Modeling the Temperature Dependence of Adsorption Equilibriums of VOC(s) onto Activated Carbons

In order to optimize the efficiency of the removal of volatile organic compounds (VOCs) by adsorption onto activated carbon beds, process simulations taking into account exothermicity effects are helpful. Significant temperature increases may arise in the bed during the VOC adsorption cycle, especially when high concentrations have to be treated. Consequently, reliable and easy-to-handle isotherms remain a key hurdle to build realistic models. In this study, adsorption models were tested to describe a set of experimental data obtained for three VOCs (acetone, ethyl formate, and dichloromethane) adsorbed onto five commercial activated carbons at four different temperatures (20, 40, 60, and 80°C). A new expression of the Freundlich equation [qe = (a1T+a2T2)Ce(1/nf)] was shown to be statistically the most efficient to describe the adsorption isotherms of VOCs, single or in mixtures. A second-order polynomial temperature-dependence was introduced in this expression. The so-adapted Freundlich relationship gave a mean coefficient of determination of 0.97 for single-component adsorption and a correlation coefficient of 0.98 for binary mixtures.     

核壳结构Fe3O4@C粒子在UV-Fenton氧化去除VOCs过程中的吸附-催化作用

采用一步水热法制备核壳结构Fe₃O₄@C微米粒子,通过比表面积及孔径分析仪、X射线衍射仪、透射电子显微镜、傅里叶变换红外光谱仪等对粒子结构和形貌进行表征,并研究了粒子作为非均相催化剂在UV-Fenton氧化去除挥发性有机物(VOCs)中的作用机制.结果表明,核壳结构Fe₃O₄@C粒子由于包覆了孔隙状碳层而具有较强的吸附能力,可显著增加VOCs气体分子与Fenton试剂的接触几率,有助于提高VOCs的去除效率.通过计算反应速率常数及协同因子,证实在核壳结构Fe₃O₄@C粒子去除VOCs的过程中存在吸附-催化氧化协同作用.      

High-resolution proton nuclear magnetic resonance spectroscopy in the detection and quantitation of ethanol in human serum

A precise, accurate, and nondestructive method for the detection and quantitation of serum ethanol in humans using proton (1H) nuclear magnetic resonance spectroscopy (MRS) was developed. The 1H MRS method was linear within the range of 30-1500 mg/L. The lowest detectable ethanol concentration was 15 mg/L, with 30 mg/L being the lowest level reproducibly quantitated. Within-run and day-to-day coefficients of variation (CV) ranged from 0.6 to 2.7% and 0.5 to 3.5%, respectively. The excellent day-to-day CVs indicate a negligible loss of ethanol due to volatilization during analysis. Fifteen human serum samples found to be negative for ethanol by headspace gas chromatography (HSGC) had no ethanol as detected by 1H MRS. Twenty-eight human serum samples with ethanol concentrations (determined by HSGC) ranging from 370 to 4440 mg/L were accurately reproduced by 1H MRS. The 1H MRS method required no pretreatment and was nondestructive, thereby allowing for further analysis by confirmatory methods.     

基于响应曲面法制备钢渣–花生壳基生态活性炭及其吸附性能研究

以钢渣超微粉和花生壳为原料制备钢渣–花生壳基生态活性炭,基于响应曲面法研究微波功率、浸渍比、钢渣掺量和钢渣细度对钢渣–花生壳基生态活性炭对甲醛气体吸附率的影响,并对其进行优化处理.利用X-射线红外光谱仪、场发射扫描电镜、比表面积及孔径测定仪等对钢渣–花生壳基生态活性炭进行表征分析.结果表明：钢渣–花生壳基生态活性炭最优制备参数为微波功率530 W,钢渣细度1160目,钢渣掺量(质量分数)10.8%,浸渍比1.25,其对甲醛气体的吸附率为94.14%.影响钢渣–花生壳基生态活性炭性能的因素次序依次为：微波功率、钢渣掺量、浸渍比、钢渣细度,其中微波功率与浸渍比、微波功率与钢渣掺量、钢渣掺量与钢渣细度均存在显著交互作用.适量钢渣改性活性炭有利于形成规则的孔结构、提高表面酸性官能团含量以及增强表面极性.     

Capture of Organic Vapors Using Adsorption and Electrothermal Regeneration

Activated-carbon-fiber cloth (ACFC) is an alternative adsorbent to granular activated carbon (GAC) for removing and recovering organic vapors from gas streams. Electrothermal desorption (ED) of ACFC provides rapid regeneration while requiring less energy compared to traditional regeneration techniques used with GAC. This paper provides proof-of-concept results from a bench-scale ACFC adsorption system. The automated system captured 1,000 ppmv of hazardous air pollutants/volatile organic compounds (HAPs/VOCs) from air streams and demonstrated the use of ED, using ac voltage, to recover the HAP/VOC as a pure liquid. The desorbed HAP/VOC condensed onto the inner walls of the adsorber and was collected at the bottom of the vessel, without the use of ancillary cooling. Seventy percent of the HAP/VOC was collected per cycle as condensate, with the balance being retained in the regenerated adsorber or recycled to the second adsorber. ED with in-vessel condensation results in minimal N2 consumption and short regeneration cycle times allowing the process to be cost competitive with conventional GAC-based adsorption processes. This technology extends the application of carbon adsorption systems to situations that were previously economically and physically impractical.     

Determining the Volatile Fatty Acid Equivalent in Thermophilic Aerobically Digested Sludge Supernatant

Thermophilic aerobically digested (TAD) sludge supernatant has been found to be a potential carbon alternative for biological nutrient removal (BNR) enhancement in wastewater treatment plants. Carbonaceous substrates, other than the volatile fatty acids (VFAs) in TAD supernatant, were also found to be utilizable in BNR enhancement; however, these carbon compounds could not be detected by conventional chemical analyses (e.g., gas chromatography). A headspace carbon dioxide (CO2) monitoring method was tested in this study to estimate the overall available carbon source, or the VFAs accumulated in a microaerated TAD operation. This on-line method uses real activated sludge and TAD supernatant samples to determine the available carbon equivalent in real time. In comparison to the gas chromatography (GC) analyses of the TAD supernatant samples, the headspace CO2 monitoring method resulted in “overestimation” of VFA concentrations, in both the phosphorus release and denitrification reactions. Operating results suggested that the CO2 monitoring approach was capable of revealing the overall VFA equivalent that could be available for the main BNR reactions.     

Effect of Moisture on the Adsorption of Volatile Organic Compounds by Zeolite 13×

The adsorption of volatile methanol, acetone, and benzene onto zeolite 13× was studied in the presence of water vapor. Breakthrough curves for these volatile organic compounds (VOCs) were measured by using a gas-phase Fourier transformation infrared (FT-IR) spectrometer instead of a gas chromatograph (GC) because a gas-phase FT-IR spectrometer provides a more rapid response to the change of gas concentration than that of GC. To observe the influences of humidity (i.e., water vapor) on the performance of zeolite 13× during the VOC adsorption, the adsorption experiments were carried out at three different initial concentrations and two humidity conditions for each VOC. The results showed a significant influence of increased humidity on the breakthrough time, the shapes of breakthrough curves, and the uptake of VOCs. For the case of the benzene and water vapor coadsorption system, the presence of the moisture caused a greater decrease in the VOC uptake as well as the breakthrough time than for the other VOC–water coadsorption systems. A modified Freundlich-type isotherm was introduced in this study to describe the decrease in the uptake of VOCs in the presence of the moisture. This modified empirical equation provided a good fit to experimental results, with an average error of 8%.     

Adsorption on Carbon and Zeolite of Pollutants from Flue Gas during Incineration

The volatile organic compound, polycyclic aromatic hydrocarbon, dioxin, and metallic components released from incineration threaten human health. These pollutants, appearing in a molecular state, cannot be effectively removed by baghouse and electrostatic precipitators through capture and filtration mechanisms. Previous studies indicate that activated carbon is conventionally used to remove organic compounds from gas at low temperatures (less than 30°C). However, the adsorption characteristics of organic compounds from a gas phase at high temperatures (over 120°C) are seldom mentioned. Moreover, the complex compositions of flue gas cause the adsorption characteristics of organic compounds and heavy metals on adsorbent tubes to be more complicated. This research examines the adsorption characteristics of organic compounds and heavy metals at various incineration conditions. The evaluated parameters include: (1) the operating temperatures; (2) the characteristics of adsorbents (activated carbon and zeolite); and (3) waste compositions and the presence of heavy metals. The results indicate that activated carbon has a high adsorption capacity compared with zeolite.     

Adsorption of 1,1,1,2-Tetrafluoroethane by Various Adsorbents

Experiments have been conducted to investigate gas-phase adsorption characteristics of 1,1,1,2-tetrafluoroethane (HFC-134a) by activated carbon fiber, extruded activated carbon, granular activated carbon, activated alumina, and molecular sieve. HFC-134a is currently regarded as an excellent replacement for chlorofluorocarbon-12, a refrigerating and cooling agent extensively used previously in all automobiles and many cooling systems. Performances of HFC-134a adsorption were characterized by the equilibrium adsorption capacity, time to reach equilibrium, and desorption efficiency of exhausted adsorbent. A simple thermal treatment process with proper operating temperature and treatment duration was found to be effective for the regeneration of exhausted adsorbents. Adsorption isotherms of the empirical Freundlich and Jossens types were observed to adequately represent the equilibrium adsorption data. A mass transfer model based on the pseudo steady state squared driving force was adopted to describe the mass transfer process of HFC-134a adsorption.     

Electrothermal Desorption Using Joule Effect on an Activated Carbon Monolith

A new adsorbing material, an activated carbon monolith, was used for the adsorption of toluene vapors and their desorption by electrothermal heating using Joule effect. The monolith appears under shape of a parallelepiped of square section including four hundred parallel channels. Equilibrium isotherms for toluene on a piece of this material at various temperatures were measured by the gravimetric method. The adsorption breakthrough fronts measured on the monolith show that it is effective for cleaning the gas. Desorption was performed by heating of the monolith by means of a continuous electric current flowing transversely to the channels. The curves of desorption show that the toluene is desorbed with a high factor of concentration. Desorption rate can be controlled by regulating electrical current and purge gas flow rate. An equilibrium model shows that the tail of the desorption curve is mainly due to the curvature of the isotherm.     

基于Freundlich吸附等温方程测定氰化提金工艺用活性炭的吸附金容量

活性炭作为金的良好吸附剂广泛地应用在氰化提金生产工艺中,因此对活性炭吸附金性能的评价是非常重要的。在参考氰化提金生产工艺的基础上,模拟活性炭吸附氰化液中金的工艺过程,基于Freundlich吸附等温方程,建立活性炭吸附金容量的测定方法。通过考察一系列对吸附金容量测定的影响因素,优化和确定了测定方法的条件:吸附振荡时间为16h,吸附溶液体积为150mL,活性炭粒度在0.074mm以下,振荡器转速为200r/min,吸附溶液pH值为11.5,振荡温度为(30±1)℃,吸附溶液中氰化钠质量浓度为0.2g/L。按照实验方法测定了2个活性炭实际样品的吸附金容量,结果的相对标准偏差(RSD,n=11)分别为4.2%和4.8%。并对不同活性炭的吸附金容量情况与碘值进行对比,结果表明实验方法具有可比性。     

基于Freundlich吸附等温方程测定氰化提金工艺用活性炭的吸附金容量

活性炭作为金的良好吸附剂广泛地应用在氰化提金生产工艺中,因此对活性炭吸附金性能的评价是非常重要的。在参考氰化提金生产工艺的基础上,模拟活性炭吸附氰化液中金的工艺过程,基于Freundlich吸附等温方程,建立活性炭吸附金容量的测定方法。通过考察一系列对吸附金容量测定的影响因素,优化和确定了测定方法的条件:吸附振荡时间为16h,吸附溶液体积为150mL,活性炭粒度在0.074mm以下,振荡器转速为200r/min,吸附溶液pH值为11.5,振荡温度为(30±1)℃,吸附溶液中氰化钠质量浓度为0.2g/L。按照实验方法测定了2个活性炭实际样品的吸附金容量,结果的相对标准偏差(RSD,n=11)分别为4.2%和4.8%。并对不同活性炭的吸附金容量情况与碘值进行对比,结果表明实验方法具有可比性。     

Applicability of Equilibrium Isotherm Models for the Biosorptive Uptakes in Comparison to Activated Carbon-Based Adsorption

The adsorption isotherm models available in the literature have generally developed for sorption onto metallic surfaces or activated carbon-based sorbents. However, biosorptive uptakes involve interactions of biopolymer-based surfaces with different types of pollutants, which are quite different from metal surfaces or activated carbon. So, in the present study, 16 different types of adsorption isotherm models have been studied. For a ready reference both types of sorbents, i.e., a biosorbent and activated carbon have been employed. Results show that in general the accuracy of models to fit experimental data improves with the degree of freedom. The Fritz–Schluender model gives the most accurate fit (R2?0.85–0.99) to all experimental data in comparison to other models used both for activated carbon and the biosorbent. However, most widely used isotherm models, i.e., Langmuir and Freundlich, could be used to describe the sorption equilibrium of biosorptive processes with a fair degree of accuracy, owing to the mathematical ease in the use of these models. Trends of the applicability of various sorption equilibrium models to biosorptive uptakes are similar to those of activated carbon-based sorptions. Comprehensive equilibrium analysis has assisted in understanding the mechanistic aspects associated with different types of sorbents.     

吸附塔工艺参数对活性炭烧结烟气脱硫的影响

活性炭可高效脱除烧结烟气中的SO₂,但同时受到吸附塔工艺参数的制约。为了揭示工艺参数对脱硫率的影响规律,采用控制变量法,通过模拟烧结烟气进行活性炭脱硫研究。结果表明,空速、烟气湿度、含氧量和活性炭床温度对脱硫影响较大,活性炭粒度对脱硫率影响较小;降低空速、活性炭床温度及活性炭粒度,均有利于SO₂物理吸附进而促进脱硫率提高;烟气湿度和含氧量的增加,有利于SO₂的化学吸附进而提高脱硫率,但湿度大于12%时,水蒸气会在活性炭上聚集形成水膜而导致脱硫率下降。     

低阶煤一步法制备活性炭的脱硫脱硝性能

 活性炭法是能实现多种污染物综合控制的烟气治理技术,可同时处理烧结过程中产生的二氧化硫和氮氧化物等有害物质,但由于活性炭较高的生产和使用成本,限制了其在烧结烟气多污染物净化领域的推广应用。以低阶煤为基炭,氧化球团为活化剂,利用低阶煤热解和气化反应与铁氧化物还原之间的耦合作用,一步完成低阶煤炭化和活化,制备活性炭(SF AC),并与商品活性炭(ZJ AC)在产品工业分析、比表面积、碘吸附值、脱硫脱硝性能和再生活性炭吸附性能等方面进行综合比较。结果表明,SF AC的碘吸附值、比表面积分别为695.13 mg/g、370.42 m2/g,而ZJ AC仅530.54 mg/g、157.50 m2/g,单独脱硫时SF AC、ZJ AC的穿透硫容分别为368.11 mg/g、73.58 mg/g,单独脱硝时SF AC、ZJ AC的穿透硝容分别为250.39 mg/g、14.99 mg/g,前者较后者具有更优的吸附性能;就再生性能而言,SF AC、ZJ AC的脱硫脱硝性能均出现下降,但前者的脱硫脱硝性能更优;与单独脱硫、脱硝相比,两种活性炭同时脱硫脱硝时脱硫性能均提高,脱硝性能却降低,采用NH₃低温催化还原可改善脱硝性能差的问题。     

Effect of rare earth addition on Cu-Fe/AC adsorbents for phosphine adsorption from yellow phosphorous tail gas

Phosphine(PH3) is a highly toxic air pollutant,commonly produced in phosphorous chemical industry.But it has received less research attention due to its handling difficultly.CO is the main content of the phosphorous chemical industry tail gas,the concentration of which is always more than 80 vol.%,and it can be the feed gas to produce various valuable products such as formate,oxalate,and methanol and so on.But,PH3 is one of the important barriers,which is harmful to the following chemical process.In order to make use of the tail gas,PH3 should be removed firstly,and CO should be covered in the whole purified procedure at the same time.In this work,the modified activated carbon(MAC) was used as the adsorbent to separate PH3 from the mixture tail gas.Series of MAC adsorbents were prepared for the adsorption of PH3,which loaded Cu-Fe and Ce(La),or separately.The PH3 adsorption capacities,chemical and physical properties of MAC were all investigated.The results showed that over 99% PH3 adsorption efficiency was achieved when used MAC adsorbents.The removal efficiency and PH3 adsorption capacity of the Cu-Fe-Ce/AC(20:1:0.4) were both much higher than those modified activated carbons.The maximum PH3 adsorption capacity was 71 mg of PH3/g of MAC on the Cu-Fe-Ce/AC,which were much higher than literature data using CuO only for adsorbing hydride gases.     

固定化芽孢对铽离子的吸附特性

微生物吸附法作为一种高效、廉价、环境友好的生物技术,已在稀土离子分离回收中逐渐被开发利用。实验通过固定化微生物技术,使用海藻酸钠包埋活性炭与枯草芽孢杆菌芽孢制备成固定化颗粒,处理含稀土离子的废水。对比了固定化芽孢加活性炭、固定化芽孢以及固定化活性炭对铽离子的吸附效果,并探究了不同条件对几种固定化吸附剂吸附铽离子的影响。结果表明:固定化芽孢加活性炭兼具包埋法与吸附法的优点,对铽离子的吸附效果更好; 在包炭量为1:100(活性炭质量:溶液总质量)、芽孢悬液浓度为OD₆₀₀(菌液在600 nm波长处的吸光值)=2、铽离子浓度为100 μmol/L、温度为15~25 ℃、pH=4.5~8.5的条件下吸附60 min,铽去除率可达90%以上。固定化芽孢加活性炭对铽离子的吸附更符合准一级动力学、Langmuir吸附等温线模型。      

煤基活性炭改性及其甲烷吸附能力

针对无烟煤制备成的煤基活性炭,采用酸式改性、碱式改性和联合改性的方法对其进行改性处理。通过低温液氮吸附实验、傅里叶红外光谱技术、高压甲烷吸附实验,分析了煤基活性炭的表面物理、化学结构、甲烷的吸附能力。借助Langmuir吸附等温模型、Freundlich模型进行数据拟合,研究了吸附热力学和动力学特征。结果表明,联合改性后的煤基活性炭比表面积和孔容均明显增大,其中比表面积增大66.66%,总孔容增大30.89%;煤基活性炭的甲烷吸附能力明显提高,甲烷吸附量提升25.686%。煤基活性炭的孔隙结构和表面官能团共同决定了其对甲烷的吸附作用,且较于孔隙结构,表面官能团的极性对甲烷吸附量起主要作用。      

Reduced oxidative susceptibility of LDL from patients participating in an intensive atherosclerosis treatment program

The goal of this investigation was to determine whether participation in an atherosclerosis treatment program would reduce the oxidative susceptibility of LDL from patients with coronary artery disease. The treatment program included intensive exercise therapy, stress management, and consumption of a diet containing 10% fat. The size and antioxidant and lipid contents of LDL particles from 25 patients were analyzed at baseline and after 3 mo of therapy. The susceptibility of LDL to copper-mediated oxidation was measured by a conjugated diene assay and headspace gas chromatography (HSGC). Atherosclerosis treatment significantly reduced plasma total cholesterol and apolipoprotein B concentrations and the molar ratio of LDL cholesterol ester to apolipoprotein B (P < 0.01). The LDL content of alpha-tocopherol and beta-carotene was increased (27% and 17%, respectively, P < 0.04) and the molar ratio of LDL cholesterol ester the sum of LDL alpha-tocopherol and LDL beta-carotene decreased from 159 at baseline to 122 at 3 mo (P < 0.01). The lag phase of LDL conjugated diene formation increased 24%, whereas the maximum rate of oxidation slowed 29% (P < 0.01). As assessed by HSGC, copper-catalyzed formation of volatile lipid oxidation products was reduced 15% (P < 0.007); the reduction in volatiles was correlated with an increase in the alpha-tocopherol content of LDL (r=-0.48, P < 0.01). The principal determinants of reduced LDL oxidative susceptibility were the particle contents of alpha-tocopherol and beta-carotene. To our knowledge, this is the first report to document a reduction in LDL oxidation in coronary artery disease patients undergoing atherosclerosis-reversal therapy.     

热改性对柱状活性炭脱硫能力的影响

在N2保护下采用不同温度对柱状活性炭进行热改性,得到了5种改性活性炭(AC-1～AC-5),将改性前后的活性炭(AC)分别置于含有SO2且有水蒸气和氧气存在的条件下进行脱硫试验,利用气体吸附仪和扫描电镜对改性前后活性炭表面的物理性质进行了表征.试验结果表明,当改性温度为700～900℃时,改性后活性炭的脱硫能力随着改性...