共查询到19条相似文献，搜索用时 203 毫秒
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以木屑为原料,高温热解制备生物炭。以聚乙烯醇为粘结剂,采用混合法将生物炭与果胶复合,并负载磁性,经烘干定型制备果胶包覆的磁性生物炭材料（果胶@生物炭-Fe3O4）。采用扫描电镜（SEM）、X射线衍射（XRD）及N2吸附-脱附（BET）等方法对果胶@生物炭-Fe3O4进行表征,结合吸附实验分析其对Cu2+的吸附特性。结果表明,当生物炭、果胶、Fe3O4质量比为5：1：1,溶液pH值为6,吸附24 h,果胶@生物炭-Fe3O4对Cu2+吸附效果最好;二级动力学方程能较好地描述果胶@生物炭-Fe3O4对Cu2+的吸附过程,Freundlich模型能较好地拟合其吸附行为;SEM结果显示该材料具有不规则的孔隙结构;XRD分析显示纳米Fe3O4是其主要的晶体结构;BET测得其比表面积为25.654 m2·g-1,平均孔径为20.18 nm。 相似文献
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研究以玉米秸秆为原料制备生物质活性炭,并分别进行NaOH和HNO3改性。考察三种生物质活性炭的用量和粒径、水溶液pH值和吸附时间对水溶液中Cu2+吸附性能的影响,并对其等温吸附特征、吸附动力学和吸附热力学进行研究。结果表明:当0.15~0.30mm的生物质活性炭投加量为0.30g,pH值为6.0时,对溶液中Cu2+具有很好的去除率,在360min时达到吸附平衡;吸附过程符合Langmuir和Freundlich模型以及准二级动力学方程,且热力学参数ΔG0＜0,ΔH0和ΔS0＞0,为自发的、吸热的和熵增的过程,对水溶液中Cu2+均具有较好的亲和力;相同条件下,三种生物质活性炭对Cu2+的吸附效果表现为:NaOH改性＞HNO3改性＞未改性。 相似文献
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文章基于密度泛函理论,研究了本征及Nb,Fe单原子掺杂单层MoSe2的电子结构及光学性质。计算发现,本征单层MoSe2和Nb-MoSe2为直接带隙半导体,Fe-MoSe2为间接带隙结构;Fe-MoSe2较本征单层MoSe2导电性大大提高,实现了由半导体向半金属的过渡。由态密度分析得出了本征及Nb,Fe单原子掺杂单层MoSe2能量状态主要由Mo 4d,Se 4p轨道电子所贡献的结论,并对各原子掺杂体系轨道电子的能量贡献和掺杂类型做了探讨。此外,还详细分析了费米能级附近的自旋态密度、杂质带、磁性之间的联系。光学性质方面,比较了本征单层MoSe2与各掺杂体系的复介电常数和光吸收系数,在红外光区Fe-MoSe2的吸收系数高于本征单层MoSe2。本征单层MoSe2的光吸收系数为9.69×104 cm-1,是区域最大吸收峰。上述研究表明,通过对单层MoSe2的Nb,Fe掺杂可使电子输运特性得到了增强,为高活性自旋电子和光电子器件设计和研究开辟了新的前景。 相似文献
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文章从断裂力学的角度开展对铁尾矿砂混凝土的研究,采用三点弯曲梁法对铁尾矿砂混凝土和河砂混凝土进行断裂试验,测定荷载-裂缝口张开位移(P-CMOD)曲线和荷载-应变(P-ε)曲线,依据混凝土双K模型确定起裂荷载(Pini)、失稳荷载(Pmax)、起裂韧度(KiniIc)和失稳韧度(KunIc),并利用扫描电镜对断裂面进行观测。通过比较断裂过程曲线和断裂参数发现,两种混凝土的断裂过程没有明显差异,铁尾矿砂混凝土的Pini,Pmax,KiniIc和KunIc均高于河砂混凝土,其中Pini和KiniIc更加明显。扫描电镜结果显示,加入铁尾矿砂能够改善混凝土界面过渡区的微观形貌。 相似文献
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以铁尾矿砂为原料,用NaOH,HNO3调节pH值,采用熔融-水热两步法制备了铁尾矿砂光催化剂。利用X射线衍射仪、紫外/可见/近红外光谱仪等对铁尾矿砂光催化剂的结构性能进行表征;以罗丹明B溶液为标准降解物,汞灯为光源,探讨在不同pH条件下合成的铁尾矿砂光催化剂的光催化活性。结果表明,铁尾矿砂光催化剂的主要成分为Fe2.35Si0.65O4和NaNO3,且具有良好的光催化效果;在pH 8.5条件下制备的样品具有多孔结构,光催化性能最强;光照120 min时此样品可降解95.1%的罗丹明B溶液;·O2-是光催化反应过程中最主要的氧化活性自由基。 相似文献
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在纯净空气与H2O/ CO2污染空气来流对比试验结果基础上,采用数值计算方法和化学动力学方法,研究了H2O和CO2污染组分对煤油燃料超声速燃烧的影响,获得了试验手段难以得到的燃烧室流场参数和性能数据。完成了相应的煤油燃料超声速燃烧室二维数值计算,其中匹配了进口总温、总压、马赫数、氧气摩尔分数和工作当量油气比。将数值计算结果与相应试验测量值进行了对比分析,并结合燃烧室流场数据、性能参数分析了H2O和CO2污染的动力学影响、以及对燃烧室性能的影响。研究表明:(1)数值计算结果与实验测量值总体上吻合,两种手段均体现了纯净空气来流时不同煤油当量油气比的燃烧室性能,并反映了一致的“污染效应”影响趋势;(2) H2O污染、H2O+ CO2污染的存在降低了煤油燃料超声速燃烧室性能,体现在燃烧诱导压升、燃烧效率、流向冲量增量的下降,而且随着污染组分含量的增加,燃烧室性能下降越加显著。 相似文献
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采用诱导法制备空心三元PdPtCu纳米材料,利用透射电镜(TEM)、扫描电镜(SEM)和X射线衍射(XRD)对其形貌、组成和结构进行表征,并在碱性条件下测试其对乙醇氧化的电催化性能。结果表明,以氧化铜为诱导剂制备的三元PdPtCu纳米材料主要呈空心结构,且其形貌和组成可控;Pd3Pt@Cu,PdPt@Cu和PdPt3@Cu三种材料的质量电流密度分别为8 510 A·g-1,9 270 A·g-1和5 490 A·g-1,无论是质量活性还是稳定性,均明显优于商业Pd/C和商业Pt/C催化剂。 相似文献
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采用X射线衍射仪、摩擦磨损试验机和扫描电镜等手段,测试分析了固溶态、T6态和ECAP时效态6063铝合金的物相组成、显微组织和摩擦磨损性能。结果表明,固溶态、T6态和ECAP时效态6063铝合金的主要物相都为ɑ-Al相、β-Mg2Si相、β''-Mg1.7Si相和β″-Mg5Si6相,但是ECAP时效态6063铝合金的β相、β''相和β″相的衍射峰更强;相同载荷下,平均摩擦系数和磨损率从大至小的顺序为固溶态>T6态>ECAP时效态,即ECAP时效态6063铝合金具有相对较低的摩擦系数和更好的耐磨性,这主要与ECAP时效处理可以起到细晶强化和弥散强化作用有关。 相似文献
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As one of the world's most produced chemicals, ammonia(NH_3) is synthesized by Haber–Bosch process. This century-old industry nourishes billions of people and promotes social and economic development. In the meantime, 3%–5% of the world's natural gas and 1%–2% of the world's energy reserves are consumed, releasing millions of tons of carbon dioxide annually to the atmosphere. The urgency of replacing fossil fuels and mitigating climate change motivates us to progress toward more sustainable methods for N_2 reduction reaction based on clean energy. Herein, we overview the emerging advancement for sustainable N_2 fixation under mild conditions, which include electrochemical, photo-, plasma-enabled and homogeneous molecular NH_3 productions. We focus on NH_3 generation by electrocatalysts and photocatalysts. We clarify the features and progress of each kind of NH_3 synthesis process and provide promising strategies to further promote sustainable ammonia production and construct state-of-the-art catalytic systems. 相似文献
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Influence of bulking agents on CH4, N2O,and NH3 emissions during rapid composting of pig manure from the Chinese Ganqinfen system 总被引：1，自引：0，他引：1
Xiang-ping SUN Peng LU Tao JIANG Frank SCHUCHARDT Guo-xue LI 《Journal of Zhejiang University. Science. B》2014,15(4):353-364
研究目的：在＂干清粪＂系统猪粪堆肥过程中,不同添加剂（玉米秸秆、锯末和蘑菇渣）处理对甲烷、氧化亚氮和氨气排放的影响。创新要点：将不同的添加剂（玉米秸秆、锯末和蘑菇渣）应用到快速堆肥系统中进行堆肥,测定了猪粪堆肥过程中甲烷、氧化亚氮和氨气的排放规律,为国内猪粪堆肥的应用提供理论指导。重要结论：玉米秸秆作为添加剂能增加猪粪堆肥过程中氧化亚氮的排放;蘑菇渣添加剂增加了堆肥过程中甲烷的排放,然而减少了氧化亚氮及氨气的排放;锯末处理能增加堆肥过程中氨气的排放。添加剂能显著影响堆肥过程中氮素的损失。 相似文献
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Yan-hong ZHOU Yi-li ZHANG Xue-min WANG Jin-xia CUI Xiao-jian XIA Kai SHI Jing-quan YU 《Journal of Zhejiang University. Science. B》2011,12(2):126-134
Cucumber and rice plants with varying ammonium (NH4
+) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence
quenching, and photosynthetic electron allocation. Compared to nitrate (NO3
−)-grown plants, cucumber plants grown under NH4
+-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO2) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O2-independent alternative electron flux, and increased O2-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH4
+-grown plants had a higher O2-independent alternative electron flux than NO3
−-grown plants. NO3
− reduction activity was rarely detected in leaves of NH4
+-grown cucumber plants, but was high in NH4
+-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to
NO3
− assimilation, an effect more significant in NO3
−-grown plants than in NH4
+-grown plants. Meanwhile, NH4
+-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for
NO3
− reduction, regardless of the N form supplied, while NH4
+-sensitive plants had a high water-water cycle activity when NH4
+ was supplied as the sole N source. 相似文献
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HNCO hydrolysis performance in urea-water solution thermohydrolysis process with and without catalysts 总被引：1，自引：0，他引：1
Zhen-chao Chen Wei-juan Yang Jun-hu Zhou Hong-kun Lv Jian-zhong Liu Ke-fa Cen 《浙江大学学报(A卷英文版)》2010,11(11):849-856
The thermolysis of urea-water solution and its product, HNCO hydrolysis is investigated in a dual-reactor system. For the thermal decomposition below about 1073 K, the main products are ammonia (NH3) and isocyanic acid (HNCO) whereas at higher temperatures the oxidation processes take effect and the products include a low concentration of nitric oxide (NO) and nitrous oxide (N2O). The gas HNCO is quite stable and a high yield of HNCO is observed. The ratio of NH3 to HNCO increases from approximately 1.2 to 1.7 with the temperature. The chemical analysis shows that H radical is in favor of HNCO hydrolysis by instigating the reaction HNCO+H·→·NH2+CO and high temperature has positive effect on H radical. The hydrolysis of HNCO over an alumina catalyst made using a sol-gel process (designated as γ-Al2O3) is investigated. The conversion of HNCO is high even at the high space velocities (6×105 h-1) and low temperatures (393–673 K) in the tests with catalysts, which enhances HNCO hydrolysis and raises the ratio of NH3 to HNCO to approximately 100. The pure γ-Al2O3 shows a better catalytic performance than CuO/γ-Al2O3. The addition of CuO not only reduces the surface area but also decreases the Lewis acid sites which are recognized to have a positive effect on the catalytic activity. The apparent activation energy of the hydrolysis reaction amounts to about 25 kJ/mol in 393–473 K while 13 kJ/mol over 473 K. The overall hydrolysis reaction rate on catalysts is mainly determined by external and internal mass-transfer limitations. 相似文献
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P. V. Sukumaran 《Resonance》1999,4(12):4-10
Molecular O2 and H2O are the vital requirements of contemporary life. The evolution of the atmosphere and oceans, therefore, necessarily predates
metazoan evolution on the earth. The prebiotic primary atmosphere had CH4, NH3 and H2 as the chief components and was O2-deficient. Dissociation of CH4 and NH3 paved the way for the secondary atmosphere composed principally of CO2. 相似文献
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Ammonium (NH4
+) is an important form of nitrogen nutrient for most plants, yet is also a stressor for many of them. However, the primary
events of NH4
+ toxicity at the cellular level are still unclear. Here, we showed that NH4
+ toxicity can induce the root cell death in a temporal pattern which primarily occurs in the cells of root maturation and
elongation zones, and then spreads to the cells in the meristem and root cap. The results from the NH4
+-hypersensitive mutant hsn1 further confirmed our findings. Taken together, NH4
+ toxicity inhibits primary root growth by inhibiting cell elongation and division and inducing root cell death. 相似文献
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Diesel emission fluid (DEF) soaking and urea deposits on selective catalytic reduction (SCR) catalysts are critical issues for real diesel engine NH3-SCR systems. To investigate the impact of DEF soaking and urea deposits on SCR catalyst performance, fresh Cu-zeolite catalyst samples were drilled from a full-size SCR catalyst. Those samples were impregnated with DEF solutions and subsequently hydrothermally treated to simulate DEF soaking and urea deposits on real SCR catalysts during diesel engine operations. Their SCR performance was then evaluated in a flow reactor with a four-step test protocol. Test results show that the DEF soaking leached some Cu from the SCR catalysts and slightly reduced their Cu loadings. The loss of Cu and associated metal sites on the catalysts weakened their catalytic oxidation abilities and caused lower NO/NH3 oxidation and lower high-temperature N2O selectivity. Lower Cu loading also made the catalysts less active to the decomposition of surface ammonium nitrates and decreased low-temperature N2O selectivity. Cu loss during DEF impregnation released more acid sites on the surface of the catalysts and increased their acidities, and more NH3 was able to be adsorbed and involved in SCR reactions at medium and high temperatures. Due to lower NH3 oxidation and higher NH3 storage, the DEF-impregnated SCR catalyst samples showed higher NO x conversion above 400 °C compared with the non-soaked one. The negative impact of urea deposits during DEF impregnation was not clearly observed, because the high-temperature hydrothermal treatment helped to remove the urea deposits. 相似文献
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The use of a biotrickling filter was investigated for a pilot field-scale elimination of NH3 gas and other odorous gases from a composting plant in Tongzhou District, Beijing. The inlet gas flow rate was 3500 m3/h and NH3 concentration fluctuated between 2.76–27.84 mg/m3, while the average outlet concentration was 1.06 mg/m3 with an average of 94.9% removal. Critical volumetric loading (removal efficiency=100%) was 11.22 g-N/(m3·h). The odor concentration removal was 86.7%. NH3 removal efficiency decreased as the free ammonia (FA) in the trickling liquid increased. The pressure drop was maintained at about 50 Pa/m and was never more than 55 Pa/m. During the experiment, there was neither backflushing required nor any indication of clogging. Overall, the biotrickling filter was highly efficient and cost-effective for the simultaneous biodegradation of NH3 and other odorous gases from composting, suggesting the possibility of treating odorous gases at the industrial level. 相似文献
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Shi-yu Qin Xue-cheng Sun Cheng-xiao Hu Qi-ling Tan Xiao-hu Zhao 《Journal of Zhejiang University. Science. B》2017,18(6):512-521