Mn203/γ-Al2O3在超临界水氧化中催化活性的研究

采用浸渍法制备了Mn2O3/γ-Al2O3催化剂,在超临界水中催化氯化降解1,5-萘二磺酸,探索了催化剂Mn2O3活性组分负载量、催化剂空速和反应溶液pH对Mn2O3/γ-Al2O3催化剂活性的影响.结果表明:Mn2O3/γ-Al2O3的催化活性在一定范围内随Mn2O3活性组分负载量的增加而提高;在一定范围内,Mn2O3/γ-Al2O3空速越小,模拟废水的COD去除率越高;Mn2O3/γ-Al2O3催化活性在反应溶液呈酸性情况下比碱性时高.     

六氯苯的O3及UV/O3高级氧化降解试验研究

采用O3、UV/O3高级氧化法对水中六氯苯(HCB)的降解效果及机理进行了研究,并对结果进行了比较,结果表明,UV本身对HCB的去除率贡献不大,HCB可被O3、UV/O3快速降解,即UV＜O3＜UV/O3;O3、UV/O3作用时,提高体系的初始pH值不利于HCB的降解,在pH=3,HCB=0.2 mg/L,反应40 min时,HCB的去除可达50%左右,酸性条件下有利于降解反应的进行;无论是O3单独作用还是UV/O3联合作用,HCB的降解基本上满足准一级反应动力学规律,如果体系的pH值基本保持恒定,这种规律就更为明显.根据离子色谱(IC)、GC对六氯苯降解中间产物进行了测定,探讨了O3、UV/O3降解六氯苯的途径和机理.     

Mn2O3/γ-Al2O3在超临界水氧化中催化活性的研究

采用浸渍法制备了Mn2O3/γ-Al2O3催化剂,在超临界水中催化氧化降解1,5-萘二磺酸,探索了催化剂Mn2O3活性组分负载量、催化剂空速和反应溶液pH对Mn2O3/γ-Al2O3催化剂活性的影响。结果表明：Mn2O3/γ-Al2O3的催化活性在一定范围内随Mn2O3活性组分负载量的增加而提高;在一定范围内,Mn2O3/γ-Al2O3空速越小,模拟废水的COD去除率越高;Mn2O3/γ-Al2O3催化活性在反应溶液呈酸性情况下比碱性时高。     

O3/H2O2/UV降解1,2,4-三氯苯的研究

采用O3/H2O2/UV工艺处理1,2,4-三氯苯(TCB)模拟废水,考察了TCB初始浓度、pH、H2O2投加量及O3转化率等因素对O3/H2O2/UV降解TCB的影响,推断了TCB可能的降解途径。结果表明:(1)H2O2、O3、UV、O3/H2O2、O3/H2O2/UV 5种体系对TCB的降解效果为H2O2相似文献   

H2O2协同O3预处理垃圾填埋场后期渗滤液的研究

应用自制微孔扩散式接触反应器,考察了H2O3/O3在不同摩尔比下对垃圾填埋场后期渗滤液的氧化处理效果.结果表明,H2O3/O3的摩尔比对处理效果有明显的影响.在试验范围内,确定H2O3/O3的最佳摩尔比为0.2:1,最佳处理时间为90 min,经过H2O3/O3处理后,垃圾填埋场后期渗滤液的BOD5/COD可从初始的0.17提高到0.36,改善了废水的可生化性,同时渗滤液的色度、浊度、腐殖酸和SS也有较高的去除率.     

煤矸石中的铝、铁在高浓度盐酸中的浸出行为

考察了煤矸石中Al2O3和Fe2O3在不同浓度盐酸中的浸出行为,着重探讨了Al2O3和Fe2O3在高浓度盐酸中的溶出规律。通过与文献中AlCl3和FeCl3在不同浓度盐酸中的溶解度数据对照,发现煤矸石中Al2O3的溶出率受AlCl3溶解度的影响显著,而Fe2O3的溶出则基本不受FeCl3溶解度影响。进一步的研究结果表明,在高浓度盐酸中,煤矸石中Al2O3的溶出率显著降低,高浓度的盐酸不影响Fe2O3的溶出。当煤矸石的煅烧温度为700℃、酸浸温度为33℃时,酸浸固液比为1∶1(g/mL),利用37%的高浓度盐酸酸浸,Fe2O3和Al2O3的溶出率分别为48.7%和7.3%,可实现煤矸石中铁铝的有效分离。     

气体循环条件下等离子体催化氧化吸附态苯

采用气体循环方式,对低温等离子体联合Mn Ox-Ag Ox、Co Ox-Ce Ox复合金属氧化物催化剂催化氧化吸附态的苯进行研究,主要考察了苯吸附存储量、氧化背景气体、催化剂对苯氧化性能的影响,并分析了催化剂对O3及N2O副产物产生的影响规律。研究结果表明,采用气体循环方式,有助于实现苯充分氧化为CO2。相同条件下,COx产率、CO2选择性及对O3的分解能力大小依次为:Mn Ox-Ag Ox/γ-Al2O3Co Ox-Ce Ox/γ-Al2O3γ-Al2O3。氧气背景下,气体循环75 min后,Mn Ox-Ag Ox/γ-Al2O3及Co Ox-Ce Ox/γ-Al2O3催化剂存在时,CO2选择性大于95%;气体循环90 min后,与γ-Al2O3所对应的COx产率相比,Mn Ox-Ag Ox/γ-Al2O3、Co Ox-Ce Ox/γ-Al2O3分别提高了38%、17%。FT-IR分析结果表明,等离子体催化氧化苯的主要产物为CO2、CO和H2O,副产物为少量的O3及N2O。     

常温常压催化湿式氧化降解偶氮染料废水的研究

以过渡金属Fe、Mn、Cu和Zn的硝酸盐为活性组分的前驱物,以γ-Al2O3为载体,制备了负载型催化剂Fe2O3/γ-Al2O3、MnO/γ-Al2O3、CuO/γ-Al2O3和ZnO/γ-Al2O3,并分别以H2O2和NaClO为氧化剂,对比了在常温常压条件下催化湿式氧化工艺处理甲基橙模拟废水的效果.结果表明,Fe2...     

TS-1分子筛催化O3/H2O2氧化乙酸

研究了酸性条件下TS-1分子筛催化O3/H2O2体系(O3/H2O2/TS-1)对降解水中乙酸效率的影响,优化了相关工艺参数,并对其作用机理进行了分析。结果表明,在pH为2.8时,TS-1的加入能显著提高臭氧化的降解效率。优化工艺参数表明,当过氧化氢投加量为3 g/L,TS-1投加量为5 g/L时,O3/H2O2/TS-1体系对乙酸具有较高的降解率,60 min后O3/H2 O2/TS-1体系对乙酸(初始浓度为100 mg/L)的去除率达到了58.7%。当pH为0.8时,O3/H2 O2/TS-1体系对乙酸的去除率仅为19.8%,降解效果较差。定量化计算表明,O3/H2O2和O3/H2O2/TS-1的Rct分别为1.62×10-8和8.67×10-7。通过测定乙酸降解过程水样中过氧化氢和液相臭氧的浓度变化,推测了具体反应机理。由于此体系在酸性条件下对乙酸有较好的降解效果,拓宽了现有O3/H2O2体系的应用范围。     

TS-1分子筛催化O_3/H_2O_2氧化乙酸

研究了酸性条件下TS-1分子筛催化O3/H2O2体系（O3/H2O2/TS-1）对降解水中乙酸效率的影响,优化了相关工艺参数,并对其作用机理进行了分析。结果表明,在pH为2.8时,TS-1的加入能显著提高臭氧化的降解效率。优化工艺参数表明,当过氧化氢投加量为3 g/L,TS-1投加量为5 g/L时,O3/H2O2/TS-1体系对乙酸具有较高的降解率,60 min后O3/H2 O2/TS-1体系对乙酸（初始浓度为100 mg/L）的去除率达到了58.7%。当pH为0.8时,O3/H2 O2/TS-1体系对乙酸的去除率仅为19.8%,降解效果较差。定量化计算表明,O3/H2O2和O3/H2O2/TS-1的Rct分别为1.62×10-8和8.67×10-7。通过测定乙酸降解过程水样中过氧化氢和液相臭氧的浓度变化,推测了具体反应机理。由于此体系在酸性条件下对乙酸有较好的降解效果,拓宽了现有O3/H2O2体系的应用范围。     

Comparison of various advanced oxidation processes and chemical treatment methods for COD and color removal from a polyester and acetate fiber dyeing effluent

In this paper, a comparison of various advanced oxidation processes (O3, O3/UV, H2O2/UV, O3/H2O2/UV, Fe2+/H2O2) and chemical treatment methods using Al2(SO4)3.18H2O, FeCl3 and FeSO4 for the chemical oxygen demand (COD) and color removal from a polyester and acetate fiber dyeing effluent is undertaken. Advanced oxidation processes (AOPs) showed a superior performance compared to conventional chemical treatment, which maximum achievable color and COD removal for the textile effluent used in this study was 50% and 60%, respectively. Although O3/H2O2/UV combination among other AOPs methods studied in this paper was found to give the best result (99% removal for COD and 96% removal for color), use of Fe2+/H2O2 seems to show a satisfactory COD and color removal performance and to be economically more viable choice for the acetate and polyester fiber dyeing effluent on the basis of 90% removal.     

Supported Mn2O3-based catalysts for NO-SCO: an experimental study

Environmental Science and Pollution Research - In this paper, the NO-SCO (the selective catalytic oxidation of NO) experiments of single-phase Mn2O3, supported Mn2O3/Al2O3, and the Ce-doped...     

Forest responses to tropospheric ozone and global climate change: an analysis

In this paper an analysis is provided on: what we know, what we need to know, and what we need to do, to further our understanding of the relationships between tropospheric ozone (O(3)), global climate change and forest responses. The relationships between global geographic distributions of forest ecosystems and potential geographic regions of high photochemical smog by the year 2025 AD are described. While the emphasis is on the effects of tropospheric O(3) on forest ecosystems, discussion is presented to understand such effects in the context of global climate change. One particular strong point of this paper is the audit of published surface O(3) data by photochemical smog region that reveals important forest/woodland geographic regions where little or no O(3) data exist even though the potential threat to forests in those regions appears to be large. The concepts and considerations relevant to the examination of ecosystem responses as a whole, rather than simply tree stands alone are reviewed. A brief argument is provided to stimulate the modification of the concept of simple cause and effect relationships in viewing total ecosystems. Our knowledge of O(3) exposure and its effects on the energy, nutrient and hydrological flow within the ecosystem are described. Modeling strategies for such systems are reviewed. A discussion of responses of forests to potential multiple climatic changes is provided. An important concept in this paper is that changes in water exchange processes throughout the hydrological cycle can be used as early warning indicators of forest responses to O(3). Another strength of this paper is the integration of information on structural and functional processes of ecosystems and their responses to O(3). An admitted weakness of this analysis is that the information on integrated ecosystem responses is based overwhelmingly on the San Bernardino Forest ecosystem research program of the 1970s because of a lack of similar studies. In the final analysis, it is recommended that systems ecology be applied in examining the joint effects of O(3), carbon dioxide and ultraviolet-B radiation on forest ecosystems.     

Impact of ozone on Mediterranean forests: a review

Ozone impact on Mediterranean forests remains largely under-investigated, despite strong photochemical activity and harmful effects on crops. As representative of O3 impacts on Mediterranean vegetation, this paper reviews the current knowledge about O3 and forests in Italy. The intermediate position between Africa and European mid-latitudes creates a complex patchwork of climate and vegetation. Available data from air quality monitoring stations and passive samplers suggest O3 levels regularly exceed the critical level (CL) for forests. In contrast, relationships between O3 exposure and effects (crown transparency, radial growth and foliar visible symptoms) often fail. Despite limitations in the study design or underestimation of the CL can also affect this discrepancy, the effects of site factors and plant ecology suggest Mediterranean forest vegetation is adapted to face oxidative stress, including O3. Implications for risk assessment (flux-based CL, level III, non-stomatal deposition) are discussed.     

PLATIN (plant-atmosphere interaction) II: Co-occurrence of high ambient ozone concentrations and factors limiting plant absorbed dose

There is an ongoing debate as to which components of the ambient ozone (O3) exposure dynamics best explain adverse crop yield responses. A key issue is regarding the importance of peak versus mid-range hourly ambient O3 concentrations. While in this paper the importance of peak atmospheric O3 concentrations is not discounted, if they occur at a time when plants are conducive for uptake, the corresponding importance of more frequently occurring mid-range O3 concentrations is described. The probability of co-occurrence of high O3 concentrations and O3 uptake limiting factors is provided using coherent data sets of O3 concentration, air temperature, air humidity, mean horizontal wind velocity and global radiation measured at representative US and German air quality monitoring sites. Using the PLant-ATmosphere INteraction (PLATIN) model, the significance of the aforementioned meteorological parameters on ozone uptake is examined. In addition, the limitations of describing the O3 exposure for plants under ambient, chamberless conditions by SUM06, AOT40 or W126 exposure indices are discussed.     

Systematic development of an artificial neural network model for real-time prediction of ground-level ozone in Edmonton, Alberta, Canada

Ground-level ozone is a secondary pollutant that has recently gained notoriety for its detrimental effects on human and vegetation health. In this paper, a systematic approach is applied to develop artificial neural network (ANN) models for ground-level ozone (O3) prediction in Edmonton, Alberta, Canada, using ambient monitoring data for input. The intent of these models is to provide regulatory agencies with a tool for addressing data gaps in ambient monitoring information and predicting O3 events. The models are used to determine the meteorological conditions and precursors that most affect O3 concentrations. O3 time-series effects and the efficacy of the systematic approach are also assessed. The developed models showed good predictive success, with coefficient of multiple determination values ranging from 0.75 to 0.94 for forecasts up to 2 hr in advance. The inputs most important for O3 prediction were temperature and concentrations of nitric oxide, total hydrocarbons, sulfur dioxide, and nitrogen dioxide.     

Application of artificial neural networks to modeling and prediction of ambient ozone concentrations

The deterministic modeling of ambient O3 concentrations is difficult because of the complexity of the atmospheric system in terms of the number of chemical species; the availability of accurate, time-resolved emissions data; and the required rate constants. However, other complex systems have been successfully approximated using artificial neural networks (ANNs). In this paper, ANNs are used to model and predict ambient O3 concentrations based on a limited number of measured hydrocarbon species, NOx compounds, temperature, and radiant energy. In order to examine the utility of these approaches, data from the Coastal Oxidant Assessment for Southeast Texas (COAST) program in Houston, TX, have been used. In this study, 53 hydrocarbon compounds, along with O3, nitrogen oxides, and meteorological data were continuously measured during summer 1993. Steady-state ANN models were developed to examine the ability of these models to predict current O3 concentrations from measured VOC and NOx concentrations. To predict the future concentrations of O3, dynamic models were also explored and were used for extraction of chemical information such as reactivity estimations for the VOC species. The steady-state model produced an approximation of O3 data and demonstrated the functional relationship between O3 and VOC-NOx concentrations. The dynamic models were able to the adequately predict the O3 concentration and behavior of VOC-NOx-O3 system a number of hourly intervals into the future. For 3 hr into the future, O3 concentration could be predicted with a root-mean squared error (RMSE) of 8.21 ppb. Extending the models further in time led to an RMSE of 11.46 ppb for 5-hr-ahead values. This prediction capability could be useful in determining when control actions are needed to maintain measured concentrations within acceptable value ranges.     

Measuring, modelling and testing ozone exposure, flux and effects on vegetation in southern European conditions--what does not work? A review from Italy

Ozone (O3) exposure at Italian background sites exceeds UN/ECE concentration-based critical levels (CLe(c)), if expressed in terms of AOT40. Yet the occurrence of adverse effects of O3 on forests and crops is controversial. Possible reasons include (i) ability of response indicators to provide an unbiased estimate of O3 effects, (ii) setting of current CLe(c) in terms of cut-off value and accumulation level, (iii) response functions adopted to infer a critical level, (iv) environmental limitation to O3 uptake and (v) inherent characteristics of Mediterranean vegetation. In particular, the two latter points suggest that critical levels based on accumulated stomatal flux (CLe(f)) can be a better predictor of O3 risk than CLe(c). While this concept is largely acknowledged, a number of factors may limit its applicability for routine monitoring. This paper reviews levels, uptake and vegetation response to O3 in Italy over recent years to discuss value, uncertainty and feasibility of different approaches to risk assessment.     

The health benefits of reduced tropospheric ozone in California

Californians are exposed daily to concentrations of ozone (O3) that are among the highest in the United States. Recently, the state adopted a new 8-hr ambient standard of 0.070 ppm, more stringent than the current federal standard. The new standard is based on controlled human studies and on dozens of epidemiologic studies reporting associations between O3 at current ambient levels and a wide range of adverse health outcomes. Clearly, the new O3 standards will require further reductions in the precursor pollutants and additional expenditures for pollution control. Therefore, it is important to quantify the incremental health benefits of moving from current conditions to the new California standard. In this paper, a standard methodology is applied to quantify the health benefits associated with O3 concentration reductions in California. O3 concentration reductions are estimated using ambient monitoring data and a proportional rollback approach in which changes are specific to each air basin, and control strategies may impact concentrations both below and above the standard. Health impacts are based on published epidemiologic studies, including O3-related mortality and morbidity, and economic values are assigned to these outcomes based on willingness-to-pay and cost-of-illness studies. Central estimates of this research indicate that attaining the California 8-hr standard, relative to current concentrations, would result in annual reductions of 630 cases of premature mortality, 4200 respiratory hospital admissions, 660 pediatric emergency room visits for asthma, 4.7 million days of school loss, and 3.1 million minor restricted activity days, with a median estimated economic value of dollar 4.5 billion. Sensitivity analyses indicate that these findings are robust with respect to exposure assessment methods but are influenced by assumptions about the slope of the concentration-response function in threshold models and the magnitude of the O3-mortality relationship. Although uncertainties exist for several components of the methodology, these results indicate that the benefits of reducing O3 to the California standard may be substantial and that further research on the shape of the O3-mortality concentration-response function and economic value of O3-related mortality would best reduce these uncertainties.     

同步硝化反硝化工艺中DO浓度对N2O产生量的影响

采用序批式生物膜反应器（SBBR）,在连续曝气全程好氧的运行条件下,考察不同溶解氧浓度对同步硝化反硝化脱氮性能及N2O产量的影响。控制溶解氧浓度恒定在1、2、2.5和3 mg/L。结果表明,DO为2 mg/L和2.5 mg/L时,氨氮去除率分别为97.9%和98.5%,同步硝化反硝化率均为99%。DO为2 mg/L时,系统中N2O产生量最低,为0.423 mg/L,占氨氮去除量的1.4%;DO为3 mg/L时N2O的产生量最高,为2.01 mg/L,是DO为2 mg/L时的4.75倍。系统中亚硝酸盐的存在可能是高溶解氧条件下N2O产量增加的主要原因,同步过程中没有NOx-的积累即稳定的SND系统有利于降低生物脱氮过程中N2O的产生量。