinetic, equilibrium and thermodynamic aspects of the process. This paper reports the kinetics results. The experimental results indicate that the process was first order in C and the overall process was assumed to involve a single, reversible adsorption–desorption process obeying a kinetic law postulated by us.
Keywords: PACS; 61.43.Gt; 67.70. +n; 68.08.−p; 68.43.MnAdsorption; Activated carbon; Kinetic constant
Interactions of xanthines with activated carbon by R. Navarrete Casas; A. GarcÃa RodrÃguez; F. Rey Bueno; A. EspÃnola Lara; C. Valenzuela Calahorro; A. Navarrete Guijosa (pp. 6026-6030).
In the present work, we have studied the adsorption of xanthine derivatives by activated carbon sorbents in aqueous solutions. The study comprised both kinetic, equilibrium and thermodynamic aspects. The kinetic results were reported in a previous paper; the equilibrium-related results are discussed here. The two types of carbon used exhibit some differences but the equilibrium isotherms obtained are all of the H-3 type in the classification of Giles. This suggests a high affinity of the sorbents for the sorbates. We also found that the overall adsorption process comprises more than one individual adsorption–desorption process of which one leads to the formation of a “monolayer� and the other to the “precipitation� of the sorbate on the sorbent surface (multilayer adsorption); the amount of sorbate adsorbed in monolayer form was seemingly greater in C-A14.
Keywords: PACS; 61.43.Gt; 67.70.+n; 68.08.–p; 68.43.MnAdsorption; Activated carbon; Kinetic constant
Nitrate removal from groundwater using Amberlite IRN-78: Modelling the system by J. Beltrán de Heredia; J.R. DomÃnguez; Y. Cano; I. Jiménez (pp. 6031-6035).
A laboratory study was conducted to investigate the ability of Amberlite IRN-78 ion-exchange resin for the removal of nitrate from different waters. Aim of the present study is to propose a simple model that simulates the equilibrium data for this ion-exchange system.Tests were performed using two synthetic waters and two groundwaters. In the case of synthetic water, experimental data are reported for the ion-exchange equilibria determination in the absence or presence of chloride. For both groundwater types, “Salvatierra city� and “Miajadas city�, an ion-exchange Langmuir-type model is proposed, taking into account the presence of other competitive anions in solution, specifically chloride, sulphate and bicarbonate. Although the model is very simple, it is consistent with the experimental results. Finally, a general Langmuir-type expressionq=4.36C*C0T+1.58C* is proposed for all water types, synthetic or natural. This equation considers the presence of other anions in solution by means of the parameter C0T.
Keywords: PACS; 66.30 Dn; 68.43 Jk; 82.39 Wj; 82.60 HAmberlite IRN-78; Equilibrium; Groundwater; Ion-exchange; Nitrate
Preparation and characterization of carbons for the retention of halogens in the condenser vacuum system of a thermonuclear plant by S. Román; J.F. González; J. Gañán; E. Sabio; C.M. González-GarcÃa; A. Ramiro; V. Mangut (pp. 6036-6041).
Activated carbons were prepared by air and carbon dioxide activation, from almond tree pruning, with the aim of obtaining carbons that reproduce the textural and mechanical properties of the carbons currently used in the filtering system of the condenser vacuum installation of a Thermonuclear Plant (CNA; Central Nuclear de Almaraz in Caceres, Spain), produced from coconut shell. The variables studied in non-catalytic gasification series with air were the temperature (215–270°C) and the time (1–16h) and the influence of the addition of one catalyst (Co) and the time (1–2h) in catalytic gasification. In the case of activation with CO2, the influence of the temperature (700–950°C) and the time (1–8h) was studied. The resulting carbons were characterized in terms of their BET surface, porosity, and pore size distribution. The N2 adsorption isotherms at 77K for both series showed a type I behaviour, typical of microporous materials. The isotherms showed that with both gasificant agents the temperature rise produced an increase in the carbon porosity. With regards to the activation time, a positive effect on the N2 adsorbed volume on the carbons was observed. The best carbons of each series, as well as the CNA (carbon currently used in the CNA), were characterized by mercury porosimetry and iodine solution adsorption isotherms. The results obtained allowed to state that several of the carbons produced had characteristics similar to the carbon that is target of reproduction (which has SBET of 741m2g−1, Vmi of 0.39cm3g−1 and a iodine retention capacity of 429.3mgg−1): carbon C (gasification with CO2 at 850°C during 1h), with SBET of 523m2g−1, Vmi of 0.33cm3g−1 and a iodine retention capacity of 402.5mgg−1, and carbon D (gasification with CO2 at 900°C during 1h), whose SBET is 672m2g−1, Vmi is 0.28cm3g−1 and has a iodine retention capacity of 345.2mgg−1.
Keywords: PACS; 81.05.RmAir gasification; Carbon dioxide gasification; Activated carbon; Almond pruning; Textural properties
Preparation of activated carbons previously treated with sulfuric acid by E.M. Cuerda-Correa; M.A. DÃaz-DÃez; A. MacÃas-GarcÃa; J. Gañán-Gómez (pp. 6042-6045).
In the present work, cedar wood has been used as raw material for the preparation of activated carbons. The influence of a previous treatment with sulfuric acid on the textural properties of the carbonized and activated samples has been investigated. Finally, the adsorption capacity of para-nitrophenol in aqueous solution has been studied and the corresponding adsorption isotherms have been fitted to Langmuir's equation. The experimental results indicate that the previous dehydration of the raw material with sulfuric acid gives rise to an improvement in the porous texture and adsorption capacity of the activated carbons.
Keywords: PACS; 61.43.Gt; 67.70.+n; 68.08.−pActivated carbon; Liquid phase adsorption
Mercury removal from aqueous solution and flue gas by adsorption on activated carbon fibres by João Valente Nabais; P.J.M. Carrott; M.M.L. Ribeiro Carrott; Marisa Belchior; Dulce Boavida; Tatiana Diall; Ibrahim Gulyurtlu (pp. 6046-6052).
The use of two activated carbon fibres, one laboratorial sample prepared from a commercial acrylic textile fibre and one commercial sample of Kynol®, as prepared/received and modified by reaction with powdered sulfur and H2S gas in order to increase the sulfur content were studied for the removal of mercury from aqueous solution and from flue gases from a fluidized bed combustor. The sulfur introduced ranged from 1 to 6wt.% depending on the method used. The most important parameter for the mercury uptake is the type of sulfur introduced rather than the total amount and it was found that the H2S treatment of ACF leads to samples with the highest mercury uptake, despite the lower sulfur amount introduced. The modified samples by both methods can remove HgCl2 from aqueous solutions at pH 6 within the range 290–710mg/g (ACF) which can be favourably compared with other studies already published. The use of a filter made with an activated carbon fibre modified by powdered sulfur totally removed the mercury species present in the flue gases produced by combustion of fossil fuel.
Keywords: PACS; 81.05.Rm; 81.05.zx; 82.80.Gk; 89.60.EcActivated carbon fibres; Mercury adsorption; Sulfur impregnation; Surface chemistry
Removal of chloridazon by natural and ammonium kerolite samples by M.M. SocÃas-Viciana; J. Tévar de Fez; M.D. Ureña-Amate; E. González-Pradas; M. Fernández-Pérez; F. Flores-Céspedes (pp. 6053-6057).
The adsorption of chloridazon (5-amino-4-chloro-2-phenylpyridazin-3(2H)-one) on natural and ammonium kerolite samples from aqueous solution at 10, 25 and 40°C has been studied by using batch experiments. The experimental data points were fitted to the Langmuir equation in order to calculate the adsorption capacities ( Xm) of the samples; two straight lines were obtained, which indicates that the adsorption process takes place in two different stages. Values for Xm1 (first stage) ranged from 1.1×10−2molkg−1 for natural kerolite at 40°C up to 5.1×10−2molkg−1 for ammonium kerolite at 10°C and the values for Xm2 (second stage) ranged from 9.1×10−2molkg−1 for natural kerolite at 40°C up to 14×10−2molkg−1 for natural kerolite at 10°C. The adsorption experiments showed on the one hand, that the ammonium kerolite is more effective than natural kerolite to adsorb chloridazon in the range of temperature studied and on the other hand, that the lower temperature, the more effective the adsorption of chloridazon on the adsorbents studied.
Keywords: PACS; 81.05.Rm; 82.65.-i; 89.60.+xClay; Pesticide; Adsorption
Characterisation under static and dynamic conditions of commercial activated carbons for their use in wastewater plants by E. Sabio; F. Zamora; J.F. González; C.M. González GarcÃa; S. Román; A. Al-Kassir (pp. 6058-6063).
The use of activated carbon for removing organic contaminants in fixed beds is increasing. This is a dynamic process in which the kinetics plays an important role. The aim of this paper is to get more insight into adsorption of p-nitrophenol (PNP) in activated carbon under equilibrium and dynamic conditions. Five commercial activated carbons were studied. The analysis carried out were PNP adsorption isotherms in aqueous solution at 20°C, N2 at 77K isotherms, FT-IR and PNP adsorption under dynamic conditions. The results indicate that the external porous affinity toward the organic contaminants determines in large extent the adsorbents behaviour under dynamic conditions.
Keywords: PACS; 81.05.Uw; 81.05.Rm; 82.20.-wActivated carbon; Adsorption; Equilibrium
Green chemistry: Efficient epoxides ring-opening with 1-butanol under microwave irradiation by Jesús A. GarcÃa-Vidal; Carlos J. Durán-Valle; Santiago Ferrera-Escudero (pp. 6064-6066).
Two activated carbons treated with mineral acids (HNO3 and sulfonitric mixture) have been tested as acid catalysts in the epoxides (1,2-epoxyhexane and styrene oxide) ring-opening reaction with 1-butanol under microwave (MW) irradiation. The mayor obtained product is that resulting of the alcohol addition to the most substituted carbon in the epoxide ring. The most active catalyst is that treated with sulfonitric mixture. The use of a MW oven allows achieving to the complete conversion of styrene oxide in only 2min.
Keywords: PACS; 82.65Epoxides; Microwaves; Activated carbon; Catalysis
Microwave enhanced synthesis of N-propargyl derivatives of imidazole by Elizabeth Perozo-Rondón; Laureano Costarrosa; Rosa M. MartÃn-Aranda; MarÃa L. Rojas-Cervantes; Miguel A. Vicente-RodrÃguez (pp. 6067-6070).
N-Propargyl imidazole has been synthesized by Knoevenagel condensation of benzaldehyde with propargyl bromide, assisted by microwave irradiation. Two alkaline-promoted clays (Li+- and Cs+-exchanged saponites) have been used as catalysts. The influence of several factors, such as irradiation power, irradiation time and alkaline promoter has been studied. The catalysts were characterized by XRD and chemical analysis. The basicity enhancement is directly connected to the presence of alkaline metal promoters in the saponite structure. In addition, a significant increase in the conversion values has been found when the reaction is activated by microwave irradiation, as compared with thermal activation. The yield to the N-propargyl imidazole shows a maximum for the Cs+-saponite at 750W in only 5min of microwave irradiation. This green and solvent-free procedure can be extended to the preparation of other N-substituted heterocycles, which could serve as precursors in the primary route to pharmaceutical compounds of interest.
Keywords: PACS; 82.65.JBasic clays; Microwave irradiation; Propargylation; Imidazole
Ultrasound accelerated Claisen–Schmidt condensation: A green route to chalcones by V. Calvino; M. Picallo; A.J. López-Peinado; R.M. MartÃn-Aranda; C.J. Durán-Valle (pp. 6071-6074).
Chalcones have been synthesized under sonochemical irradiation by Claisen–Schmidt condensation between benzaldehyde and acetophenone. Two basic activated carbons (Na and Cs-Norit) have been used as catalysts. The effect of the ultrasound activation has been studied. A substantial enhancing effect in the yield was observed when the carbon catalyst was activated under ultrasonic waves. This “green� method (combination of alkaline-doped carbon catalyst and ultrasound waves) has been applied to the synthesis of several chalcones with antibacterial properties achieving, in all cases, excellent activities and selectivities. A comparative study under non-sonic activation has showed that the yields are lower in silent conditions, indicating that the sonication exerts a positive effect on the activity of the catalyst. Cs-doped carbon is presented as the optimum catalyst, giving excellent activity for this type of condensation. Cs-Norit carbon catalyst can compete with the traditional NaOH/EtOH when the reaction is carried out under ultrasounds. The role of solvent in this reaction was studied with ethanol. High conversion was obtained in absence of solvent. The carbons were characterized by thermal analysis, nitrogen adsorption and X-ray photoelectron spectroscopy.
Keywords: PACS; 43.35; 82.65 JvUltrasound activation; Catalysis; Activated carbon; Chalcones; Fine chemicals
Surface and catalytic properties of acid metal–carbons prepared by the sol–gel method by J. Aguado-Serrano; M.L. Rojas-Cervantes; R.M. MartÃn-Aranda; A.J. López-Peinado; V. Gómez-Serrano (pp. 6075-6079).
The sol–gel method has been applied for the synthesis of a series of acid metal–carbon xerogels (with M=V, Cr, Mo and Ni) by polymerisation of resorcinol with formaldehyde in the presence of metallic precursors. A blank sample was also prepared without any metal addition. The xerogels were heated in nitrogen at 1000°C to obtain the pyrolysed products. The samples were characterised by different techniques such as thermal-mass spectrometry analysis, gas physisorption, and mercury porosimetry. In addition, the acid character of the pyrolysed products was tested by the Claisen–Schmidt condensation between benzaldehyde and acetophenone for the formation of chalcones.
Keywords: PACS; 81.20.Fw; 81.05.Uw; 82.65.+rSol–gel; Carbon xerogels; Textural properties; Catalytic properties
Catalysis by basic carbons: Preparation of dihydropyridines by E. Perozo-Rondón; V. Calvino-Casilda; R.M. MartÃn-Aranda; B. Casal; C.J. Durán-Valle; M.L. Rojas-Cervantes (pp. 6080-6083).
The condensation of benzaldehyde and different substituted benzaldehydes, such as 2-nitrobenzaldehyde, 3-nitrobenzaldehyde, and 2,4-dichlorobenzaldehyde, with ethyl cyanoacetate was carried out using two alkaline carbons (Na-Norit and Cs-Norit) as catalysts in the absence of solvent. The reaction products are precursors in the production of 1,4-dihydropyridine derivatives, which have expanding practical applications as pharmaceuticals in the line of calcium channel blockers. High values of activity and selectivity were obtained. The most active carbon (Cs-Norit), which contains basic sites with p Kb=11.2, is more active than pyridine, and less than piperidine. The selectivity to the desired condensation product when using these activated carbons is, at least, as high as in the case of the homogeneous catalyst. This “green� and “clean� method (alkaline doped carbon catalyst in the absence of solvent) can be extended to the preparation of other intermediates with medical applications.
Keywords: PACS; 82.65JvCatalysis; Activated carbon; Dihydropyridines; Fine chemicals
Catalytic supports on the base of activated anthracites and synthetic carbons by S.B. Lyubchik; L.P. Tikhonova; Yu.A. Tarasenko; O.L. Galushko; L.Ya. Galushko; I.M. Fonseca (pp. 6084-6088).
Selective adsorption of platinum group metals (PMG) on activated carbons from a multi-component model and technological solutions was proposed for the preparation of heterogeneous-supported catalysts. Activated natural anthracites and a nitrogen-containing synthetic carbon are considered as carriers for Pd-supported catalysts. Their catalytic activity was studied in the Pd-catalyzed reactions of hydrogen peroxide decomposition and chloride ions oxidation by manganese(III). On the base of the obtained results, novel high sensitive analytical methods both for direct determination of supported-metal quantity and palladium oxidation states on the surface of spent adsorbents are suggested.
Keywords: PACS; 82.65.+r; 82.45. Jn; 82.80. PvCarbon; Adsorption; Supported catalyst
Alkylation of imidazole under ultrasound irradiation over alkaline carbons by L. Costarrosa; V. Calvino-Casilda; S. Ferrera-Escudero; C.J. Durán-Valle; R.M. MartÃn-Aranda (pp. 6089-6092).
N-Alkyl-imidazole has been synthesized by sonochemical irradiation of imidazole and 1-bromobutane using alkaline-promoted carbons (exchanged with the binary combinations of Na, K and Cs). The catalysts were characterized by X-ray photoelectron spectroscopy, thermal analysis and N2 adsorption isotherms. Under the experimental conditions, N-alkyl-imidazoles can be prepared with a high activity and selectivity. It is observed that imidazole conversion increases in parallel with increasing the basicity of the catalyst. The influence of the alkaline promoter, the reaction temperature, and the amount of catalyst on the catalytic activity has been studied. For comparison, the alkylation of imidazole has also been performed in a batch reactor system under thermal activation.
Keywords: PACS; 82.65; 81.05.Uw; 61.43.GtAlkaline carbons; Ultrasound irradiation; Imidazole; Alkylation
Mediated and non-mediated electrochemical oxidation of isopropanol by C.A.C. Sequeira; D.M.F. Santos; P.S.D. Brito (pp. 6093-6096).
Kinetic studies of the electrochemical generation of Ag(II) and Co(III) ions and the catalytic oxidation of isopropanol in acidic media are presented. Its mediated and non-mediated electrooxidation up to carbon dioxide is considered.
Keywords: PACS; 82.45.Hk; 82.45JnIsopropanol destruction; Carbon dioxide; Acetic acid; Organic electrooxidation; Electron transfer mediators
Geometrical relationship between elemental composition and molecular size in carbonaceous materials by Carlos J. Durán-Valle (pp. 6097-6101).
Thermal treatment of carbonaceous materials shows two related phenomena: the graphene molecule (or carbon layer) increases in size and its carbon content also increases. In this work, a simple relationship between both effects was deducted, based on the structure geometry of carbonaceous materials. This relationship provides an approach to the mean size of graphene molecules which is more accurate than that acquired through different experimental techniques.
Keywords: PACS; 36.20.Hb; 81.05.Uw; 68.43.FgChemical structure; Carbonaceous materials
Determination of the fractal dimension of activated carbons: Two alternative methods by E.M. Cuerda-Correa; M.A. DÃaz-DÃez; A. MacÃas-GarcÃa; J. Gañán-Gómez (pp. 6102-6105).
The fractal dimension of three samples of activated carbon has been determined according to two different experimental methods. The first method is based on the vaporization of gas species from the sample into a CO2 flow up to a constant temperature of 573K, and the adsorption of CO2 from the CO2 flow onto the surface of the sample under cooling. The second method is based on the application of the equation proposed by Frankel, Halsey and Hill. The degree of concordance between both methods is excellent.
Keywords: PACS; 61.43.Gt; 61.43.HvActivated carbon; Fractal dimension; Thermogravimetry