Application of powdered activated carbon coating to fabrics in a hybrid filter to enhance mercury removal

Elemental mercury(Hg0) is predominant constituent of flue gas emitted from coal-fired power plants. Adsorption has been considered the best available technology for removal of Hg0 from flue gas. However, adsorbent injection increases the amount of ash generated. In the present study, powdered activated carbon(PAC) was coated on polytetrafluoroethylene/glass fiber filters to increase Hg0 removal while concurrently reducing the amount of ash generated. The optimal PAC coating rate was determined in laboratory experiments to ensure better Hg0 removal with low pressure drop. When PAC of particle size less than 45 μm was used, and the areal density was 50 g/m2, the pressure drop remained under 30 Pa while the Hg0 removal efficiency increased to 15.8% from4.3%. The Hg0 removal efficiency also increased with decrease in filtration velocity. The optimal PAC coating rate was applied on a hybrid filter(HF), which was combined with a bag filter and an electrostatic precipitator in a single chamber. Originally designed to remove fine particulates matter, it was retrofitted to the flue gas control device for simultaneous Hg0 removal. By employing the PAC coating, the Hg removal efficiency of the HF increased to 79.79% from 66.35%. Also, a temporary reduction in Hg removal was seen but this was resolved following a cleaning cycle in which the dust layer was removed.     

A nanofilter composed of carbon nanotube-silver composites for virus removal and antibacterial activity improvement

We have developed a new nanofilter using a carbon nanotube-silver composite material that is capable of efficiently removing waterborne viruses and bacteria.The nanofilter was subjected to plasma surface treatment to enhance its flow rate,which was improved by approximately 62%.Nanoscale pores were obtained by fabricating a carbon nanotube network and using nanoparticle fixation technology for the removal of viruses.The pore size of the nanofilter was approximately 38 nm and the measured flow rate ranged from 21.0 to 97.2 L/(min·m~2)under a pressure of 1–6 kgf/cm~2 when the amount of loaded carbon nanotube-silver composite was 1.0 mg/cm~2.The nanofilter was tested against Polio-,Noro-,and Coxsackie viruses using a sensitive real-time polymerase chain reaction assay to detect the presence of viral particles within the outflow.No trace of viruses was found to flow through the nanofilter with carbon nanotube-silver composite loaded above 0.8 mg/cm~2.Moreover,the surface of the filter has antibacterial properties to prevent bacterial clogging due to the presence of 20-nm silver nanoparticles,which were synthesized on the carbon nanotube surface.     

活性炭催化氧化处理电镀厂含氰废水

本文在理论研究成果基础上尝试活性炭催化氧化处理电镀厂含氰废水的运行试验，结果表明三相流化床工艺由于传质性能优越，处理效率高，配合固定床可连续实现废水的达标排放，给企业带来了良好的环境与经济效益．     

Effects of temperature and SO3 on re-emission of mercury from activated carbon under flue gas conditions

Mercury(Hg) is a toxic and bio-accumulating heavy metal that is predominantly released via the combustion of coal. Due to its toxicity, the Environmental Protection Agency(EPA)has introduced Mercury and Air Toxics Standards(MATS) Rule regarding allowable Hg emissions. In order to reduce emissions, power plants have widely adopted activated carbon(AC) injection. AC injection has proven to be an effective method to reduce Hg emissions, but the re-emission of previously adsorbed Hg during unit operation, likely due to changing temperature or flue gas composition, could be problematic. This study specifically examined the effects of temperature and sulfur trioxide(SO3) concentration,by ramping temperature and SO3 concentration independently and simultaneously, on AC samples that are already exposed to flue gas and saturated in presence of Hg, sulfur dioxide(SO2) and nitric oxide(NO). Of these two suspected factors to cause re-emission,temperature had the greater impact and resulted in re-emission of both elemental and oxidized Hg with a greater fraction of oxidized Hg, which can be attributed to elemental Hg being more strongly bonded to the AC surface. Surprisingly, exposing the samples to increasing concentrations of SO3 had nearly no effect under the conditions examined in this study, possibly as a result of the samples being already saturated with sulfur prior to the SO3 ramp tests to simulate transient conditions in the plant.     

Coating independent cytotoxicity of citrate- and PEG-coated silver nanoparticles on a human hepatoma cell line

The antibacterial potential of silver nanoparticles(AgNPs) resulted in their increasing incorporation into consumer,industrial and biomedical products.Therefore,human and environmental exposure to AgNPs(either as an engineered product or a contaminant)supports the emergent research on the features conferring them different toxicity profiles.In this study,30 ran AgNPs coated with citrate or poly(ethylene glycol)(PEG) were used to assess the influence of coating on the effects produced on a human hepatoma cell line(HepG2),namely in terms of viability,apoptosis,apoptotic related genes,cell cycle and cyclins gene expression.Both types of coated AgNPs decreased cell proliferation and viability with a similar toxicity profile.At the concentrations used(11 and 5 μg/mL corresponding to IC50 and-IC10 levels,respectively) the amount of cells undergoing apoptosis was not significant and the apoptotic related genes BCL2(anti-apoptotic gene)and BAX(pro-apoptotic gene) were both downregulated.Moreover,both AgNPs affected HepG2 cell cycle progression at the higher concentration(11 μg/mL) by increasing the percentage of cells in S(synthesis phase) and G2(Gap 2 phase) phases.Considering the cell-cycle related genes,the expression of cyclin B1 and cyclin E1 genes were decreased.Thus,this work has shown that citrate- and PEG-coated AgNPs impact on HepG2 apoptotic gene expression,cell cycle dynamics and cyclin regulation in a similar way.More research is needed to determine the properties that confer AgNPs at lower toxicity,since their use has proved helpful in several industrial and biomedical contexts.     

Competitive effects of humic acid and wastewater on adsorption of Methylene Blue dye by activated carbon and non-imprinted polymers

Natural organic matter(NOM), present in natural waters and wastewater, decreases adsorption of micropollutants, increasing treatment costs. This research investigated mechanisms of competition for non-imprinted polymers(NIPs) and activated carbon with humic acid and wastewater. Three different types of activated carbons(Norit PAC 200,Darco KB-M, and Darco S-51) were used for comparison with the NIP. The lower surface area and micropore to mesopore ratio of the NIP led to decreased adsorption capacity in comparison to the activated carbons. In addition, experiments were conducted for single-solute adsorption of Methylene Blue(MB) dye, simultaneous adsorption with humic acid and wastewater, and pre-loading with humic acid and wastewater followed by adsorption of MB dye using NIP and Norit PAC 200. Both the NIP and PAC 200 showed significant decreases of 27% for NIP(p = 0.087) and 29% for PAC 200(p = 0.096) during simultaneous exposure to humic acid and MB dye. There was no corresponding decrease for NIP or PAC 200 pre-loaded with humic acid and then exposed to MB. In fact, for PAC 200, the adsorption capacity of the activated carbon increased when it was pre-loaded with humic acid by 39%(p = 0.0005). For wastewater, the NIP showed no significant increase or decrease in adsorption capacity during either simultaneous exposure or pre-loading. The adsorption capacity of PAC 200 increased by 40%(p = 0.001) for simultaneous exposure to wastewater and MB. Pre-loading with wastewater had no effect on MB adsorption by PAC 200.     

Adsorption and desorption of SO2, NO and chlorobenzene on activated carbon

Activated carbon (AC) is very effective for multi-pollutant removal; however, the complicated components in flue gas can influence each other''s adsorption. A series of adsorption experiments for multicomponents, including SO₂, NO, chlorobenzene and H₂O, on AC were performed in a fixed-bed reactor. For single-component adsorption, the adsorption amount for chlorobenzene was larger than for SO₂ and NO on the AC. In the multi-component atmosphere, the adsorption amount decreased by 27.6% for chlorobenzene and decreased by 95.6% for NO, whereas it increased by a factor of two for SO₂, demonstrating that a complex atmosphere is unfavorable for chlorobenzene adsorption and inhibits NO adsorption. In contrast, it is very beneficial for SO₂ adsorption. The temperature-programmed desorption (TPD) results indicated that the binding strength between the gas adsorbates and the AC follows the order of SO₂ > chlorobenzene > NO. The adsorption amount is independent of the binding strength. The presence of H₂O enhanced the component effects, while it weakened the binding force between the gas adsorbates and the AC. AC oxygen functional groups were analyzed using TPD and X-ray photoelectron spectroscopy (XPS) measurements. The results reveal the reason why the chlorobenzene adsorption is less affected by the presence of other components. Lactone groups partly transform into carbonyl and quinone groups after chlorobenzene desorption. The chlorobenzene adsorption increases the number of C = O groups, which explains the positive effect of chlorobenzene on SO₂ adsorption and the strong NO adsorption.     

Long-term effects of environmentally relevant concentrations of silver nanoparticles on microbial biomass, enzyme activity, and functional genes involved in the nitrogen cycle of loamy soil

The increasing production and use of engineered silver nanoparticles (AgNP) in industry and private households are leading to increased concentrations of AgNP in the environment. An ecological risk assessment of AgNP is needed, but it requires understanding the long term effects of environmentally relevant concentrations of AgNP on the soil microbiome. Hence, the aim of this study was to reveal the long-term effects of AgNP on soil microorganisms. The study was conducted as a laboratory incubation experiment over a period of one year using a loamy soil and AgNP concentrations ranging from 0.01 to 1?mg?AgNP/kg soil. The short term effects of AgNP were, in general, limited. However, after one year of exposure to 0.01?mg?AgNP/kg, there were significant negative effects on soil microbial biomass (quantified by extractable DNA; p?=?0.000) and bacterial ammonia oxidizers (quantified by amoA gene copy numbers; p?=?0.009). Furthermore, the tested AgNP concentrations significantly decreased the soil microbial biomass, the leucine aminopeptidase activity (quantified by substrate turnover; p?=?0.014), and the abundance of nitrogen fixing microorganisms (quantified by nifH gene copy numbers; p?=?0.001). The results of the positive control with AgNO3 revealed predominantly stronger effects due to Ag⁺ ion release. Thus, the increasing toxicity of AgNP during the test period may reflect the long-term release of Ag⁺ ions. Nevertheless, even very low concentrations of AgNP caused disadvantages for the microbial soil community, especially for nitrogen cycling, and our results confirmed the risks of releasing AgNP into the environment.     

ZnO纳米颗粒对SBR活性污泥活性的影响

建立了模拟的SBR反应器,并研究了ZnO纳米颗粒(ZnO-NPs)对SBR活性污泥活性的影响.结果表明低浓度(10mg/L)ZnO-NPs对活性污泥活性无明显抑制作用.较高浓度下,ZnO-NPs对活性污泥沉降性能?呼吸速率?EPS和SMP产量及其组成?有机物降解效率等具有明显影响.20,50,100mg/L ZnO-NPs使COD去除率分别降低8.1%, 19.5%和27.7%,使污泥沉降性能分别降低24.2%,35.0%和36.0%,使MLVSS/MLSS比值分别降低8.0%,14.7%和21%,使活性污泥呼吸速率抑制率达到54.0%, 79.0%和80.3%;使EPS产量分别降低29.0%,49.9%和65.4%,使SMP产量分别升高48.9%,102.6%和203.0%.研究表明,较高浓度ZnO-NPs能够抑制污泥代谢,降低活性污泥生物量,显著抑制活性污泥活性.     

Study on sulfur migration in activated carbon adsorption-desorption cycle: Effect of alkali/alkaline earth metals

Activated carbon (AC) has been widely used in the removal of SO₂ from flue gas owing to its well-developed pore structure and abundant functional groups. Herein, the effect of alkali/alkaline earth metals on sulfur migration was investigated based on the dynamic adsorption and temperature programmed desorption experiment. The adsorption and desorption properties of six types of AC (three commercial and three laboratory-made) were carried out on a fixed-bed experimental device, and the physical and chemical properties of samples were determined by X-ray fluorescence, X-ray diffraction, scanning electron microscopy/energy dispersive X-ray, and X-ray photoelectron spectroscopy analysis. The experimental results showed that the adsorbed SO₂ cannot be completely desorbed by increasing the regeneration temperature (350 – 850°C), while the SO₂ fixed in the AC combines with the Ca-based minerals in the ash to form a stable sulfate. For different samples, higher ash content, higher CaO content in the ash and a more developed pore structure lead to a higher SO₂ fixation rate. Moreover, the multiple adsorption-desorption cycles experiment showed that the effect of SO₂ fixation is mainly reflected in the first cycle, after which the adsorption and desorption amount are approximately the same. This study elucidates the effect of alkali/alkaline earth metals on the adsorption-desorption cycle of AC, which provides a deeper understanding of sulfur migration in the AC flue gas desulfurization process.     

青藏高原土壤有机碳密度垂直分布研究

通过对青藏高原土壤普查数据的整理分析,定量研究了青藏高原28个典型土壤类型、14个主要生态系统类型0～20cm、20～50em及50～100cm深度内土壤有机碳密度的垂直分布规律.结果表明,青藏高原28个典型土壤类型3个土层的有机碳密度平均值为(6.16±1.08)kg·m-2、(5.06 ±0.85)kg·m-2、(5.30±0.82)kg·m-2;在0～100cm土层内,暗棕壤、沼泽土的有机碳密度显著高于其它土壤类型,而高山漠土、灰棕漠土、亚高山漠土的有机碳密度不仅远远低于区域平均水平,而且显著低于其它土壤类型.14个典型生态系统土壤的有机碳密度均值为(7.47±1.38)kg·m-2、(6.07±1.24)kg·m-2、(6.46±1.16)kg·m-2;其中,以沼泽草甸、针叶林土壤的有机碳密度最高,而温性荒漠、高寒荒漠、高寒草原及亚高山草原土壤有机碳密度显著低于其它生态系统.这不仅体现了青藏高原土壤-植被显著的地带性分布,而且为青藏高原土壤有机碳循环模型,及有机碳对全球变化的响应研究提供重要的基础数据.     

南长山岛不同土地利用方式下的土壤有机碳密度

土壤有机碳库是陆地生态系统中重要的碳库之一,以往对海岛生态系统土壤有机碳储量估算及其影响因素的研究较少.因此,本研究在南长山岛实测了不同土地利用方式下表层土壤的有机碳密度,比较了相互之间的差别,分析了与土壤理化性质的相关性.结果表明,南长山岛不同土地利用方式土壤有机碳密度差异显著(p0.01),表现为:针阔混交林刺槐黑松侧柏农田水库沿岸草地果园;森林土壤有机碳密度高于其他类型土壤.森林土壤有机碳密度与坡度(r=-0.459,p=0.085)、海拔相关性不显著.在土壤理化性质中,土壤全氮(r=0.763,p0.01)、有机质(r=0.833,p0.01)含量与森林土壤有机碳密度呈显著正相关.     

氯改性活性炭吸附单质铅(Pb0)的机理

利用量子化学中密度泛函方法系统研究氯改性活性炭吸附单质铅（Pb⁰）的机理,明确了氯改性对活性炭吸附Pb⁰的影响,计算得到吸附过程中各个吸附构型的吸附能、重要键长、对应的Mayor键级和铅的Mulliken原子电荷.几何优化选用B3LYP方法结合def2-SVP基组,单点能任务选用PWPB95双杂化泛函结合def2-TZVP基组进行计算.结果表明：对于扶手椅型（armchair）活性炭,氯改性将使活性炭对Pb⁰的吸附能降低74.034kJ/mol;对于锯齿型（zigzag）活性炭,氯改性基本不会改变活性炭对Pb⁰的吸附能力,因此氯改性总体上会减弱活性炭对Pb⁰的吸附作用,但是吸附类型依然为强烈的化学吸附.分别应用电子密度分布和Mayor键级进一步验证纯活性炭和氯改性活性炭对Pb⁰吸附类型,结果与吸附能分析一致.Mayor键级分析表明氯原子通过改变周围碳原子活性影响Pb⁰的吸附,而不是与Pb⁰直接作用.Mulliken原子电荷分析表明铅的原子电荷正相关于活性炭对其的吸附能,铅的原子电荷越大,对应的吸附构型的吸附能越高.此外笔者发现Pb⁰的引入对氯改性活性炭继续吸附Pb⁰有抑制作用.     

Effect of Na+ impregnated activated carbon on the adsorption of NH4+-N from aqueous solution

Two kinds of activated carbons modified by Na+ impregnation after pre-treatments involving oxidation by nitric acid or acidification by hydrochloric acid (denoted as AC/N-Na and AC/HCl-Na, respectively), were used as adsorbents to remove NH4+-N. The surface features of samples were investigated by BET, SEM, XRD and FT-IR. The adsorption experiments were conducted in equilibrium and kinetic conditions. Influencing factors such as initial solution pH and initial concentration were investigated. A possible mechanism was proposed. Results showed that optimal NH4+-N removal efficiency was achieved at a neutral pH condition for the modified ACs. The Langmuir isotherm adsorption equation provided a better fit than other models for the equilibrium study. The adsorption kinetics followed both the pseudo second-order kinetics model and intra-particle kinetic model. Chemical surface analysis indicated that Na+ ions form ionic bonds with available surface functional groups created by pre-treatment, especially oxidation by nitric acid, thus increasing the removal efficiency of the modified ACs for NH4+-N. Na+-impregnated ACs had a higher removal capability in removing NH4+-N than unmodified AC, possibly resulting from higher numbers of surface functional groups and better intra-particle diffusion. The good fit of Langmuir isotherm adsorption to the data indicated the presence of monolayer NH4+-N adsorption on the active homogenous sites within the adsorbents. The applicability of pseudo second-order and intra-particle kinetic models revealed the complex nature of the adsorption mechanism. The intra-particle diffusion model revealed that the adsorption process consisted not only of surface adsorption but also intra-particle diffusion.     

电厂烟气中SO2对活性炭吸附单质铅(Pb0)的影响机理

利用密度泛函理论系统研究了SO_2对活性炭吸附单质铅(Pb~0)的影响,其中,结构优化与频率计算采用B3LYP/def2-SVP级别方法和基组,单点能计算采用B3LYP/def2-TZVP级别方法和基组.同时,利用玻尔兹曼分布函数分析了SO_2与Pb~0在活性炭表面的竞争吸附关系,结果表明,Pb~0在纯净活性炭上的吸附能力大于SO_2.此外,本研究发现,SO_2的预吸附会增强活性炭对Pb~0的吸附效果.通过静电势分布揭开了SO_2促进活性炭吸附Pb~0的深层原因,结果发现,吸附SO_2以后活性炭表面静电势极大值增大,极小值减小,吸附剂吸附能力因此增强.最后,利用电子密度差分图揭示出SO_2改性活性炭在吸附Pb~0时,SO_2对Pb~0吸附的影响可以分为直接影响和间接影响两种.     

从分子质量的变化分析有机物对GAC吸附内分泌干扰物(BPA)的影响

从分子质量分布的角度研究了水中有机物对颗粒活性炭(GAC)吸附双酚A(BPA)容量及吸附速率的影响.结果表明,相对于以去离子水为本底的BPA溶液来说,GAC吸附以滤后水、臭氧后出水和原水为本底的BPA溶液的Langmuir模型的最大吸附容量q_m值分别下降了29.95%、43.56%和44.44%,而其拟二级动力学模型的k₂值分别下降了43.05%、49.75%和56.38%.相对分子质量3 000以上,尤其是10 000以上的有机物堵塞GAC的二级微孔;3 000以下,尤其是1 000以下的有机物与BPA分子之间存在直接的竞争吸附,是导致GAC对BPA的吸附容量以及吸附速率下降的主要原因.