聚合氯化铝-腐殖酸(PACl-HA)絮体的物理与分形特征研究

采用低温急速冷冻-真空干燥技术制备了PACl-HA絮体的粉末样品,研究了这些样品的物理与分形特征.结果表明,PACl-HA絮体具有无定形结构,主要组成元素为C、O、Al,所含特征官能团保留了絮体组成原料的一些特征;絮体的BET比表面积为130～161 m²·g^-1,BJH累积吸附孔体积为0.38～0.52 cm³·g^-1,BJH脱附平均孔径为7.7～9.6nm,PSD峰值对应孔径8.4～11.2nm.PACl-HA絮体具有自相似性的粗糙表面,呈现多尺度分形特征;图象法和N₂吸附/脱附等温线法确定的表面分形维数Ds分别为2.03～2.26、2.24～2.37,前者的分形尺度大约处于23～390nm之间,主要属于絮体外表面尺度,而后者的分形特征尺度区间的下限大约为0.2nm,属于孔表面尺度;另外,对同一絮体,N₂吸附法和脱附法确定的孔表面分形维数不同.热力学模型计算出的D_s远大于3,与Sahouli等的研究不符.     

Formation of dioxins from combustion of polyvinylidene chloride in a well-controlled incinerator

Polyvinylidene chloride (PVDC; polymer of 1,1-dichloroethylene) was combusted with paper in a well-controlled, small-scale incinerator at an average grate temperature of 700 °C, and then dioxins (PCDDs, PCDFs, and coplanar-PCBs) formed in the exhaust gases were analyzed by gas chromatography/mass spectrometry. PVDC lowered the combustion temperature due to its less flammable character. The amount of total dioxins (PCDDs + PCDFs + coplanar-PCBs) formed in the exhaust gas was 58.0 ng/g of a combustion sample and its toxicity equivalency quantity (TEQ) value was 0.64 ng-TEQ/g. The amount of PCDDs formed in the sample ranged from 2.33 ng/g (Cl₈-isomer) to 0.048 ng/g (Cl₁-isomer). The lower the number of chloride, the less production of PCDDs. On the other hand, there was no relation between the number of chloride and PCDF formation. The amount of PCDFs formed in the sample ranged from 8.02 ng/g (Cl₂-isomer) to 4.46 ng/g (Cl₈-isomer). A polyvinylchloride (PVC) sample produced 207 ng/g of total dioxins and a PVDC sample produced 57.4 ng/g of total dioxins when they were combusted under the same conditions. An approximately equal composition of dioxin isomers was formed from PVDC and PVC samples. Paper was found to contribute to PCDF formation when it was combusted with plastics.     

北京大气PM10中水溶性氯盐的观测研究

氯盐是大气气溶胶中重要水溶性无机盐,对2004年全年北京大气可吸入颗粒中氯盐的变化进行了监测,结果表明北京大气中可溶性氯盐的年均值在(3.1±1.7)μg·m^-3,采暖期平均浓度为(4.6±2.1)μg·m^-3,非采暖期平均浓度为(2.6±1.6)μg·m^-3.最低值出现在5月,为(1.3±0.8)μg·m^-3;最高值出现在12月,为(5.8±5.3)μg·m^-3.日变化在秋冬季多为白天浓度低,晚上浓度高,夏春季多呈现上午高,下午低的特征;季节变化呈现秋冬季高,春夏季低的特点.     

Al13形态在混凝中的作用机制

从铝的水解形态转化角度考察了铝盐在高碱度和高有机物浓度水体中的混凝行为.结果表明,铝盐的混凝效能是与混凝过程中的Al₁₃含量成正比.高投药量时氯化铝(AlCl₃)既可以有效调节水体pH值又能在混凝过程中原位水解产生较多的Al₁₃形态,因而混凝效能要高于聚合氯化铝(PACl).在铝盐混凝中,调节pH值到6～7之间可以控制铝形态分布从而达到提高混凝效能和减少残留铝的目的.在调节pH值强化混凝的方法中使用传统铝盐的效果要好于无机高分子絮凝剂.     

三丁基氯化锡对红鳍笛鲷的急性毒性及不同组织生化指标的影响

为研究有机锡化合物对海洋生物抗氧化防御系统和神经系统的影响,以我国东南沿海常见的中下层增养殖鱼类红鳍笛鲷(Lutjanus erythopterus)幼鱼为实验生物,采用半静态毒性实验方法,分别研究了三丁基氯化锡(tributyltin chloride,TBTCl)的急性毒性和96 h暴露时间内对红鳍笛鲷幼鱼鳃、脑和...     

The influence of ClO− and acidity in the reaction between H2O2 and CuCl2

The potentially explosive reaction of hydrogen peroxide (H₂O₂) and copper chloride (CuCl₂) was investigated. Pressure tests revealed that the reaction was strongly temperature - dependent and can easily undergo runaway reaction. Nevertheless, there was only a slight pressure increase at the low temperatures studied or when using low concentrations of CuCl₂. Under the conditions generating the slight pressure increase, hypochlorite anions (ClO⁻) are generated and the acidity increases. As the reaction reaches completion, ClO⁻ disappears, and the acidity decreases. Interestingly, the addition of phosphate buffer to maintain the weakly acid conditions led to a runaway reaction, and the use of basic ClO⁻ promoted the exothermic reaction. Based on the results, acidity has a strong impact on the reaction behaviour.     

Ammonium nitrate thermal decomposition with additives

Runaway reactions present a potentially serious threat to the chemical process industry and the community; such reactions occur time and time again often with devastating consequences. The main objective of this research is to study the root causes associated with ammonium nitrate (AN) explosions during storage. The research focuses on AN fertilizers and studies the effects of different types of fertilizer compatible additives on AN thermal decomposition. Reactive Systems Screening Tool (RSST) has been used for reactivity evaluation and to better understand the mechanisms that result in explosion hazards. The results obtained from this tool have been reported in terms of parameters such as “onset” temperature, rate of temperature and pressure rise and maximum temperature. The runaway behavior of AN has been studied as a solid and solution in water. The effect of additives such as sodium sulfate (Na₂SO₄) and potassium chloride (KCl) has also been studied. Multiple tests have been conducted to determine the characteristics of AN decomposition accurately. The results show that the presence of sodium sulfate can increase the “onset” temperature of AN decomposition thus acting as AN thermal decomposition inhibitor, while potassium chloride tends to decrease the “onset” temperature thus acting as AN thermal decomposition promoter.     

Effects of pond salinization on survival rate of amphibian hosts infected with the chytrid fungus

The chytrid fungus Batrachochytrium dendrobatidis has been implicated in the decline and extinction of amphibian populations worldwide, but management options are limited. Recent studies show that sodium chloride (NaCl) has fungicidal properties that reduce the mortality rates of infected hosts in captivity. We investigated whether similar results can be obtained by adding salt to water bodies in the field. We increased the salinity of 8 water bodies to 2 or 4 ppt and left an additional 4 water bodies with close to 0 ppt and monitored salinity for 18 months. Captively bred tadpoles of green and golden bell frog (Litoria aurea) were released into each water body and their development, levels of B. dendrobatidis infection, and survival were monitored at 1, 4, and 12 months. The effect of salt on the abundance of nontarget organisms was also investigated in before and after style analyses. Salinities remained constant over time with little intervention. Hosts in water bodies with 4 ppt salt had a significantly lower prevalence of chytrid infection and higher survival, following metamorphosis, than hosts in 0 ppt salt. Tadpoles in the 4 ppt group were smaller in length after 1 month in the release site than those in the 0 and 2 ppt groups, but after metamorphosis body size in all water bodies was similar . In water bodies with 4 ppt salt, the abundance of dwarf tree frogs (Litoria fallax), dragonfly larvae, and damselfly larvae was lower than in water bodies with 0 and 2 ppt salt, which could have knock‐on effects for community structure. Based on our results, salt may be an effective field‐based B. dendrobatidis mitigation tool for lentic amphibians that could contribute to the conservation of numerous susceptible species. However, as in all conservation efforts, these benefits need to be weighed against negative effects on both target and nontarget organisms.     

氯化铁和硫酸铁对酸性土壤中有效态镉和铅污染的修复作用

采用浸泡实验法研究了氯化铁和硫酸铁对酸性土壤中有效态镉和铅污染的修复效果,结果表明,氯化铁和硫酸铁均能有效去除土壤有效态镉和铅污染,Fe(Ⅲ)用量为50～100 mmol/kg时,有效态Cd和Pb的去除效果可达70％～96％.氯化铁和硫酸铁能去除土壤中的水溶态、碳酸盐结合态、腐殖酸结合态、铁锰氧化物结合态和强有机结合态Cd和Pb及交换态Cd.氯化铁和硫酸铁对Cd均既有洗脱修复作用又有固定修复作用,且洗脱修复作用的贡献稍大;氯化铁用量较小时(50 mmol/kg)对Pb既有固定修复又有洗脱修复作用,固定修复作用稍大;用量较大时(100 mmol/kg),对Pb只有洗脱修复作用.硫酸铁对Pb的修复作用则以固定修复作用为主,洗脱修复作用很小.     

氯化钠/纳米疏水二氧化硅超细干粉制备及灭火性能研究

选用氯化钠为基体制备金属火灾超细干粉灭火剂。应用反溶剂法对其改性,使纳米疏水二氧化硅吸附在氯化钠晶体表面,其中分散剂为PEG-1000。结果表明,纳米疏水二氧化硅的添加有利于细化氯化钠颗粒,但过量的添加会起反作用,最佳用量为3 wt%左右,平均粒径为2.18μm。镁片灭火实验证明超细复合干粉的灭火性能明显好于传统氯化钠灭火剂(商用D类灭火剂),纳米疏水二氧化硅最佳添加量为3 wt%,此时灭火时间仅需传统灭火剂的一半。最后利用FDS5.0模拟干粉颗粒与燃烧火焰作用过程,模拟结果表明干粉覆盖对火焰具有一定的抑制效果,并分析了复合干粉灭火机理。