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 and Desorption of Gold on the Magnetic Activated Carbon

Adsorption and desorption of gold on the magnetic activated carbon (MAC) were investigated The adsorption rate of gold is higher than that of conventional coconut carbon in cyanide leach solution The loading gold can be easily desorbed as coconut carbon. Crushed fine magnetic carbon can be selected by a magnetic separator, It is suggested that the MAC can be used in carbon-in-pulp (CIP)process for increasing the recovery rate of gold

Preparation of Solid Waste-Based Activated Carbon and Its Adsorption Mechanism for Toluene

Regenerated activated carbon(RAC)samples were prepared by carbon activation using waste activated carbon from solid waste resources as the carbon source precursor coupled with adding alkaline additives,and then were further modified by potassium ferrate to finally prepare high-performance carbon for VOCs adsorption.At the same time,the samples before and after modification were systematically studied through characterization techniques such as SEM,Raman spectrometry,FT-IR,XPS,and dynamic/static adsorption.The results showed that the specific surface area and pore volume of the RAC after modification by the strong oxidant potassium ferrate increased by 1.4 times;the degree of defects was enhanced and the content of oxygen-containing functional groups on the surface increased significantly.Among them,the sample modified with potassium ferrate for 24 h had the best dynamic toluene adsorption performance(375.5 mg/g),and the dynamic adsorption capacity was twice that of the original sample(192.8 mg/g).The static adsorption test found that the maximum adsorption capacity of RAC-6%K_(2)FeO_(4)+H_(2)SO_(4)-24h was 796 mg/g,which indicated that the potassium ferrate modification treatment could significantly increase the VOCs adsorption performance of RAC.In addition,through consecutive toluene adsorption-desorption cycle tests,it was found that the RAC-6%K_(2)FeO_(4)+H_(2)SO_(4)-24h sample still retained 91%of adsorption activity after the fifth regeneration cycle.This indicates that RAC-6%K_(2)FeO_(4)+H_(2)SO_(4)-24h has good cycle stability and great application value for the efficient purification of industrial waste VOCs gas.

NO adsorption and temperature programmed desorption on K_2CO_3 modified activated carbons

Fuel cell stacks as the automotive power source can be severely poisoned by a trace amount of NOx in atmosphere,which makes it necessary to provide clean air for fuel cell vehicles.In this work,activating commercial activated carbons with K2CO3 for the large enhancement of NO capture was studied.K2CO3 modified activated carbons(K2CO3 ACs)were prepared by impregnating activate carbons in K2CO3 solution under ultrasound treatment,followed by temperature programmed baking at 800 oC.The dynamic NO flow tests on K2CO3 ACs at room temperature indicated that NO adsorption capacity reached the maximum(96 mg/g)when K2CO3 loading was 19.5 wt%,which corresponded to a specific surface area of 1196.1 m2/g and total pore volume of 0.70 cm3/g.The ten-fold enhancement of NO adsorption on K2CO3 ACs compared to the unimpregnated activated carbon was mainly attributed to the formation of potassium nitrite,which was confirmed by FTIR and temperature programmed desorption measurements.Regeneration tests of NO adsorption on the optimum sample revealed that 76%of the NO adsorption capacity could be remained after the fourth cycle.

Surface Modification of Commercial Activated Carbon (CAG) for the Adsorption of Benzene and Toluene

In this work, we determined the surface characteristics of natural (CA-1) and HNO3 treated (CA-2) CAG. Equilibrium, kinetics and breakthrough for adsorption of benzene and toluene by CA-1 and CA-2 were studied. Concentrations of benzene and toluene (mg/L) were determined by gas chromatography with headspace extraction. The data of adsorption kinetic and equilibrium were best fitted by pseudo-second order model and Langmuir isotherm, respectively. The best results of benzene and toluene adsorption from fixed bed were obtained at volumetric flow rate (Q1 = 70 mL/min) using adsorbent CA-2. The study of inferential statistics revealed that CA-1 and CA-2 adsorbents are statistically different at a 5% significance level.

Enhanced adsorption of phenol from aqueous solution by carbonized trace ZIF-8-decorated activated carbon pellets

Trace zeolitic imidazolate framework-8(ZIF-8)-decorated activated carbon(AC)pellets were synthesized by a facile wet impregnation technique.After pyrolysis of the above composite material,the obtained carbon had a large surface area and pore volume,with traces of Zn on its surface.Subsequently,the capacity of the ZIF8/AC samples to adsorb and remove phenol from aqueous media was evaluated in both batch and column experimental setups.The equilibrium adsorption capacity reached 155.24 mg·g^(-1),which was 2.3 times greater than that of the pure AC(46.24 mg·g^(-1)).In addition,adsorption kinetics were examined by pseudofirst and pseudosecond order models,and adsorption isotherms were fitted into Langmuir and Freundlich equations.The adsorbent could be easily filtered from the solution and washed with methanol and water,while maintaining an efficiency N90% after 4 cycles.The above results make it a potentially reusable candidate for water purification.

Heteroatomic Modification of Solid-Waste-Based Mesoporous Carbon for Volatile Organic Compound Adsorption

Solid-waste-based activated carbon(AC)was utilized as a carbon source to synthesize a series of carbon-based functional material RAC-X(X=P and S,where P and S denote phosphoric and sulfuric acids,respectively).The toluene adsorption capacities of the regeneration AC(RAC)samples can be significantly improved by adopting the heteroatomic modification strategy.RAC-P and RAC-S have the same specific surface area(1156 m^(2)/g)and similar porous structures.However,they have different toluene adsorption capacities,with 316.22 mg/g for RAC-P and 460.12 mg/g for RAC-S,which are 1.6 and 2.4 times greater than that for RAC.The X-ray photoelectron spectroscopy measurements showed that the increase in the amount ofπ–π^(2)chemical bond over the AC surface results in the improvement of the toluene adsorption performance.The density functional theory results showed that the S-containing functional groups loaded near the defect sites of RAC-S promote toluene adsorption.Moreover,reusability tests showed that RAC-S still retains 86%of its adsorption activity after four consecutive adsorption–desorption experiments.This indicates that the heteroatomic modification method affords excellent toluene adsorption performance and recycling practicability,which not only is beneficial for achieving the rational utilization of solid waste resources but also provides a practical method for the efficient elimination of volatile organic compounds.

Behaviors and kinetics of toluene adsorption-desorption on activated carbons with varying pore structure

This work was undertaken to investigate the behaviors and kinetics of toluene adsorption and desorption on activated carbons with varying pore structure. Five kinds of activated carbon from different raw materials were selected. Adsorption isotherms and breakthrough curves for toluene were measured. Langmuir and Freundlich equations were fitted to the equilibrium data, and the Freundlich equation was more suitable for simulating toluene adsorption. The process consisted of monolayer, multilayer and partial active site adsorption types. The effect of the pore structure of the activated carbons on toluene adsorption capacity was investigated. The quasi-first-order model was more suitable for describing the process than the quasi-second-order model. The adsorption data was also modeled by the internal particle diffusion model and it was found that the adsorption process could be divided into three stages. In the external surface adsorption process, the rate depended on the specific surface area. During the particle diffusion stage, pore structure and volume were the main factors affecting adsorption rate. In the final equilibrium stage, the rate was determined by the ratio of meso-and macro-pores to total pore volume. The rate over the whole adsorption process was dominated by the toluene concentration. The desorption behavior of toluene on activated carbons was investigated,and the process was divided into heat and mass transfer parts corresponding to emission and diffusion mechanisms, respectively. Physical adsorption played the main role during the adsorption process.

Adsorption of benzene and toluene from waste gas using activated carbon activated by ZnCl2

A series of activated carbons with high surface area were prepared from walnut shell using chemical activation with ZnCl2. In this research the carbonization stage was carried out at 500℃. The performance of the synthesized carbons evaluated in adsorption of benzene and toluene from waste gas. The influence of impregnation ratio on the characteristics of synthesized activated carbons as well as their adsorption capacity was investigated. The ratio of activation agent to walnut shell was selected in the range of 0.5-2.0 wt/wt. The synthesized activated carbons were characterized using XRD, SEM, BET and FTIR techniques. The highest activated carbon production yield was obtained at impregnation ratio of 1.5 wt/wt. The XRD analysis illustrated that peaks intensity decreased with increasing impregnation ratio showing that amorphous property of samples was increased. The SEM analysis revealed successful pore development in synthesized activated carbons obtained at high impregnation ratios. The surface area of the activated carbons increased with increasing impregnation ratio and its maximum value reached 2643 m2.g 1 at impregnation ratio of 2/1. FTIR analysis indicated that the relative amount of different acidic surface groups on synthesized carbons was a function of impregnation ratio. Experimental results for benzene and toluene adsorption showed a high potential of employing synthesized impregnated activated carbon for treatment of waste gas. Generally, the amount of VOC adsorbed on the surface was affected by physicochemical properties of synthesized activated carbons.

Performance evaluation of LPG desulfurization by adsorption for hydrogen production

The adsorption of sulfur compounds,in commercially available LPG,has been studied using different adsorbents,namely Zeolite,Zn O and house made date pits activated carbon（DP-AC）. It was found that the three adsorbents are capable of effectively removing sulfur compounds at different feed sulfur concentrations. The effects of height to diameter aspect ratio of the adsorption column,flow rate of LPG and input sulfur concentrations have been studied. A first order kinetics model has been used to describe the adsorption,and the kinetics constant was found to increase by increasing the flow rate of LPG and decrease by increasing the amount of adsorbent used. The developed model described the system fairly well,and can be used in designing and scaling-up of fixed-bed adsorption columns.

Adsorption dynamics of ethane from air in structured fixed beds with different microfibrous composites

Adsorption dynamics of ethane in two granular fixed beds and structured fixed beds with microfibrous composites was studied.5A zeolite membrane 5A/PSSF(paper-like sintered stainless steel fiber)and microfibrous entrapped activated carbon(MEAC)composites were prepared by wet layup papermaking/sintering technique and in-situ hydrothermal method.Microfibrous composites were characterized by X-ray diffraction,scanning electron microscopy and N2 adsorption/desorption.Structured fixed beds were designed by filling granular adsorbents(5A zeolite or activated carbon)and microfibrous composites at the inlet and outlet of the beds,respectively.Effects of flow rate,bed height and structure on the breakthrough curves were investigated.The length of unused bed(LUB)was determined,and Yoon–Nelson model was used to fit the breakthrough curves.The experimental results showed ethane was effectively adsorbed on the granular adsorbents and microfibrous composites.Both composites could decrease the LUB values and enhance bed utilization.All breakthrough curves fitted well to Yoon–Nelson model,with correlation coefficient exceeding 0.89.The adsorption rate of ethane could be improved in the structured fixed beds,which showed an enhanced mass transfer efficiency for ethane adsorption.LUB values of structured fixed beds with 5A/PSSF composites were larger,the bed utilization values were lower,and the adsorption rate constants were higher than those with MEAC composites under the same conditions.

表面活性剂改性吸附材料在水处理中的研究进展

表面活性剂在工业生产中扮演重要角色,近年来有诸多将表面活性剂用于改性吸附剂的应用。通过使用表面活性剂改性,可以改变吸附剂材料表面的化学性质,从而增加对阴离子或非极性有机物的吸附能力。介绍了表面活性剂及其改性吸附材料机理,总结了表面活性剂改性活性炭、粘土矿物、沸石、纳米材料和农业废弃物等吸附剂材料的研究,应用于包括吸附重金属离子、有机污染物和农药等,并提出关于改性可能需要关注的研究方向,有效拓展表面活性剂改性材料的应用前景。

CuO-modified activated carbon for the improvement of toluene removal in air

We used an impregnation method to prepare CuO/AC(activated carbon) composite materials of different CuO content and characterized them via scanning electron microscope(SEM), Brunauer–Emmett–Teller(BET), and Fourier transform infrared spectroscopy(FT-IR).The effect of CuO content on toluene adsorption/desorption was evaluated.We explored the reusability of AC and AC03(CuO modified AC with CuO loading 0.3 wt.%) adsorbents via toluene adsorption/desorption cycle testing.We used quasi-firstand quasi-second-order models, the Bangham model, and the Weber–Morris model to fit the toluene adsorption data.The introduction of CuO species evidently improved the adsorption performance of activated carbon toward toluene.The CuO content markedly affected the specific surface area, CuO dispersal, the numbers of oxygen-containing functional groups on the surface, and adsorption performance of the prepared composite adsorbents.Low CuO content was not favorable for the formation of active adsorption sites,while high content greatly reduced the specific surface area, and even covered active adsorption sites.The toluene adsorption performance varied in the order AC03 > AC02 >AC05 > AC08 > AC01(AC03, AC02, AC05, AC08 and AC01 are CuO modifying AC with CuO loading 0.3, 0.2, 0.5 0.8 and 0.1 wt.%, respectively).The breakthrough time and toluene adsorption capacity of the AC03 composite adsorbent were 94 min and 701.8 mg/g,respectively, and the recycling efficiency was 92.8% after thermal desorption at 200°C.The adsorption process was best described by the Bangham model and adsorption could be divided into three stages.

一种VOCs处理装置应用问题和优化改造

挥发性有机物(VOCs)作为有毒有害物质,对空气质量造成了严重影响。其中活性炭吸附脱附及催化燃烧装置被广泛用于VOCs的控制排放,VOCs浓度较高时,存在无法稳定达标排放问题。通过对活性炭吸附脱附与催化燃烧原理及装置实际工况分析,对其进行了针对性的优化改造。改造后,非甲烷总烃平均排放浓度、平均排放速度分别达到7.61 mg/m^(3)和289.94 g/h,分别降低了76.70%和78.24%,完全满足VOCs排放标准。结果表明:通过优化改造,不仅提高了该装置对VOCs的处理效果,而且实现了VOCs稳定达标排放,达到了该区域空气质量控制的目的。

氢气纯化吸附材料研究进展

氢能作为未来重要的能源组成,其来源具有多样性。其中工业制氢和副产氢过程通常会伴随多种杂质,如H_(2)O、CO_(2)、CO、N_(2)、烃类、硫化物等,而杂质对氢气的实际应用影响较大,因此对工业粗氢和副产氢进行纯化处理是满足各类合格用氢需求的关键环节。吸附分离是目前工业上最为常用的氢气纯化技术之一,其中吸附材料的性能直接影响分离效率和工艺操作成本,研发高性能、低成本吸附材料是吸附分离技术应用于氢气纯化的重点研究方向。本文简述了常见的氢气纯化技术及吸附分离机理,重点归纳总结了活性炭、沸石分子筛和金属有机骨架材料(MOFs)对氢气中所含CH_(4)、CO_(2)、CO杂质的吸附脱除行为,讨论了吸附材料性能优化的研究现状,总结了上述吸附材料在工业应用中的优缺点,并认为未来氢气纯化吸附材料的研究应在吸附机理和计算方面有所侧重。

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。

活性炭吸附脱附+催化燃烧工艺处理喷涂中的有机废气

针对常州某机械制造企业喷涂有机废气排放不达标问题,将传统的活性炭吸附工艺提升为“干式过滤+活性炭吸附脱附+催化燃烧工艺”,经监测,废气污染物非甲烷总烃排放浓度低于50 mg/m^(3),去除效率达80%~90%,废气污染物排放满足《大气污染物综合排放标准》(DB 32/4041—2021)相关要求。废气处理设施年运行费用大大降低,环保达标的同时取得一定的经济效益。

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。

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.

沸石分子筛和活性炭吸附/脱附甲苯性能对比

考察了甲苯在NaY型沸石分子筛(简写为NaY)、13X型沸石分子筛(简写为13X)、Hβ型沸石分子筛(简写为Hβ)、MCM-22型沸石分子筛(简写为MCM-22)和ZSM-5型沸石分子筛(简写为ZSM-5)上的吸附/脱附性能,同时与椰壳活性炭(AC)的吸附/脱附性能进行对比。结果表明,各吸附剂对甲苯的平衡吸附量大小依次为:AC>NaY>Hβ>13X>MCM-22>ZSM-5,甲苯从吸附剂表面脱附难易程度依次为:AC>NaY、13X>Hβ>MCM-22>ZSM-5;ZSM-5对甲苯的平衡吸附量和吸附强度都最小,这是由于甲苯无法进入ZSM-5的内部孔道造成的;在低甲苯质量浓度(<1000mg/m3)时,NaY平衡吸附量超过AC,因此NaY更适合应用在低浓度有机废气吸附治理中;Langmuir吸附方程比Freundlich吸附方程更符合沸石分子筛吸附甲苯的行为。