Theoretical and Experimental Study on the Adsorption and Desorption of Methane by Granular Activated Carbon at 25 ℃

A theoretical and experimental study was conducted to accurately determine the amount of adsorption and desorption of methane by various Granular Activated Carbon(GAC)under different physical conditions.To carry out the experiments,the volumetric method was used up to 500 psia at constant temperature of 25℃.In these experiments,adsorption as well as desorption capacities of four different GAC in the adsorption of methane,the major constituent of natural gas,at various equilibrium pressures and a constant temperature were studied.Also,various adsorption isotherm models were used to model the experimental data collected from the experiments.The accuracy of the results obtained from the adsorption isotherm models was compared and the values for the regressed parameters were reported.The results shows that the physical characteristics of activated carbons such as BET surface area,micropore volume,packing density,and pore size distribution play an important role in the amount of methane to be adsorbed and desorbed.     

Adsorption of Carbon Dioxide on Activated Carbon

The adsorption of CO2 on a raw activated carbon A and three modified activated carbon samples B, C, and D at temperatures ranging from 303 to 333 K and the thermodynamics of adsorption have been investigated using a vacuum adsorption apparatus in order to obtain more information about the effect of CO2 on removal of organic sulfur-containing compounds in industrial gases. The active ingredients impregnated in the carbon samples show significant influence on the adsorption for CO2 and its volumes adsorbed on modified carbon samples B, C, and D are all larger than that on the raw carbon sample A. On the other hand, the physical parameters such as surface area, pore volume, and micropore volume of carbon samples show no influence on the adsorbed amount of CO2. The Dubinin-Radushkevich (D-R) equation was the best model for fitting the adsorption data on carbon samples A and B, while the Preundlich equation was the best fit for the adsorption on carbon samples C and D. The isosteric heats of adsorption on carbon samples A, B, C, and D derived from the adsorption isotherms using the Clapeyron equation decreased slightly increasing surface loading. The heat of adsorption lay between 10.5 and 28.4 kJ/mol, with the carbon sample D having the highest value at all surface coverages that were studied. The observed entropy change associated with the adsorption for the carbon samples A, B, and C (above the surface coverage of 7 ml/g) was lower than the theoretical value for mobile adsorption. However, it was higher than the theoretical value for mobile adsorption but lower than the theoretical value for localized adsorption for carbon sample D.     

Single and Mixed Gas Adsorption Equilibria of Carbon Dioxide/Methane on Activated Carbon

Single gas adsorption isotherms of methane and carbon dioxide on micro-porous Norit RB1 activated carbon were determined in a gravimetric analyser in the temperature range of 292 to 349 K and pressures to 0.8 Mpa. Furthermore binary isotherms of carbon dioxide and methane mixtures were determined at 292 K and pressures up to 0.65 MPa. Adsorbed phase compositions were determined from the gravimetric data by the rigorous thermodynamic method of Van Ness.These experimental binary equilibrium data were compared with equilibrium data calculated by the Ideal Adsorbed Solution (IAS) model. Only moderate agreement could be obtained.Finally, activity coefficients, accounting for the non-ideality of the adsorbate mixture, were calculated from the experimental data. The Wilson equation, derived for bulk solutions, was fitted on these activity data and the Wilson interaction parameters were determined. The Wilson equation proved to correlate the experimental data reasonably. However, the Wilson interaction parameters are not only completely different from those found for bulk solutions, but also the physical interpretation of these parameter values is completely lacking.It is concluded that new solution models should be developed encompassing both non-ideal solution behaviour and surface heterogeneity.     

High Pressure Adsorption Data of Methane, Nitrogen, Carbon Dioxide and their Binary and Ternary Mixtures on Activated Carbon

Adsorption equilibria of the gases CH₄, N₂, and CO₂ and their binary and ternary mixtures on activated carbon Norit R1 Extra have been measured in the pressure range 0 P 6 MPa at T = 298 K. Pure gas adsorption equilibria were measured gravimetrically. Coadsorption data of the three binary mixtures CH₄/N₂, CH₄/CO₂, and CO₂/N₂ were obtained by the volume-gravimetric method. Isotherms of five ternary mixtures CH₄/CO₂/N₂ were measured using the volumetric-chromatographic method. First, we present in a short overview the method and procedure of measurement. In a second part, the measured data of pressures, surface excess amounts adsorbed and absolute amounts adsorbed are presented and analyzed. In the last part of the paper the resulting pure gas adsorption data are correlated using a generalized dual-site Langmuir isotherm. Mixture adsorption can be predicted by this model using only pure component parameters with fair accuracy. Results are presented and discussed in several tables and figures.     

Adsorption Study of Methane on Activated Meso-carbon Microbeads by Density Functional Theory

A combined method of density functional theory (DFT) and statistics integral equation (SIE) for the determination of the pore size distribution (PSD) is developed based on the experimental adsorption data of nitrogen on activated mesocarbon microbead (AMCMB) at 77K. The pores of AMCMB are described as slit-shaped with PSD.Based on the PSD, methane adsorption and phase behavior are studied by the DFT method. Both nitrogen and methane molecules are modeled as Lennard-Jones spherical molecules, and the well-known Steele‘s 10-4-3 potential is used to represent the interaction between the fluid molecule and the solid wall. In order to test the combined method and the PSD model, the Intelligent Gravimetric Analyzer (IGA-003) was used to measure the adsorption of methane on the AMCMB. The DFT results are in good agreement with the experimental data. Based on these facts,we predict the adsorption amount of methane, which can reach 32.3ω at 299K and 4 MPa. The results indicate that the AMCMBs are a good candidate for adsorptive storage of methane and natural gas. In addition, the capillary condensation and hysteresis phenomenon of methane are also observed at 74.05K.     

改性活性炭对土壤镉的吸附性影响

目的研究3种改性活性炭对菜地、河流底泥、荷花底泥镉吸附性的影响。方法对活性炭进行酸改性、碱改性和氧化改性,采用双硫腙分光光度法测定镉含量。结果对实验土样,最佳活性炭添加量为0.025 g/g。随着初始镉含量的升高,土壤对镉的吸附量不断增大。结论 3种改性活性炭相比普通活性炭对湿地土壤的镉吸附量均有不同程度的提升,荷花底泥中,酸性、氧化改性活性炭相比普通活性炭,吸附效果提高7.7%,8.3%,吸附效果提升显著。     

A Study of the Influence of Hydrophobicity of Activated Carbon on the Adsorption Equilibrium of Aromatics in Non-Aqueous Media

The effect of hydrophobicity on the adsorption of aromatics on metal-free activated carbons was studied. Adsorption isotherms for phenol, aniline, benzene, and xylene were generated in cyclohexane and heptane media, using seven carbons with different surface heterogeneity. The hydrophobicity of these carbons was probed using flow microcalorimetry (FMC). Surface polarity and solvent and adsorbate hydrophobicity were found to influence the adsorption capacity. For adsorbates that do not form hydrogen bonds with oxygen on the carbon surface, higher surface acidity lowers adsorption capacity due to increased polarity. In contrast, for adsorbates that can form hydrogen bonds with surface oxygen, the capacity is enhanced at higher surface acidities. A higher solvent hydrophobicity was found to decrease capacity for all the aromatic adsorbates studied, except at high surface polarity, where the effect of the solvent was found to be minimal.     

Competitive Adsorption of Chloroform and Iron Ion onto Activated Carbon Fiber

Chloroform in tap water has been a significant problem because it may be a carcinogenic substituent. Iron ion exists in tap water because of dissolution from iron water pipes. Iron ions in tap water cause discoloration and a bad odor. The isotherms of chloroform and iron ion adsorption onto activated carbon fibers in a single solution (chloroform or iron ion) and in a binary mixture solution (chloroform and iron ion) were investigated to estimate the competitiveness between chloroform and iron ions. The amount of adsorbed iron ions increased with increasing pore volume of the activated carbon fibers, while that of chloroform decreased. The amount of chloroform adsorbed onto the activated carbon fibers in the binary mixture solution was greater than that in the single solution. These results indicate that the adsorption of chloroform and iron ion onto activated carbon fibers could be competitive.     

活性炭的zeta电位对各种染料吸附的影响3．活性炭对阴离子染料洋红的吸附

测定了在不同pH下活性炭吸附阴离子染料洋红的变化规律,发现活性炭表面的电位(ζ对洋红吸附量的影响起着重要作用.当溶液pH小于活性炭的零电位pH(pHZPC=6.2)时,活性炭表面带正电,它对洋红阴离子具有静电引力,而当pH增大时活性炭的ζ电位下降,静电引力减弱,使得吸附量下降;另一方面由于洋红变色(pH3.5橙色,～pH6.8玫瑰红)后,洋红的溶解度增大,所以导致吸附量很快下降并趋于零.通过活性炭对洋红在不同pH下的吸附动力学和吸附热力学参数的估算,进一步揭示了活性炭在不同pH下对洋红的吸附机理.     

Optimization of the Conditions for the Cr (III) Adsorption on Activated Carbon

In order to understand the patterns of the adsorption equilibrium of Cr (III) on activated carbon, the adsorption process was studied by two different ways: classical batch experiments on commercial Norit and Merck activated carbons and their oxidized forms in a wide range of pHs; and extended time-based tests at the same pH values on the same adsorbents. This approach allowed us to understand the role of texture, chemical carbon surface functionality and experimental conditions (initial pH of the solution, contact time and adsorbate/adsorbent ratio) on the effectiveness of Cr (III) removal. The adsorption process of Cr (III) at (24 ± 1^∘C) on Merck and Norit activated carbons and their oxidized forms were studied at pH values between 1.5 and 5 (either adjusted or buffered). Chromium concentration was fixed at 200 ppm. The carbon loading ranged from 1.2 to 20 g/l. The carbon/Cr (III) solution contact time was varied from 0.5–1 month to 5 months, to ensure that the saturation of the carbon level was reached. According to the data obtained, the presence of carboxylic groups on carbon surface seems to enhance Cr (III) uptake at initial pH of the solution in the range between 2 and 4. Depending on the nature of the adsorbent surface chemistry, the contact time to reach equilibrium may range from 3 to 5 months. There is an optimum carbon loading which limits the Cr (III) uptake/removal at given pH value. In order to understand the adsorption process, an ion exchange, surface complex and surface precipitation were considered. This paper was presented in the 5th Brazilian Meeting on Adsorption, held at Natal, Brazil, 18-21 July, 2004.     

Adsorption of p-Nitrophenol in Untreated and Treated Activated Carbon

The adsorption of p-nitrophenol in one untreated activated carbon (F100) and three treated activated carbons (H₂, H₂SO₄ and Urea treated F100) was carried out at undissociated and dissociated conditions.To characterize the carbon, N₂ and CO₂ adsorption were used. X-ray Photoelectron Spectroscopy (XPS) was used to analyze the surface of the activated carbon.The experimental isotherms are fitted via the Langmuir homogenous model and Langmuir binary model. Variation of the model parameters with the solution pH is studied. Both Q _max and the adsorption affinity coefficient (K ₁) were dependent on the PZC of the carbons and solution pH. The Effect of pH must be considered due to its combined effects on the carbon surface and on the solute molecules. Adsorption of p-nitrophenol at higher pH was found to be dependent on the concentration of the anionic form of the solute.     

活性炭的zeta电位对各种染料吸附的影响3.活性炭对阴离子染料洋红的…

测定了在不同ｐｈ下活性炭吸附阴离子染料洋红的变化规律，发现活性炭表面的电位（ξ）对洋红吸附量的影响起着重要作用。当溶液ＰＧＨ小于活性炭的零电位ＰＨ（ＰＨｚｐｃ＝６．２）时，活性炭表面带正电，这绎洋红阴离子具有静电引力，而当ＰＨ增大时活性炭的ξ电位下降，静电引力减弱，使得吸附量下降；另一方面由于洋红变色（ＰＨ３．５橙色，－ＰＨ６．８玫瑰红后），洋红我溶解度增大，所以导致吸附量很快下降并趋于零， 通过     

Structural Characterization and Property Study on the Activated Alumina-activated Carbon Composite Material

AlCl3,NH3·H2O,HNO3 and activated carbon were used as raw materials to prepare one new type of activated alumina-activated carbon composite material.The influence of heat treatment conditions on the structure and property of this material was discussed;The microstructures of the composite material were characterized by XRD,SEM,BET techniques;and its formaldehyde adsorption characteristic was also tested.The results showed that the optimal heat treatment temperature of the activated alumina-activated carbon composite material was 450 ℃,iodine adsorption value was 441.40 mg/g,compressive strength was 44 N,specific surface area was 360.07 m2/g,average pore size was 2.91 nm,and pore volume was 0.26 m3/g.According to the BET pore size distribution diagram,the composite material has dual-pore size distribution structure,the micro-pore distributes in the range of 0.6-1.7 nm,and the meso-pore in the range of 3.0-8.0 nm.The formaldehyde adsorption effect of the activated alumina-activated carbon composite material was excellent,much better than that of the pure activated carbon or activated alumina,and its saturated adsorption capacity was 284.19 mg/g.     

Effects of Surface Oxygen of Activated Carbon on Alkaloid Adsorption: A Molecular Dynamics Simulation Study

The influence of the density and the type of surface oxygen on the adsorption of berberine alkaloid onto activated carbon was investigated using the molecular dynamics simulation method in vacuum. The carbon surface consisted of a basal plane of graphite and surface oxygen groups which were bonded on the graphite plane in a regular square array with various densities. Two types of surface oxygen groups, =O and —OH, were employed. The simulation results showed that the berberine alkaloids were favorable to be adsorbed on the negative charged carbon surfaces. It was indicated that the vdw attraction of the carbon surface to the alkaloid molecule dominates the adsorption only at the lower surface density of oxygen. It is also indicated that a good adsorptive selectivity for a certain berberine alkaloid can be obtained by controlling the density of surface oxygen.The adsorption simulation of berberine alkaloids onto activated carbon in the presence of water was also carried out by using a dome-shape molecular model for presenting the alkaloid/water/carbon system. It was found that the adsorption of berberine alkaloids on the activated carbon which has a higher density of surface oxygen was strongly inhibited by the presence of water.     

Carbon Dioxide/Methane Separation by Adsorption on Sepiolite

In this work,the use of sepiolite for the removal of carbon dioxide from a carbon diox- ide/methane mixture by a pressure swing adsorption(PSA)process has been researched.Adsorption equilibrium and kinetics have been measured in a fixed-bed,and the adsorption equilibrium parameters of carbon dioxide and methane on sepiolite have been obtained.A model based on the LDF approxima- tion has been employed to simulate the fixed-bed kinetics,using the Langmuir equation to describe the adsorption equilibrium isotherm.The functioning of a PSA cycle for separating carbon dioxide/methane mixtures using sepiolite as adsorbent has also been studied.The experimental results were compared with the ones predicted by the model adapted to a PSA system.Methane with purity higher than 97% can be obtained from feeds containing carbon dioxide with concentrations ranging from 34% to 56% with the proposed PSA cycle.These results suggest that sepiolite is an adsorbent with good properties for its employment in a PSA cycle for carbon dioxide removal from landfill gases.     

金离子的活性炭吸附及微波解吸

金离子的活性炭吸附及微波解吸杨春芬，王光灿（云南大学化学系实验中心昆明６５００９１）关键词金，硫脲，吸附，微波解吸用硫脲浸出法提取金、银具有速度快、毒性小，再生净化工序简单等优点￣［１］．用活性炭自硫腺浸金溶液中吸附金是极为有效的方法，但吸附后不易洗...     

载铜活性炭吸附一氧化碳的密度泛函理论计算

应用密度泛函理论和相对论有效核势方法, 用C₁₆H₁₀, C₁₃H₉, C₁₂H₁₂原子簇模型模拟活性炭表面, 计算得到了CO在载铜活性炭上的吸附位、吸附构型和吸附能. 研究表明: 载铜活性炭吸附CO的过程, 本质上是Cu(I)通过σ-π配键与CO络合, 形成Cu—C键的过程. 载铜活性炭对CO的络合吸附能在50～60 kJ/mol之间, 远大于活性炭对CO的物理吸附能(9.15 kJ/mol), 因而络合吸附更稳定, 选择性也更高. Cu(I)选择吸附在活性炭表面的顶位和桥位, 一个Cu(I)至多可以吸附一个到两个CO分子, 但吸附一个CO比吸附两个CO稳定.     

染料在剑麻基活性碳纤维上吸附速度的研究

本文研究了单组分染料在活性碳纤维上的吸附速度及双组分染料的竞争吸附速度。研究结果表明,不同染料分子在ＳＡＣＦ上吸附速度差异较大,结晶紫的吸附速度比亚甲基蓝或铬蓝黑Ｒ慢行多。亚甲基蓝和铬蓝黑Ｒ双组分共存时,其吸附速度与单组分时的相近,但初始阶段亚甲基蓝的吸附比铬蓝黑Ｒ快得多。由于染料的分子尺寸与ＡＣＦ的微孔大小相近,染料在活性碳纤维上的七染料孤及活怀碳纤维的孔结构密切相关。因此,不同染料分子在ＡＣＦ