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131.
Adsorption behavior of condensed phosphate on aluminum hydroxide 总被引:1,自引:0,他引:1
Sodium pyrophosphate (pyro-P, Na4P2OT), sodium tripolyphosphate (tripoly-P, Na3P3O10), and sodium hexametaphosphate (meta-P, (NaPO3)6) were selected as the model compounds of condensed phosphate to investigate the adsorption behavior of condensed phosphate on aluminum hydroxide. The adsorption was found to be endothermic and divisible into two stages: (1) fast adsorption within 1 h; and (2) slow adsorption between 1 and 24 h. The modified Freundlich model simulated the fast adsorption stage well; the slow adsorption stage was described well by the first-order kinetics. The activation energies of pyro-P, tripoly-P, and meta-P adsorption on aluminum hydroxide were determined to be 20.2, 22.8 and 10.9 kJ/mol P adsorbed, respectively, in the fast adsorption stage and to be 66.3, 53.5 and 72.5 kJ/mol P adsorbed, respectively, in the slow adsorption stage. The adsorption increased the negative charge of the aluminum hydroxide surface. Transmission electron microscopy and energy dispersive X-ray analysis analyses provided evidence that the adsorption was not uniform on the surface and that the small crystals contributed more to the fast adsorption than the normal sites did. The results from X-ray fluorescence spectrometry and X-ray photoelectron spectroscopy tests also revealed the uneven adsorption of condensed phosphate as a function of the penetration depth. More condensed phosphates were adsorbed on the outer surface of aluminum hydroxide than in its inner parts. 相似文献
132.
Anaerobic biodegradation of benzene series compounds by mixed cultures
based on optional electronic acceptors 总被引:6,自引:2,他引:4
A series of batch experiments were performed using mixed bacterial consortia to investigate biodegradation performance of benzene, toluene, ethylbenzene and three xylene isomers (BTEX) under nitrate, sulfate and ferric iron reducing conditions. The results showed that toluene, ethylbenzene, m-xylene and o-xylene could be degraded independently by the mixed cultures coupled to nitrate, sulfate and ferric iron reduction. Under ferric iron reducing conditions the biodegradation of benzene and p-xylene could be occurred only in the presence of other alkylbenzenes. Alkylbenzenes can serve as the primary subs'rates to stimulate the transformation of benzene and p-xylene under anaerobic conditions. Benzene and p-xylene are more toxic than toluene and ethylbenzene, under the three terminal electron acceptors conditions, the degradation rates decreased with toluene 〉 ethylbenzene 〉 m-xylene 〉 o-xylene〉 benzene 〉 p- xylene. Nitrate was a more favorable electron acceptor compared to sulfate and ferric iron. The ratio between sulfate consumed and the loss of benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene was 4.44, 4.51, 4.42, 4.32, 4.37 and 4.23, respectively; the ratio between nitrate consumed and the loss of these substrates was 7.53, 6.24, 6.49, 7.28, 7.81, 7.61, respectively; the ratio between the consumption of ferric iron and the loss of toluene, ethylbenzene, o-xylene, m-xylene was 17.99, 18.04, 18.07, 17.97, respectively. 相似文献
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134.
A. Bhatia A. GhoshV. Kumar R. TomerS.D. Singh H. Pathak 《Agriculture, ecosystems & environment》2011,144(1):21-28
Physiological changes in crop plants in response to the elevated tropospheric ozone (O3) may alter N and C cycles in soil. This may also affect the atmosphere-biosphere exchange of radiatively important greenhouse gases (GHGs), e.g. methane (CH4) and nitrous oxide (N2O) from soil. A study was carried out during July to November of 2007 and 2008 in the experimental farm of Indian Agricultural Research Institute, New Delhi to assess the effects of elevated tropospheric ozone on methane and nitrous oxide emissions from rice (Oryza sativa L.) soil. Rice crop was grown in open top chambers (OTC) under elevated ozone (EO), non-filtered air (NF), charcoal filtered air (CF) and ambient air (AA). Seasonal mean concentrations of O3 were 4.3 ± 0.9, 26.2 ± 1.9, 59.1 ± 4.2 and 27.5 ± 2.3 ppb during year 2007 and 5.9 ± 1.1, 37.2 ± 2.5, 69.7 ± 3.9 and 39.2 ± 1.8 ppb during year 2008 for treatments CF, NF, EO and AA, respectively. Cumulative seasonal CH4 emission reduced by 29.7% and 40.4% under the elevated ozone (EO) compared to the non-filtered air (NF), whereas the emission increased by 21.5% and 16.7% in the charcoal filtered air (CF) in 2007 and 2008, respectively. Cumulative seasonal emission of N2O ranged from 47.8 mg m−2 in elevated ozone to 54.6 mg m−2 in charcoal filtered air in 2007 and from 46.4 to 62.1 mg m−2 in 2008. Elevated ozone reduced grain yield by 11.3% and 12.4% in 2007 and 2008, respectively. Global warming potential (GWP) per unit of rice yield was the least under elevated ozone levels. Dissolved organic C content of soil was lowest under the elevated ozone treatment. Decrease in availability of substrate i.e., dissolved organic C under elevated ozone resulted in a decline in GHG emissions. Filtration of ozone from ambient air increased grain yield and growth parameters of rice and emission of GHGs. 相似文献
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为探究煤的孔裂隙结构分形特征,以贵州富煤区4个煤层的煤样为研究对象,基于扫描电镜和低温液氮实验综合表征煤样的孔裂隙发育程度及连通性,应用Photoshop,Image-Pro-Plus图像处理技术对煤的SEM图像进行二值化处理及主要参数提取;结合小岛法计算煤样的孔裂隙分形维数值,并与扫描电镜、低温液氮实验分析结果进行对比。结果表明:经扫描电镜和低温液氮实验发现,4个煤层的孔裂隙连通性优先顺序依次为六盘水煤田3#煤层>黔北煤田9#煤层>黔北煤田8#煤层>织纳煤田8#煤层;借助图像处理技术并结合小岛法对实验煤样的孔裂隙分形维数进行计算,各实验煤层分形维数由小到大依次为六盘水煤田3#煤层<黔北煤田9#煤层<黔北煤田8#煤层<织纳煤田8#煤层,该分形维数排序所反馈的煤样孔裂隙发育程度及连通性信息与前述2个实验结果相互印证,表明数字图像技术与小岛法分形相结合能真实、准确地反映煤的分形特征。 相似文献
139.
介绍LED产品常见的失效分析手段,主要包含外观检查、电性能测试、X-Ray透视检查、开封检查、金相切片分析、扫描电镜和能谱分析等手段,并结合实际案例对几种方法进行描述。 相似文献
140.
The inhibitory effect of silver nanoparticles (AgNPs) on photochemical reactions of photosynthesis was investigated using the green alga model Chlamydomonas reinhardtii. Algal cells were exposed to 1, 5, and 10?µmol?L?1 of AgNPs under both light and dark conditions during 6?h. The rapid rise of chlorophyll a fluorescence and the fluorescence imaging system were employed to investigate the alteration of photosystem II (PSII) photochemical reactions and the associated electron transport activity. When algal cells were exposed to 5 and 10?µmol?L?1 of AgNPs, our results showed the evidence of a structural deterioration of PSII reaction center, the alteration of the oxygen evolving complex and the inhibition of electron transport activity, which was stronger for AgNPs treatment under light exposure. Under these conditions, there was no activation of regulated photoprotective mechanisms against excess absorbed light-energy by the antenna system of the PSII complex. The highest deteriorating effect on the structural and functional integrity of PSII was observed for algal cells exposed 6?h in light condition to 10?µmol?L?1 of AgNPs. Therefore, we provide valuable data in this study permitting to use photosynthetic-based fluorescence parameters for aquatic toxicological risk investigation of polluted water that may contain AgNP suspension. 相似文献