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.     

廉价吸附剂处理重金属离子废水的研究进展

随着现代工业的迅速发展,生产过程中排出的有害重金属离子废水日益增加.寻找较为廉价的废水净化材料,对其中有害重金属离子的有效处理已成为环境保护中亟待解决的问题.廉价吸附剂的使用取代了目前成本较高的从溶液中回收重金属离子的方法,同时吸附剂改性会大大提高其吸附量.阐述了壳聚糖、海泡石、膨润土、海藻和泥炭等结构组成、吸附和离子交换性能等,报道廉价吸附剂对一些重金属离子的最大吸附量是:796 mg Pb/g壳聚糖,1123 mg Hg/g壳聚糖,92 mg Cr(Ⅲ)/g壳聚糖,76 mg Cr(Ⅲ)/g泥炭,41 mg Pb/g膨润土,558 mg Cd/g壳聚糖,215 mg Cd/g海藻.由此展现了廉价吸附剂在重金属离子废水处理过程中的巨大优势和良好的发展前景.     

分散液液微萃取技术在环境金属离子分析中的影响因素及应用

分散液液微萃取技术作为新型的样品前处理技术,由于其具有操作简便、费用低、富集倍数高等优点,已得到广泛认可和应用。文章综述了近5年来分散液液微萃取技术在环境金属离子分析中的进展,特别叙述了分析过程中的影响因素以及在环境分析中的应用,对此方法的原理作了简要介绍。     

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。     

齐齐哈尔市春季PM2.5中水溶性离子特征分析

2014年4—6月,在齐齐哈尔大学设立采样点,采集PM2.5样品。采用离子色谱法测定其中的主要水溶性无机离子,分析主要组成及污染来源。结果表明,齐齐哈尔市春季PM2.5平均质量浓度为46μg/m3,水溶性无机离子平均质量浓度为20.67μg/m3,占PM2.5质量浓度的42.82%。齐齐哈尔市PM2.5中二次组分主要以酸式硫酸盐形式存在。来源分析发现,PM2.5主要来源于移动源(如汽车尾气)、生物质燃烧及垃圾焚烧、固定源(化石燃料燃烧)、土壤及建筑尘。     

沈阳市城区采暖期PM2.5中水溶性离子的化学特征

2013年11月—2014年3月采暖期在沈阳市沈河区设置采样点采集环境空气中的PM2.5。利用离子色谱法测定PM2.5中水溶性无机离子,分析PM2.5中水溶性无机离子的组成和污染特征等。结果表明,沈阳市冬季采暖期PM2.5平均质量浓度为106μg/m3,PM2.5中总水溶性离子占PM2.5的比例为41.7%,含量较高的二次离子依次为SO2-4、NO-3、NH+4,三者均有较好的相关性,SO2-4以(NH4)2SO4形式存在,采暖期PM2.5偏酸性。