老化前后轮胎磨损微粒与聚氯乙烯微粒对抗生素的吸附-解吸行为

近年来,微塑料(microplastics,MPs)作为一类新型污染物,广泛存在于水环境中而备受关注.与典型微塑料(PVC、PP、PE和PS)相比,轮胎磨损微粒(tire wear particles,TWP)在组成成分、添加剂种类和理化特性上存在显著差异.为深入比较TWP与典型MPs对有机污染物吸附-解吸行为的不同....     

污泥龄对膜生物反应器性能的影响

研究了膜生物反应器污泥龄对胞外聚合物(EPS)含量、污泥特性、污泥颗粒粒径分布及膜过滤阻力的影响.结果表明,污泥龄(SRT)为30 d时混合液中胞外聚合物(EPS)和膜面上的EPS含量分别约为90 mg/g、0.8 g/m2,随污泥龄的延长二者同步增加,EPS在膜面上几乎没有积累;混合液EPS含量的增加改变了细菌表面电荷且增大了细菌表面亲水基和疏水基的比例,使细菌存在状态由不稳定型(R型)向稳定型(S型)转变.造成污泥的沉降困难;在长污泥龄运行中.混合液中污泥颗粒呈现双峰分布,泥龄30 d时在O.5 μm和16 μm处有2个峰且平均粒径约14μm,污泥龄延长双峰分布向颗粒小的方向移动;混合液中微细颗粒含量及粒径分布对膜污染起决定性作用.综合考虑膜污染和污泥特性,膜生物反应器的污泥龄应控制在优势菌最小世代时间(运行温度下的最大比增长速度)的120倍以下.     

单纤维捕集过程中亚微米颗粒的布朗团聚

针对亚微米颗粒(0.1～0.5μm)在单纤维捕集过程中的布朗团聚规律,基于计算流体动力学-颗粒群平衡模型(CFD-PBM)对粉尘颗粒在单纤维捕集过程中的布朗团聚行为进行了数值模拟研究,采用分区法对颗粒群平衡方程(PBE)进行求解,综合考虑了停留时间、入口粉尘粒径、气流温度、Pe数对布朗团聚的影响,并将数值模拟与实验结果...     

电气石球负载纳米二氧化钛光催化剂的制备及其对水中邻苯二甲酸酯的降解作用

以电气石微球为载体,采用溶胶–凝胶法制备电气石负载纳米二氧化钛(TiO_2)光催化材料。用X射线衍射分析、扫描电镜对微球负载TiO_2光催化剂的晶型结构和形貌进行了表征。以6种邻苯二甲酸酯为降解对象,考察了热处理温度、辐射强度对TiO_2光催化活性的影响。发现TiO_2以纳米颗粒的形式牢固负载在电气石微球表面;以天然电气石微球为载体所制得的TiO_2光催化剂对于6种邻苯二甲酸酯具有较好的光催化降解效果。     

Experimental Investigation on the Removal of Toner Particles from Laser-Printed Office Waste Papers

Abstract

In this work the deinking process was simulated in a small high speed blender of about 2 L capacity. The effects of polyethylene (PE) and wax-coated PE on the removal of toner particles in the pulper slurry has been experimentally investigated. The effect of one commercial surfactant (30% anionic, 5% nonionic) on the toner release efficiency was also studied. The average area of toner particles retained on filter papers were determined using an image analysis system that consists of a high-resolution video camera mounted on an optical polarizing microscope, an image software processor, a Pentium PC, and a high-resolution image monitor. The effect of low density PE on toner detachment from laser-printed standard paper was investigated over a concentration range of 0 –200% PE (relative to paper mass). It is found that PE has a certain capabilty of removing (adsorbing) toner particles. In the second phase of this research work, the effect of wax-coated PE was investigated. It was found that wax-coated PE enhances the removal of toner particles beyond that obtained using only PE. Finally, the effect of a commercial surfactant on the release of toner particles have been investigated over a range of surfactant mass percentage (relative to the paper mass).     

Flame propagation behaviors of nano- and micro-scale PMMA dust explosions

Flame propagation behaviors of nano- and micro-polymethyl methacrylate (PMMA) dust explosions were experimentally studied in the open-space dust explosion apparatus. High-speed photography with normal and microscopic lenses were used to record the particle combustion behaviors and flame microstructures. Simple physical models were developed to explore the flame propagation mechanisms. High-speed photographs showed two distinct flame propagation behaviors of nano- and micro-PMMA dust explosions. For nano-particles, flame was characterized by a regular spherical shape and spatially continuous combustion structure combined with a number of luminous spot flames. The flame propagation mechanism was similar to that of a premixed gas flame coupled with solid surface combustion of the agglomerates. In comparison, for micro-particles, flame was characterized by clusters of flames and the irregular flame front, which was inferred to be composed of the diffusion flame accompanying the local premixed flame. It was indicated that smaller particles maintained the leading part of the propagating flame and governed the combustion process of PMMA dust clouds. Increasing the mass densities from 105 g/m³ to 217 g/m³ for 100 nm PMMA particles, and from 72 g/m³ to 170 g/m³ for 30 μm PMMA particles, the flame luminous intensity, scale and the average propagation velocity were enhanced. Besides, the flame front became more irregular for 30 μm PMMA dust clouds.     

HRT对A2O工艺中典型多环麝香迁移转化的影响

研究了不同水力停留时间(hydraulic retention time,HRT)条件下佳乐麝香(galaxolide,HHCB)与吐纳麝香(tonalide,AHTN)在A2O工艺各池水相和泥相中的变化情况.采用固相萃取与气相质谱联用的方法对水相与泥相中目标物的质量浓度进行检测.结果表明,HRT主要影响HHCB在A2O工艺中的生物降解和随剩余污泥排放的比重,影响AHTN随剩余污泥排放的比重.随着HRT的增大,HHCB、AHTN在厌氧池中的去除率与去除贡献率逐渐减小,而缺氧池与好氧池的去除率与去除贡献率相对增大.2种目标物在4个HRT工况(6、8、10、12 h)下的总去除率分别为73.93%、73.05%、75.14%、76.00%和48.76%、44.27%、57.17%、62.9%.A2O工艺对HHCB的去除效果较好,而对AHTN的去除效果较差.HRT的增大对HHCB的去除影响不大,而对AHTN的去除有促进作用.     

Seasonal variation and source apportionment of organic and inorganic compounds in PM2.5 and PM10 particulates in Beijing, China

The distribution and source of the solvent-extractable organic and inorganic components in PM 2.5(aerodynamics equivalent diameter below 2.5 microns),and PM 10(aerodynamics equivalent diameter below 10 microns) fractions of airborne particles were studied weekly from September 2006 to August 2007 in Beijing.The extracted organic and inorganic compounds identified in both particle size ranges consisted of n-alkanes,PAHs(polycyclic aromatic hydrocarbons),fatty acids and water soluble ions.The potential emission sources of these organic compounds were reconciled by combining the values of n-alkane carbon preference index(CPI),%waxC n,selected diagnostic ratios of PAHs and principal component analysis in both size ranges.The mean cumulative concentrations of n-alkanes reached 1128.65ng/m3 in Beijing,74% of which(i.e.,831.7ng/m3) was in the PM 2.5 fraction,PAHs reached 136.45ng/m3(113.44ng/m3 or 83% in PM 2.5),and fatty acids reached 436.99ng/m3(324.41ng/m3 or 74% in PM 2.5),which resulted in overall enrichment in the fine particles.The average concentrations of SO42-,NO3-,and NH4+ were 21.3±15.2,6.1±1.8,12.5±6.1μg/m3 in PM 2.5,and 25.8±15.5,8.9±2.6,16.9±9.5μg/m3 in PM 10,respectively.These three secondary ions primarily existed as ammonium sulfate((NH4)2SO4),ammonium bisulfate(NH4HSO4) and ammonium nitrate(NH4NO3).The characteristic ratios of PAHs revealed that the primary sources of PAHs were coal combustion,followed by gasoline combustion.The ratios of stearic/palmitic acid indicated the major contribution of vehicle emissions to fatty acids in airborne particles.The major alkane sources were biogenic sources and fossil fuel combustion.The major sources of PAHs were vehicular emission and coal combustion.     

自然坑塘对夏季降雨径流污染的截流净化效果

选取上海市临港新城4种不同类型的自然坑塘,比较其在夏季对降雨径流污染的截留效应以及水质净化效果。结果表明:场地主要降雨径流污染物为TN、COD,自然坑塘对降雨径流污染具有较好的截留效应,但自然坑塘的截流效率并未得到最大程度的发挥。自然坑塘对于水质的净化处理效果总体较好,研究期内4个自然坑塘的TP平均净化率分别为:46.4%、4.6%、57.6%、57.4%;TN平均净化率分别为:34.7%、40.7%、46.4%、26.9%;COD平均净化率分别为:21.6%、40.5%、47.3%、-4.3%。在高温少雨、水深过浅的情况下,自然坑塘易出现水华现象,影响水质净化效果。因此,需要对自然坑塘进行优化设计、改造,保持自然坑塘生态系统的稳定与自我更新能力,才能最大限度地发挥其对于城市雨洪调蓄、径流污染控制等方面的综合生态价值。     

腐殖酸絮凝体形成过程中初期搅拌条件对其形态结构的影响

以腐殖酸为研究对象,采用硫酸铝为混凝剂进行混凝杯罐实验,借助PDA在线监测系统、图像解析法及粒子图像测速技术分析评价絮凝体的构造特征,着重探讨了混凝过程中初期快速搅拌条件对絮凝体形态结构的影响.结果表明,快速搅拌条件对腐殖酸絮凝体的形成过程及形态结构有着显著影响.最佳快速搅拌条件为:搅拌历时l min,搅拌强度300 r·min-,此时形成的絮凝体结构密实,抗剪切能力强,整体性能最优,絮凝体分形维数、强度及平均粒径分别为1.8842、0.164 N·m-2、0.43 mm.腐殖酸絮凝体的形成包括不溶性微粒的产生及初期颗粒的形成与结合等过程,其中,不溶性微粒的形成及初期颗粒的致密化过程是决定最终絮凝体形态构造的重要环节,而快速搅拌条件影响着混凝剂扩散混合效果和初期颗粒的形成速率与致密化程度,这也是初期快速搅拌条件对于腐殖酸混凝过程有显著影响的一个重要因素.