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Cellulose based activated carbon cloth has been oxidized by air, nitric acid, hydrogen peroxide and iron nitrate cristallohydrate melt treatments. Thermogravimetric analysis, selective neutralization, X-ray photoelectron spectroscopy and electrical resistance measurements have been applied to characterize the products. The amount and type of oxygen surface groups have been determined for the different...
Thermal desorption, acid-base depletion, mass titration and calorimetric measurements on a series of porous BPL carbons are interpreted as indicating that acid surface sites are oxygen based while basic sites are associated with the carbon itself. Both acidic and basic sites were found on all carbons whether they were heat treated to 900°C in nitrogen or oxidized, chemically with nitric acid or electrochemically...
The adsorption of various heavy transition metal compounds was studied using two different flow adsorption methodologies: flow injection adsorption and flow equilibrium adsorption analyses. In both cases the determinations were made of the heats of adsorption and the amounts of adsorption from dilute aqueous solutions.The carbons used for the work included two different types of graphitised carbon...
Previous studies showed that activated carbons exhibit significantly different behavior for the removal of phenolic compounds in the presence and absence of molecular oxygen. Increase in capacity under oxic conditions (presence of oxygen) as high as 2.5 fold was observed for 2-methylphenol adsorption on a bituminous coal-based activated carbon. The present study was initiated to evaluate some of...
Two activated carbons with different degree of activation, 20 and 46% burn-off, were obtained from olive stones by steam activation. These samples were oxidized with a concentrated solution of (NH 4 ) 2 S 2 O 8 for different periods of time, up to a maximum of 24 hours, studying the variation in surface area, pore texture and surface chemistry during the oxidation...
High strength, PAN-based carbon fibers were treated with oxygen plasmas and isobutylene plasmas. The effects of exposure time, plasma power and gas pressure on the quantity of acidic functional groups introduced onto the fiber surfaces were examined. NaOH uptake measurements provided a quantitative determination of the surface acidic functions. Plasma treatments were able to generate a three-to-five-fold...
An activated carbon obtained from olive stones and with very low ash content (0.10%) was treated with either HCl, HF or HNO 3 . The changes in surface area and porosity resulting from the acid treatments were studied by N 2 and CO 2 adsorption at 77 and 273 K, respectively and by mercury porosimetry. The changes in surface chemistry were studied by temperature-programmed...
Pitch-based activated carbon fiber (ACF) supporting silver (ACF (Ag)) was prepared by pre-oxidization, carbonization, activation, immersion and decomposition processes. The structures, surface photographs and functional groups of the ACF and the ACF (Ag) were investigated. The ACF exhibited increased oxygen-containing functional groups and decreased BET specific surface areas after supporting silver...
Physical and chemical properties of carbons previously used for air purification in sewage plants are investigated. The chosen samples are characterized by pH values (estimated according to ASTM D 3838) between 2 and 10. Their H 2 S breakthrough capacities are less than 0.01 g of H 2 S/cm 3 of carbon. The surface chemistry and porous structure are determined using sorption...
The increasing importance of carbon materials in catalytic processes is analyzed in terms of the most important characteristics of these materials when acting as catalysts or catalyst supports. Thus, surface area, porosity, chemical inertness and oxygen surface groups affect not only the preparation, but also influence the resistance to sintering and the catalytic activity and selectivity of the...
In a previous paper [Carbon, 1997, 35, 83] it was shown for a series of activated carbons with acidic behavior that surface characterization with a continuous pK distribution was possible based on potentiometric titration provided that several experimental precautions were taken during data collection. The number and strength of acid functionalities calculated from the proton affinity distribution...
The formation of the surface functional group during oxygen reduction on a platinum-dispersed carbon (Pt/C) electrode has been investigated in an 85% H 3 PO 4 solution at 145°C with concurrent blowings of a mixture of oxygen and nitrogen by using Fourier transform infrared (FTIR) spectroscopy supplemented by AC-impedance spectroscopy. AC-impedance spectra indicated that the reactivity...
This paper deals with the radiochemical titration of carbon fibres (ex-PAN AS4 from Hercules) with 14 C labelled succinic anhydride in view of quantifying the reactivity between anhydride groups and the functionalities (amine, hydroxyl, etc.) of C fibres. A transesterification reaction due to the chemical labelling procedure is observed and is confirmed by time-of-flight secondary ion...
In order to approve the possibility for side reactions the catalytic activity of carbon absorbents intended for adsorgants and hemosorbents in the process of the hydrolysis of soya bean oil under conditions similar to those in the human body is investigated.It was established that the oxidized carbons with acid reaction accelerate the hydrolysis of the oil. Activated carbons with basic reaction have...
The effect of a previous oxidation treatment of the carbonaceous support on the catalytic behavior of platinum in the gas phase hydrogenation of crotonaldehyde (trans-2-butenal) over Pt/carbon black catalysts has been analyzed. Two heat-treated carbon blacks, one of them subjected to an oxidizing treatment with hydrogen peroxide, have been used as supports for platinum, which was introduced using...
Chars were prepared by heating rockrose (Cistus ladaniferus L) under dynamic and isothermal conditions between 200 and 1000 o C in nitrogen. Several techniques including chemical analysis, Fourier transform infrared (FTIR) spectroscopy, molecular simulation, density measurements, mercury porosimetry and adsorption were used to study the chemical structure and pore structure. The chars prepared...
In an investigation of the reaction of chlorine with carbon surfaces and the relationship between chlorine fixation and other heteroatoms (such as oxygen and hydrogen) on the surface, various porous carbons have been treated with gaseous chlorine. The diversity of the carbons was depicted not only by precursor material (coal, coconut shell, sugar, polymer) and porosity, but also by pretreatment which...
A high surface area activated carbon, graphitized carbon fibers and synthetic diamond powder were characterized by X-ray diffraction, temperature-programmed desorption and diffuse reflectance infrared (IR) spectroscopy (DRIFTS). The activated carbon was analyzed as received as well as after either a nitric acid treatment to introduce oxygen functional groups on its surface or a high temperature treatment...
The effects of acidic oxidation and carbonisation temperature on the pore structures of chars from coal reject were studied in this work. The oxidation reactions were carried out by refluxing coal reject samples in nitric acid solutions under various conditions. Treated and untreated samples were then carbonised at 600°C. Acid concentration, residence time and reaction temperature were varied to investigate...
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