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.     

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.     

Equilibrium and kinetics of adsorption of phosphate onto iron-doped activated carbon

Purpose

Two series of activated carbons modified by Fe (II) and Fe (III) (denoted as AC/N-Fe^II and AC/N-Fe^III), respectively, were used as adsorbents for the removal of phosphate in aqueous solutions.

Method

The synthesized adsorbent materials were investigated by different experimental analysis means. The adsorption of phosphate on activated carbons has been studied in kinetic and equilibrium conditions taking into account the adsorbate concentration, temperature, and solution pH as major influential factors.

Results

Maximum removals of phosphate are obtained in the pH range of 3.78?C6.84 for both adsorbents. Langmuir isotherm adsorption equation well describes the experimental adsorption isotherms. Kinetic studies revealed that the adsorption process followed a pseudo-second order kinetic model. Results suggest that the main phase formed in AC/N-Fe^II and AC/N-Fe^III is goethite and akaganeite, respectively; the presence of iron oxides significantly affected the surface area and the pore structure of the activated carbon.

Conclusions

Studies revealed that iron-doped activated carbons were effective in removing phosphate. AC/N-Fe^II has a higher phosphate removal capacity than AC/N-Fe^III, which could be attributed to its better intra-particle diffusion and higher binding energy. The activation energy for adsorption was calculated to be 22.23 and 10.89 kJ mol^?1 for AC/N-Fe^II and AC/N-Fe^III, respectively. The adsorption process was complex; both surface adsorption and intra-particle diffusion were simultaneously occurring during the process and contribute to the adsorption mechanism.     

粉末活性炭对水中农药的吸附性能研究

研究了粉末活性炭对2,4-滴、呋喃丹、甲萘威和莠去津的吸附过程和吸附规律以及投炭量和水质对粉末活性炭吸附性能的影响。结果表明,粉末活性炭能有效去除4种农药;吸附规律符合Freundlich吸附等温线和Langmuir吸附等温线;吸附时间为30 min时,去离子水中的去除率已达到80%以上;随着投炭量的增加,去除率提高,粉末活性炭的吸附容量降低;在不同水质条件下,粉末活性炭的吸附等温线可能不同,因此在应急处理中,首先应该确定该水质下的吸附等温线,然后求出投炭量。     

活性炭吸附化学战剂--沙林染毒水的试验研究

研究了 5种国产活性炭吸附水中沙林的性能及影响因素。果壳质活性炭的吸附性能优于煤质活性炭。果壳活性炭WP 2 0 2的吸附等温线方程为 qe=11 45C0 39e ,其粉状炭在 10min时能达到吸附容量的 98%。活性炭颗粒小则吸附速度快 ,温度升高不利于吸附。活性炭与水中的氯反应后 ,吸附性能下降 3 0 % ,在含盐量 2 0 0 0mg/L的苦咸水中吸附量降低 5 %。处理化学战剂 -沙林染毒水宜多种水处理技术相结合 ,并采用活性炭吸附作为最后一级处理单元     

The adsorption of benzene and methylethylketone onto activated carbon: thermodynamic aspects.

The adsorption of volatile organic compounds (VOCs), exemplified by benzene and methylethylketone (MEK), onto seven different types of activated carbon was investigated. Results show that for benzene adsorption the adsorption characteristic energy, enthalpy, free energy and entropy are in the range 17.12-36.86, -20.8 to -44.7, -11.89 to -16.22 kJ/mole and -29.4 to -85.3 J/mole/K, respectively. For the adsorption of MEK, the adsorption characteristic energy, enthalpy, free energy and entropy are in the range 14.47-32.34, -18.3 to -40.8, -10.78 to -15.56 kJ/mole and -24.8 to approximately -60.3 J/mole/K, respectively. The adsorption enthalpy can be calculated indirectly from statistical thermodynamic method and directly from the immersion enthalpy method. The adsorption characteristic energy is calculated by the Dubinin-Astokhov equation. The free energy is calculated by the measured equilibrium adsorption constant.     

Influence of resorcinol chemical oxidation on the removal of resulting organic carbon by activated carbon adsorption

Activated carbon adsorption and chemical oxidation followed by activated carbon adsorption of resorcinol in water has been studied. Three chemical oxidants have been used: hypochlorite, permanganate and Fenton's reagent. The influence of concentrations of resorcinol and activated carbon on adsorption removal rates has been investigated. Both isotherm and adsorption kinetics have been studied. Results are fit well by Freundlich isotherms and adsorption rates of resorcinol were found to follow a pseudo-second-order kinetic model. However, pyrogallol, an intermediate of resorcinol oxidation with permanganate and Fenton's reagent, showed an unfavourable isotherm type. At the conditions investigated, chemical oxidation allows slight reductions of TOC and intermediates formed were found to inhibit the adsorption rate of TOC in the case of permanganate and Fenton's reagent oxidation, likely due to formation of some polymer pyrogallol product. The adsorption process was found to be controlled by pore internal diffusion, which justifies the poor affinity of oxidation intermediates toward activated carbon since molecules of larger size should diffuse rapidly for the adsorption to be effective.     

Prediction of the adsorption capacity for volatile organic compounds onto activated carbons by the Dubinin-Radushkevich-Langmuir model

Prediction of the adsorption capacity for volatile organic compounds (VOCs) onto activated carbons is elucidated in this study. The Dubinin-Radushkevich (D-R) equation was first used to predict the adsorption capacity of nine aromatic and chlorinated VOCs onto two different activated carbons. The two key parameters of the D-R equation were estimated simply from the properties of the VOCs using quantitative structure-activity relationship and from the pore size distribution of the adsorbent. The approach based on the D-R equation predicted well the adsorption capacity at high relative pressures. However, at the relative pressures lower than -1.5 x 10(-3), the D-R approach may significantly overestimate adsorption capacity. To extrapolate the approach to lower relative pressures, the integration of the D-R equation and the Langmuir isotherm, called the D-R-L model, was proposed to predict adsorption capacity over a wide range of relative pressures of VOCs. In this model, the Langmuir isotherm parameters were extracted from the predicted D-R isotherm at high relative pressures. Therefore, no experimental effort was needed to obtain the parameters of the D-R-L model. The model successfully predicted the adsorption capacity of aromatic and chlorinated hydrocarbons tested onto BPL and Sorbonorit B carbons over relative pressures ranging from 7.4 x 10(-5) to 0.03, suggesting that the model is applicable at the low relative pressures of VOCs often observed in many environmental systems. In addition, the molecular size of organic compounds may be an important factor affecting the adsorption capacity of activated carbons. For BPL carbon, an ultramicroporous adsorbent, the limiting pore volume Wo of the D-R equation decreased when the kinetic diameter of the adsorbate was larger than 6 angstroms. However, for Sorbonorit B carbon, no reduction of Wo was found, suggesting that the Wo may be related to the pore size distribution of the adsorbents, as well as to their molecular size. This size exclusion effect may play an important role in predicting the adsorption capacity of VOCs onto microporous adsorbents in the D-R-L model and in the corresponding D-R equation.     

三氯乙酸与其他有机物在活性炭上的竞争吸附

通过等温吸附实验,考察了三氯乙酸(TCAA)与十二烷基苯磺酸钠(DBS)、腐殖酸(HA)在活性炭(GAC)上的竞争吸附现象。结果表明,GAC对TCAA的吸附符合Langmuir模型,对DBS和HA的吸附均符合Freudlich模型;在GAC上,DBS和HA对TCAA构成竞争吸附,大分子HA阻塞GAC的微孔,使得TCAA与DBS难以进入微孔;GAC对3种物质的吸附能力由大到小依次为DBS、TCAA和HA;离子型表面活性剂DBS憎水性一端与TCAA竞争吸附位,亲水性一端与TCAA形成吸附,使GAC总饱和吸附量有所加大。     

活性炭吸附室内空气中挥发性有机化合物

活性炭吸附室内空气中挥发性有机化合物的１０％穿透时间与气相浓度及挥发性有机化合物的种类有关,通过对苯、甲苯和丙酮的实验研究,得出了由高浓度估算室内低浓度时炭床１０％穿透时间的经验公式ｔｂ,１＝ｔｂ,ｈ（Ｃ０,１／Ｃ０,ｈ）＾ａ,其中ａ值是与炭床性能及挥发性有机化合物种类有关的参数,可通过实验确定。     

水蒸气对改性椰壳活性炭吸附VOCs的影响

选取甲苯、甲基丙烯酸甲酯、吡啶3种不同极性的有机物作为吸附质,改性椰壳活性炭作为吸附剂,使用穿透曲线法研究了水蒸气对这3种VOCs在活性炭上吸附行为的影响,并同时讨论了水蒸气预处理对活性炭吸附的影响。结果表明,改性椰壳活性炭对3种有机废气均具有良好的吸附性能,但水蒸气的存在对极性小的甲苯吸附影响较大,尤其当甲苯浓度较低时,水分子易与甲苯产生竞争吸附。在对活性炭吸湿预处理后发现,吡啶、甲基丙烯酸甲酯分子可以置换出活性炭预先吸附的水分子,并且通过低温水蒸气加热再生法可以方便地完成活性炭再生过程,重复再生率可以维持在85%。     

二次活化活性炭纤维吸附回收二氯甲烷

为了提高活性炭纤维对二氯甲烷气体的吸附回收性能,我们通过二次活化的方法制备出一系列的活化后样品,并表征其基本性质。二次活化样品对二氯甲烷的静态吸附实验表明,800℃活化60 min所得样品的吸附容量最高;之后又采用自制的溶剂回收吸附装置对其进行动态吸附实验,结果显示,在100%含水率条件下,其动态吸附量比原ACF提高了40%。这表明了二次活化能够大幅提升ACF对二氯甲烷的吸附性能。为了探究吸附性能提升的原因,又通过氮吸附的方法对二次活化样品和原样品进行孔径分析,结果显示,800℃活化60 min所得样品的BET比表面积提升了47.1%,对吸附二氯甲烷起主要作用的微孔孔容提高了77.6%。     

Co-contaminant effects on ofloxacin adsorption onto activated carbon,graphite, and humic acid

Given their voluminous application, significant amounts of fluoroquinolones are discharged into the environment through wastewater effluent. Adsorption has been shown to be a critical process controlling the environmental behaviors of fluoroquinolones. Competition between ofloxacin (OFL) and naphthalene (NAP)/bisphenol A (BPA) and their adsorption on activated carbon (AC), graphite (GP), and humic acid (HA) were investigated. The suppressed adsorption of OFL was observed on AC and GP, but not on HA, by NAP or BPA. Moreover, for AC, the competition by NAP was slightly stronger than that by BPA. However, for GP, the competition with BPA was higher than that with NAP. These observations indicate that competitive adsorption of OFL with respect to NAP/BPA depends on the degree of overlap of adsorption sites, as interpreted by the following: (i) AC can provide overlapping adsorption sites for OFL, BPA, and NAP, which include non-specific adsorption sites, such as hydrophobic sites, π-π interactions, and micropore filling; (ii) π-π interactions and hydrogen bonding might be responsible for the strong competitive adsorption between BPA and OFL on GP; and (iii) OFL adsorbs on HA through specific adsorption force—electrostatic attraction, with which NAP and BPA cannot compete.

     

Determination of the organic aerosol mass to organic carbon ratio in IMPROVE samples

The ratio of organic mass (OM) to organic carbon (OC) in PM(2.5) aerosols at US national parks in the IMPROVE network was estimated experimentally from solvent extraction of sample filters and from the difference between PM(2.5) mass and chemical constituents other than OC (mass balance) in IMPROVE samples from 1988 to 2003. Archived IMPROVE filters from five IMPROVE sites were extracted with dichloromethane (DCM), acetone and water. The extract residues were weighed to determine OM and analyzed for OC by thermal optical reflectance (TOR). On average, successive extracts of DCM, acetone, and water contained 64%, 21%, and 15%, respectively, of the extractable OC, respectively. On average, the non-blank-corrected recovery of the OC initially measured in these samples by TOR was 115+/-42%. OM/OC ratios from the combined DCM and acetone extracts averaged 1.92 and ranged from 1.58 at Indian Gardens, AZ in the Grand Canyon to 2.58 at Mount Rainier, WA. The average OM/OC ratio determined by mass balance was 2.07 across the IMPROVE network. The sensitivity of this ratio to assumptions concerning sulfate neutralization, water uptake by hygroscopic species, soil mass, and nitrate volatilization were evaluated. These results suggest that the value of 1.4 for the OM/OC ratio commonly used for mass and light extinction reconstruction in IMPROVE is too low.     

电增强活性炭滤芯吸附去除水中微污染物

选取了10种市售活性炭滤芯并测试其相关理化性质,筛选出比表面积高、导电性好的滤芯用于电增强吸附二氯乙酸(DCAA)、左氧氟沙星(LVFX)和环丙沙星(CIP) 3种典型饮用水中的微污染物。3种污染物的电增强吸附符合二级动力学模型,电增强活性炭滤芯吸附DCAA、LVFX和CIP的最佳初始吸附速率v₀分别达到12.4 mg·(g·h)⁻¹ (2 V)、45.3 mg·(g·h)⁻¹ (−2 V)和93.1 mg·(g·h)⁻¹ (−2 V),相比不加电情况下提高了1.2~1.7倍;3种污染物的电增强吸附等温线符合Langmuir模型,电辅助下DCAA、LVFX和CIP的最大吸附容量q_m可达到26.3 mg·g⁻¹ (2 V)、207.9 mg·g⁻¹ (−2 V)和106.1 mg·g⁻¹ (−2 V),相比于不加电时提升了1.2~3.2倍。在流动态吸附实验中,活性炭滤芯在电增强吸附下的出水的DCAA质量浓度比不加电时更低,出水水质更佳。电增强吸附下的处理水量达到1 300床体积,比不加电条件下提升了2.2倍。以上研究结果表明活性炭滤芯的电增强吸附在饮用水深度处理中有着较好的应用前景。     

Competitive kinetics of adsorption onto activated carbon for emerging contaminants with contrasting physicochemical properties

Environmental Science and Pollution Research - Activated carbon (AC) can be used for the removal of emerging contaminants (e.g., drugs) in water and wastewater treatment plants. In the present...     

臭氧—生物活性炭工艺去除水中有机微污染物

在臭氧化的反应柱中填装陶粒滤料,构成了臭氧－陶粒→生物活性炭不深度净化流程,用该流程去除水中有机微污染物,ＣＯＤＭＮ去除率近近４０％,浊度和色度大大降低,色－质联机分析表明,原水中有机物由５８种降至３０种,潜在有毒有害物质由１３种减少到４种。     

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。     

磁性活性炭的制备及其对水中甲基橙的吸附

活性炭被广泛应用于水处理领域,然而吸附饱和后难以分离和再生的缺点却限制了其应用。本研究采用化学共沉淀法将铁氧化物和活性炭进行复合,制备出同时具有磁分离性能和较强的吸附性能的磁性活性炭复合材料,并对制备的复合材料进行表征,考察其对水中甲基橙的吸附性能。结果表明,制备的磁性活性炭的比表面积为666.72 m2/g,平均孔径为3.16 nm,具有良好的磁性能,在外加磁场下能快速地从溶液中分离出来且磁性能相对稳定,铁氧化物对活性炭吸附性能的影响不大。在温度为25℃、pH为5、吸附剂用量为3 g/L的情况下,吸附3 h后,该磁性活性炭对甲基橙的吸附率可达99.1%,预示着该磁性活性炭在水处理方面具有潜在的应用前景。     

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%.