Concurrent catalytic removal of typical volatile organic compound mixtures over Au-Pd/α-MnO2 nanotubes

α-MnO_2 nanotubes and their supported Au-Pd alloy nanocatalysts were prepared using hydrothermal and polyvinyl alcohol-protected reduction methods, respectively. Their catalytic activity for the oxidation of toluene/m-xylene, acetone/ethyl acetate, acetone/m-xylene and ethyl acetate/m-xylene mixtures was evaluated. It was found that the interaction between Au-Pd alloy nanoparticles and α-MnO_2 nanotubes significantly improved the reactivity of lattice oxygen, and the 0.91 wt.% Au0.48 Pd/α-MnO_2 nanotube catalyst outperformed the α-MnO_2 nanotube catalyst in the oxidation of toluene, m-xylene, ethyl acetate and acetone. Over the0.91 wt.% Au0.48 Pd/α-MnO_2 nanotube catalyst,(i) toluene oxidation was greatly inhibited in the toluene/m-xylene mixture, while m-xylene oxidation was not influenced;(ii) acetone and ethyl acetate oxidation suffered a minor impact in the acetone/ethyl acetate mixture; and(iii) m-xylene oxidation was enhanced whereas the oxidation of the oxygenated VOCs(volatile organic compounds) was suppressed in the acetone/m-xylene or ethyl acetate/m-xylene mixtures. The competitive adsorption of these typical VOCs on the catalyst surface induced an inhibitive effect on their oxidation, and increasing the temperature favored the oxidation of the VOCs. The mixed VOCs could be completely oxidized into CO_2 and H_2 O below 320°C at a space velocity of 40,000 m L/(g·hr). The 0.91 wt.% Au0.48 Pd/α-MnO_2 nanotube catalyst exhibited high catalytic stability as well as good tolerance to water vapor and CO_2 in the oxidation of the VOC mixtures. Thus, the α-MnO_2 nanotube-supported noble metal alloy catalysts hold promise for the efficient elimination of VOC mixtures.     

β-环糊精/环氧氯丙烷聚合物的制备及其对双酚S的吸附特性

BPS（双酚S）用途广泛,但存在水环境污染问题,容易引起类似于双酚A的雌激素反应,因此需要寻求高效的吸附剂从水溶液中将其脱除.在NaOH水溶液中,以环氧氯丙烷为交联剂,合成了β-CDP（β-环糊精/环氧氯丙烷聚合物）,用于吸附水溶液中的BPS.基于此,考察了吸附时间、pH、初始ρ（BPS）、β-CDP用量对吸附性能的影响以及β-CDP的再生性能,探讨了吸附动力学、等温吸附模型和吸附机理.结果表明:①在温度为298 K、pH为5.4、β-CDP用量为0.05 g、初始ρ（BPS）为100 mg/L、BPS溶液体积为50 mL、吸附时间为60 min的条件下,BPS吸附量为69.7 mg/g,吸附率为69.7%;②吸附动力学符合准二级动力学模型,表明化学吸附为速率控制步骤;③Langmuir吸附等温模型的成功拟合表明,吸附BPS在β-CDP表面上形成了单分子层覆盖;④β-CDP吸附BPS为放热过程,低温有利于吸附的进行;⑤与初始吸附量（69.7 mg/g）相比,β-CDP连续再生6次,BPS吸附量仍可达68.1 mg/g;⑥吸附机理是通过BPS的羟基与β-CDP形成氢键作为推动力,并借助β-CD（β-环糊精）空腔内部的疏水作用,使得BPS进入空腔形成包结物.研究显示,β-CDP对水溶液中的BPS具有良好的吸附性能,再生循环使用稳定性高,具有较高的性价比.      

紫外诱变选育高原环境絮凝菌及其絮凝条件优化

为获得耐低温且絮凝优异的絮凝菌,对一株分离得到的絮凝菌进行紫外诱变和5℃低温胁迫培养,并对诱变优势菌进行应用条件优化.结果表明:①原始菌为蜡状芽孢杆菌（Bacillus cereus）.②紫外诱变和低温胁迫培养得到的目标诱变菌FB-5对生活污水絮凝率达75.35%,具有良好的遗传稳定性.③单因素试验确定最佳絮凝条件,即絮凝菌投加量为0.90 mL/（50 mL）、pH为7.4、助凝剂加量为1.0 mL/（50 mL）、处理时间为15 min;筛选出影响诱变菌絮凝能力最显著的3个因素为絮凝菌投加量、pH和助凝剂加量;通过Box-Behnken响应面试验得到最佳净化的应用条件,即絮凝菌投加量为0.90 mL/（50 mL）、pH为7.38、助凝剂加量为1.04 mL/（50 mL）.④验证试验确定絮凝率达97.01%,BOD₅、COD_Cr、浊度和色度去除率均达到97%以上,出水水质满足GB 18918—2002《城镇污水处理厂污染物排放标准》一级A标准.研究显示,紫外诱变联合低温胁迫技术以及单因素与响应面结合优化絮凝条件可以大幅度提高原始菌株的絮凝能力,低温诱变菌FM-5能使高寒地区城市生活污水中悬浮固体大幅降低,同时去除水体中多种污染物.      

中国2000—2010年耕地低效转化的空间特征

耕地向经济效益相对较低的用地类型转化具有多重社会及生态效应。论文首先将耕地向草地、灌丛地和裸地的转化定义为“耕地低效转化”,然后以GlobeLand30为基础,提取2000—2010年的低效转化耕地,并结合耕地资源禀赋和地形条件,从多尺度、多角度深入揭示了我国耕地低效转化的空间分布特征。结果表明：1）全国总体的耕地低效转化率仅为1.50%,但区域差异明显,空间分布极不均衡;2）耕地低效转化依照地势的三级阶梯呈现明显的区域分异规律,农牧交错带的耕地转化问题最为严重,但耕作条件好、原有耕地比例高的东部地区,耕地低效转化水平一般较低;3）耕地低效转化率大体随海拔和坡度的增加而增加,但会受到地形复杂度的影响。     

Insights into the formation of secondary organic carbon in the summertime in urban Shanghai

To investigate formation mechanisms of secondary organic carbon(SOC) in Eastern China,measurements were conducted in an urban site in Shanghai in the summer of 2015. A period of high O_3 concentrations(daily peak 120 ppb) was observed, during which daily maximum SOC concentrations exceeding 9.0 μg/(C·m~3). Diurnal variations of SOC concentration and SOC/organic carbon(OC) ratio exhibited both daytime and nighttime peaks. The SOC concentrations correlated well with O_x(= O_3+ NO_2) and relative humidity in the daytime and nighttime, respectively, suggesting that secondary organic aerosol formation in Shanghai is driven by both photochemical production and aqueous phase reactions. Single particle mass spectrometry was used to examine the formation pathways of SOC. Along with the daytime increase of SOC, the number fraction of elemental carbon(EC) particles coated with OC quickly increased from 38.1% to 61.9% in the size range of 250–2000 nm, which was likely due to gas-to-particle partitioning of photochemically generated semi-volatile organic compounds onto EC particles. In the nighttime, particles rich in OC components were highly hygroscopic, and number fraction of these particles correlated well with relative humidity and SOC/OC nocturnal peaks. Meanwhile, as an aqueous-phase SOC tracer, particles that contained oxalate-Fe(III) complex also peaked at night. These observations suggested that aqueous-phase processes had an important contribution to the SOC nighttime formation. The influence of aerosol acidity on SOC formation was studied by both bulk and single particle level measurements, suggesting that the aqueous-phase formation of SOC was enhanced by particle acidity.     

Alkali resistance promotion of Ce-doped vanadium-titanic-based NH3-SCR catalysts

The effect of K deactivation on V_2O_5/WO_3-TiO_2 and Ce-doped V_2O_5/WO_3-TiO_2 catalysts in the selective catalytic reduction(SCR) of NOxby NH_3 was studied.Ce-doped V_2O_5/WO_3-TiO_2 showed significantly higher resistance to K deactivation than V_2O_5/WO_3-TiO_2.Ce-doped V_2O_5/WO_3-TiO_2 with K/V = 4(molar ratio) showed 90% NOxconversion at 350°C,whereas in this case V_2O_5/WO_3-TiO_2 showed no activity.The fresh and K-poisoned V_2O_5/WO_3-TiO_2 and Ce-doped V_2O_5/WO_3-TiO_2 catalysts were investigated by means of in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS),NH_3-temperature progress decomposition(NH_3-TPD),X-ray photoelectron spectroscopy(XPS) and H2-temperature program reduction(H_2-TPR).The effect of Ce doping on the improving resistance to K of V_2O_5/WO_3-TiO_2 were discussed.     

Behaviors and kinetics of toluene adsorption‐desorption on activated carbons with varying pore structure

This work was undertaken to investigate the behaviors and kinetics of toluene adsorption and desorption on activated carbons with varying pore structure. Five kinds of activated carbon from different raw materials were selected. Adsorption isotherms and breakthrough curves for toluene were measured. Langmuir and Freundlich equations were fitted to the equilibrium data, and the Freundlich equation was more suitable for simulating toluene adsorption. The process consisted of monolayer, multilayer and partial active site adsorption types. The effect of the pore structure of the activated carbons on toluene adsorption capacity was investigated. The quasi-first-order model was more suitable for describing the process than the quasi-second-order model. The adsorption data was also modeled by the internal particle diffusion model and it was found that the adsorption process could be divided into three stages. In the external surface adsorption process, the rate depended on the specific surface area. During the particle diffusion stage, pore structure and volume were the main factors affecting adsorption rate. In the final equilibrium stage, the rate was determined by the ratio of meso-and macro-pores to total pore volume. The rate over the whole adsorption process was dominated by the toluene concentration. The desorption behavior of toluene on activated carbons was investigated,and the process was divided into heat and mass transfer parts corresponding to emission and diffusion mechanisms, respectively. Physical adsorption played the main role during the adsorption process.     

三峡库区EFDC模型集成与应用

为满足三峡库区大尺度的水质预测需求,降低专业水质模型使用门槛,实现模型业务化运行,采用涵盖"模型封装-接口服务-系统集成"全过程的模型封装集成技术方法,开展了EFDC模型集成研究,并在三峡库区水质安全评估与预警系统中进行验证和应用.结果表明:①基于实例化模型建立的模型预置参数库,是模型业务化运行中参数简化的前提,可有效解决模型本地驯化及模型实例的基础数据复用问题;②依据参数识别结果,将模型参数识别为"必调参数、可调参数、默认参数"三类,并采用B/S架构对输入文件、输出文件和主控文件中的不同参数进行分类封装,达到参数简化目的;③采用半紧密型方式建立的基于Web services的EFDC模型集成接口服务及标准,可为信息系统提供通用的EFDC模型计算服务;④该方法在EFDC模型与三峡库区水质安全评估与预警系统集成中得到验证,实现了全库区干流及主要支流COD_Cr、总磷、总氮等污染因子的长时间序列水动力水质预测联机在线运算,满足了用户在水质影响预测预警中低修改量、高运算效率和良好用户体验等需求,实现了模型的业务化运行.      

浅谈煤气化生产过程中硫化氢的控制措施

绘出煤气化生产装置的硫元素平衡图,分析了硫化氢易中毒环节,提出防硫化氢泄漏、中毒的措施,为同行业防止硫化氢泄漏及中毒提供借鉴。     

化工物料包装过程静电危害分析

高绝缘化工物料在包装过程中极易带电,以聚酯切片包装为研究对象,对聚酯切片在输送、包装过程物料静电起电机理进行了分析,并对聚酯切片输送包装过程中的包装袋表面电位及物料荷质比进行现场检测,探讨了聚酯切片打包过程中静电危害及预防措施。