受限空间瓦斯爆炸与氢气促进机理研究

为探索受限空间中瓦斯爆炸及氢气对爆炸过程的影响,采用GRI-Mech 3.0甲烷燃烧机理,建立受限空间中瓦斯爆炸的数学模型,应用CHEMKIN软件,对受限空间内瓦斯爆炸过程及氢气对反应物浓度、活化中心浓度、主要致灾性气体浓度的影响进行模拟分析。通过对反应机理的敏感性分析,找出影响瓦斯爆炸及爆炸后主要致灾性气体生成的关键反应步。结果表明:混合气中分别充入0.5%,2%,3.5%氢气时,爆炸时间分别提前0.005 7,0.010 5,0.011 1 s;爆炸后压力分别提高2.53,4.05,7.60 kPa;爆炸后温度分别提高20,60,100 K。由此可见,随着混合气中氢气含量的增加,瓦斯引爆时间越来越短,其爆炸强度也随之增大,且氢气在一定程度上对有害气体CO,CO2,NO,NO2的生成有很大影响。     

An experimental study on fermentative H2 production from food waste as affected by pH

Batch dark fermentation experiments were performed on food waste and mixtures of food waste and wastewater activated sludge to evaluate the influence of pH on biological H₂ production and compare the process performance with and without inoculum addition. The effect of a preliminary thermal shock treatment of the inoculum was also investigated as a means to harvest the hydrogenogenic biomass. The best performance in terms of both H₂ generation potential and process kinetics was observed at pH = 6.5 under all experimental conditions (no inoculum, and untreated or thermally treated inoculum added). H₂ production from food waste was found to be feasible even without inoculum addition, although thermal pre-treatment of the inoculum notably increased the maximum production and reduced the lag phase duration. The analysis of the fermentation products indicated that the biological hydrogen production could be mainly ascribed to a mixed acetate/butyrate-type fermentation. However, the presence of additional metabolites in the digestate, including propionate and ethanol, also indicated that other metabolic pathways were active during the process, reducing substrate conversion into hydrogen. The plateau in H₂ generation was found to mirror the condition at which soluble carbohydrates were depleted. Beyond this condition, homoacetogenesis probably started to play a role in the degradation process.     

A detailed kinetic investigation on the effects of hydrogen enrichment on the performance of gas-fueled SI engine

This study investigates the effects of hydrogen enrichment on formation of pollutants and greenhouse gases in gas-fueled spark ignition engines. To this end, a previously validated detailed mechanism is embedded with a comprehensive one-dimensional engine model and the results are verified with experimental observations at different compression ratios and engine loads. The simulations are then performed for different mixtures of hydrogen and natural gas. The results indicate that adding hydrogen increases the cylinder peak pressure at different loads and compression ratios, despite the fact that reduces the amount of carbon monoxide, carbon dioxide, and methane in all the conditions.     

Super effective Zn-Fe-doped TiO2 nanofibers as photocatalyst for ammonia borane hydrolysis

In this study, the photocatalytic activity of TiO₂ nanofibers toward ammonia borane hydrolysis has been strongly modified by doping the nanostructure by ZnO and Fe₂O₃ oxides. Due to the differences in the work function and band gap energy among the three semiconductors (TiO₂, ZnO and Fe₂O₃), illumination of TiO₂ leads to accumulate the electrons and holes on the conduction and valance bands of Fe₂O₃ and ZnO, respectively. Accordingly, the experimental results indicated that the surface of the obtained nanofibers is very active which results in an instant hydrolysis of ammonia borane molecules reaching the active zone surrounding the nanofibers. Moreover, negative activation energy was determined as increasing the temperature led to decrease the photocatalytic performance. Furthermore, kinetic studies indicated that the heterogeneous catalytic reaction describing the ammonia borane hydrolysis process is zero order which additionally supports the super activity of the introduced nanofibers. It was also observed that Fe₂O₃ content in the introduced nanofibers has distinct influence as the best performance was obtained at 1 wt%. The modified TiO₂ nanofibers were prepared by calcination of electrospun nanofibers composed of titanium isopropoxide, zinc acetate and iron acetate in air at 700 °C for 1 h. Overall, the present study opens a new avenue to overcome the fast electrons/holes recombination dilemma facing TiO₂-based nanostructures.     

成都次降水稳定氢氧同位素特征及水汽来源分析

基于对成都地区2016年9月至2017年10月采集的113场次降水样品氢氧同位素的分析,发现大气次降水中δD、δ~(18)O、~(17)O、d-excess和~(17)O-excess有显著的季节性变化,旱季高雨季低,反映了该地区旱、雨两季水汽来源不同;地区大气降水线斜率和截距都偏小,表明成都降水来源于具有不同稳定同位素比率的源地,且雨滴在降落过程中发生了二次蒸发;三氧同位素大气降水线(δ'~(17)O=0. 528 9δ'~(18)O+0. 007 5)斜率介于海洋气团(0. 529)与干空气(0. 518)之间,表明成都地区处于海洋气团向内陆迁移的路径上; d值接近全球平均值,而~(17)O-excess值远较海水大,表明成都的水汽来源由海洋气团主导,且到达该地区的过程中同位素经历了严重的富集; d-excess在旱季出现的极低值可能是受到了人工降雨的影响,~(17)O-excess除了与水汽源地的相对湿度有关外,还会受到上游气团对流作用的影响,此外,成都当地的气象因素对不同季节次降水的~(17)O-excess值有不同程度的影响.     

分光光度法测定氯化氢的实验条件改进

硫氰酸汞分光光度法测定大气中的氯化氢,所使用的硫氰酸汞-乙醇溶液配置时间长,浓度低,曲线线性不好,不适用于环境现场监测。通过对氯化氢测定过程中遇到的问题进行分析,对硫氰酸汞-乙醇溶液的配置方法进行改进,提高该溶液的浓度。实验证明,使用定性滤纸过滤后的0.40%硫氰酸汞-乙醇溶液,曲线线性关系好,标样准确度高,适用于现场监测分析。     

In situ preparation of g-C3N4/polyaniline hybrid composites with enhanced visible-light photocatalytic performance

The graphic carbon nitride/polyaniline (g-C₃N₄/PANI) hybrid composites were successfully synthesized by a facile in situ polymerization process under ice water bath. The photocatalytic activities of the g-C₃N₄/PANI composites were evaluated by using oxytetracycline (OTC) as model pollutants. The optimal g-C₃N₄/PANI composite (5%PANI: the g-C₃N₄/PANI hybrid with 5 wt.% of PANI) showed an enhancement degradation rate of 5-fold compared to that of conventional g-C₃N₄ under simulated-sunlight irradiation. In addition, the 5%PANI demonstrate significantly photocatalytic evolution H₂ rate (163.2 μmol/(g?hr)) under the visible light irradiation. Furthermore, based on the results of optical performance and electrochemical testing, a possible mechanism was proposed, indicating that the incorporation of PANI into the traditional g-C₃N₄ can effectively tune the electronic structures, improve the photo-generated electrons-holes separation and enhance extensive absorption of visible light. Such a g-C₃N₄/PANI hybrid nanocomposites could be envisaged to possess great potentials in practical wastewater treatment and water splitting.     

载铁ACF/Ni阴极电化学体系除藻效能与机制

采用化学浸渍法将Fe@Fe₂O₃纳米线负载在活性炭纤维/泡沫镍上组成Fe@Fe₂O₃/ACF/Ni复合阴极,以钛基铂（Pt/Ti）为阳极,考察载铁量、初始pH值和不同电化学体系对除藻效果的影响,探究无供氧条件下Pt/Ti-Fe@Fe₂O₃/ACF/Ni电化学体系除藻的效能;基于·OH间接检测、铁离子浓度、H₂O₂浓度及pH值的分析和·O₂^-的检测研究Pt/Ti-Fe@Fe₂O₃/ACF/Ni中性电化学体系反应机制.结果表明,当制备阴极阶段投加0.03g FeCl₃×6H₂O,初始藻浓度为0.7×10⁹~0.8×10⁹个/L,电流密度为75mA/cm²,初始pH6.2时,电解60min,该体系除藻率可达到92.3%.在Pt/Ti-Fe@Fe₂O₃/ACF/Ni电化学体系中,Fe@Fe₂O₃/ACF/Ni阴极可通过电化学反应产生大量·OH和·O₂^-,使藻细胞破裂死亡;该体系除藻的主要机理是非均相电Fenton反应.     

亚砷酸钠对酵母细胞H2S代谢的影响

以模式生物酿酒酵母为研究对象,采用醋酸铅试纸条法、BIGGY琼脂及qRT-PCR技术检测了不同浓度亚砷酸钠胁迫下H₂S产量及产H₂S酶编码基因表达的变化,以探讨砷化物对酵母细胞H₂S代谢的影响.结果显示,0.5~2 mmol·L^-1的亚砷酸钠可诱导酵母细胞内源H₂S的产生,且H₂S合成相关基因的相对表达量与对照相比均有不同程度的上调.经0.05~0.2 mmol·L^-1的外源H₂S预处理后,酵母细胞对砷的耐受性明显提高.研究表明,亚砷酸钠可影响酵母细胞H₂S代谢,而H₂S含量可在一定程度上调控砷对酵母的毒性.     

团絮状双效催化聚苯硫醚滤料反应参数及机理

以N-油酰基多肽表面活化聚苯硫醚滤料,以酸性KMnO₄在60~80℃操作温度下正向滴定,在氧化作用下实现活性组分氧化.实验研究了催化滤料的低温NO还原和Hg⁰氧化性能,并通过SEM、EDX及TPD表征手段对催化滤料物化结构进行分析.分别考察了（0.9）Mn-Ce-Fe-Co-O_x/PPS反应体系温度、气相O₂浓度、初始NO浓度、氨氮比（NSR）、入口SO₂浓度的最佳反应参数.结果表明,有效组分MnO_x、CeO_x、CoO_x、Fe₂O₃以团絮状均匀分散在纤维表面;在反应温度170℃、O₂≥5%、NO≤500×10^-6、氨氮比1.0、SO₂≤100 500×10^-6条件下,催化滤料对NO还原及Hg⁰氧化效率基本达到80%左右;程序升温脱附实验Hg-TPD结果表明SO₂的Hg⁰氧化促进作用机理于SO₃与Hg⁰非均相反应优于SO₂硫酸化反应,而NO-TPD结果则表明NO与O₂在PPS表面相互作用类型以吸附态亚硝酸盐为主,吸附态NO₂次之.