对苯二甲酸氧化残渣中的有色杂质在活性炭上的吸附规律

为了去除对苯二甲酸氧化残渣中的有色杂质,考察了活性炭类型、吸附温度及溶剂体系含水量对吸附过程的影响.结果表明:以二甲基亚砜作为溶剂的吸附体系中,有色杂质在活性炭上的吸附遵循Langmuir吸附规律;不同类型的活性炭AC-1(木质)与AC-2(煤质)的吸附性能具有不同的温度敏感性,温度对AC-2影响更显著;在溶剂体系中加少量的水有利于杂质吸附.     

Effect of textural property of coconut shell-based activated carbon on desorption activation energy of benzothiophene

In this work, the effect of the textural property of activated carbons on desorption activation energy and adsorption capacity for benzothiophene (BT) was investigated. BET surface areas and the textural parameters of three kinds of the activated carbons, namely SY-6, SY-13 and SY-19, were measured with an ASAP 2010 instrument. The desorption activation energies of BT on the activated carbons were determined by temperature-programmed desorption (TPD). Static adsorption experiments were carried out to determine the isotherms of BT on the activated carbons. The influence of the textural property of the activated carbons on desorption activation energy and the adsorption capacity for BT was discussed. Results showed that the BET surface areas of the activated carbons, SY-6, SY-13 and SY-19 were 1106, 1070 and 689 m²·g⁻¹, respectively, and their average pore diameters were 1.96, 2.58 and 2.16 nm, respectively. The TPD results indicated that the desorption activation energy of BT on the activated carbons, SY-6, SY-19 and SY-13 were 58.84, 53.02 and 42.57 KJ/mol, respectively. The isotherms showed that the amount of BT adsorbed on the activated carbons followed the order of SY-6 > SY-19 > SY-13. The smaller the average pore diameter of the activated carbon, the stronger its adsorption for BT and the higher the activation energy required for BT desorption on its surface. The Freundlich adsorption isotherm model can be properly used to formulate the adsorption behavior of BT on the activated carbons. __________ Translated from Journal of Functional Materials, 2007, 38(10): 1664–1668 [译自: 功能材料]     

Activated Carbons from Lignin: Their Application in Liquid Phase Adsorption

Abstract

The extent of the methylene blue (MB) adsorption from an aqueous solution is a convenient indicator in the evaluation of activated carbons. The adsorption of MB (cationic dye) from aqueous solution has been studied using twenty activated carbons. The activated carbons were prepared from acid‐precipitated eucalyptus kraft lignin following a two‐step process consisting of CO₂ partial gasification after carbonization in N₂ atmosphere. The adsorbed amount was studied as a function of the contact time, temperature, pH, concentration of adsorbate, and burn‐off of the activated carbons. The equilibria results obtained in a batch contactor were fitted by the Langmuir equation. The calculated values of ΔG demonstrate that the adsorption of the dye onto these activated carbons occurs by physical adsorption. Both the apparent values of ΔH and ΔS are positive, indicating that the adsorption process is endothermic and can produce spontaneously in our experimental conditions. The kinetic study was developed using a second‐order exponential decay equation and the results were correlated using the Lagergren first‐order equation relative to the concentration on the solid phase. The intraparticle diffusion coefficients have been estimated on the basis of an internal diffusion controlling mechanism for the net adsorption rate.     

Deep desulfurization of diesel fuels by catalytic oxidation

Reaction feed was prepared by dissolving dibenzothiophene (DBT), which was selected as a model organosulfur compound in diesel fuels, in n-octane. The oxidant was a 30 wt-% aqueous solution of hydrogen peroxide. Catalytic performance of the activated carbons with saturation adsorption of DBT was investigated in the presence of formic acid. In addition, the effects of activated carbon dosage, formic acid concentration, initial concentration of hydrogen peroxide, initial concentration of DBT and reaction temperature on the oxidation of DBT were investigated. Experimental results indicated that performic acid and the hydroxyl radicals produced are coupled to oxidize DBT with a conversion ratio of 100%. Catalytic performance of the combination of activated carbon and formic acid is higher than that of only formic acid. The concentration of formic acid, activated carbon dosage, initial concentration of hydrogen peroxide and reaction temperature affect the oxidative removal of DBT. The higher the initial concentration of DBT in the n-octane solution, the more difficult the deep desulfurization by oxidation is. Translated from Journal of Chemical Engineering of Chinese Universities, 2006, 20(4): 616–621 [译自: 高校化学工程学报]     

Role of microporosity and surface functionality of activated carbon in methylene blue dye removal from water

Activated carbons have been prepared from jute stick by both chemical and physical activation methods using zinc chloride and steam, respectively. They were characterized by evaluating surface area, iodine number, pore size distribution, and concentration of surface functional groups. The chemically activated carbon largely featured micropore structure, while the physically activated carbon mainly featured macropore structure. The specific surface area of chemically and physically activated carbons was 2,325 and 723 m ² /g, while the iodine number was 2,105 and 815mg/g, respectively. The concentration of surface functional groups was determined by Boehm titration method, which suggested that different types of surface functional groups are randomly distributed on chemical activated carbons, while it is limited for physical activated carbon. The microporosity along with surface functional groups provided a unique property to chemically activated carbon to adsorb Methylene Blue dye to a large extent. The adsorption of dye was also affected by the adsorption parameters such as adsorption time, temperature and pH. Comparatively, higher temperature and pH significantly facilitated dye adsorption on chemically activated carbon.     

Activated carbons for the adsorption of ibuprofen

Powdered activated carbons prepared from cork waste were studied for the ibuprofen removal from liquid phase. Two carbons were used: CAC obtained by chemical activation with K₂CO₃, and CPAC prepared by a two-step method, chemical activation with K₂CO₃ followed by steam activation. The ash content analysis showed that, for this raw material, the previous acid treatment can be omitted. The textural properties of the samples, evaluated by low temperature N₂ adsorption, show that the main difference is related with the volume of the larger micropores (supermicropores), which is more developed for CPAC. The surface chemistry characterization, made by the determination of the point of zero charge (PZC) and Boehm’s titration, show that the second activation step led to an activated carbon with less acidic groups, associated with the absence of the strongest acidic groups. Kinetic and equilibrium adsorption data show that the process obeys to the pseudo-second order kinetic equation and Langmuir adsorption model. Between 25 and 40 °C no significant influence of the temperature on ibuprofen adsorption was observed. Results indicate that the removal efficiency is higher than 90% between pH 2 and 4 and decreases as pH values increase to a value of 11. The results show that both samples are suitable for ibuprofen removal, although CPAC has advantages, namely, high initial adsorption rate, high adsorption capacity and high removal efficiency, in some cases 100%, for a large range of pH.     

Adsorption capacity and removal efficiency of heavy metal ions by Moso and Ma bamboo activated carbons

In order to understand the adsorption capacity and removal efficiency of heavy metal ions by Moso and Ma bamboo activated carbons, the carbon yield, specific surface area, micropore area, zeta potential, and the effects of pH value, soaking time and dosage of bamboo activated carbon were investigated in this study. In comparison with once-activated bamboo carbons, lower carbon yields, larger specific surface area and micropore volume were found for the twice-activated bamboo carbons. The optimum pH values for adsorption capacity and removal efficiency of heavy metal ions were 5.81–7.86 and 7.10–9.82 by Moso and Ma bamboo activated carbons, respectively. The optimum soaking time was 2–4 h for Pb²⁺, 4–8 h for Cu²⁺ and Cd²⁺, and 4 h for Cr³⁺ by Moso bamboo activated carbons, and 1 h for the tested heavy metal ions by Ma bamboo activated carbons. The adsorption capacity and removal efficiency of heavy metal ions of the various bamboo activated carbons decreased in the order: twice-activated Ma bamboo carbons > once-activated Ma bamboo carbons > twice-activated Moso bamboo carbons > once-activated Moso bamboo carbons. The Ma bamboo activated carbons had a lower zeta potential and effectively attracted positively charged metal ions. The removal efficiency of heavy metal ions by the various bamboo activated carbons decreased in the order: Pb²⁺ > Cu²⁺ > Cr³⁺ > Cd²⁺.     

Mechanisms of Cr(VI) removal from water by various types of activated carbons

The removal mechanisms of Cr(VI) from water using different types of activated carbons, produced from coconut shell, wood and dust coal, were investigated in this project. Different types of activated carbons have different surface characteristics. The coconut shell and dust coal activated carbons have protonated hydroxyl groups on the surface (H‐type carbons), while the surface of the wood‐based activated carbon has ionised hydroxyl groups (L‐type carbons). The adsorption kinetics of chromium onto the activated carbons at pH values ranging from 2 to 6 were investigated. It was found that the optimum pH to remove total chromium was 2 for wood‐based activated carbon, while for coconut shell and dust coal activated carbons, the optimum pH was around 3–4. The difference in the optimum pH for different activated carbons to remove Cr(VI) from water can be explained by the different surface characteristics and capacity of the activated carbons to reduce Cr(VI) to Cr(III). © 1999 Society of Chemical Industry     

污泥活性炭处理亚甲基蓝染料废水的研究

采用污泥活性炭处理亚甲基蓝模拟染料废水,研究了模拟废水初始浓度、污泥活性炭投加量、pH值、水浴吸附时间等因素对染料废水的脱色率和COD去除率的影响,探讨污泥活性炭处理染料废水的适宜工艺条件。实验结果表明:随着染料废水初始浓度的增大,脱色率和COD去除率均表现出下降趋势;随着污泥活性炭投加量的增加,脱色率和COD去除率效果均十分明显;随着模拟废水pH值的增大,其脱色率基本呈现增大趋势,而COD去除率则先增大后减小,当pH在7.6～7.8时,脱色率与COD去除率均出现最大值;在延长水浴时间的同时,脱色率和COD去除率均表现出较好的效果。本实验处理染料废水的适宜条件为:染料废水的初始浓度为2.5mg/L,调节染料废水的pH值7~8,加入0.8g污泥活性炭,30℃条件下2h。     

Thermodynamic and Kinetic Behaviors of Trinitrotoluene Adsorption on Powdered Activated Carbons

Abstract

Regulations on the removal of trinitrotoluene (TNT) from wastewater have become increasingly more stringent, demanding faster, less expensive, and more efficient treatment. This study focuses on the adsorption equilibrium and kinetics of TNT on powered activated carbons (PAC). Three types of PACs (i.e., wood based, coal based, and coconut‐shell based) were studied as functions of temperature and pH. Thermodynamic properties including Gibbs free energy, enthalpy, and entropy, were evaluated by applying the Van't Hoff equation. In addition, the adsorption energy distribution functions which describe heterogeneous characteristics of porous solid sorbents were calculated by using the generalized nonlinear regularization method. Adsorption kinetic studies were carried out in batch adsorber under important conditions such as PAC types, temperature, pH, and concentration. We found that fast and efficient removal of TNT dissolved in water can be successfully achieved by PAC adsorption.     

Adsorption of carbon dioxide on ionic liquids-modified active carbons and amino-modified polymer

Active carbons with various particle sizes (38–150, 300–500 and 800–1,200 μm) were modified by ionic liquids (ILs), and organic polymer was modified by acrylamide using a simple procedure, and these materials were applied to capture carbon dioxide (CO₂). The CO₂ adsorption amounts were calculated using a mass balance equation at three different temperatures (298.15, 308.15 and 318.15 K), respectively, and the influences of gas pressure, particle size and temperature on adsorption were discussed. Experimental results showed that the CO₂ adsorption capacity of ILs-modified active carbons was better than amino-modified polymer, and the smaller particle size (38–150 μm) ILsmodified active carbons had the largest adsorption capacity at 298.15 K. Compared with previous research about polyethyleneimine (PEI)-modified silica gel, the adsorption amount of CO₂ on ILs-modified active carbons has been greatly improved with lower cost.     

氯霉素在活性炭上的吸附平衡与动力学

为去除水体中残留的氯霉素,采用生物相容性佳的活性炭作吸附剂,测定了25,30,35℃下氯霉素在自制活性炭上的吸附平衡与动力学,并与商用竹炭作对比。结果表明高比表面积活性炭是去除水体中残留氯霉素的高效吸附剂,活性炭的吸附容量随着吸附剂比表面积和孔容的增大而增大,但随温度从25,30到35℃升高而减小,自制高比表面积活性炭的吸附容量达到3种市售活性炭样品吸附容量的10倍以上;Freundlich吸附等温线方程可较好地描述氯霉素在活性炭上的吸附平衡,准二级方程是用来描述氯霉素在活性炭上吸附的合适动力学模型,并通过拟合得到了其动力学参数。随着温度的升高吸附容量逐渐减小。本研究为活性炭对水体中残留氯霉素的吸附处理提供了科学依据。     

Coniferous Wood Sawdust-based Activated Carbons as Adsorbents Obtained with the Use of Microwave Radiation

Activated carbons were prepared by physical and direct activation of sawdust pellets coming from coniferous trees, with the use of microwave radiation. The activated carbons obtained were used as adsorbents for the removal of methylene blue (MB) from aqueous solutions. Liquid-phase adsorption experiments were conducted and the maximum adsorption capacity of each activated carbon sample was determined. The effects of activation procedure as well as adsorption tests parameters i.e., temperature, pH, initial methylene blue concentration, and contact time on the sorption capacity of each activated carbon were investigated. The kinetic models for MB adsorption on the activated carbons were also studied. Better fit to the experimental data was obtained with the Langmuir isotherm than Freundlich one, for all samples.     

花生壳活性炭脱除溶液中Cr（Ⅲ）的研究

本文研究了花生壳活性炭脱除溶液中的Cr（Ⅲ）,考察了溶液pH值和接触时间对Cr（Ⅲ）脱除率的影响。结果表明,溶液的pH值是影响Cr（Ⅲ）脱除率的主要因素,pH值越高活性炭对Cr（Ⅲ）的吸附能力越强,吸附速度越快。等温吸附实验结果表明,用H3PO4活化的活性炭吸附能力低于用ZnCl2活化的活性炭,并且热裂解温度600℃要好于400℃。用Langmuir和Freundlich等温吸附模型模拟结果表明,初始pH值为5时,用H3PO4和ZnCl2活化的花生壳活性炭的饱和吸附能力分别达到66．7和111．1mg·g^-1。     

Preparation and characterization of active carbons from olive stones

Olive stones have been carbonized under a flow of nitogen in the temperature range from 700 to 900°C and activated in a CO₂ flow in the range from 675 to 875°C. ZnCl₂ was used in some of the activation processes. The adsoptive characteristics of the carbonized and activated samples have been determined by adsorption of nitrogen (77 and 90 K), carbon dioxide (195 and 273 K), n-butane (273 K) and methylene blue (aqueous solution at 298 K). Meso and macroporosity have been followed by mercury porosimetry. The resulting activated carbons have very large surface areas as well as a highly developed microporosity. The most adequate experimental conditions for the preparation of active carbons, highly microporous but with a well developed meso and macroporosity, are discussed. All active carbons prepared have a very low ash content and complete absence of sulphur, both very attractive characteristics.     

Activated carbon surface modifications by adsorption of bacteria and their effect on aqueous lead adsorption

The adsorption of Escherichia coli on different activated carbons has been studied. The activated carbon samples used have been characterized, determining their surface area, pore size distribution, elemental analysis, mineral matter analysis and pH of the point of zero charge. The adsorption capacity of these carbons increased with their hydrophobicity and macropore volume. The number of bacteria adsorbed on the demineralized activated carbon in a solution of pH value equal to the iso‐electric point of the carbon was negligible. However, in the presence of cations the proportions of bacterial cells adsorbed were 87.8% (Fe³⁺), 54.7% (Ca²⁺) and 24.8% (Mg²⁺) respectively. This increase in adsorption capacity in the presence of electrolytes has been explained on the basis of both the reduction in electrostatic free energy and the increase in cell surface hydrophobicity due to the metal bound by some compounds of the cell membrane. When the solution pH was intermediate between the pH values of the point of zero charge of the carbon and bacteria the number of bacteria adsorbed increased due to the attractive interactions between the carbon and bacteria. The adsorption of bacteria on activated carbons decreased the porosity and increased the negative charge density of the latter. Depending on the experimental conditions used, the presence of bacteria can enhance the capacity of activated carbons to adsorb lead. © 2001 Society of Chemical Industry     

Adsorption removal of thiophene and dibenzothiophene from oils with activated carbon as adsorbent: effect of surface chemistry

Commercial coconut-based activated carbons (AC), before and after being treated using 65 wt% HNO₃ at different temperatures (termed as AC–Hs), were used as adsorbents to remove thiophene (T) or dibenzothiophene (DBT) from model oils. The fresh AC sample and all of the AC–Hs samples were characterized by Boehm titration, Fourier-transform infrared spectroscopy, and thermal analysis, which yield the information of the surface chemistry properties of the carbon materials. The results show that in comparison to the fresh AC sample, the quantity of oxygen-containing functional groups on the surface of AC–Hs samples increases as the pretreatment temperature of the fresh AC sample increases. The adsorption capabilities of the AC samples for removal of T and DBT from model oils were evaluated in a batch-type reactor. It has been found that the refractory DBT can be removed easily over the untreated commercial AC with the removal efficiency even being higher than that of T. In the case of acid modified AC–Hs samples, the efficiency for removal of T has been greatly improved, but this is not the case for the removal of DBT. The possible mechanism for adsorption removal of T and DBT over activated carbons is discussed in terms of the quantity of surface oxygen-containing functional groups of adsorbents and the chemical structure of sulfur compounds. The effect of olefin (1-octene) and aromatic hydrocarbons (benzene) in the model oils on the selective adsorption DBT over AC is also evaluated, revealing that in the case of DBT, the competitive adsorption is involved in the process, and the removal efficiency levels off at a level over 80%.     

Adsorption Characteristics of Sulfamethoxazole and Metronidazole on Activated Carbon

In this work, the removal of two pharmaceuticals i.e., an antibiotic drug, sulfamethoxazole and an antiparasitary drug, metronidazole onto activated carbon from aqueous solutions were studied. Batch adsorption studies were carried out at different pH, adsorbent concentrations, and temperatures. Adsorption isotherms have been modeled by Freundlich, Langmuir, and Dubinin-Raduskevitch (D-R) equations. The adsorption of these drugs was better represented by the Langmuir equation. The effect of the solution pH on the adsorbed amount of SM and MN was studied by varying the initial pH under constant process parameters at equilibrium conditions. The increase in pH of the solutions caused to decrease adsorption of SM and MN on AC. The kinetics of adsorption in view of three kinetic models, i.e., the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model was discussed. The pseudo-second-order kinetic model describes the adsorption of both sulfamethoxazole and metronidazole on activated carbon. Rate constants for adsorption and desorption, and surface coverage have been evaluated with the help of another approach of the kinetic scheme. The effect of temperature was also studied at the range between 293 and 313 K. Thermodynamic parameters were calculated. The negative value of enthalpy change (ΔH°) indicated the exothermic nature of the adsorption process, and the negative values of free energy change (ΔG°) were indicative of spontaneity of the adsorption process. In this work adsorption behaviour of SM and MN on activated carbon was also evaluated by the data obtained from column experiments.     

Tailoring activated carbons for enhanced removal of natural organic matter from natural waters

Several pathways have been employed to systematically modify two granular activated carbons (GACs), F400 (coal-based) and Macro (wood-based), for examining adsorption of dissolved natural organic matter (DOM) from natural waters. A total of 24 activated carbons with different physical and chemical characteristics was produced. The impact of carbon treatment on the DOM adsorption was examined by conducting isotherm experiments at a neutral pH using the modified carbons and a DOM isolated from the influent to Myrtle Beach drinking water treatment plant in South Carolina (USA). Adsorption of the DOM by two activated carbon fibers, with relatively uniform pore size distributions, showed that only pores with widths larger than 1 nm were accessible to the DOM macromolecules. Increases in the carbon supermicropore and mesopore volume (i.e., >1 nm) increased the DOM uptake, if the surface chemistry was favorable. The isotherms normalized on a surface area basis showed the significance of carbon surface chemistry on the DOM uptake. At neutral pH, adsorption of negatively charged DOM molecules was favored by basic and positively charged surfaces, while the DOM uptake was minimized when the surface had acidic characteristics. High temperature ammonia treatment of oxidized carbons considerably enhanced the DOM uptake, mainly due to the increase in accessible surface area and surface basicity. Iron-impregnated carbons indicated an enhanced affinity of iron-laden carbon surface toward the DOM species, if the surface was not negatively charged.     

Effect of carbon-oxygen and carbon-sulphur surface complexes on the adsorption of mercuric chloride in aqueous solutions by activated carbons

Several activated carbons obtained from commercial sources have been tested for their ability to remove mercuric chloride (HgCl₂) from aqueous solutions. The chemical nature of the surface of the activated carbons was changed by introducing carbon-oxygen and carbon-sulphur surface complexes. The influence of these types of complexes on the adsorption of HgCl₂ by the activated carbons has been studied. It seems that the existence of hydroquinonic, phenolic and hydrosulphide groups on the surface of the carbon reduces Hg(II) to Hg(I). However, there was an increase in the adsorption of Hg(II) when sulphide or hydrosulphide groups were present on the surface of the carbon. The effect of the pH of the solutions on HgCl₂ adsorption was also studied; when the pH was changed from 1 to 7 there was an enhancement of the adsorption of HgCl₂ by the activated carbons.