Kinetics study on photochemical oxidation of polyacrylamide by ozone combined with hydrogen peroxide and ultraviolet radiation

An investigation on the process of ozone combined with hydrogen peroxide and ultraviolet radiation has been carried out in order to establish the kinetics for photochemical oxidation of polyacrylamide （PAM） in aqueous solution. Effects of operating parameters, including initial PAM concentration, dosages of ozone and hydrogen peroxide, UV radiation and pH value on the photochemical oxidation of PAM, have been studied. There was an increase in photochemical oxidation rate of PAM with increasing of dosages of 03, H2O2 and ultraviolet radiation. Upon increasing of the initial PAM concentration, the photochemical oxidation rate of PAM decreased. Slight effect of pH value on the photochemical oxidation rate of PAM was observed in the experiments. The kinetics equation for the photochemical oxidation of PAM by the system has been established.     

A Study of Sorptive Loss Patterns for Reduced Sulfur Compounds in the Use of the Bag Sampling Method

In this work, the basic properties of the bag sampling method were examined and characterized in terms of recovery rate with respect to four reduced sulfur compounds (RSC) including H₂S, CH₃SH, DMS, and DMDS. For this comparative study, two types of calibration approaches were performed to evaluate the relative RSC loss due to bag sampling. As a reference calibration tool, a syringe dilution (SD) method was applied. The working standards prepared by diluting the primary standard in a gas-tight syringe (as a mixing chamber) were injected to the GC/PFPD through a loop-injection system to yield a background calibration information. In contrast, the target calibration was performed based on a bag dilution (BD) method. To this end, working standards for multiple calibration points were prepared by two different bag types (Tedlar bag (TB) and polyester bag (PB)). These standards were then drawn by the same syringe and injected into the GC/PFPD via loop. On the basis of these comparative analyses, both absolute and relative differences in RSC recovery rates (RR) were evaluated (e.g., comparison of wall-loss effect). The results indicate that TB has a mean RR of 87% for the four RSC with their values ranging from 82 (CH₃SH) to 91% (DMDS). On the other hand, the results of PB generally exhibited slightly reduced RR with their mean values of 77% (range: 73% of H₂S to 83% of DMS). The results of this study generally suggest that the losses of RSC samples, while inevitable with the bag sampling method, exhibit certain patterns between different RSCs and between different grab sampling materials.     

Short-term Distributions of Reduced Sulfur Compounds in the Ambient Air Surrounding a Large Landfill Facility

In order to explore the environmental behavior of reduced sulfur compounds (RSC) as malodorous components emitted from diverse source processes, the distribution characteristics of four sulfur (S) compounds - hydrogen sulfide (H₂S), methyl mercaptan (CH₃SH), dimethyl sulfide (DMS: (CH₃)₂S), and dimethyl disulfide (DMDS: (CH₃)₂S₂) – were investigated in a municipal landfill area. In the course of this study, their ambient concentration levels were measured during two time periods from 13 individual spots selected as a function of distance from the center of the landfill site. The results generally indicated the absolute dominance of H₂S over the other S compounds investigated (up to 5 km radius) such that their mean values were found as 1415 (H₂S), 148 (DMS), 20.6 (CH₃SH), and 14.4 ppt (DMDS). When our data were compared in terms of either varying distance from the source or relationship with meteorological conditions, the H₂S data sets were most evident to reflect the potential effects of strong source processes in the landfill environment, relative to other S gases (or to volatile organic compounds measured concurrently). The results of this study further indicated the relatively good correspondence between the measured H₂S concentration level and humans' intuitive sensory of odor and nuisance.     

脱氮硫杆菌氧化硫化氢过程中的生物氧化和化学氧化

在好氧反应器中研究了不同条件下H2S生物氧化和化学氧化之间的关系.结果表明,在pH为6～8、温度为25～35℃和溶解氧浓度为10.5 mg·L-1时,当硫化氢进气摩尔流速稳定在2.1 mmok·L-1·h-1时,脱氮硫杆菌(Thiobacillus denitrificans)氧化硫化氢的生物氧化速率可达到1.9 mmol·L-1·h-1以上,此时硫化物在液相的累积摩尔速率和H2S出口摩尔流速均很低;化学氧化速率随pH、温度和溶解氧浓度的增加而增大,可达到0.33 mmol·L-1·h-1～0.45 mmol·L-1·h-1;化学氧化速率在最佳菌体生长条件范围内占总氧化速率的比值较小,为8.6～19.1%,而随着pH值、温度的降低这一比值上升至29%～43.7%.     

UV-B增强对番茄的伤害及H2O2的防护作用

UV-B辐射使番茄叶片的叶绿素a,叶绿素b及总叶绿素含量先升高后降低,同样使叶片的抗氧化酶过氧化氢酶(CAT)和过氧化物酶(POD)活性先升高随后降低,而使超氧化物歧化酶(SOD)活性升高,膜脂过氧化产物MDA的含量增加;中等剂量(5mmol*l-1)的H2O2预处理能提高叶绿素b的含量,明显提高抗氧化酶的活性,并延缓CAT活性的降低,抑制膜质过氧化产物MDA的产生.中等浓度H2O2预处理能提高番茄对UV-B增强的抗性.     

采样条件对固定排放源废气中氯化氢测定的影响

研究了采样条件对固定排放源废气中氯化氢测定的影响。结果发现,采样条件对测定的准确度影响极大,过低的吸收液浓度会导致测定结果严重偏低,进入吸收装置的气体温度过低时也会导致测定结果偏低。目前常用的采样条件(包括有些标准中规定的采样条件)都不合适。推荐合适的Na OH吸收液浓度为2.0 mol/L,合适的进入吸收装置的气体温度为110℃以上。     

EDTA及其回收溶液治理重金属污染土壤的研究

试验结果表明,EDTA能够有效地萃取土壤重金属,由于其价格较贵和不易被降解等特点,限制了它的广泛运用.在运用MINTEQA2模型对萃取液中重金属离子形态分析的基础上,选用Na2S沉淀法将重金属从EDTA萃取液中有效分离.同时将回收的EDTA连续进行萃取土壤重金属,由于回收EDTA浓度下降的原因,其效果比新鲜EDTA的要稍微差一点,但从经济和效率上来说,仍旧可以用来治理重金属污染的土壤.     

臭氧氧化水中壬基酚的反应机理研究

采用臭氧氧化浓度为20 mg/L的壬基酚溶液,研究了臭氧氧化去除壬基酚的效果及氧化过程中中间产物的变化情况,探讨了臭氧氧化壬基酚的反应机理.结果表明,臭氧氧化涉及2种氧化方式,臭氧分子的单独反应和臭氧/羟基自由基的联合氧化.2种氧化方式在18 min内均能完全去除壬基酚,联合氧化方式在4 min内即能达到96％的去除率,而单独臭氧分子氧化需要12 min.氧化过程中检测到甲醛的产生,单独臭氧氧化下甲醛产生量在8 min左右达到稳定,而混合氧化方式下甲醛量逐步增加.     

发酵生物制氢反应器的产氢菌生物强化作用研究

将发酵产氢菌Ethanoligenens sp. B49投加到连续流搅拌槽式反应器（CSTR）的活性污泥中,以糖蜜废水为底物,进行强化活性污泥产氢效能的研究.对生物强化前和生物强化后反应系统的产氢能力、发酵产物组成和pH值进行了对比分析.结果表明,在COD容积负荷为12 kg/(m³·d)条件下,投加产氢菌可显著提高反应系统的产氢能力并改善发酵产物组成.反应系统的比产氢速率从强化前的3.6 mmol/(kg·d)提高到强化后的5.7 mmol/(kg·d),是生物强化前的1.5倍.生物强化前,反应系统液相发酵产物乙醇、乙酸和丙酸的平均浓度分别为6.8、 5.3和4.8　mmol/L,生物强化后乙醇、乙酸和丙酸的平均浓度分别为10.5、 7.5和1.7 mmol/L,其中乙醇型发酵目的产物乙醇和乙酸在总发酵产物中的比例从生物强化前的72.0%提高为强化后的86.8%.生物强化作用使出水pH值从4.5～4.7下降为4.3.产氢菌的生物强化作用有助于反应器在低负荷运行期迅速形成产氢能力较高的乙醇型发酵.     

氧化剂在超声波法降解有机废水中的应用研究

超声波法是近年来逐步发展起来的一项水处理技术,它操作简单方便,无二次污染,但是单纯超声处理废水的降解效率并不十分理想,且能量消耗较大,在超声处理过程中加入适当的氧化剂,则可以大大提高超声降解的效果,并且降低能耗。文章分别研究了双氧水、Fenton试剂等氧化剂在超声波处理中的应用及其作用机理,对其发展进行了展望。