pH对砂柱反硝化脱氮的影响

在不同的初始pH条件下,72h后砂柱中不同深度溶液的pH值,都出现了上升的现象;但是在不同初始pH条件下,砂柱中同一深度溶液pH值变化幅度不同。在不同的初始pH条件下,砂柱中硝酸盐的去除效率各不相同;当初始pH=7．00时,在砂柱的400mm、800mm深度处的取样样品中分别测得硝酸盐浓度为44．89mg／L、14．98mg／L,砂柱对硝态氮的脱除效果最好;当初始pH=5．00时,在砂柱的400mm、1200mm深度处的取样样品中分别测得硝酸盐浓度为132．56mg／L、56．68mg／L,砂柱对硝态氮的脱除效果最差。     

单基硝酸铵发射药的能量及燃烧性能

单基硝酸铵发射药已实现了洁净燃烧,为进一步研究其应用价值,从理论上计算了单基硝酸铵发射药的能量示性数。通过静态燃烧实验研究其燃烧性能,并用弹道试验检验其在某口径火炮上的适用性,结果表明其满足该火炮的内弹道指标要求。     

混合添加剂硝酸镧与纳米氧化锌对ZL205A铝合金微弧氧化膜层性能的影响

在硅酸盐电解液中添加复合添加剂硝酸镧(La(NO3)3)和纳米氧化锌(纳米ZnO)对铸造铝合金进行微弧氧化实验。通过涡流测厚仪、扫描电镜、显微硬度计、X射线衍射仪等分析复合添加对膜层的厚度、硬度、腐蚀性能的影响。结果表明,复合添加剂La(NO3)3+纳米ZnO的加入可提高膜层的耐蚀性,增加膜层的厚度和硬度。当La(NO3)3含量为0.5g/L,纳米ZnO含量为3g/L时,获得的膜层厚度和硬度较大。     

水-溴化锂-硝酸锂与水-溴化锂吸收式制冷循环的比较

比较了水-溴化锂-硝酸锂三元工质与传统的水-溴化锂工质的单、双效吸收式制冷循环，分析了发生温度、冷凝温度和蒸发温度对系统性能的影响；同时也分析了直燃型双效制冷系统。结果表明：采用新工质后，系统的热力系数COP有了明显的提高，其它表征系统热力性能的经济指标也均有不同程度的改善，尤其在直燃型双效冷热水机组中有明显的优势，热力系数COP提高约30％，溶液循环倍率f降低12％。因此，该新工质与传统的水-溴化锂工质相比，具有较好的热力性能。     

中空纤维膜生物反应器去除地下水中硝酸盐的效能

采用聚氯乙烯中空纤维膜生物反应器处理受硝酸盐污染的地下水,在生物膜驯化成熟后硝酸盐还原得较彻底.在进水硝酸盐浓度为10 mgN/L和HRT为37.5 min的条件下,平均反硝化速率达383.01 gN/(m<'3>·d),平均表面去除负荷达1.39 gN/(m<'2>·d).反应器运行稳定阶段的出水水质好,出水中氢气散逸所致空气中的氢气浓度低于其爆炸极限.这表明,将聚氯乙烯中空纤维膜生物反应器用于净化受硝酸盐污染的地下水具有经济和技术上的可行性.     

Determination of polydatin by gold nanoparticle-enhanced chemiluminescence of silver nitrate and luminol

A novel flow injection method for the determination of polydatin is reported based on the inhibition of silver nitrate, luminol, and gold nanoparticles chemiluminescence. Under the optimum condition, the decrease in chemiluminescence was proportional to the concentration of polydatin from 1.0 × 10^?8 to 1.0 × 10^?5 mol/L. The detection limit was 2.1 × 10^?9 mo1/L and the relative standard deviation was 2.1% for the determination of 1.0 × 10^?6 mol/L polydatin. This method was successfully employed for the determination of polydatin in Polygonum cuspidatum roots and human urine.     

A Burning Rate Equation as a Function of Pressure and Temperature for a BTA · NH3/PSAN Mixture

The burning rate of propellants is affected by pressure and temperature. The relation between the burning rate and pressure has been well studied. However, the effect of the initial temperature on the burning rate has not been investigated quantitatively. In this study, the burning rate of bis (1H-tetrazolyl) amine ammonium salt and potassium nitrate phase-stabilized ammonium nitrate mixtures was examined and an equation for the burning rate as a function of pressure and temperature was obtained. In general, the burning rates predicted by the regression equations were in good agreement with the observed values. The temperature sensitivities were also predicted using the regression equation and compared with the observed values and good agreement was found between the predicted and observed values.     

冷藏对蔬菜中亚硝酸盐及硝酸盐含量的影响

目的 探索冰箱冷藏(4℃)条件下蔬菜中硝酸盐和亚硝酸盐含量随时间的变化,对冷藏食品的安全性进行评价.方法 分别采用重氮偶合分光光度法和麝香草酚分光光度法对生菜、菠菜、油麦菜及苦苣4种常用蔬菜在冷藏条件下其亚硝酸盐及硝酸盐的含量变化进行测定.结果 1～4d内,生菜、苦苣中的亚硝酸盐含量随着时间的延长逐渐增加;菠菜、油麦菜中亚硝酸盐含量分别在第2天和第3天达到最大,之后逐渐降低,而菠菜中亚硝酸盐含量在第4天又出现上升趋势.4种蔬菜中亚硝酸盐含量4d中最大值仅为0.419 4 mg/kg(生菜),均＜4 mg/kg的限量值.苦苣和油麦菜中硝酸盐含量在1～4d内逐渐上升.菠菜中硝酸盐含量第2天达到418.48 mg/kg,之后又降低至20.83 mg/kg.生菜中硝酸盐含量在第3天达到最大值317.26 mg/kg,之后逐渐下降,但均在安全范围内(432 mg/kg).结论 在4℃下冷藏4d后,4种常见蔬菜均可安全食用.可见,冷藏能有效减缓亚硝酸盐和硝酸盐含量的升高.     

Burning Characteristics of Ammonium Nitrate‐based Composite Propellants Supplemented with MnO2

Ammonium nitrate (AN)‐based composite propellants have several major problems, namely, a low burning rate, poor ignitability, low energy, and high hygroscopicity. The addition of a burning catalyst proved to be effective in improving the burning characteristics of AN‐based propellants. In this study, the burning characteristics of AN‐based propellants supplemented with MnO₂ as a burning catalyst were investigated. The addition of MnO₂ is known to improve the ignitability at low pressure. The most effective amount of MnO₂ added (ξ) for increasing the burning rate is found to be 4 %. The increasing ratio with ξ is virtually independent of the burning pressure and the AN content. However, the pressure exponent unfortunately increased by addition of MnO₂. The apparent activation energy of the thermal decomposition for AN and the propellant is decreased by addition of MnO₂. From thermal decomposition kinetics it was found that MnO₂ could accelerate the thermal decomposition reaction of AN in the condensed phase, and therefore, the burning characteristics of the AN‐based propellant are improved.     

Combustion Characteristics of Ammonium Nitrate and Carbon Mixtures Based on a Thermal Decomposition Mechanism

In order to obtain a better understanding of the combustion characteristics of ammonium nitrate (AN) and carbon (C) mixtures (AN/C), burning tests and differential scanning calorimetry (DSC) were performed. AN mixed with carbon that is oxidized by nitric acid (HNO₃), such as activated carbon (AC), burned at 1 MPa. However, AN mixed with carbon that is not oxidized by HNO₃, such as graphite, did not burn under 7 MPa. Compositions with more than stoichiometric amounts of activated carbon had higher burning rates. Heat characteristic examinations found a similar trend. The burning rate of AN/AC mixed with CuO as a combustion catalyst deteriorated faster than an additive‐free one. From the DSC result, AN/AC/CuO had a higher onset temperature and a lower heat of reaction than AN/AC. These results suggested that, in the combustion wave of AN/C, a thermal decomposition zone is formed on the burning surface, and combustion performance was affected by the thermal decomposition of AN/C.