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151.
152.
《环境科学学报(英文版)》2023,35(4):263-274
The cryptomelane-type manganese oxide (OMS-2)-supported Co (xCo/OMS-2; x = 5, 10, and 15 wt.%) catalysts were prepared via a pre-incorporation route. The as-prepared materials were used as catalysts for catalytic oxidation of toluene (2000 ppmV). Physical and chemical properties of the catalysts were measured using the X-ray diffraction (XRD), Fourier transform infrared spectroscopic (FT-IR), scanning electron microscopic (SEM), X-ray photoelectron spectroscopy (XPS), and hydrogen temperature-programmed reduction (H2-TPR) techniques. Among all of the catalysts, 10Co/OMS-2 performed the best, with the T90%, specific reaction rate at 245°C, and turnover frequency at 245°C (TOFCo) being 245°C, 1.23 × 10−3 moltoluene/(gcat·sec), and 11.58 × 10−3 sec−1 for toluene oxidation at a space velocity of 60,000 mL/(g·hr), respectively. The excellent catalytic performance of 10Co/OMS-2 were due to more oxygen vacancies, enhanced redox ability and oxygen mobility, and strong synergistic effect between Co species and OMS-2 support. Moreover, in the presence of poisoning gases CO2, SO2 or NH3, the activity of 10Co/OMS-2 decreased for the carbonate, sulfate and ammonia species covered the active sites and oxygen vacancies, respectively. After the activation treatment, the catalytic activity was partly recovered. The good low-temperature reducibility of 10Co/OMS-2 could also facilitate the redox process accompanied by the consecutive electron transfer between the adsorbed O2 and the cobalt or manganese ions. In the oxidation process of toluene, the benzoic and aldehydic intermediates were first generated, which were further oxidized to the benzoate intermediate that were eventually converted into H2O and CO2. 相似文献
153.
二叠纪—三叠纪之交的环境恶化事件不但导致了生物大绝灭,而且造成了自然界正常的碳循环崩溃。为了研究三叠纪早期生物复苏过程中的环境特征、碳氧同位素演化上的地层学意义,对巢湖平顶山西坡剖面下三叠统碳酸盐岩取样分析。研究结果表明,巢湖平顶山西坡剖面早三叠世碳氧同位素地层曲线与已知的平顶山北坡剖面碳氧同位素地层曲线相似。δ13C值在Induan阶、Olenekian阶底部首先表现为大幅度负漂,随后呈上升趋势。δ18O值除了表现出1Ma的周期性波动之外,与δ13C低值区对应处也具负偏趋势。δ13C、δ18O值的演化趋势反映了早三叠世海洋环境恶化、生物复苏十分缓慢。 相似文献
154.
大孔强碱阴树脂去除饮用水中微量有机物 总被引:2,自引:0,他引:2
比较了大孔强碱阴树脂和颗粒活性炭在饮用水的深度处理中对有机物的去除效果。结果表明:(1)大孔强碱阴树脂的吸附容量比颗粒活性炭的大。在pH为8时,大孔强碱阴树脂对TOC的去除率最高。pH6~8时,对TOC的去除率没有明显的区别,而颗粒活性炭在pH为2时。对TOC的去除率最高;水温低能提高2种吸附材料的吸附容量。(2)在动态实验条件下。当流速相同,大孔强碱阴树脂的穿透时间明显比颗粒活性炭的长,大孔强碱阴树脂的制水量约是吸附床的10000倍。而颗粒活性炭却只有吸附床的4000倍。在饮用水的深度处理中,大孔强碱阴树脂可作为活性炭的最佳替代品。 相似文献
155.
156.
157.
不同前处理方法对活性炭吸附一氧化碳的影响 总被引:1,自引:0,他引:1
本文采用颗粒状活性炭(GH-A)作吸附剂,通过不同的前处理方法,以一氧化碳CO与空气的混合物为分离测定对象,用气固色谱法测定被活性炭充分吸附前、后的混合气体中CO的含量,对比评价几种前处理方法。结果表明,对CO的吸附量显著提高的前处理方法分别是研磨筛分至32—38目、酸洗、添加改性剂So而水洗则降低了活性炭吸附CO的能力。 相似文献
158.
V. Krishna Prasad K.V.S. Badarinath H. Tsuruta S. Sudo S. Yonemura John Cardina Benjamin Stinner Richard Moore Deborah Stinner Casey Hoy 《The Environmentalist》2003,23(2):175-187
Forests and soils are a major sink of carbon, and land use changes can affect the magnitude of above ground and below ground carbon stores and the net flux of carbon between the land and the atmosphere. Studies on methods for examining the future consequences of changes in patterns of land use change and carbon flux gains importance, as they provide different options for CO2 mitigation strategies. In this study, a simulation approach combining Markov chain processes and carbon pools for forests and soils has been implemented to study the carbon flows over a period of time. Markov chains have been computed by converting the land use change and forestry data of India from 1997 to 1999 into a matrix of conditional probabilities reflecting the changes from one class at time t to another class time t+1. Results from Markov modeling suggested Indian forests as a potential sink for 0.94 Gt carbon, with an increase in dense forest area of about 75.93 Mha and decrease of about 3.4 Mha and 5.0 Mha in open and scrub forests, if similar land use changes that occurred during 1997–1999 would continue. The limiting probabilities suggested 34.27 percent as dense forest, 6.90 as open forest, 0.4 percent mangrove forest, 0.1 percent scrub and 58 percent as non-forest area. Although Indian forests are found to be a potential carbon sink, analysis of results from transition probabilities for different years till 2050 suggests that, the forests will continue to be a source of about 20.59 MtC to the atmosphere. The implications of these results in the context of increasing anthropogenic pressure on open and scrub forests and their contribution to carbon source from land use change and forestry sector are discussed. Some of the mitigation aspects to reduce greenhouse gas emissions from land use change and forestry sector in India are also reviewed in the study. 相似文献
159.
160.
Subsidence is a primary factor governing marsh deterioration in Mississippi River deltaic plain coastal marshes. Marsh surface-water level relationships are maintained primarily through soil organic matter accumulation and inorganic sediment input. In this study we examined the role of soil organic matter accumulation in maintaining marsh elevation in a brackish Spartina patens marsh. Measured rates of soil organic accumulation were compared to plant biomass production and soil respiration (carbon dioxide and methane emission) at the study sites. The study demonstrated the importance of plant biomass production to soil organic carbon accumulation in maintaining viable Spartina patens marshes in sediment-deficient coastal environments. The role of Mississippi River freshwater reintroduction in maintaining conditions for organic accretion is discussed. 相似文献