Modeling VOCs adsorption onto activated carbon

The activated carbon adsorption process is affected by the characteristics of adsorbent, adsorbate and environmental conditions. In this study, both adsorption and desorption processes are assumed to occur simultaneously and a numerical model was developed with a non-linear driving force in conjunction with the Langmuir model for predicting the overall adsorption process. The numerical model provides both adsorption and desorption rate constants and activation energies. The resultant equilibrium constants are of the same order of magnitude as reported by other studies. Results show that the model could well predict the adsorption isotherms and breakthrough curves under various conditions.     

活性炭固定床操作参数的优化

研究了操作参数对活性炭固定床处理有机废气的影响。温度升高，吸附容量下降。湿度的存在会减少活性炭对有机物的吸附容量。适当的操作气速为0.1-0.5m/s，在此范围内，气速与压降在对数坐标上呈线性关系。     

Kinetics of benzene adsorption onto activated carbon

An activated carbon bed adsorption process is influenced by the adsorbents' characteristics, volatile organic compound (VOC) characteristics, and process conditions. In the literatures, the adsorption processes of the adsorbents and VOCs were usually considered to be in equilibrium. In this study, the VOC adsorption processes by activated carbon were considered to be a kinetic process, i.e. they are not in equilibrium. Then, isothermal adsorption curves and a small column experiment were simulated.     

Entrained-flow adsorption of mercury using activated carbon

Bench-scale experiments were conducted in a flow reactor to simulate entrained-flow capture of elemental mercury (Hg0) by activated carbon. Adsorption of Hg0 by several commercial activated carbons was examined at different C:Hg ratios (by weight) (350:1-29,000:1), particle sizes (4-44 microns), Hg0 concentrations (44, 86, and 124 ppb), and temperatures (23-250 degrees C). Increasing the C:Hg ratio from 2100:1 to 11,000:1 resulted in an increase in removal from 11 to 30% for particle sizes of 4-8 microns and a residence time of 6.5 sec. Mercury capture increased with a decrease in particle size. At 100 degrees C and an Hg0 concentration of 86 ppb, a 20% Hg0 reduction was obtained with 4- to 8-micron particles, compared with only a 7% reduction for 24- to 44-micron particles. Mercury uptake decreased with an increase in temperature over a range of 21-150 degrees C. Only a small amount of the Hg0 uptake capacity is being utilized (less than 1%) at such short residence times. Increasing the residence time over a range of 3.8-13 sec did not increase adsorption for a lignite-based carbon; however, increasing the time from 3.6 to 12 sec resulted in higher Hg0 removal for a bituminous-based carbon.     

Removal of carbonyl sulfide using activated carbon adsorption

Wastewater treatment plant odors are caused by compounds such as hydrogen sulfide (H2S), methyl mercaptans, and carbonyl sulfide (COS). One of the most efficient odor control processes is activated carbon adsorption; however, very few studies have been conducted on COS adsorption. COS is not only an odor causing compound but is also listed in the Clean Air Act as a hazardous air pollutant. Objectives of this study were to determine the following: (1) the adsorption capacity of 3 different carbons for COS removal; (2) the impact of relative humidity (RH) on COS adsorption; (3) the extent of competitive adsorption of COS in the presence of H2S; and (4) whether ammonia injection would increase COS adsorption capacity. Vapor phase react (VPR; reactivated), BPL (bituminous coal-based), and Centaur (physically modified to enhance H2S adsorption) carbons manufactured by Calgon Carbon Corp. were tested in three laboratory-scale columns, 6 in. in depth and 1 in. in diameter. Inlet COS concentrations varied from 35 to 49 ppmv (86-120 mg/m3). RHs of 17%, 30%, 50%, and 90% were tested. For competitive adsorption studies, H2S was tested at 60 ppmv, with COS at 30 ppmv. COS, RH, H2S, and ammonia concentrations were measured using an International Sensor Technology Model IQ-350 solid state sensor, Cole-Parmer humidity stick, Interscan Corp. 1000 series portable analyzer, and Drager Accuro ammonia sensor, respectively. It was found that the adsorption capacity of Centaur carbon for COS was higher than the other two carbons, regardless of RH. As humidity increased, the percentage of decrease in adsorption capacity of Centaur carbon, however, was greater than the other two carbons. The carbon adsorption capacity for COS decreased in proportion to the percentage of H2S in the gas stream. More adsorption sites appear to be available to H2S, a smaller molecule. Ammonia, which has been found to increase H2S adsorption capacity, did not increase the capacity for COS.     

Dynamic NO adsorption characteristics of iron-treated activated carbon fibers

The breakthrough curve for NO adsorption on the activated carbon fibers treated in iron salt solutions was determined. They can adsorb much more NO than granular activated carbon by a factor of more than 10 from a flowing 300 ppm NO-N₂ mixed gas at 100°C and 20 ml min⁻¹; the most effective one of the iron-treated carbon fibers of 0.2 g is able to reduce the NO concentration from 300 ppm to 30 ppm. These adsorbents can adsorb the same amount of NO from even a 300 ppm NO-500 ppm SO₂-10% CO₂-10% H₂O-1% O₂-N₂ mixed gas.     

氧化、还原改性对活性炭吸附草甘膦的影响

研究了氧化、还原改性对活性炭吸附草甘膦的影响.以傅立叶红外光谱定性表面官能团变化,以扫描电镜观察表面形貌,以化学吸附分析仪测定后再通过测定样品的氮气吸附/脱附等温线计算比表面积和孔径.结果表明:(1)氧化改性使活性炭比表面积增大;还原改性使活性炭比表面积减小.还原阶段使先前氧化阶段中产生的孔道以及原有孔道均发生塌陷,导致还原改性活性炭比表面积减小.(2)在静态吸附的条件下,氧化改性和还原改性活性炭对草甘膦的吸附均为吸热反应.还原改性在活性炭表面产生的还原性官能团有利于活性炭对草甘膦的吸附,而氧化改性产生的氧化性官能团并不利于活性炭对草甘膦的吸附.(3)热力学参数的计算进一步表明,改性活性炭对草甘膦的吸附为吸热反应.     

Fixed bed adsorption of acid dyes onto activated carbon

The context of the study here is the adsorption of acid dyes from wastewater arising from a nylon carpet printing plant which currently receives no treatment. Since nylon is a particularly difficult fibre to dye, acid dyes are required for successful coloration. However, their presence, in high concentrations, in aqueous effluent arising from the plant can create major problems with respect to disposal. A treatment method based on adsorption onto granular activated carbon (GAC F400) in a fixed column configuration is described and breakthrough data of the dyes determined. The breakthrough data were correlated using a model based on liquid and pore diffusion with a good fit of experimental results obtained. Trends in the effective diffusivity used in the model correlated with other authors. A slight decrease in effective diffusivity was found with decrease in particle size and was attributed to interactions between the relatively large molecular sized dye and the microspore structure found in granular activated carbon.     

废食用油活性炭脱色工艺的研究

脱色处理是提高废食用油油品质量、利用其生产生物柴油的关键环节之一.研究餐饮废食用油活性炭吸附脱色工艺,考察典型木质活性炭和煤基活性炭对脱色效果的影响,并将活性炭结构、性能指标与其脱色能力进行关联.结果表明,以弱粘性煤和褐煤为原料制备的活性炭对废食用油脱色效果较好;活性炭的总孔容积、总比表面积、微孔比表面积、微孔容积、碘值和亚甲基蓝值等性能指标与脱色效果关联度不大,而活性炭的孔径和中孔容积是决定活性炭脱色效果的主要指标.优化后废食用油活性炭脱色工艺的主要参数是:活性炭用量7%,炭粒度100～300目,脱色温度90～120℃,吸附时间为30 min,搅拌速度为10 r/min,废食用油的脱色率在50%～65%.     

微波法对吸附扑热息痛废水活性炭的再生

通过微波加热的方式对用于扑热息痛废水的吸附的活性炭进行再生处理。考察了再生温度和再生时间两个因素对活性炭吸附性能和得率的影响。在最佳微波再生条件(温度为600℃,微波再生时间为15 min)下结果表明,活性炭在的亚甲基蓝吸附值和得率分别为187.5 mg/g和41.82%。对最佳条件下再生得到的活性炭进行孔结构表征,结果为,比表面积达947.9 m2/g,总孔体积为0.97 m L/g。中孔的比例占到71.18%说明活性炭主要以中孔为主。同时对废活性炭和再生活性炭进行了扫描电镜分析,结果表明,通过微波再生后的活性炭表面杂质明显减少。     

树脂与活性炭吸附油气的实验研究

吸附剂的性能对油气吸附分离的效果起着决定性的作用。测定了活性炭和吸附树脂在常温下对油气的静态吸附和脱附特性,比较吸附树脂与活性炭的吸附率、解吸率。实验结果表明,吸附树脂吸附率高,解吸容易。测定了活性炭和吸附树脂对油气的吸附穿透曲线和热效应。实验结果表明,吸附树脂的穿透时间长,温升略低,适于油气吸附分离。同时,利用Yoon Nelson模型较好地模拟了吸附树脂吸附油气的穿透曲线,从而可为吸附树脂吸附塔设计提供理论依据。     

电增强载铝活性炭纤维吸附氟离子性能

以载铝活性炭纤维毡为电极,在电场作用条件下对模拟含氟水进行静态吸附实验。结果表明,该载铝活性炭纤维毡正极化可以强化吸附除氟效果,吸附动力学数据很好地符合Lagergren二级速率方程,加电场时二级反应速率常数为4.50 g/（mg·h）;其对高浓度含氟饮用水也有较高去除率,Freundlich吸附等温方程能很好地描述吸附平衡数据。加电场情况下,该载铝炭毡对氟离子的最大吸附量为16.584 mg/g,去除氟离子的最佳pH范围是5.5~8.9。共存阴离子Cl-、SO42-和NO3-对炭毡吸附除氟没有抑制作用,但CO32-的存在会导致除氟吸附量显著下降。     

椰壳活性炭吸附消除VOCs

对一种椰壳活性炭对甲基丙烯酸甲酯的吸附消除行为进行了研究,重点考察了甲基丙烯酸甲酯的浓度、流速和吸附温度等条件以及水汽存在时对活性炭吸附行为的影响。结果表明,该颗粒活性炭对甲基丙烯酸甲酯有良好的吸附效果,甲基丙烯酸甲酯进口浓度和进气量的改变均会影响吸附饱和时间,导致其增加或减少。通过变温吸附实验确定降低环境温度对其吸附有促进作用。湿度为50%时吸附量相对干气饱和吸附量影响较小,说明该活性炭抗水汽能力较好。经多次重复再生实验,其饱和吸附量未见明显下降。     

磺胺类抗生素的活性炭吸附过程研究

采用煤质活性炭对3种磺胺类抗生素(浓度在1～2 mg/L之间)的吸附处理过程做了深入研究。结果表明,3种磺胺类抗生素在2～3 h之内可以达到吸附平衡;准一级动力学对其吸附动力学的模拟结果良好,且SMZ、SM1和SM2的一级吸附动力学常数k1分别为0.029、0.024和0.017 min-1,3种抗生素的平衡吸附容量分别为3.75、3.23和2.95 mg/g,SMZ的平衡吸附容量最大,最先达到吸附平衡,且平衡浓度也最低。3种磺胺类抗生素的吸附过程中,吸附前期的阻力主要是内扩散,而吸附后期较低浓度的抗生素吸附过程的阻力主要来自于膜扩散;采用Freundlich等温线方程描述3种磺胺类抗生素的吸附过程更为合理。     

应急处理苯胺污染水源水的粉末活性炭吸附工艺的研究

以浑河水为原水,模拟突发苯胺污染,通过投加粉末活性炭(PAC)进行应急处理的试验研究.试验结果表明:PAC对苯胺的吸附在30 min内能达到80%～90%的吸附容量;PAC对苯胺的吸附等温线符合弗兰德里希(Freundlich)吸附模式,在苯胺的平衡质量浓度为0.030 mg/L时,PAC对其吸附容量约为5 mg/g;比表面积较大的木屑炭对苯胺的吸附效果比煤质炭好,但粒度以300目左右为宜;炭浆浓度越小对苯胺的吸附效果越好;溶液pH以不小于5为最好;絮凝剂最佳的投加顺序是先投加炭浆然后投加絮凝荆;对突发的浑河水苯胺污染,在取水口处投加PAC是十分有效的应急处理措施.     

活性炭对含铅废水吸附特性研究

采用静态法用活性炭吸附处理含铅废水,考察了活性炭对含铅废水的吸附特性。结果表明:活性炭对铅离子吸附平衡时间为100 m in;吸附等温方程为:Ce/qe=0.4298+0.0594Ce(25℃),该方程符合Langmu ir型吸附模式,不同温度下吸附平衡参数0RL1,表示该吸附为有利吸附。实验数据应用数学模型拟合,二级相关系数R2=0.9998,显示吸附过程动力学与二级动力学模型相关性较好;计算不同温度下各热力学参数:△Hθ大于零、△Gθ小于零,证实该吸附过程是一个自发吸热过程。△Sθ大于零,表明铅离子在固液界面有序性减小、混乱度增大。△Hθ值很小,说明该过程为物理吸附。     

Quaternary adsorption equilibria from aqueous systems onto decolourizing activated carbon

An experimental study has been conducted to obtain the adsorption isotherms of four typical pollutants from quaternary aqueous systems onto decolourizing activated carbon. The four materials investigated are: Phenol, 1,4-dihydroxybenzene, 4-amino-l-naphthalene sulfonic acid-sodium salt and Benzoic acid. The study has concentrated on the dilute region of concentrations which range from 10 to 165 ppm (mg/L) at an operating temperature of 30 °C.

The quaternary adsorption equilibria have been modeled using the extended Langmuir predictive model and the ideal adsorbed solution (IAS) theory. In employing these models for the prediction of multicomponent adsorption equilibria, the single-solute isotherms are needed. These isotherms have been fitted to Langmuir, Freundlich, and Dubinin models and the resulting model parameters, which are needed for the prediction of multicomponent adsorption equilibria, are reported. Predictions obtained from the extended Langmuir predictive model and the ideal adsorbed solution (IAS) model are in agreement, however, they deviate to an appreciable extent from experimental observations.     

活性炭孔隙结构在其甲苯吸附中的作用

选用4种商用活性炭(AC),利用氮气绝热吸附、扫描电子显微镜(SEM)和傅立叶变换红外光谱(FTIR)测试了活性炭的物化性质。以甲苯为吸附质,在温度为298.15 K下进行了静态和动态吸附实验,研究了活性炭孔结构对其吸附性能、吸附行为、表面覆盖率和吸附能的影响。结果表明:活性炭的比表面积和孔容是其吸附性能主要影响因素,孔径在0.8～2.4 nm之间的孔容和甲苯吸附量之间存在较好的线性关系,且线性斜率随甲苯浓度增加而变大。甲苯吸附行为符合Langmuir吸附等温模型和准一阶动力学方程式。活性炭孔结构是甲苯吸附速率的主要制约因素。在甲苯快速吸附阶段,微孔为吸附速率主要制约因素,在甲苯颗粒内扩散阶段,微孔和表面孔为吸附速率的主要制约因素,在吸附末尾阶段,中孔和大孔为吸附速率的主要制约因素。4种活性积炭对甲苯的吸附能随其比表面变大而变大。     

废弃物基活性炭吸附挥发性有机污染物特性的研究

研究了废弃物基活性炭对挥发性有机污染物中的典型组分--甲苯的吸附特性.结果表明,废弃物基活性炭吸附甲苯等温线的类型系优惠型吸附等温线,表明具有良好的吸附能力;同时其吸附甲苯时穿透时间的对数与甲苯入口浓度的对数之间具有良好的线性相关性,即可由吸附高浓度甲苯时的穿透时间估算低浓度时的穿透时间;动态吸附时废弃物基活性炭的中孔对甲苯亦具有一定的吸附性能.