壳聚糖/纳米CdS复合颗粒可见光光催化降解猩红B动力学研究

采用仿生矿化法制备了壳聚糖/纳米CdS复合颗粒光催化剂,并用于可见光光催化降解猩红B染料模拟废水,研究了猩红B初始浓度、pH、催化剂投加量和催化剂重复使用次数等因素对猩红B光催化降解的影响.X射线衍射(XRD)分析表明,壳聚糖能有效负载CdS纳米微晶.采用Langmuir-Hinshelwood模型描述壳聚糖/纳米CdS复合颗粒可见光光催化降解猩红B反应动力学行为,在猩红B初始质量浓度较低(≤20 mg/L)时,光催化降解过程符合假一级动力学方程.降低猩红B初始浓度和溶液pH都可显著增大光催化降解速率常数;催化剂投加量小于0.7 g/L时,光催化降解速率随其增加而增大,但催化剂投加量过大会使光催化降解速率减小;催化剂重复使用第5次时,猩红B光催化降解速率常数仍为第1次使用时的63.4%.     

降低FCC再生烟气NOx排放助剂的实验室评价

通过采用ACE装置与烟气NOx分析仪器联用的实验室评价方法,可在更接近实际催化裂化反应-再生过程的条件下,评价助剂对再生烟气中NOx的催化转化性能,同时还可考察助剂的加入对催化裂化产品分布的影响。采用该方法对几种降NOx助剂的性能进行了评价,结果表明,在催化剂体系中含有Pt基CO助燃剂的情况下,加入4％的RDNO;助剂后,烟气NOx降低幅度约30％～40％,且催化裂化产品分布基本不受影响。     

Air pollutant concentrations near three Texas roadways, part II: Chemical characterization and transformation of pollutants

Spatial gradients of vehicular emitted air pollutants were measured in the vicinity of three roadways in the Austin, Texas area: (1) State Highway 71 (SH-71), a heavily traveled arterial highway dominated by passenger vehicles; (2) Interstate 35 (I-35), a limited access highway north of Austin in Georgetown; and (3) Farm to Market Road 973 (FM-973), a heavily traveled surface roadway with significant truck traffic. A mobile monitoring platform was used to characterize the gradients of CO and NO_x concentrations with increased distance from each roadway, while concentrations of carbonyls in the gas-phase and fine particulate matter mass and composition were measured at stationary sites upwind and at one (I-35 and FM-973) or two (SH-71) downwind sites. Regardless of roadway type or wind direction, concentrations of carbon monoxide (CO), nitric oxide (NO), and oxides of nitrogen (NO_x) returned to background levels within a few hundred meters of the roadway. Under perpendicular wind conditions, CO, NO and NO_x concentrations decreased exponentially with increasing distance perpendicular to the roadways. The decay rate for NO was more than a factor of two greater than for CO, and it comprised a larger fraction of NO_x closer to the roadways than further downwind suggesting the potential significance of near roadway chemical processing as well as atmospheric dilution. Concentrations of most carbonyl species decreased with distance downwind of SH-71. However, concentrations of acetaldehyde and acrolein increased farther downwind of SH-71, suggesting chemical generation from the oxidation of primary vehicular emissions. The behavior of particle-bound organic species was complex and further investigation of the size-segregated chemical composition of particulate matter (PM) at increasing downwind distances from roadways is warranted. Fine particulate matter (PM_2.5) mass concentrations, polycyclic aromatic hydrocarbons (PAHs), hopanes, and elemental carbon (EC) concentrations generally exhibited concentrations that decreased with distance downwind of SH-71. Concentrations of organic carbon (OC) increased from upwind concentrations immediately downwind of SH-71 and continued to increase further downwind from the roadway. This behavior may have primarily resulted from condensation of semi-volatile organic species emitted from vehicle sources with transport downwind of the roadway.     

Air pollutant concentrations near three Texas roadways,Part I: Ultrafine particles

Vehicular emitted air pollutant concentrations were studied near three types of roadways in Austin, Texas: (1) State Highway 71 (SH-71), a heavily traveled arterial highway dominated by passenger vehicles; (2) Interstate 35 (I-35), a limited access highway north of Austin in Georgetown; and (3) Farm to Market Road 973 (FM-973), a heavily traveled surface roadway dominated by truck traffic. Air pollutants examined include carbon monoxide (CO), oxides of nitrogen (NO_x), and carbonyl species in the gas-phase. In the particle phase, ultrafine particle (UFP) concentrations (diameter < 100 nm), fine particulate matter (PM_2.5, diameter < 2.5 μm) mass and carbon content and several particle-bound organics were examined. All roadways had an upwind stationary sampling location, one or two fixed downwind sample locations and a mobile monitoring platform that characterized pollutant concentrations fall-off with increased distance from the roadways. Data reported in this paper focus on UFP while other pollutants and near-roadway chemical processes are examined in a companion paper. Traffic volume, especially heavy-duty traffic, wind speed, and proximity to the road were found to be the most important factors determining UFP concentrations near the roadways. Since wind directions were not consistent during the sampling periods, distances along wind trajectories from the roadway to the sampling points were used to study the decay characteristics of UFPs. Under perpendicular wind conditions, for all studied roadway types, particle number concentrations increased dramatically moving from the upwind side to the downwind side. The elevated particle number concentrations decay exponentially with increasing distances from the roadway with sharp concentration gradients observed within 100–150 m, similar to previously reported studies. A single exponential decay curve was found to fit the data collected from all three roadways very well under perpendicular wind conditions. No consistent pattern was observed for UFPs under parallel wind conditions. However, regardless of wind conditions, particle concentrations returned to background levels within a few hundred meters of the roadway. Within measured UFP size ranges, smaller particles (6–25 nm) decayed faster than larger ones (100–300 nm). Similar decay rates were observed among UFP number, surface, and volume.     

Concentrations,seasonal variations,and transport of carbonaceous aerosols at a remote Mountainous region in western China

Carbonaceous aerosol concentrations were determined for total suspended particle samples collected from Muztagh Ata Mountain in western China from December 2003 to February 2006. Elemental carbon (EC) varied from 0.004 to 0.174 μg m^?3 (average = 0.055 μg m^?3) while organic carbon (OC) ranged from 0.12 to 2.17 μg m^?3 and carbonate carbon (CC) from below detection to 3.57 μg m^?3. Overall, EC was the least abundant fraction of carbonaceous species, and the EC concentrations approached those in some remote polar areas, possibly representing a regional background. Low EC and OC concentrations occurred in winter and spring while high CC in spring and summer was presumably due to dust from the Taklimakan desert, China. OC/EC ratios averaged 10.0, and strong correlations between OC and EC in spring–winter suggest their cycles are coupled, but lower correlations in summer–autumn suggest influences from biogenic OC emissions and secondary OC formation. Trajectory analyses indicate that air transported from outside of China brings ～0.05 μg m^?3 EC, ～0.42 μg m^?3 OC, and ～0.10 μg m^?3 CC to the site, with higher levels coming from inside China. The observed EC was within the range of loadings estimated from a glacial ice core, and implications of EC-induced warming for regional climate and glacial ice dynamics are discussed.     

沸石改性及其去除水中氨氮的实验研究

通过实验研究了沸石改性条件及其对水中氨氮吸附去除的影响。结果表明,加热改性与无机酸改性不能显著提高沸石对氨氮的吸附量。利用NaOH改性的最佳浓度为1 mol/L,此条件下对氨氮吸附量可提高到650.68 mg/kg,为天然沸石的2.82倍。利用无机盐改性时,对氨氮吸附效果最好的是NaCl改性沸石,其次为KCl改性沸石与CaCl₂改性沸石。随着NaCl溶液浓度和改性时间的增加,改性沸石对氨氮的吸附量显著增加,可达天然沸石的3～4倍;在NaCl浓度为150 g/L与改性时间为18 h条件下,改性沸石对氨氮吸附量可达887.35 mg/kg,为天然沸石的3.84倍。     

生活垃圾加载介质层填埋法对初期渗滤液污染抑制效果研究

以传统卫生填埋柱R2为对照,通过往生物反应器填埋柱R1内加载可渗透反应介质层1和2进行模拟试验,主要探讨了填埋柱R1垃圾渗滤液COD、总氮、氨氮及总磷的变化趋势,探索一种新型的加载介质层垃圾填埋处理方法。试验结果表明,填埋20周后, R1柱COD浓度基本维持在40 000～45 000 mg/L间,约为R2柱的20%～30%;第24周,R1柱总氮和氨氮分别为206.5 mg/L和167.3 mg/L,在16～24周内,R1总氮和氨氮分别约为R2的14.5%～17.5%和36.2%～43.6%;18周时,R1柱总磷达最大值1.704 mg/L,至第24周降为0.673 mg/L, 整个实验过程R1柱总磷约为R2的0.15%～0.56%。     

活性污泥体系中聚糖菌的富集与鉴定

活性污泥体系中,聚糖菌(GAOs)在厌氧环境下与聚磷菌(PAOs)形成对底物的竞争关系,对聚糖菌的研究对于优化生物除磷工艺有重要意义。以葡萄糖为惟一碳源,在磷限制条件下,利用特殊运行方式对活性污泥进行驯化培养出了稳定的聚糖菌颗粒污泥,厌氧阶段磷释放量与有机物吸收量浓度(mg/L)比从7.4%下降为0.25%。从培养好的活性污泥反应器中分离获得2株聚糖菌,经菌落PCR和16S rRNA序列分析确定了所得聚糖菌菌株G1和菌株G2分别是枯草芽孢杆菌(Bacillus subtilis)和解鸟氨酸克雷伯氏菌(Klebsiella ornithinolytica)。     

基于生态安全的DAT-IAT城市污水处理工艺改进研究

通过正交试验,得到了DAT-IAT工艺和A/DAT-IAT工艺处理城市污水的常规指标去除和生态毒理指标削减的最优运行条件。结果表明,在正交试验的同一工艺中,COD去除最优运行条件的出水COD值优于生态毒性削减最优运行条件的出水COD值,但前者出水的生态毒性较大。由于厌氧池的水解酸化作用,A/DAT-IAT工艺对COD和生态毒性的处理效果均优于DAT-IAT工艺,并且回流总能耗低于DAT-IAT工艺,但是出水COD仍不达标。为了降低进入工艺的COD的总量,以絮凝沉淀做为预处理工艺,并采用Al残留量最小的絮凝剂投药量以降低出水中残留Al带来的生态风险。结果表明,在COD去除最优运行条件下,具有絮凝预处理的工艺对COD的去除效果优于没有絮凝预处理的工艺。絮凝-A/DAT-IAT工艺在COD去除最优运行条件下出水COD为104.46 mg/L,满足排放标准。在毒性削减最优运行条件下,具有絮凝预处理的工艺的出水生态毒性有所上升,但是污染物的总量得到了大幅削减。絮凝-A/DAT-IAT工艺与DAT-IAT工艺相比,在污染物去除效率得到大幅增加的同时,生态毒性得到有效控制,生态安全得到了有效的保障。     

季铵化木屑纤维素的制备及其对水中苯酚的吸附性能研究

以3-氯-2-羟丙基三甲基氯化铵(CTA)为醚化剂,对木屑纤维素进行了改性。探讨了改性木屑纤维素用量、pH值、吸附温度、吸附时间和苯酚初始浓度等因素对静态吸附效果的影响。结果表明,木屑纤维素经改性后,对水中的苯酚的吸附过程存在化学吸附,对水中的苯酚的吸附容量得到明显提高。