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.     

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 Cd(II) Ions onto Activated Carbon Prepared from Hazelnut Husks

In this study, a batch adsorption of Cd(II) ions onto activated carbon (AC) produced from hazelnut husks were investigated. The factors controlling the adsorption process such as initial pH, agitation time, dosage and initial concentration have been examined. The AC was showed a high affinity to Cd(II) ions at pH values between 5.0 and 7.0. The equilibrium time was found to be 300 minutes. Cd(II) adsorption equilibrium was analyzed with both Langmuir and Freundlich isotherm equations and it was found that Langmuir equations fitted well with the experimental data. Maximum Cd(II) adsorption capacity of AC was calculated to be 20.9 mg g^?1. Cd(II) adsorption kinetics described well with the pseudo second order model. The activated carbon prepared from hazelnut husks is efficient sorbent material for the removal of Cd(II) ions from aqueous solutions.     

Adsorption of Toxic Tetracycline,Thiamphenicol and Sulfamethoxazole by a Granular Activated Carbon (GAC) under Different Conditions

Activated carbon can be applied to the treatment of wastewater loading with different types of pollutants. In this paper, a kind of activated carbon in granular form (GAC) was utilized to eliminate antibiotics from an aqueous solution, in which Tetracycline (TC), Thiamphenicol (THI), and Sulfamethoxazole (SMZ) were selected as the testing pollutants. The specific surface area, total pore volume, and micropore volume of GAC were 1059.011 m²/g, 0.625 cm³/g, and 0.488 cm³/g, respectively. The sorption capacity of GAC towards TC, THI, and SMZ was evaluated based on the adsorption kinetics and isotherm. It was found that the pseudo-second-order kinetic model described the sorption of TC, THI, and SMZ on GAC better than the pseudo-first-order kinetic model. According to the Langmuir isotherm model, the maximum adsorption capacity of GAC towards TC, THI, and SMZ was calculated to be 17.02, 30.40, and 26.77 mg/g, respectively. Thermodynamic parameters of ΔG⁰, ΔS⁰, and ΔH⁰ were obtained, indicating that all the sorptions were spontaneous and exothermic in nature. These results provided a knowledge base on using activated carbon to remove TC, THI, and SMZ from water.     

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.     

A Film-Pore-Surface Diffusion Model for the Adsorption of Acid Dyes on Activated Carbon

The sorption of acid dyes from aqueous effluents onto activated carbon has been studied. The effects of initial dye concentration and activated carbon mass on the rate of Acid Blue 80, Acid Red 114 and Acid Yellow 117 removal have been investigated. A three-resistance mass transport model based on film, pore and surface diffusion control has been applied to model the concentration decay curves. The model incorporates an effective diffusion coefficient D _eff, which is dependant on the equilibrium solid phase concentration or fractional surface coverage. The results of the film-pore-surface diffusion model are compared with the data obtained from the basic film-pore diffusion model. It has been found that the film-pore-surface diffusion model provides a major improvement over the data correlated by the film-pore diffusion model. Also, the relationship between surface diffusion and fractional surface coverage has been investigated for the adsorption of acid dyes on activated carbon.     

A Film-Pore-Surface Diffusion Model for the Adsorption of Acid Dyes on Activated Carbon

The sorption of acid dyes from aqueous effluents onto activated carbon has been studied. The effects of initial dye concentration and activated carbon mass on the rate of Acid Blue 80, Acid Red 114 and Acid Yellow 117 removal have been investigated. A three-resistance mass transport model based on film, pore and surface diffusion control has been applied to model the concentration decay curves. The model incorporates an effective diffusion coefficient D _eff, which is dependant on the equilibrium solid phase concentration or fractional surface coverage. The results of the film-pore-surface diffusion model are compared with the data obtained from the basic film-pore diffusion model. It has been found that the film-pore-surface diffusion model provides a major improvement over the data correlated by the film-pore diffusion model. Also, the relationship between surface diffusion and fractional surface coverage has been investigated for the adsorption of acid dyes on activated carbon.     

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.     

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     

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.     

负载Pt活性炭纤维对NO的吸附活性

 采用电化学方法制备了负载Pt的活性炭纤维，为研究其微孔结构、Pt的分散性以及对NO的吸附活性，分别考察了其对氮气、水和NO的吸附．电沉积Pt活性炭纤维的氮吸附等温线仍呈Langmuir型，表面积和微孔孔径基本不变；对水的初始吸附点数远远大于活性炭纤维．这表明电沉积Pt没有改变活性炭纤维的微孔结构，Pt粒高度分散在活性炭纤维的外表面．而NO的吸附量显著增加，说明存在化学吸附．     

杂多酸在活性炭上的固载化：III.活性炭在酸性介质中对钨硅杂多酸（SiW12…

在氢离子浓度均为３ｍｏｌ／Ｌ的硫酸，盐酸，磷酸，醋酸水溶液中和冰醋酸中研究了具有Ｋｅｇｇｉｎ结构的硅钨杂多酸（ＳｉＷ１２）在不同来源活性炭上的吸附作用，各活性炭对ＳｉＷ１２吸附等温线的形式是不相同的，吸附剂载体的微孔结构以及杂多酸的溶剂化起着重要的，工且在无机酸介质中，杂多酸的吸附量比在水溶液中成规律地增加，且与酸强度正比关系，在有机酸介质中，吸附作用比较复杂，根据所得结果，提出了在酸性中杂多酸在     

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     

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.     

Experimental and Theoretical Study of the Effect of Moisture on Methane Adsorption and Desorption by Activated Carbon at 273.5 K

Adsorption and desorption of methane by activated carbon (AC) at constant temperature and at various pressures were investigated. The effect of moisture was also studied. A volumetric method was used, up to 40 bar, at a temperature of 273.5 K. Results of a dry AC sample were compared with those obtained from a moist sample and two different ACs with different physical and surface properties were used. As expected, the results showed that the existence of moisture, trapped in the AC pores, could lead to a decrease in the amount of methane adsorbed and a decrease in the amount of methane delivered during desorption. To model the experimental results, a large variety of adsorption isotherms were used. The regressed parameters for the adsorption isotherms were obtained using the experimental data generated in the present study. The accuracy of the results obtained from the different adsorption isotherms was favorably compared.     

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.     

The Adsorption Kinetics of Cethyltrimethylammonium Bromide (CTAB) onto Powdered Active Carbon

This study investigates the adsorption kinetics of CTAB (cethyltrimethylammonium bromide), a cationic surfactant, onto PAC from aqueous solution with respect to the initial CTAB concentration at 20C. The pseudo-first-order, second-order kinetic models and intraparticle diffusion model were used to describe the kinetic data and the rate constants were calculated. The rate parameter, k_i, of intraparticle diffusion, the rate parameter, k₂, of the pseudo-second-order and k₁, the rate parameter for the pseudo-first-order mechanism were compared. It was found that the pseudo-second-order adsorption mechanism is predominant and the overall rate of the CTAB adsorption process appears to be controlled by more than one step, namely both the external mass transfer and intraparticle diffusion mechanisms.     

Multicomponent Adsorption of Pesticides onto Activated Carbon Fibers

The adsorption equilibria of pesticides and metabolites (atrazine, deethylatrazine, deisopropylatrazine and simazine) are studied onto activated carbon fibers –ACF– with a broad pore size distribution (32% mesopore volume, 68% micropore volume). Mono-and multi-component isotherms have been determined for low concentrations, from 0.23×10⁻⁶ to 9.52×10⁻⁶ mol L⁻¹. Single solute isotherms, modeled by Freundlich and Langmuir models, tend to prove the influence of the adsorbate's solubility in the adsorption capacity of activated carbon fibers. Binary solute isotherms confirm the strong influence of pesticide solubility on the competitive adsorption mechanism: the competition is higher in the case of adsorbates of different solubilities (atrazine and DEA or DIA for example). Multicomponent experimental data were modeled by extended Langmuir-based equations and the Ideal Adsorbed Solution theory. Whereas the first ones failed to model accurately binary adsorption due to restrictive hypothesis, the IAS model showed a good agreement between experimental and predicted data. It emphasised also the difficulty in satisfying the hypothesis of the model in the case of highly adsorbed compounds. Finally, the simultaneous adsorption of atrazine and NOM (in a natural water, DOC = 18.2 mg L⁻¹) shows no adsorption competition effects between natural organic matter and atrazine. This is due to the presence of secondary micropores (0.8–2 nm) and mesopores in the ACF, which limit a pore blockage phenomenon by NOM.