GC-C-IRMS测定污染场地土壤中苯系物单体碳同位素比值

选取苯系物中的代表性组分苯、甲苯和二甲苯等化合物,通过热脱附、气相色谱质谱条件的优化及方法学考察,建立了热脱附进样-气相色谱-同位素比值质谱(GC-C-IRMS)测定苯系物单体碳同位素比值的方法。结果表明,单体化合物进样量在0.3μg以上均能满足测定要求;与直接进样方式相比,热脱附进样对单体碳同位素比值测定无分馏影响;标准溶液和苯系物土壤样品测定结果的RSD分别为1.0%~1.7%和0.3%~2.6%。     

Initial carbon release characteristics, mechanisms and denitrification performance of a novel slow release carbon source

External carbon source addition is one of the effective methods for the treatment of wastewater with low carbon to nitrogen ratio (C/N). Compared with fast-release liquid carbon sources, slow-release solid carbon sources are more suitable for the denitrification process. A novel slow-release solid carbon source (corncob-polyvinyl alcohol sodium alginate- poly-caprolactone, i.e. CPSP) was prepared using corn cob (CC) and poly-caprolactone with polyvinyl alcohol sodium alginate as hybrid scaffold. The physical properties and carbon release characteristics of CPSP and three other carbon sources were compared. CPSP had stable framework and good carbon release performance, which followed the second order release equation. The formic acid, acetic acid, propionic acid and butyric acid released from CPSP accounted for 8.27% ± 1.66 %, 56.48% ± 3.71 %, 18.46% ± 2.69% and 16.79% ± 3.02% of the total released acids respectively. The start-up period of CPSP was shorter than that of the other carbon sources in denitrification experiment, and no COD pollution was observed in the start-up phase (25–72 h) and stable phase (73–240 hr). The composition and structure of the dissolved organic compounds released by CPSP and other carbon sources were analyzed by UV-Vis absorption spectroscopy and three-dimensional fluorescence spectroscopy, which indicated that CPSP was more suitable for denitrification than the other studied carbon sources.

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Spray and explosion characteristics of methanol and methanol-benzene blends near azeotrope formation: Effects of temperature,concentration, and benzene content

The explosion hazard of flammable liquids leaking to form spray in storage and transportation at ambient temperature has not been systematically investigated. This work presents new results from experimental investigations of the atomization and explosion characteristics of methanol, and methanol-benzene blends forming near the azeotrope under different initial conditions (initial temperature (298.15–318.15 K), methanol concentration (198–514.8 g/m³) and benzene content (41–81%)) in a 20-L spherical vessel. The empirical formulas for Sauter Mean Diameter (SMD) of the droplets and the maximum explosion pressure with respect to the initial temperature and methanol concentration were obtained from the quantitative analysis. Compared to the explosion hazard of pure methanol and methanol-benzene blends spray, the results showed that the maximum rate of pressure rise and maximum explosion temperature of methanol-benzene blends were relatively low. Furthermore, the effect of carbon soot formation on the explosion hazard during explosion development was analyzed.