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排序方式: 共有125条查询结果,搜索用时 125 毫秒
61.
化肥厂含氮废水的生物硝化处理试验 总被引:3,自引:0,他引:3
用维纶软性纤维作填料,进行了生物膜法三级硝化处理化肥厂含氮废水的试验,TKN的去除负荷最高可达0.377kg/m^3.d,总硝化率可达93%。三级硝化后,出水中Urea-N〈3mg/L、NH3-N〈17mg/L。若投加痕量Mg^2(50μg/L)可以促进尿素的水解 。 相似文献
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环保型脲醛树脂胶粘剂的合成研究 总被引:8,自引:0,他引:8
介绍了聚乙烯醇(PVA)、三聚氰胺在脲醛树脂胶粘剂合成过程中所起的改性作用,研究了反应温度、反应体系pH、甲醛与尿素摩尔比、PVA和三聚氰胺用量对脲醛树脂胶粘剂性能的影响。试验结果表明,在反应温度为80℃、反应体系pH为5.0、甲醛与尿素摩尔比为1.5、PVA和三聚氰胺用量分别为尿素与甲醛溶液总质量的1.0%和5%的条件下,合成的脲醛树脂胶粘剂的剪切强度为2.99MPa,游离甲醛的质量分数由传统工艺生产产品的0.6%~0.8%降低至0.063%,耐沸水时间为108min,且贮存稳定性好,达到了HJBZ-1998国家环境标志产品技术要求。 相似文献
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Obed RI Ademola AK Vascotto M Giannini G 《Journal of environmental radioactivity》2011,102(11):1012-1017
Radon measurements were performed in secondary schools in the Oke-Ogun area, South-west, Nigeria, by solid state nuclear track detectors (SSNTDs). About seventy CR-39 detectors were distributed in 35 high schools of the Oke-Ogun area. The CR-39 detectors were exposed in the schools for 3 months and then etched in NaOH 6 N solution at 90 °C for 3 h. The tracks were counted manually at the microscope and the radon concentration was determined at the Radioactivity Laboratory, Department of Physics, University of Trieste, Trieste, Italy. The overall average radon concentration in the surveyed area was 45 ± 27 Bq m−3. The results indicate no radiological health hazard. The research also focused on parameters affecting radon concentrations such as the age of the building in relation to building materials and floor number of the classrooms. The results show that radon concentrations in ground floors are higher than in upper floors. 相似文献
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M. Tayyeb Javed W. Nimmo Asif Mahmood Naseem Irfan 《Journal of environmental management》2009,90(11):3429-3435
An experimental investigation was performed to study the effect of oxygenated liquid additives, H2O2, C2H5OH, C2H4(OH)2 and C3H5(OH)3 on NOx removal from flue gases by the selective non-catalytic reduction (SNCR) process using urea as a reducing agent. Experiments were performed with a 150 kW pilot scale reactor in which a simulated flue gas was generated by the combustion of methane operating with 6% excess oxygen in flue gases. The desired levels of initial NOx (500 ppm) were achieved by doping the fuel gas with ammonia. Experiments were performed throughout the temperature range of interest, i.e. from 800 to 1200 °C for the investigation of the effects of the process additives on the performance of aqueous urea DeNOx. With H2O2 addition a downward shift of 150 °C in the peak reduction temperature from 1130 to 980 °C was observed during the experimentation, however, the peak reduction efficiency was reduced from 81 to 63% when no additive was used. The gradual addition of C2H5OH up to a molar ratio of 2.0 further impairs the peak NOx reduction efficiency by reducing it to 50% but this is accompanied by a downward shift of 180 °C in the peak reduction temperature. Further exploration using C2H4(OH)2 suggested that a 50% reduction could be attained for all the temperatures higher than 940 °C. The use of C3H5(OH)3 as a secondary additive has a significant effect on the peak reduction efficiency that decreased to 40% the reductions were achievable at a much lower temperature of 800 °C showing a downward shift of 330 °C. 相似文献
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Martha P. GarcÍa De Llasera Adriana RodrÍguez-Castillo Luz E. Vera-Avila 《Journal of environmental science and health. Part. B》2013,48(6):615-627
The effect of organic matter on the solid-phase extraction (SPE) efficiency for pesticides belonging to different chemical groups (urea-derivatives, carbamates and triazines) and having different polarities, was simultaneously studied for the first time in pure and simulated water samples. SPE was carried out in precolumns packed with C18 silica or styrene-divinylbenzene copolymer PLRP-S phases on-line coupled to high performance liquid chromatography (HPLC) analysis. Retention factors in water (k'W) were estimated for 25 compounds and used for the calculation of the theoretical breakthrough volume (VbT) in pure water. Experimental breakthrough volumes (VbE) were first determined using purified and deionized water as the matrix for selected compounds having VbT < 500 mL; then, the same water with an added humic acid sodium salt (HA) at 0.4–5.6 mg/L of dissolved organic carbon (DOC) content, was used as the matrix for compounds having VbE < 500 mL in pure water. Several polar pesticides showed negative linear or logarithmic VbE curves depending on HA content; their recoveries were also determined in environmental samples having low dissolved organic carbon values, between 0.5–6.4 mg/L. A similar behavior was observed for these compounds in simulated and natural water samples, where DOC concentration and the percolated volume (Vp) mainly determine the solute recoveries values. However, the variation of recoveries as a function of DOC content could be negative or null depending on the two examined conditions (Vp lower or larger than VbE in pure water). Results demonstrated that breakthrough volume must always be considered to correctly interpret the participation of dissolved humic material on the SPE efficiency of organic micropollutants in water. 相似文献
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间种高粱及施用大颗粒尿素对茶园N2O排放的影响 总被引:1,自引:0,他引:1
茶园施肥量大、氧化亚氮(N_2O)排放系数高,且近年来我国茶园面积不断扩大,使茶园成为重要的农业N_2O排放源,亟需有效的茶园N_2O减排措施.本研究在我国中亚热带典型丘陵茶园,通过设置间种高粱、施用大颗粒尿素和常规施肥3种管理措施,观测不同管理措施下茶园土壤N_2O及相关环境因子动态,旨在解析茶园土壤N_2O排放的主控因子和明确提出的减排措施的有效性. 2 a的田间试验结果表明:①茶园土壤N_2O排放通量与土壤化学性质、温度及降雨有显著的相关性,土壤物理性质和土壤化学性质的交互作用对N_2O排放影响最大,土壤化学性质中的NO~-_3-N含量是决定N_2O排放量大小的最主要因素,茶园土壤N_2O减排研究的工作重点在于如何减小土壤中的NO~-_3-N含量;②间种高粱在未影响茶叶产量的前提下减少了51.2%的N_2O排放,从缓解全球气候变暖角度看,间种高粱是本研究中最佳的茶园管理措施;③施用大颗粒尿素在提高29.5%的茶叶产量同时减少了34.7%的N_2O排放,从兼顾经济效益及缓解全球气候变暖的角度看,茶园中施用大颗粒尿素则是本研究中最佳的施肥措施. 相似文献