Adsorption Properties Of Carbons Research Articles

Production of Activated Carbon from Carbonaceous Agricultural Waste Material: Coconut Fibres

Activated carbon was produced from Cocos nucifera (coconut) fibers by carbonization and activation processes. The sample was first pretreated before carbonization and activation processes at 450°C and 700°C respectively in an electric furnace. Chemical activation using Potassium hydroxide (KOH) 4:1 (weight basis) was carried out to increase the activated carbon adsorption properties. The element contained in the sample was analyzed using the Energy Dispersive Spectroscopy (EDS) while the surface morphological composition was determined by Scanning Electron Microscope (SEM) and the chemical bonds present in the sample was characterized using Fourier transform infrared reflection (FT-IR). From the research carried out, the results show that activated carbon produced from coconut fibers would be useful and effective for adsorbent purposes, considering its large pores.

Carbon sorbents based on oxidized Kuznetsk Basin coal

Some physicochemical properties of carbon adsorbents produced by chemical activation with alkali are determined: specifically, their total ash content, the content of water-soluble ash, the total iron content (recalculated for Fe3+), and the content of water-soluble iron compounds. Their content of water-soluble ash and the total iron content are minimal; no water-soluble iron compounds are observed in the sorbents. However, the total ash content in the sorbents is impermissibly high. With increase in potassium content in the initial content, the total ash content of the sorbents is reduced to 16.5%.

Evidence for the effect of the cooling down step on activated carbon adsorption properties

Two activated carbons are prepared by chemical activation of olive residue using zinc chloride. The first sample is cooled down slowly after the carbonization in the furnace under a flow of nitrogen, while the second is directly removed from the furnace just after the carbonization and put at ambient temperature and pressure. The textural and structural characteristics of the two samples are determined by nitrogen adsorption at −196 °C and X-ray diffraction (XRD). The oxygen functional groups are characterized via Boehm's titration and Fourier transformed infrared spectroscopy (FTIR). The cooling down step at different rates is followed by thermogravimetry–mass spectroscopy analysis (TG/MS). Slow cooling down of the sample after carbonization leads to CO2, O2, and CO consumption creating more active sites, which are responsible of the formation of surface oxygen groups, and especially carboxylic groups. The latter dramatically enhance water vapor adsorption at low relative humidity. The cyclohexane adsorption on activated carbons, which is carried out by thermogravimetric analysis (TGA), shows that the cooling down step has an effect on both the initial rate of adsorption and the adsorption uptake at equilibrium.

Effect of nitrogen- and sulfur-containing modifying additives on porous structure and sorption properties of carbon adsorbents

Modified nitrogen- and sulfur-containing sorbent were produced on the basis of industrial activated carbons by their thermal treatment with preliminary impregnation with thiourea and ammonium rhodanide. It was found tat the modification affects the porous structure, surface physicochemical properties, and sorption characteristics of carbon sorbents. The increase in the protection duration of thiourea-modified carbons by 67%, compared with the starting carbons, at a relative air humidity of 70% is illustrated.

Nanoscale carbon materials from hydrocarbons pyrolysis: Structure, chemical behavior, utilisation for non-aqueous supercapacitors

This work systematically studies adsorption properties of carbon nanomaterials that are synthesized through hydrocarbons that is a powerful technique to fabricate different kinds of carbon materials, e.g., nanotubes, nanoshells, onions, including nitrogen substituted. The adsorption properties of the as-synthesized carbons are achieved by low temperature nitrogen adsorption and organic vapors sorption. Heptane, acetonitrile, water, ethanol, benzene and 1-methylimidazole, which are of great importance for development of supercapacitors, are used as substrates. It is discovered that while nitrogen adsorption reveals a high specific surface area, this parameter for most of organic compounds is rather small depending not only on the size of its molecule but also on chemical interactions for a pair adsorbent–adsorbate. The experimental values of heat of adsorption for carbon and N-substituted structures, when Coulomb cross-coupling of nitrogen atoms in adsorbent and adsorbate takes place, confirms this supposition.

Study of sorption and bactericidal properties of carbon adsorbents and fullerenes

Disinfection properties of activated carbons and C60 and C70 fullerenes, as introduced into the structure of the activated carbon and in the form of aqueous dispersions, are studied. The most efficient method was determined for the modification of activated carbon with fullerenes. It was shown that the presence of a modifier intensifies suppression of microorganism growth in an aqueous medium without reducing its absorption characteristics.

Large surface area sucrose-based carbons via template-assisted routes: Preparation, microstructure, and hydrogen adsorption properties

We report the preparation of sucrose-based nanoporous carbons via template-assisted routes using zeolite USY as the hard-template. Sulfuric acid-pretreated sucrose solution is polymerized and carbonized via adjusting the mass ratios of zeolite over sucrose and temperatures. Large surface area carbons with wide micropore size, developed mesoporosity and moderate storage capacity were obtained. We find that preparation parameters have great effects on the pore structure of carbons. Total pore volume of carbons develops with an increase of carbonization temperature and the presence of zeolite in carbonization processes can effectively enlarge the surface area and pore volume. However, the morphology of carbons is not transferred from zeolites, and micropore in the carbons is almost wholly from the sucrose precursor itself. The hydrogen adsorption properties of carbons at 77K and 20bar are further investigated in this work. Carbon with a surface area of 1200m2/g exhibits a hydrogen storage capacity of up to 3.65wt% at 77K and 20bar, and the hydrogen capacities at higher pressures are found to be much more correlated with surface area and micropore volume of carbons.

Comparisons of porous, surface chemistry and adsorption properties of carbon derived from Enteromorpha prolifera activated by H4P2O7 and KOH

Enteromorpha prolifera based-activated carbons were prepared using chemical activation by H4P2O7 (PAC) and KOH (KAC) and applied as a potential adsorbent for the adsorption of acid scarlet (GR). N2 adsorption–desorption isotherms, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Boehm titration were used to compare the porous structure, surface chemical property and adsorption behavior of carbon. KAC presented higher surface area (3500m2/g) and larger total pore volume (2.872cm3/g). To account for the adsorption mechanisms, the kinetic models, including pseudo-first-order model, pseudo-second-order model, intraparticle diffusion model and Boyd model were introduced. The Langmuir isotherm model was better fitted with the equilibrium data than Freundlich and Dubinin–Radushkevich models. The maximum adsorption capacities of GR onto KAC and PAC were 2500mg/g and 454mg/g, respectively. The physical adsorption and ion-exchange were the dominating adsorption mechanism.

Comparison on Pore Development of Activated Carbon Produced from Scrap Tire by Hydrochloric Acid and Sulfuric Acid

Two activated carbons employing Scrap Tire as precursor were produced by using two different activating agents, HCl and H2SO4 (fixed impregnation ratio 1:1). Both of activated carbons were allowed by single-step to get difference carbonized at 500, 600 and 700°C in a muffle furnace for 1 h. Activated carbons differed with the physical structure, chemical and adsorption properties which were derived from Scanning Electron Microscope, and N2 adsorption/desorption isotherms. Batched sorption studies were performed to compare the iodine and methylene blue adsorption properties of two carbons. The carbon materials obtained from sulfuric acid activation of 500°C has BET surface area as high as 1066.70 m2/g, Methylene blue adsorption and Iodine number of 288.90 and 590.50 mg/g, respectively. The surface area and adsorption properties of carbon produced using sulfuric acid activation were higher than that produced using hydrochloric acid activation. The results suggest the feasibility of the process from the point of view of both porous texture and adsorption yield.

Carbon Dioxide Adsorption Properties in Ion-exchanged Zeolites Rho

Abstract The carbon dioxide adsorption properties of zeolite Rho materials, containing various exchangeable cations have been investigated. All carbon dioxide adsorption properties were measured at a temperature of 25 °C over a pressure range of 0–100 kPa. The results show that the carbon adsorption properties are dependent on the cations present. The highest amount of CO2 absorbed, measured at 4.0 mmol g−1, was obtained for a proton-exchanged zeolite Rho (HRho), which was prepared by the calcination of NH4+-exchanged zeolite Rho at 350 °C.

First Molecular Dynamics simulation insight into the mechanism of organics adsorption from aqueous solutions on microporous carbons

The results of 84 MD simulations showing the influence of porosity and carbon surface oxidation on adsorption of three organic compounds from aqueous solutions on carbons are reported. Based on a model of ‘soft’ activated carbon, three carbon structures with gradually changed microporosity were created. Next, different number of surface oxygen groups was introduced. We observe quantitative agreement between simulation and experiment i.e. the decrease in adsorption from benzene down to paracetamol. Simulation results clearly demonstrate that the balance between porosity and carbon surface chemical composition in organics adsorption on carbons, and the pore blocking determine adsorption properties of carbons.

Sulfur fixation on bagasse activated carbon by chemical treatment and its effect on acid dye adsorption

Heteroatoms are known to introduce specific surface functionalities that can enhance the adsorption properties of carbons. Sulfur fixation on bagasse-activated carbon was conducted by a low temperature chemical treatment with sulfuric acid followed by physical activation with CO2 at 900 °C. The effect of sulfur fixation on the surface chemical properties of bagasse-activated carbons were investigated and on their subsequent acid dye removal (CIBA AB80) behavior. Surface chemical development were examined and followed using Fourier transform infrared spectroscopy (FTIR), heteroatom analysis and carbon surface acidity. Functional group stability with thermal treatment was also investigated. The textural properties of the activated carbons were characterized by nitrogen adsorption. Chemical pre-treatment and gasification was able to fix up to 0.2 wt% of sulfur on the activated carbon. Although the sulfur fixed by chemical treatment is low, this method introduced several advantages in comparison to fixation by thermal methods. The chemical method did not interfere with the textural development of the carbon, as found in thermal methods. In addition, the surface chemistry generated by these levels of sulfur groups was sufficient to increase the uptake of acid blue dyes by more than 700% based on adsorption capacities normalized by the surface area of the carbon.

Biological activation of carbon filters

To prepare biological activated carbon (BAC), raw surface water was circulated through granular activated carbon (GAC) beds. Biological activity of carbon filters was initiated after about 6 months of filter operation and was confirmed by two methods: measurement of the amount of biomass attached to the carbon and by the fluorescein diacetate (FDA) test. The effect of carbon prewashing on WG-12 carbon properties was also studied. For this purpose, the nitrogen adsorption isotherms at 77 K and Fourier transform-infrared (FT-IR) spectra analyses were performed. Moreover, iodine number, decolorizing power and adsorption properties of carbon in relation to phenol were studied. Analysis of the results revealed that after WG-12 carbon prewashing its BET surface increased a little, the pH value of the carbon water extract decreased from 11.0 to 9.4, decolorizing power remained at the same level, and the iodine number and phenol adsorption rate increased. In preliminary studies of the ozonation-biofiltration process, a model phenol solution with concentration of approximately 10 mg/l was applied. During the ozonation process a dose of 1.64 mg O 3/mg TOC (total organic carbon) was employed and the contact time was 5 min. Four empty bed contact times (EBCTs) in the range of 2.4–24.0 min were used in the biofiltration experiment. The effectiveness of purification was measured by the following parameters: chemical oxygen demand (COD Mn), TOC, phenol concentration and UV 254-absorbance. The parameters were found to decrease with EBCT.

Effect of Surface Area, Micropores, Secondary Micropores, and Mesopores Volumes of Activated Carbons on Reactive Dyes Adsorption from Solution

The ability of six activated carbons to remove the problematic reactive dyes from textile solution was correlated to their physical characteristics. Specific surface area, micro‐, meso‐, and total volume were established using the Braunnaur, Emmet, and Teller (BET) and Dubinin–Radushkevich (D–R) equations. According to the N2 adsorption method, five of the carbons exhibited type I adsorption characteristics with one carbon showing a type III isotherm. Activated carbon Filtrasorb 400 outperformed the carbons under investigation by showing the presence of advanced primary and secondary micropores. A poor linear correlation between carbon surface area and performance was found. Adsorption properties of carbons were better related to their pore volumes. It was found that secondary micropore volume of carbons (0.8 nm < D secondary micropore < 2 nm) has an important role in reactive dyes adsorption.

Comparisons of porous and adsorption properties of carbons activated by steam and KOH

In this work, fir woods and pistachio shells were used as source materials to prepare porous carbons, which were activated by physical (steam) and chemical (KOH) methods. Pore properties of these activated carbons including the BET surface area, pore volume, pore size distribution, and pore diameter were first characterized by a t-plot method based on N 2 adsorption isotherms. Highly porous activated carbons with BET surface area up to 1009–1096 m 2/g were obtained. The steam and KOH activation methods produced carbons with mesopore content in the range 9–15 and 33–49%, respectively. The adsorption equilibria and kinetics of tannic acid, methylene blue, 4-chlorophenol, and phenol from water on such carbons at 30 °C were then investigated to check their chemical characteristics. The Freundlich equation gave a better fit to all adsorption isotherms than the Langmuir equation. On the other hand, the intraparticle diffusion model could best follow all adsorption processes. In comparison with KOH-activated carbons, it was shown that the rate of external surface adsorption with steam-activated carbons was significantly higher but the rate of intraparticle diffusion was much lower.

Comparison of chemical and physical properties of carbon blacks for sampling and analysis of environmental pollutants

Some of the most commonly employed carbon blacks (Carbograph 1,2,4,5 from Lara and Carbopack X form Supelco), were evaluated by the BET surface characterization method for pore size distribution, porosity and specific surface. This information is often incomplete as furnished by manufacturers and is needed for a deeper understanding of carbon adsorption properties in chromatography.

Realistic molecular models for saccharose-based carbons

We used a simulation protocol based on reverse Monte Carlo that we had developed in a previous work to build models for three carbons produced by the pyrolysis of saccharose and subsequent heat treatment at three different temperatures. In order to characterize the resulting models, we calculated the radial distribution function and the pore size distribution of the three structures. From this analysis, we found that the size of the graphene layers increases with the treatment temperature and that the carbons treated at higher temperatures present longer-range correlations. The short-range structural properties are in excellent agreement with HRTEM image analysis results. We performed grand canonical Monte Carlo (GCMC) simulations of nitrogen at 77 K in the resulting structural models to show how our models can be used to predict the effects of heterogeneity on the adsorption properties of carbons.

Preferential adsorption of fluorescing fulvic and humic acid components on activated carbon using flow field-flow fractionation analysis.

Activated carbon treatment of drinking water is used to remove natural organic matter (NOM) precursors that lead to the formation of disinfection byproducts. The innate hydrophobic nature and macromolecular size of NOM render it amenable to sorption by activated carbon. Batch equilibrium and minicolumn breakthrough adsorption studies were performed using granular activated carbon to treat NOM-contaminated water. Ultraviolet (UV) absorption spectroscopy and flow field-flow fractionation analysis using tandem diode-array and fluorescence detectors were used to monitor the activated carbon sorption of NOM. Using these techniques, it was possible to study activated carbon adsorption properties of UV absorbing, fluorescing and nonfluorescing, polyelectrolytic macromolecules fractionated from the total macromolecular and nonmacromolecular composition of NOM. Adsorption isotherms were constructed at pH 6 and pH 9. Data were described by the traditional and modified Freundlich models. Activated carbon capacity and adsorbability were compared among fractionated molecular subsets of fulvic and humic acids. Preferential adsorption (or adsorptive fractionation) of polyelectrolytic, fluorescing fulvic and humic macromolecules on activated carbon was observed. The significance of observing preferential adsorption on activated carbon of fluorescing macromolecular components relative to nonfluorescing components is that this phenomenon changes the composition of dissolved organic matter remaining in equilibrium in the aqueous phase relative to the composition that existed in the aqueous phase prior to adsorption. Likewise, it changes the composition of dissolved organic matter remaining in equilibrium in the aqueous phase relative to the adsorbed phase. This research increases our understanding of NOM interactions with activated carbon which may lead to improved methods of potable water production.

Prediction of the micropore structure parameters and adsorption properties of activated carbons

A regularity govering variations of volume and linear size of micropores in carbon adsorbents during their vapor-gas activation was found. A parameter was proposed that characterizes the degree of development of the micropore system in activating carbons and an initial carbonized material. The parameter is defined as the number (or surface area) of micropores in the volume unit of the micropore zones. This parameter allows one to rationalize the choice of carbonized materials for the preparation of activated carbons with specified adsorption properties and to establish the range of activation beyond which the structure of the micropores loses stability. Furthermore, the parameter serves to predict how activation affects micropore structure parameters and adsorption properties of carbons. This in turn indicates the optimal degrees of microporosity of carbons needed to attain required adsorption properties.

00/02276 Synthesis and properties of carbon adsorbents form brown coals

00/02276 Synthesis and properties of carbon adsorbents form brown coals