杉木活性炭吸附处理水溶液中的尼古丁

用不同孔径及化学性质的活性炭对尼古丁水溶液进行吸附研究. 以杉木屑为原料, 分别用氯化锌化学活化法和水蒸气物理活化法制备活性炭, 并分别命名为AC-Z和AC-H. 同时选用椰壳基商品活性炭作为对比吸附剂, 命名为AC-C. 采用比表面积孔径测定分析仪及Boehm滴定法对活性炭进行表征, 分别测定其比表面积、孔径分布和表面官能团含量. 吸附实验主要考虑吸附时间、温度和尼古丁溶液的初始浓度三个因素, 实验数据分析结果表明微孔有利于物理吸附的进行, 而表面酸性官能团及金属原子作为吸附活性位的作用更加重要. 由改变温度对各样品的吸附量影响也能说明活性位在吸附中的作用. AC-Z拥有较多的活性位, 温度变化时尼古丁的吸附量先升高后减小, 这主要是由于适合的温度能加快尼古丁分子的离解并促使其与活性位相结合, 而过高的温度会造成尼古丁分子动能增加, 导致分子间碰撞的机率和强度增大, 使吸附在活性炭表面的尼古丁分子脱落. AC-H和AC-C由较多的微孔和不同程度的活性位组成, 优先发生物理吸附, 并且伴随发生吸附剂表面分子团簇现象, 其吸附趋势与AC-Z相反. 动力学研究表明活性炭对尼古丁的吸附反应非常迅速, 并且符合准二阶动力学程模型. 各热力学参数ΔG⁰, ΔH⁰和ΔS⁰的计算结果表明吸附剂对尼古丁的吸附为吸热和自发性过程.AC-Z和AC-H的ΔH⁰值远低于AC-C, 说明吸附剂表面的活性位对尼古丁分子有强烈的吸引作用, 所以吸附相同数量吸附质分子所需的吸附热更小, 这也说明了活性位在吸附过程中发生作用.     

Adsorption of phenol on supercritically activated carbon fibres: effect of texture and surface chemistry

The influence of texture and surface chemistry on the phenol adsorption capacity of activated carbon fibres (ACFs) was studied. ACFs were prepared by carbonization of a phenolic textile fibre under nitrogen flow, followed by activation with H(2)O and CO(2) (under atmospheric pressure and supercritical state). The materials were characterised by N(2) and CO(2) adsorption, and by temperature programmed desorption studies. A strong correlation between the amount of adsorbed phenol and the micropore volume has been observed. The relationship between surface oxygen concentration and amount of physisorbed and chemisorbed phenol was assessed, and it was shown that higher amounts of surface oxygen groups decreased the phenol chemisorption capacity of ACFs.     

Comparative study for the removal of methylene blue via adsorption and photocatalytic degradation

Physically and chemically activated carbons were prepared from date pits and olive stones. Titania and WO(x)-TiO(2)/MCM-41 were prepared as photoactive catalysts. Surface characterizations were investigated from ash content, pH, base neutralization capacities and FT-IR techniques. The textural characteristics, namely specific surface area (S(BET)) and pore texture, were determined from low temperature adsorption of N(2) at 77 K. The decolorization of aqueous solution of methylene blue was performed by means of two alternative methods. Steam-activated carbons own higher surface area compared with ZnCl(2)-activated carbons, and the micropore surface area represents the major contribution of the total area. Steam-activated carbons were the most efficient decolorizing adsorbents owing to its higher surface area, total pore volume and the basic nature of the surface. The calculated values of DeltaG(0), DeltaH(0) and DeltaS(0) indicate the spontaneous behavior of adsorption. The photocatalytic degradation is more convenient method in decolorizing of methylene blue compared with the adsorption process onto activated carbons.     

On the adsorption/oxidation of hydrogen sulfide on activated carbons at ambient temperatures

Activated carbons of various origins (bituminous coal, wood, coconut shells, and peat) were studied as adsorbents of hydrogen sulfide. Before the experiments the surface of the adsorbents was characterized by using the sorption of nitrogen, Boehm and potentiometric titrations, thermal analysis, and FTIR. The adsorbents were chosen to differ in their surface areas, pore volumes, and surface acidities. To broaden the spectrum of surface acidity, carbons were oxidized by using nitric acid and ammonium persulfate. After hydrogen sulfide adsorption the species present on the surface were analyzed using thermal analysis, ion chromatography, and elemental analysis. The H(2)S breakthrough capacity tests showed that the performances of different carbons differ significantly. For a good performance of carbons as hydrogen sulfide adsorbents a proper combination of surface chemistry of carbon and porosity is needed. It was demonstrated that a more acidic environment promotes the formation of sulfur oxides and sulfuric acid despite yielding small H(2)S removal capacities. On the other hand, a basic environment favors the formation of elemental sulfur (sulfur radicals) and yields high capacities. The presence of a sufficient amount of water preadsorbed on the carbon surface to facilitate dissociation also plays an important role in the process of H(2)S adsorption/oxidation. The results showed that there is a critical value in carbon surface acidity, which when exceeded results in a negligible hydrogen sulfide breakthrough capacity. This is consistent with the mechanism of H(2)S adsorption on unmodified carbons, where the rate-limiting step is the reaction of adsorbed hydrogen sulfide ion with dissociatively adsorbed oxygen. When the acidity is expressed as pH, its value should be higher than 5 to ensure the effective removal of hydrogen sulfide from the gas phase. Study of carbon regeneration using water washing and heat treatment showed that the adsorbents can be regenerated to about 40% of their initial capacity.     

稻壳多孔碳材料的电容性能及模型计算

采用NaOH和H₃PO₄化学活化法, 由廉价的稻壳制备了2种高比表面积的介孔活性碳, 测试了其比表面积和平均孔径, 利用循环伏安、 恒流充放电和交流阻抗测试了其电化学性能, 其比电容分别达到145.8和168.5 F/g. 利用一种多分支的三级孔道模型对其进行交流阻抗谱拟合, 拟合结果符合度较高, 表明该模型对分析活性碳电极结构有一定指导意义.     

Adsorption of tetraalkylammonium ions on microporous and mesoporous activated carbons prepared from vinylidene chloride copolymer

The adsorption of tetraalkylammonium ions on microporous (AC-micro) and mesoporous (AC-meso) activated carbons prepared from vinylidene chloride copolymer was investigated. The adsorbed amounts on AC-micro decreased in the order of tetraethyl-, tetrapropyl-, hexadecyltrimetyl-, and tetrahexylammonium bromide. Consequently it is suggested that the pore size of the activated carbon plays an important role in the adsorption. The adsorbed amounts on AC-meso increased with increasing alkyl chain length. In the case of mesoporous activated carbon, hydrophobic interaction between tetraalkylammonium ions and the surface of activated carbons contributes to in the adsorption.     

Adsorption properties of activated carbon from waste newspaper prepared by chemical and physical activation

Adsorption properties of activated carbons prepared from waste newspaper by chemical and physical activation were investigated using water vapor, ammonia, methane, and methylene blue (MB) as adsorbents. The water vapor adsorption isotherms show type V behavior and the maximum vapor adsorption of the chemically and physically activated products is about 1050 and 450 ml/g, respectively. The higher water vapor adsorption of the chemically activated products is attributed to the higher specific surface area (S(BET)) and greater hydrophilic activity (arising from the surface oxygen-containing functional groups) than in the physically activated products. The adsorption of ammonia and methane was measured by temperature-programmed desorption (TPD). NH(3) adsorption is found to be higher in the chemically activated product than in the physically activated product while methane adsorption is slightly higher in the physically activated products even though these have lower S(BET) values. In the MB adsorption, the chemically activated products show higher adsorption (390 mg/g) than the physically activated product. These results are suggested to be related to the surface characteristics.     

Microporous activated carbons prepared from palm shell by thermal activation and their application to sulfur dioxide adsorption

Textural characterization of activated carbons prepared from palm shell by thermal activation with carbon dioxide (CO(2)) gas is reported in this paper. Palm shell (endocarp) is an abundant agricultural solid waste from palm-oil processing mills in many tropical countries such as Malaysia, Indonesia, and Thailand. The effects of activation temperature on the textural properties of the palm-shell activated carbons, namely specific surface area (BET method), porosity, and microporosity, were investigated. The activated carbons prepared from palm shell possessed well-developed porosity, predominantly microporosity, leading to potential applications in gas-phase adsorption for air pollution control. Static and dynamic adsorption tests for sulfur dioxide (SO(2)), a common gaseous pollutant, were carried out in a thermogravimetric analyzer and a packed column configuration respectively. The effects of adsorption temperature, adsorbate inlet concentration, and adsorbate superficial velocity on the adsorptive performance of the prepared activated carbons were studied. The palm-shell activated carbon was found to have substantial capability for the adsorption of SO(2), comparable to those of some commercial products and an adsorbent derived from another biomass.     

几种植物基活性炭材料的表面结构与吸附性能比较——(II)表面化学结构与吸附性能研究

用X-射线光电子能谱对3种植物基活性炭材料:椰壳活性炭 (CAC4)、剑麻茎基活性炭(SSAC)和剑麻基活性碳纤维 (SACF) 的表面化学结构进行了表征,并研究和对比了它们的吸附性能,包括对碘、苯酚和亚甲基蓝的液相吸附性能,对有机蒸汽的吸附性能以及对Au3+的还原吸附性能等。结果表明,3个样品表面均含有多种含氧官能团,吸附能力SACF>SSAC> CAC4。样品的吸附性能主要取决于自身孔结构,与其表面化学结构也有密切的关系。     

Adsorption equilibrium and kinetics of copper ions and phenol onto modified adsorbents

The adsorption equilibrium and kinetics of single and binary component copper ions and phenol onto powdered activated carbon (PAC), alginate beads and alginate-activated carbon beads (AAC) were studied. Adsorption equilibrium data for single component copper ions and phenol onto the adsorbents could be represented by the Langmuir equation. Multicomponent equilibrium data were correlated by the extended Langmuir and ideal adsorbed solution theory (IAST). The IAST gave the best fit to our data. The amount of copper ions adsorbed onto the AAC beads in the binary component was greater than that of phenol. The internal diffusion coefficients were determined by comparing the experimental concentration curves with those predicted from surface diffusion and pore diffusion model.     

Pore structure and adsorption performance of the KOH-activated carbons prepared from corncob

Carbonaceous adsorbents with controllable surface area were chemically activated with KOH at 780 degrees C from chars that were carbonized from corncobs at 450 degrees C. The pore properties, including BET surface area, pore volume, pore size distribution, and mean pore diameter of these activated carbons, were characterized by the t-plot method based on N(2) adsorption isotherms. Two groups are classified according to the types of adsorption/desorption isotherms. Group I corncob-derived activated carbons, with KOH/char ratios from 0.5 to 2, exhibited BET surface area ranging from 841 to 1221 m(2)/g. Group II corncob-derived activated carbons, with KOH/char rations from 3 to 6, showed high BET surface areas, from 1976 to 2595 m(2)/g. From scanning electron microscopic (SEM) results, the surface morphology of honeycombed holes on corncob-derived activated carbons was significantly influenced by the KOH/char ratios. The adsorption kinetics of methylene blue, basic brown 1, acid blue 74, 2,4-dichlorophenol, 4-chlorophenol, and phenol from water at 30 degrees C were studied on the two groups of activated carbons, which were suitably described by two simplified kinetic models, pseudo-first-order and pseudo-second-order equations. The effective particle diffusivities of phenols and dyes at the corncob-derived activated carbons of group II are higher than those of ordinary activated carbons. The high-surface-area activated carbons were demonstrated to be promising adsorbents for pollution control and for other applications.     

Influence of organics on the structure of water adsorbed on activated carbons

The influence of organics on the structure of water adsorbed on activated carbons was studied using adsorption of nitrogen, benzene, and water, and by (1)H NMR spectroscopy with freezing out of bulk water with the presence of benzene-d(6) or chloroform-d. It was found that interactions of water with the activated carbon surface depend on both structural characteristics (contributions of micro- and mesopores, pore size distributions) of adsorbents and chemical properties (changed by oxidation or reduction) of the adsorbents. Moreover, the interfacial behavior of water is affected by water-insoluble organics such as benzene and chloroform. Changes in the Gibbs free energy of water adsorbed on carbons exposed to air, water, chloroform-d, or benzene-d(6) are related to textural properties of adsorbents and the degree of their oxidation. Since chloroform-d and benzene-d(6) are strongly adsorbed on activated carbons and immiscible with water they replace a significant portion of adsorbed water in micropores, on the walls of mesopores, and in the transport pores of carbons causing changes in the Gibbs free energy and other characteristics of water.     

The use of microwave radiation for obtaining carbonaceous adsorbents from biomass and their use in elimination of inorganic pollutants

A new technology of obtaining activated carbons by physical and direct activation of biomass with the use of microwave radiation is described. The effect of activation temperature (700 and 800 °C) and two periods of time (15 and 30 min) on the textural parameters, acid–base character of the surface and sorption properties of activated carbons was tested. The resulting carbons were characterized by low-temperature nitrogen sorption and determination of pH as well as the number of surface oxygen groups. The sorption properties of the activated carbons obtained were characterized by determination of nitrogen dioxide and hydrogen sulphide adsorption in dry and wet conditions as well as by iodine removal from aqueous solution. The final products were adsorbents of surface area ranging from 291 to 368 m²/g and pore volume from 0.20 to 0.26 cm³/g, showing basic character of the surface. The results obtained in our study have proved that suitable choice of the pyrolysis and activation procedure for hay with the use of microwave radiation permit producing adsorbents with good capacity toward toxic gases of acidic character as well as inorganic pollutants of molecules of size similar to that of iodine molecules.     

Dynamic Adsorption of Vapours by Activated Carbons and by Polymer-Derived Adsorbents: 1. Adsorption at 0% R.H.

The uptakes of volatile organic compounds from a nitrogen carrier gas at 0% R.H. onto packed beds of adsorbents have been measured by monitoring the effluent vapour concentration profile as a function of time. The profiles have been quantitatively fitted by a modified Bohart-Adams equation which was then integrated to yield the adsorbent capacities. Traditional activated carbons, carbonised macroreticular resins and a macroreticular polymer were used in the study. Performance in the dynamic tests has been related to the pore volume characteristics and surface areas determined from nitrogen adsorption isotherms. Whilst the extent of micropore filling basically increased as the sorbate boiling point increased and increased capacities reflected increased micropore volumes, these trends were interrupted by size exclusion and specific polar interaction effects.     

CuSO_4/TiO_2催化剂在氨选择性催化还原氮氧化物反应中的性能(英文)

氮氧化物(NO_x)是主要的大气污染物之一.氨气选择性催化还原法(NH_3-SCR)是目前去除固定源排放的氮氧化物的最有效方法,被广泛用于燃煤或者生物质的火电厂中.催化剂是NH_3-SCR法的核心,其中V_2O_5-WO_3/TiO_2催化剂是主要的商业SCR催化剂;但是V_2O_5有毒,对环境的影响很大;另外,该催化剂具有较高的SO_2氧化性能.因而研究者一直在探索新型的SCR催化剂.SO_2是燃煤电厂烟气中的典型气体之一,所以抗硫性能是催化剂的一个重要指标.在SCR反应条件下,SO_2和O_2容易与氧化物催化剂发生反应生成稳定性较高的硫酸盐,覆盖在催化剂表面从而引起催化剂失活.但已有研究发现,硫化会提高K中毒后的V_2O_5-WO_3/TiO_2催化剂的活性.并且,短时间的硫化可以明显提高CuO/Al_2O_3的NH_3-SCR活性.硫酸盐催化剂或许具有较低毒性和较高抗硫性能,应该是一种有前景的SCR催化剂.本文以商业纳米TiO_2为载体,采用湿式浸渍法制备了一系列的CuSO_4/TiO_2催化剂.在自制的活性评价装置上测试了样品的NH_3-SCR活性并且在340℃下连续24 h测试了SO_2、水蒸气及两者共同作用对催化剂活性的影响.使用N_2等温吸附-脱附、X射线衍射(XRD)、X射线光电子能谱(XPS)、H_2程序升温还原(H2-TPR)和NH_3程序升温脱附(NH_3-TPD)对催化剂进行了表征.另外,采用原位红外漫反射光谱研究了CuSO_4/TiO_2催化剂上的NH_3-SCR反应过程.N_2等温吸附-脱附结果表明,负载的CuSO_4没有明显改变载体的孔结构.而XRD结果仅显示锐钛矿TiO_2的衍射峰,说明CuSO_4在载体上有较好的分散度或者CuSO_4的含量低于检测限.XPS结果显示,催化剂中的铜主要以Cu~(2+)形式存在,硫主要以SO_4~(2-)形式存在,而氧主要以晶格氧和吸附氧两种形式存在,并且CuSO_4的存在会增加催化剂中吸附氧的含量.H_2-TPR结果表明,随着CuSO_4含量的增加,催化剂的氧化还原能力逐渐增强.NH_3-TPD结果表明,催化剂表面的酸性位数目随着样品中CuSO_4含量的增加而增加.纯TiO_2的NH_3-SCR活性很差,当温度从300℃增加到450℃时,最高NO_x转化率仅为32.7%.但当CuSO_4负载到TiO_2上以后,催化剂活性明显提高.在反应温度高于340℃时,CuSO_4/TiO_2催化剂的NO_x转化率在94%以上,与商业V_2O_5-WO_3/TiO_2催化剂相当,并且其N_2O生成量低于商业催化剂.不过,当温度低于340℃时,CuSO_4/TiO_2催化剂的NO_x转化率明显低于商业催化剂,说明CuSO_4/TiO_2催化剂的活性仍有待改善.连续24 h测试了SO_2、水蒸汽及两者的共同作用对CuSO_4/TiO_2催化剂活性的影响.结果显示,单独的水蒸气会导致活性轻微下降,但SO_2以及两者共同存在时对催化剂的活性基本没有影响.CuSO_4/TiO_2催化剂的NH_3吸附红外光谱表明,催化剂上存在Lewis和Bronsted两种酸性位,但Bronsted酸性位上的NH_4~+稳定性较差,280℃时即基本消失.在高温时,NH_3主要吸附在Lewis酸性位上且CuSO_4/TiO_2催化剂对NO_x的吸附能力较差,红外光谱未检测到NO_x的吸附峰.380℃下,当NO和O_2通入预吸附NH_3的催化剂样品时,属于Lewis酸性位上NH_3的红外峰明显下降,说明Lewis酸性位上吸附的NH_3参与了反应.CuSO_4/TiO_2显示出高的抗硫抗水性能和比较好的NH_3-SCR活性,应该是一种有应用前景的SCR催化剂.CuSO_4可以增加催化剂的酸性位数目和吸附氧量.根据原位红外漫反射结果,CuSO_4/TiO_2上的SCR反应遵循Eley-Rideal机理.气相的NO与吸附在Lewis酸性位上的NH_3反应生成N_2和H_2O或许是主要的反应途径,并且吸附氧可能会促进这个过程.     

Structural characteristics of activated carbons and ibuprofen adsorption affected by bovine serum albumin

Structural characteristics of a series of MAST carbons were studied using scanning electron microscopy images and the nitrogen adsorption isotherms analyzed with several models of pores and different adsorption equations. A developed model of pores as a mixture of gaps between spherical nanoparticles and slitlike pores was found appropriate for MAST carbons. Adsorption of ibuprofen [2-(4-isobutylphenyl)propionic acid] on activated carbons possessing different pore size distributions in protein-free and bovine serum albumin (BSA)-containing aqueous solutions reveals the importance of the contribution of mesopores to the total porosity of adsorbents. The influence of the mesoporosity increases when considering the removal of the drug from the protein-containing solution. Cellulose-coated microporous carbon Norit RBX adsorbs significantly smaller amounts of ibuprofen than uncoated micro/mesoporous MAST carbons whose adsorption capability increases with increasing mesoporosity and specific surface area, burnoff dependent variable. A similar effect of broad pores is observed on adsorption of fibrinogen on the same carbons. Analysis of the ibuprofen adsorption data using Langmuir and D'Arcy-Watt equations as the kernel of the Fredholm integral equation shows that the nonuniformity of ibuprofen adsorption complexes diminishes with the presence of BSA. This effect may be explained by a partial adsorption of ibuprofen onto protein molecules immobilized on carbon particles and blocking of a portion of narrow pores.     

Preparation of highly porous carbon from fir wood by KOH etching and CO2 gasification for adsorption of dyes and phenols from water

Fir wood was first carbonized for 1.5 h at 450 degrees C, then soaked in a KOH solution KOH/char ratio of 1, and last activated for 1 h at 780 degrees C. During the last hour CO2 was poured in for further activation for 0, 15, 30, and 60 min, respectively. Carbonaceous adsorbents with controllable surface area and pore structure were chemically activated from carbonized fir wood (i.e., char) by KOH etching and CO2 gasification. The pore properties, including the BET surface area, pore volume, pore size distribution, and pore diameter, of these activated carbons were first characterized by the t-plot method based on N2 adsorption isotherms. Fir-wood carbon activated with CO2 gasification from 0 to 60 min exhibited a BET surface area ranging from 1371 to 2821 m2 g(-1), with a pore volume significantly increased from 0.81 to 1.73 m2 g(-1). Scanning electron microscopic (SEM) results showed that the surfaces of honeycombed holes in these carbons were significantly different from those of carbons without CO2 gasification. The adsorption of methylene blue, basic brown 1, acid blue 74, p-nitrophenol, p-chlorophenol, p-cresol, and phenol from water on all the carbons studied was examined to check their chemical characteristics. Adsorption kinetics was in agreement with the Elovich equation, and all equilibrium isotherms were in agreement with the Langmuir equation. These results were used to compare the Elovich parameter (1/b) and the adsorption quantity of the unit area (q(mon)/Sp) of activated carbons with different CO2 gasification durations. This work facilitated the preparation of activated carbon by effectively controlling pore structures and the adsorption performance of the activated carbon on adsorbates of different molecular forms.     

The physical and surface chemical characteristics of activated carbons and the adsorption of methylene blue from wastewater

Adsorption of a basic dye, methylene blue, from aqueous solutions onto as-received activated carbons and acid-treated carbons was investigated. The physical and surface chemical properties of the activated carbons were characterized using BET-N(2) adsorption, X-ray photoelectron spectroscopy (XPS), and mass titration. It was found that acid treatment had little effect on carbon textural characteristics but significantly changed the surface chemical properties, resulting in an adverse effect on dye adsorption. The physical properties of activated carbon, such as surface area and pore volume, have little effect on dye adsorption, while the pore size distribution and the surface chemical characteristics play important roles in dye adsorption. The pH value of the solution also influences the adsorption capacity significantly. For methylene blue, a higher pH of solution favors the adsorption capacity. The kinetic adsorption of methylene blue on all carbons follows a pseudo-second-order equation.     

NO2 removal on adsorbents prepared from coffee industry waste materials

A technology for obtaining carbonaceous adsorbents by physical and chemical activation of waste materials from coffee industry is described. The effect of pyrolysis temperature and type of activation procedure on the textural parameters, acid–base character of the surface and sorption properties of activated carbons has been tested. The resulting carbons were characterized by low-temperature nitrogen sorption, determination of pH and the number of surface oxygen groups. The sorption properties of the activated carbons obtained were characterized by evaluation of nitrogen dioxide adsorption in dry and wet conditions. The final products were adsorbents of specific surface area ranging from 5 to 2,076 m²/g and pore volume from 0.03 to 1.25 cm³/g, showing very diverse acidic–basic character of the surface. The results obtained in our study have proved that a suitable choice of the pyrolysis and activation procedure for coffee industry wastes permits production of adsorbents with high sorption capacity of nitrogen dioxide, reaching to 44.5 and 84.1 mg NO₂/g in dry and wet conditions, respectively.     

ACTIVATION ENERGY OF DESORPTION OF DIBENZOFURAN ON ACTIVATED CARBONS

Three kinds of commercial activated carbons, such as Norit RBI, Monolith and Chemviron activated carbons, were used as adsorbents for adsorption of dibenzofiuran. The average pore size and specific surface area of these activated carbons were measured Temperature Programmed Desorption (‘TPD) experiments were conducted to measure the TPD curves of dibenzofuran on the activated carbons, and then the activation energy for desorption of dibenzofuran on the activated carbons was estimated. The results showed that the Chemviron and the Norit RB1 activated carbon maintained higher specific surface area and larger micropore pore volume in comparison with the Monolith activated carbon, and the activation energy for the desorption of dibencofuran on these two activated carbons was higher than that on the Monolith activated carbon. The smaller the pore of the activated carbon was, the higher the activated energy of dibenzofiuran desorption was.