Adsorption onto Activated Carbon Fiber Cloth and Electrothermal Desorption of Volatile Organic Compound(VOCs):A Specific Review

A general research program, focusing on activated carbon fiber cloths （ACFC） and felt for environmental protection was performed. The objectives were multiple： （i） a better understanding of the adsorption mecha- nisms of these kinds of materials; （ii） the specification and optimization of new processes using these adsorbents; （iii） the modeling of the adsorption of organic pollutants using both the usual and original approaches; （iv） applications of ACFC in industrial processes. The general question was： how can activated carbon fiber cloths and felts be used in air treatment processes for the protection of environment. In order to provide an answer, different approaches were adopted. The materials （ACFC） were characterized in terms of macro structure and internal porosity. Specific studies were performed to get the air flow pattern through the fabrics. Head loss data were generated and modeled as a fi.mction of air velocity. The performances of ACF to remove volatile organic compounds （VOCs） were approached with the adsorption isotherms and breakthrough curves in various operating conditions. Regenera- tion by Joule effect shows a homogenous heating of adsorber modules with rolled or pleated layers. Examples of industrial developments were presented showing an interesting technology for the removal of VOCs, such as dichloromethane, benzene, isopropyl alcohol and toluene, alone or in a complex mixture.

Adsorption of volatile organic compounds on three activated carbon samples:Effect of pore structure

To investigate the influence of the activated carbon pore structure on the adsorption of volatile organic compounds （VOCs）, three commercial activated carbon samples were chosen. The fixed-bed thermostatic adsorption experiments were conducted under certain conditions, where toluene, acetone, and 1, 2-dichloroethane acted as adsorbents. Then, the incidence relation between the experimental results and the activated carbon pore structure was analyzed. After that, the results of the correlation analysis were verified in accordance with fractal theory and adsorption characteristic curve analysis. The results show that the pore diameter gradient is helpful for strengthening the intemal diffusion. Under the same condition, the adsorption of organic gases tends to be selective, and the positions of toluene, acetone and 1, 2-dichloroethane adsorbed on the activated carbon are mainly in the ranges of 1.27-1.49 nm, 0.67-0.84 nm and 1.39-1.75 nm, respectively. The relationship between adsorption capacity and activated carbon pore volume can accurately explain the spreading process of the adsorbents in the activated carbon.

A mini-review on the modeling of volatile organic compound adsorption in activated carbons: Equilibrium, dynamics, and heat effects

The research on the adsorption equilibria,kinetics,and increase in process temperature of the volatile organic compound(VOC)adsorption in porous materials ensures safe production,thereby reducing production costs and improving separation efficiency.Therefore,it is critical in predicting the entire adsorption process based on minimal or no experimental input of the adsorbate and adsorbent.We discuss,in this review,the factors that affect the adsorption performance of VOCs in activated carbons,including the adsorption equilibrium,adsorption kinetics,and exotherm during adsorption.Subsequently,the existing prediction models are summarized and compared concerning the adsorption equilibrium,adsorption kinetics,and exothermic process of adsorption.We then propose a new prediction model based on intermolecular interaction and provide an outlook toward the design and manipulation of efficient adsorbents for the VOC system.

Hierarchical pore structure of activated carbon fabricated by CO_2/microwave for volatile organic compounds adsorption

An activated carbon pore-expanding technique was achieved through innovative reactivation by CO_2/microwave.The original and modified activated carbons were characterized by nitrogen adsorption–desorption,scanning electron microscopy,transmission electron microcopy,and Fourier transform infrared spectroscopy.The mesopore volume increased from 0.122 cm^3·g^(-1) to 0.270 cm^3·g^(-1),and a hierarchical pore structure was formed.A gradual decrease in the phenolic hydroxyl and carboxyl groups on the surface of activated carbon enhanced the surface inertia of granular activated carbon(GAC).The toluene desorption rate of the modified sample increased by 8.81% compared with that of the original GAC.Adsorption isotherm fittings revealed that the Langmuir model was applicable for the original and modified activated carbons.The isosteric adsorption heat of toluene on the activated carbon decreased by approximately 50%,which endowed the modified sample with excellent stability in application.The modified samples showed an enhanced desorption performance of toluene,thereby opening a way to extend the cycle life and improve the economic performance of carbon adsorbent in practical engineering applications.

ORGANIC CHELATING REAGENT ON REDOX ADSORPTION OF ACTIVATED CARBON FIBER TOWARDS Au^(3+)

Organic chelating reagent influences upon the redox adsorption of activated carbon fiber towards Au3+ were systematically investigated. The experimental results indicated that the presence of organic chelating reagent on activated carbon fiber strongly affects adsorption capacity of activated carbon fiber towards Au3+. The reduction-adsorption amount of Au3+ increased three times by the presence of 8-quinolinol. Furthermore, The reduction-adsorption amount of Au3+ depended on the pH value of adsorption and temperature.

STUDIES ON THE DYNAMIC COMPETITIVE ADSORPTION OF ORGANIC VAPORS ON THE ACTIVATED CARBON FIBERS ACTIVATED WITH PHOSPHORIC ACID

The dynamic competitive adsorption behaviors of different binary organic vapor mixtures on ACF-Ps under different operation conditions were investigated by gas chromatography in this paper. The studied mixtures included benzene/toluene, toluene/xylene, benzene/isopropylbenzene, ethyl acetate/toluene and benzene/ethyl acetate. Experimental results show that various ACF-Ps, as with ACF-W, can remove both vapors in binary vapor mixtures with over 99% of removal efficiency before the breakthrough point of the more weakly adsorbed vapor. In dynamic competitive adsorption, the more weakly adsorbed vapor not only penetrates early, but also will be displaced and desorbed consequently by stronger adsorbate and therefore produces a rolling up in the breakthrough curve. The ACF-Ps prepared at different temperatures have somewhat different adsorption selectivity. The feed concentration ratio of vapors, the length/diameter ratio and the thick of bed have effect on competitive adsorption. The competitive adsorption ability of a vapor is mainly related to its boiling point. Usually, the higher the boiling point, the stronger the vapor adsorbed on ACF-P.

高比电容MOF衍生的介孔球状Co_(3)O_(4)/NiO/CuO

通过溶剂热合成了CoNiCu-MOF金属有机框架化合物,并通过后续的煅烧制备了Co_(3)O_(4)/NiO/CuO电极材料。对材料的形貌和比表面积进行表征,并测量了材料在不同扫描速率下的循环伏安曲线和不同电流密度下的恒流充放电曲线以及循环稳定性。将所得材料作为正极,活性炭作为负极组装了超级电容器器件,测量了器件的电化学性能。结果表明:Co_(3)O_(4)/NiO/CuO材料具有多孔结构和较大的可用比表面积(50.24 m2·g^(-1))。当电流密度为1 A·g^(-1)时,Co_(3)O_(4)/NiO/CuO的比电容高达3682.2 F·g^(-1)。所组装的Co_(3)O_(4)/NiO/CuO//AC非对称超级电容器的能量密度在1.45 V的电势窗口内达到186.8 Wh·kg^(-1),功率密度高达7249.8 W·kg^(-1)。Co_(3)O_(4)/NiO/CuO是一种性能优良的超级电容器电极材料,具有广阔的应用前景。

Structure evolution of oxygen removal from porous carbon for optimizing supercapacitor performance

The presence of oxygen functional groups is detrimental to the capacitive performance of porous carbon electrode in organic electrolyte. In this regards, hydrogen thermal reduction has been demonstrated effective approach in removing the unstable surface oxygen while maintaining the high porosity of carbon matrix. However, the exact evolution mechanism of various oxygen species during this process, as well as the correlation with electrochemical properties, is still under development. Herein, biomass-based porous carbon is adopted as the model material to trace its structure evolution of oxygen removal under hydrogen thermal reduction process with the temperature range of 400–800 °C. The optimum microstructure with low oxygen content of 0.90% and proper pore size distribution was achieved at 700°C. XPS, TPRMS and Boehm titration results indicate that the oxygen elimination undergoes three distinctive stages(intermolecular dehydration, hydrogenation and decomposition reactions). The optimum microstructure with low oxygen content of 0.90% and proper pore size distribution was achieved at 700 °C. Benefiting from the stable electrochemical interface and the optimized porous structure, the as-obtained HAC-700 exhibit significantly suppressed self-discharge and leak current, with improved cycling stability, which is attributable to the stabilization of electrochemical interface between carbon surface and electrolyte. The result provides insights for rational design of surface chemistry for high-performance carbon electrode towards advanced energy storage.

钯炭催化剂催化氧化乙酸乙酯和甲苯的研究

以微孔球形活性炭为载体,通过浸渍法制备了钯炭催化剂(PP),研究了钯负载量、气体空速和进气浓度对甲苯和乙酸乙酯催化性能的影响。利用ICP、XRD、XPS等对催化剂进行表征。结果表明,PP催化剂的催化性能随钯负载量的增加逐渐提升,钯负载量为3.0%时所制PP催化剂在空速为12000 mL/(g·h)的条件下分别将乙酸乙酯和甲苯的T90降至276.8℃和198.1℃。同时,在模拟VOC催化氧化环境下运行168 h后,PP对乙酸乙酯和甲苯的T90分别升高了2.8℃和4.7℃,表明该催化剂具有良好的稳定性。

城市排水系统中挥发性有机污染物检测及处理措施研究

针对目标城市污水排水系统中挥发性有机污染物含量超标的问题,以排水系统出水端水样为研究对象,对水样中的典型挥发性有机污染物含量进行了检测,并在原有混凝处理工艺的基础上进行改进,形成了混凝+活性炭吸附处理工艺,优化了相关处理参数。结果表明:经原有混凝工艺处理后,污水中三种挥发性有机污染物的含量均较高,无法达到GB 18918—2002中规定的排放要求。D型活性炭对污水的处理效果最好;活性炭的投加量越大,吸附时间越长,污水中挥发性有机污染物的含量越小,去除率越大;随着污水p H值的升高,污水中挥发性有机污染物的含量先减小后增大,去除率则先增大后减小。确定最佳处理参数为选择活性炭类型为D型、投加质量浓度为150 mg/L,吸附时间为6 h,污水p H值为5,此时污水中三种挥发性有机污染物的含量均能达到GB 18918—2002中规定的排放要求。

热压法制备MIL-100(Fe)/ACF复合材料及其对染料的光催化脱色

以七水合硫酸亚铁为金属盐,均苯三甲酸(H3BTC)为配体,活性炭纤维(ACF)为基材,采用热压法制备了MIL-100(Fe)/ACF复合材料。以活性黑KN-R染料为脱色对象,通过正交试验优化了MIL-100(Fe)/ACF复合材料的制备工艺:七水合硫酸亚铁与H3BTC的物质的量之比为1.5∶1、热压温度为150℃、热压时间为40 min。利用SEM、FT-IR、XRD表征手段,证明MIL-100(Fe)成功负载到ACF上。研究了复合材料在不同条件下对染料的脱色性能,结果表明:随着染液中H2O2添加量的增加,脱色率提高,但当H2O2加入量超过0.16 mL/L后,脱色率变化不大。复合材料对不同染料的脱色效果不同,对活性黑KN-B和罗丹明B的脱色率超过96.0%,对活性红3BS的脱色率达到90.0%以上,对活性艳蓝KN-R的脱色率仅为65.6%。重复使用4次后,对活性黑KN-B染液的脱色率为75.4%。

挥发性有机废气吸附浓缩+催化燃烧技术的研究及应用

双碳目标下,挥发性有机物(VOCs)的治理成为大气污染控制方向的关键与重点。文章介绍了挥发性有机废气活性炭吸附浓缩+催化燃烧技术和沸石转轮吸附浓缩+催化燃烧处理技术,探讨了该技术的实际应用情况。通过对某机械装备厂基础装备等车间,喷漆、烘干过程产生的有机废气的处理研究表明,经吸附浓缩+催化燃烧处理系统后,VOCs综合去除效率>90%,达到当地环保要求。

水性聚酯纺织浆料生产废气挥发治理技术优化与应用研究

研究了水性聚酯纺织浆料生产废气挥发治理技术优化与应用。通过试验对比不同工艺单元的处理效率,选择了水喷淋、干式过滤、活性炭吸脱附和催化燃烧装置等多种治理技术,并通过优化组合方案,达到了较好的治理效果。同时,本文也对治理技术的优缺点进行了分析和评价,为类似企业废气治理提供参考。

Binary Adsorption Equilibrium of Benzene-Water Vapor Mixtures on Activated Carbon

Adsorption equilibrium isotherms of benzene in the concentrationrange of 500-4000 mg·m^-3 on two commercial activated carbons wereobtained using long-column method under 30 deg. C and differenthumidity condi- tions. Results show that the benzene and water vaporshave depression effects upon the adsorption of each other and thatthe unfavorable effect of water vapor resembles its single-componentisotherm on activated carbon. A com- petitive adsorption model wasproposed to explore the depression mechanisms of the non-ideal,non-similar binary adsorption systems.

Removal of Volatile Organic Compounds by Adsorption and Photocatalytic Oxydation

Based on the study of equilibrium adsorption on viscose rayon-based activated carbon fiber （ACF） by gravimetric method, mounting of TiO2 on PAN-based activated carbon cloth （ACC） and their photocatalytic activity as well as adsorption performance for benzene were investigated. The crystallinity of TiO2 and pore structure were characterized by XRD and N2 adsorption. The results show that crystallinity of TiO2 and pore structure could be postulated by heat treatment condition. Both crystallinity of TiO2 and pore structure of hybrid have effects on photocatalytic performance of TiO2-mounted ACC. It would be more attractive and prospective for the combination of TiO2 photocatalytic activity and adsorption ability of porous materials.

锆基金属有机骨架材料/活性碳纤维复合材料的制备及其降解性能

为改善活性碳材料在芥子气防护过程中存在的吸附易饱和、处置不当易造成二次污染等问题,制备了一种以活性碳纤维(ACF)为基材的新型降解材料。首先利用抽滤法将纳米锆溶胶沉积到ACF表面,随后采用层层自组装法,以ZrCl 4为金属簇、对苯二甲酸为有机配体,在纤维表面原位生长锆基金属有机骨架材料(Zr-MOF),最终制备出一种对芥子气模拟剂2-氯乙基乙基硫醚(CEES)有较高降解性能的Zr-MOF/ACF复合材料,综合采用扫描电子显微镜、X射线衍射、比表面积及孔结构分析等手段进行表征,并测试了其对CEES的降解性能和力学性能。结果表明:锆溶胶的引入有效提高了Zr-MOF在ACF表面的负载量,从而提升了所得材料对CEES的降解性能,并且力学性能也获得显著提高;综合考虑样品的降解性能、拉伸强度与制备效率,将经锆溶胶处理后进行15次循环处理的样品定为最佳工艺样品,经过24 h反应后,对CEES的降解率为83.08%,断裂强度为0.40 MPa,相比于酸化处理的活性碳纤维毡,复合材料的拉伸强度提升了80.99%。

中药渣制备超高比表面积活性炭及其甲苯吸附性能研究

以中药渣为碳源,采用KOH辅助活化制备了具有超高比表面积的中药渣活性炭吸附剂。探索了碱炭质量比(mKOH/mC)、活化温度对吸附剂孔隙结构及其对甲苯吸附行为的影响。在mKOH/mC为5、温度为800℃的热解条件下,活性炭的比表面积和总孔容分别达到了3549 m^(2)/g和2.12 cm^(3)/g,微孔比表面积和微孔孔容分别为2529 m^(2)/g和1.33 cm^(3)/g,微孔占比达到了62.7%。在25℃、相对压力P/P0为0.9~1时的甲苯吸附量更是高达2612 mg/g。该中药渣活性炭吸附剂在挥发性有机物去除方面具有广阔的应用前景。

金属氧化物低温催化氧化VOCs的研究进展

一直以来,开发强氧化活性和高抗性的金属氧化物催化剂都是催化脱除挥发性有机化合物(VOCs)领域的研究热点。本文从氧空位、活性氧物种、结构和晶面等角度,比较分析了催化剂的组成比例、形貌、焙烧温度、制备方法和载体等制备因素对增强催化氧化VOCs活性和二氧化碳选择性的影响。阐述了实际工况中的水蒸气、氮氧化物和二氧化硫在氧化反应过程中的中毒机制。展望了利用DFT计算,深入探索氧空位、晶格氧和表面吸附氧在VOCs催化氧化过程中的作用机理,并从活性组分分散度、高活性晶面占比、氧空位强度等关键方面来指导优化催化剂,为相关催化体系的研发提供了科学参考。

多层吸附床层中活性炭对烷烃的吸附特性

为了解活性炭对小分子直链烷烃的吸附情况,通过在多层床层结构中测试颗粒活性炭吸附剂对烷烃的吸附,试验发现颗粒活性炭对C4-C7直链烷烃的吸附量随碳原子数目增加,饱和吸附量从22 mg/g增加至145 mg/g,穿透时间从5 min延长至35 min。碳原子数目从C7增加到C8时,吸附量无改变,但穿透时间缩短至25 min。实验发现颗粒活性炭的吸附容量与烷烃的液相饱和蒸气压成负相关,与相对分子量、沸点、极化率成正相关。在多层吸附床层结构中处理以C5-C8直链烷烃为主的废气,吸附剂吸附容量可被完全利用,使用2层床层结构设计即可满足排放及换料需求,吸附以C4为主的废气,则需使用更多层床层设计。

工程机械制造企业涂装废气处理工程实例

在工程机械的制造过程中,涂装时使用的涂料、固化剂、稀释剂等原辅料中含挥发性有机物成分。项目通过建设高效的“干式过滤+活性炭吸附+脱附催化氧化”废气处理系统,对废气进行处理后,废气中各污染物浓度大幅下降,排放的废气各挥发性有机物指标可达到《表面涂装(汽车制造及维修)挥发性有机物、镍排放标准》(DB43/1356—2017)中标准限值的要求,有效降低了挥发性有机物的排放。