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.     

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.     

Preparation of mesoporous carbon from commercial activated carbon with steam activation in the presence of cerium oxide

Mesoporous carbon was prepared from the commercial activated carbon by steam activation with cerium oxide as catalyst. Steam activation with a catalyst loading of 0.5-2.0 wt% at 680-870 degrees C was examined. The surface area and pore size were evaluated by nitrogen adsorption at 77 K, and the structure of cerium oxide was characterized by XRD, XPS, and TEM. The results showed that the catalyst promoted the development of a mesopore at lower temperature (680-740 degrees C), and the mesopore was concentrated around 4-10 nm. The noncatalytic activation was advantageous in mesopore development and the catalyst would restrict the formation of mesopores at high temperature (800-870 degrees C). Higher loading of cerium oxide and higher activation temperature caused the aggregation of cerium oxide and then resulted in scattered pore size distribution.     

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.     

KOH活化木屑生物炭制备活性炭及其表征

以木屑热裂解的生物质炭为原料,氢氧化钾为活化剂,采用化学活化法制备活性炭,探讨了碱炭比、活化温度和活化时间对活性炭吸附亚甲基蓝吸附值的影响。 利用N2吸附实验、XRD和FTIR等实验技术,对原料与制备活性炭的结构与性能进行了表征。 结果表明,在碱炭质量比为1.5、活化温度750 ℃、活化时间2 h的条件下,所制备的活性炭对亚甲基蓝吸附值为255 mg/g,BET总比表面积为1514 m2/g,中孔比表面积为110 m2/g,吸附总孔容为0.821 cm3/g,中孔孔容为0.117 cm3/g,吸附平均孔径为2.170 nm。     

多微孔活性炭的制备及对二甲苯的吸附研究

研究了以木质活性炭颗粒为原料, 通过KOH再活化的方法制备多微孔活性炭的方法。考察了活性炭和KOH的最佳质量比例, 并通过低温氮吸附、SEM、XRD等手段表征了样品的比表面、孔结构、孔分布、颗粒形貌和晶体结构;通过对含间二甲苯50 mg·L^-1的气流的吸附实验表征了所制备活性炭的二甲苯去除能力, 实验结果表明, 经过KOH再活化显著调高了样品的间二甲苯吸附容量, 这很可能和样品中发达的微孔结构有关。     

The study of controlling pore size on electrospun carbon nanofibers for hydrogen adsorption

Polyacrylonitrile (PAN)-based carbon nanofibers (CNFs) were prepared by using electrospinning method and heat treatment to get the media for hydrogen adsorption storage. Potassium hydroxide and zinc chloride activations were conducted to increase specific surface area and pore volume of CNFs. To investigate the relation between pore structure and the capacity of hydrogen adsorption, textural properties of activated CNFs were studied with micropore size distribution, specific surface area, and total pore volume by using BET (Brunauer-Emmett-Teller) surface analyzer apparatus and the capacity of hydrogen adsorption was evaluated by PCT (pressure-composition-temperature) hydrogen adsorption analyzer apparatus with volumetric method. The surface morphology of activated CNFs was observed by SEM (scanning electron microscope) images to investigate the surface change through activation. Even though specific surface area and total pore volume were important factors for increasing the capacity of hydrogen adsorption, the pore volume which has pore width (0.6-0.7 nm) was a much more effective factor than specific surface area and pore volume in PAN-based electrospun activated CNFs.     

Preparation and structural characterization of activated carbons based on polymeric resin

In this work, activated carbons (ACs) with high porosity were synthesized from polystyrene-based cation-exchangeable resin (PSI) by chemical activation with KOH as the activating agent. And the influence of the KOH-to-PSI ratio on the porosity of the ACs studied was investigated by using nitrogen adsorption isotherms at 77 K and a scanning electron microscope (SEM). As a result, PSI could be successfully converted into ACs with well-developed micro- and mesopores. The specific surface area and pore volumes increased with an increase in the KOH-to-PSI ratio. However, it was found that the addition of KOH did lead to the transformation of the micropores to the meso- and macropores. From the results of pore size analysis, quite different pore size distributions were observed, resulting from the formation of new pores and the widening of the existing micropores during KOH activation. A SEM study showed that the resulting carbons possessed a well-developed pore structure and the pore size of the ACs studied increased with the KOH-to-PSI ratio.     

多微孔活性炭的制备及对二甲苯的吸附研究

研究了以木质活性炭颗粒为原料,通过KOH再活化的方法制备多微孔活性炭的方法。考察了活性炭和KOH的最佳质量比例,并通过低温氮吸附、SEM、XRD等手段表征了样品的比表面、孔结构、孔分布、颗粒形貌和晶体结构;通过对含间二甲苯50mg.L-1的气流的吸附实验表征了所制备活性炭的二甲苯去除能力,实验结果表明,经过KOH再活化显著调高了样品的间二甲苯吸附容量,这很可能和样品中发达的微孔结构有关。     

碳化硅衍生碳/球形天然石墨复合材料的制备及其结构调控

为满足储能领域对于材料兼具高能量密度和高功率密度的需求, 本文旨在将具有特殊孔隙结构的碳化物衍生碳与具有高导电性和高能量存储密度的石墨化碳(球形天然石墨)相复合, 制备得到一种多孔碳化硅衍生碳/球形天然石墨(SiC-CDCs@NG)复合材料. 采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、拉曼光谱、N₂吸/脱附等方法对材料的组成、结构、形貌、孔结构和比表面积等进行了表征. 结果表明,SiC-CDCs@NG材料具有较大的且可调节的比表面积和微孔体积, 微孔孔径集中在0.5-0.7 nm范围内; 通过改变NG/Si 摩尔比, 可以有效调控CDCs壳和NG核在复合材料中的组成分布、CDCs微孔的体积、孔径分布和比表面积.     

活性炭孔径和比表面积对TiO2/AC光催化性能的影响

采用“同步物理-化学活化法”二次活化商品活性炭, 制备不同孔径和比表面积的系列活性炭(AC)载体, 以偏钛酸为钛源, 利用均匀沉淀法制备TiO2负载型光催化剂(TiO2/AC), 用氮吸附、XRD、SEM等方法表征, 研究活性炭的孔径和比表面积对TiO2/AC性能的影响; 并通过降解水溶液中的亚甲基蓝(MB)研究TiO2/AC光催化氧化特性, 考察催化剂投加量、不同MB浓度等因素对光催化氧化的影响. 结果表明, 负载的TiO2粒子粒径为12-20 nm, 活性炭的比表面积大、平均孔径大有利于TiO2的均匀分散, 阻止TiO2晶粒生长, 有利于充分发挥TiO2小尺度效应; 另外, 活性炭吸附和TiO2光解的协同效应使TiO2/AC光催化剂对MB降解的效率显著提高. 动力学研究表明, TiO2/AC光催化降解MB反应符合表观一级动力学特征.     

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 degrees 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.     

介孔二氧化钛的合成及其对甲基橙降解的光催化活性

以十六烷基三甲基溴化铵为模板剂,通过水解钛酸正丁酯合成了介孔二氧化钛分子筛,探讨了合成条件的影响。采用X射线粉末衍射(XRD)、红外光谱(FT-IR)、透射电子显微镜(TEM)和N2吸附-脱附等技术对介孔二氧化钛的晶相、结构、形貌、比表面积和孔径分布进行了表征。实验结果表明:得到的介孔二氧化钛分子筛的孔径为4-4.3nm,用抽提的方法去除模板剂得到的介孔二氧化钛的比表面积比焙烧的要高。以甲基橙为模型污染物,检验了所合成介孔二氧化钛的光催化性质。     

孔结构对活性炭吸附水溶液中铅离子的影响

选取三种表面化学性质相近的活性炭(AC),通过等温吸附实验考察活性炭对水溶液中铅离子的吸附性能,利用扫描电子显微镜(SEM)观察活性炭的表面微观形貌,通过低温(77 K)液氮吸附测定活性炭的比表面积和孔容,并分别以密度泛函理论(DFT)和Barrett-Joyner-Halenda (BJH)法计算微孔和中孔的孔径分布.结果表明:选用的三种活性炭AC1、AC2、AC3在比表面积和总孔容上呈依次下降的趋势,但表面开放孔均匀分布的AC2,具有最高的饱和吸附量,孔结构类似颗粒堆积孔的AC3,具有与表面开放孔分布集中的AC1相近的饱和吸附量;通过对孔结构与吸附量的关联分析可知,在活性炭吸附铅离子的过程中, 0.4-0.6 nm的孔是有效吸附孔, 10.5-20.6 nm、20.6-55.6 nm、5.2-10.5 nm三个区间的孔则会对吸附产生阻碍作用.     

纳米Fe(OH)3为模板的三维石墨烯类多孔碳的制备及其催化氧还原性能研究

以煤焦油沥青为碳源,纳米Fe(OH)₃为模板制备了一种三维石墨烯类多孔碳材料,通过测试氧还原性能,确定了最佳制备工艺为：反应物煤沥青,纳米Fe(OH)₃,KOH的质量配比为6:8:4,热解温度为800 ℃. 扫描电镜（SEM）测试结果表明,制得的产品具有明显的孔结构且分布均匀. 透射电镜（TEM）测试结果进一步表明,产品具有泡沫状的多孔结构,高分辨透射电子显微镜图像表明该产品具有多层的三维石墨烯结构. X射线衍射（XRD）数据表明,在29^o位置出现的衍射峰是多层石墨烯结构,42^o位置的衍射峰表明,产品具有一定程度的石墨化. 由拉曼光谱结果计算I_G与I_2D的比值表明产品为多层石墨烯结构. X射线光电子能谱分析（XPS）检测到的C元素含量约为88.7%,主要包含C-C键,图谱中未发现铁元素的存在,证明纳米Fe(OH)₃模板已被洗净. 根据比表面积测定（BET）可知,多孔碳的比表面积为2040 m²•g^-1,孔径集中分布在10~400 nm,这与TEM测试得到的结果一致. 在0.1 mol•L^-1 KOH中进行催化氧还原性能测试,起始还原电位为0 V (vs. Hg/HgO),电子转移数为3.58。测试结果表明,制得的三维石墨烯类多孔碳具有良好的催化氧还原性能.     

Effect of synthesis conditions on preparation of mesoporous titania-silica by a modified sol-gel technique using a cationic surfactant

Titania-silica mesoporous materials have been synthesized by a modified sol-gel technique using a cationic surfactant. The synthesis process was studied using statistical design of experiments to achieve the best conditions for titania-silica preparation. The synthesized materials were characterized by XRD, FT-IR, SEM and surface area measurements. The XRD and SEM results showed an amorphous structure of titania-silica. The surface area measurements using nitrogen adsorption showed type-IV isotherms which indicate the formation of mesoporous structure. A high surface area can be obtained (685 m²/g). The crystal size of titania-silica calculated using Scherrer’s equation was found to be in the range 8–15 nm.     

Preparation and characteristics of electrospun activated carbon materials having meso- and macropores

Mesoporous activated carbon samples were prepared from electrospun PAN-based carbon fibers using physical activation with silica. Textural characterization was performed using nitrogen adsorption at 77 K. The BET specific surface area and pore size distribution of silica activated carbon materials were investigated. According to the increment of silica, BET specific surface area was increased about thirty times and it was found that silica activated carbon materials were highly mesoporous by studying pore surface distribution and pore volume distribution. Surface morphology of silica activated carbon materials were observed by SEM images. The spherical typed carbon materials were investigated. The diameter of spherical typed carbon materials was increased in proportional of the increment of silica.     

汉麻杆基活性炭表面织构与储氢性能的研究

以天然汉麻杆为原料,采用KOH化学活化的方法改变活化时间制备出了高比表面积活性炭,并且对其表面进行硝酸氧化处理,研究活性炭表面化学状态对其吸附性能的影响。采用77 K低温氮气吸附和FTIR对样品进行了表征,并在77 K、100 kPa的条件下测定样品的氢气吸附等温线。结果表明,所有样品具有较高的比表面积(2 435.93～3 240.95 m²·g^-1)和总孔容(1.3～1.98 cm³·g^-1),且随活化时间的延长而增加,3.5 h达到最大值,之后由于骨架坍塌有所减小。所有样品的孔径分布较为一致呈多峰型分布,主要以小于2 nm的微孔为主,同时含有少量的中孔和大孔。活化3.5 h样品的吸氢量最大,达到3.28wt%。研究发现,吸氢量受比表面积和孔容等参数影响较大,77 K下不仅小于2 nm的微孔对活性炭吸氢行为贡献较大,中孔也有十分重要的影响。样品经硝酸氧化处理后,BET比表面积和总孔容均在一定程度上减小,而氢气吸附量也有所降低。     

Study on the Adsorption Characteristics of Inorganic Activated Charcoal Gel on Formaldehyde

In this paper, the powdered activated carbon is taken as the main raw material to develop a new material of inorganic activated charcoal gel by using silicate cement as the gelling agent. The micro-structure of this material is characterized by XRD, BET, SEM, EDS and so on; and the adsorption and cyclic regeneration characteristics of formaldehyde on the material are primarily studied. The experimental results show that this material is an adsorbent on the basis of micropores distributed between 0.60-1.12 nm, with specific surface area of 452.86 m2/g, average pore size of 2.62 nm and total pore space of 0.30 m3/g. The samples have excellent formaldehyde adsorption ability with saturation adsorption of 268.00 mg/g; after 20 times of cyclic adsorption and desorption, the formaldehyde adsorption rate of the samples can remain 49% of the original value, showing good cyclic regeneration of the samples.     

KOH activation and characterization of glass fibers-supported phenolic resin

In this work, glass-fiber-supported activated carbons (GFACs) were prepared by KOH activation using phenolic resin. Two different preparation methods were chosen: (a) filling and (b) impregnation methods. The structural properties of the GFACs studied were characterized by using N2 adsorption isotherms at 77 K and transformed models, such as the DR equation and the alphas-plot. A scanning electron microscope (SEM) was also used to investigate the external pore structure of the resulting carbons. The specific surface areas and pore volumes for both methods increased with increasing content of KOH. However, the pore evolution for the filling method was superior to that for the impregnation method. DR plots for all samples showed a good linearity at low relative pressure. Also, all samples displayed a slight upward deviation at the linear portion of the alphas-plots, indicating the presence of mesopores and external surface area. SEM studies showed that GFACs possessed a well-developed pore structure and exhibited a change in the pore evolution according to the preparation conditions.