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1.
Purpose Gamma ray irradiation is considered as an effective way to degrade diclofenac. However, due to the extensive coexisting substances
in natural waters, the use of gamma ray irradiation for degradation is often influenced by multiple factors. The various factors
that affect degradation efficiency, such as initial diclofenac concentration, initial pH, and the concentration of the additives
including H 2O 2 (·OH radical promoter), CH 3OH (·OH radical scavenger), thiourea (·OH, H·, and e aq− scavenger), humic acid, and NO 3− (coexisting substances in natural waters), are investigated. Furthermore, possible intermediate products are identified and
corresponding transformation pathways are proposed. 相似文献
2.
Background, aim, and scope In literature, the environmental applications of green rust (GR) have mainly been pointed out through the reduction of inorganic
contaminants and the reductive dechlorination of chlorinated organics. However, reactions involving GR for the oxidation and
mineralization of organic pollutants remain very scantly described. In this study, the ability of three synthetic Fe(II)–Fe(III)
green rusts, GR(CO 32−), GR(SO 42−), and GR(Cl −), to promote Fenton-like reaction was examined by employing phenol as a model pollutant. Unlike the traditional Fenton’s
reagent (dissolved Fe(II) + H 2O 2), where the pH values have to be lowered to less than 4, the proposed reaction can effectively oxidize the organic molecules
at neutral pH and could avoid the initial acidification which may be costly and destructive for the in situ remediation of
contaminated groundwater and soils. The green rust reactivity towards the oxidative transformation of phenol was thoroughly
evaluated by performing a large kinetic study, chemical analyses, and spectroscopic investigations. 相似文献
3.
Purpose The purpose this research is to investigate the interaction of Cr(VI) species, present as Cr 2O 72−, at ambient temperature with brick clay pre-fired at different temperatures. 相似文献
4.
Background Cuttings and seedlings of Jatropha curcas L. were exposed to different regimes of lead (Pb) stress as Pb(NO 3) 2 at 0 (CK), 0.5, 1, 2, 3, and 4 mM kg −1 soil. 相似文献
5.
Background, aim and scope Precipitation samples collected from 1995 to 2000 at meteorological station in the eastern outskirts of Herceg Novi (Montenegro)
were analysed on Na +, K +, Mg 2+, Ca 2+, Cl –, SO 4
2–, NO 3
– and NH 4
+. Four-day backward trajectory simulations were conducted during the precipitation period to investigate the regional transport
of main ions and their deposition in the region of the southeastern Adriatic Sea. The air mass trajectories were classified
into six trajectory categories by the origin and direction of their approach to Herceg Novi. 相似文献
6.
The non-ionic surfactant Brij 35 was effectively removed from concentrated aqueous solution by the peroxymonosulfate/Co(II) system, using oxone (2KHSO 5·KHSO 4·K 2SO 4) as a source of peroxymonosulfate. At pH = 2.3 and initial Brij 35 concentration in the range 680-2410 mg L −1, 86-94% removal was achieved after 24 h, using Co(II) = 15 μM and oxone = 5.9 mM. The effectiveness of removal did not change when initial pH was in the range 2.3-8.2. After five subsequent additions of Co(II) and oxone to the solution, COD and TOC removals increased up to 64% and 33%, respectively. Radical quenching tests confirmed that sulfate radical was the dominant radical species in the system. The main identified by-products from surfactant degradation were: (a) low molecular weight organic acids; (b) aldehydes and formates with shorter ethoxy chain than Brij 35; (c) alcohol ethoxylates carrying hydroxyl groups bonded to ethoxy chain. By-products identification allowed to hypothesize the pathways of Brij 35 degradation. 相似文献
7.
Background, aim and scope Photocatalytic oxidation using UV irradiation of TiO 2 has been studied extensively and has many potential industrial applications, including the degradation of recalcitrant contaminants
in water and wastewater treatment. A limiting factor in the oxidation process is the recombination of conduction band electrons
(e
−
cb) with electron holes (h vb+) on the irradiated TiO 2 surface; thus, in aqueous conditions, the presence of an effective electron scavenger will be beneficial to the efficiency
of the oxidation process. Ferrate (FeO 42−) has received much recent attention as a water treatment chemical since it behaves simultaneously as an oxidant and coagulant.
The combination of ferrate [Fe(VI)] with UV/TiO 2 photocatalysis offers an oxidation synergism arising from the Fe(VI) scavenging of e
−
cb and the corresponding beneficial formation of Fe(V) from the Fe(VI) reduction. This paper reviews recent studies concerning
the photocatalytic oxidation of problematic pollutants with and without ferrate. 相似文献
8.
The degradation of a common textile dye, Reactive-brilliant red X-3B, by several advanced oxidation technologies was studied in an air-saturated aqueous solution. The dye was resistant to the UV illumination (wavelength λ 320 nm), but was decolorized when one of Fe 3+, H 2O 2 and TiO 2 components was present. The decolorization rate was observed to be quite different for each system, and the relative order evaluated under comparable conditions followed the order of Fe 2+–H 2O 2–UV Fe 2+–H 2O 2 > Fe 3+–H 2O 2–UV > Fe 3+–H 2O 2 > Fe 3+–TiO 2–UV > TiO 2–UV > Fe 3+–UV > TiO 2–visible light ( λ 450 nm) > H 2O 2–UV > Fe 2+–UV. The mechanism for each process is discussed, and linked together for understanding the observed differences in reactivity. 相似文献
9.
用高压电弧放电产生的低温等离子体对含偶氮染料的废水进行了处理,以甲基橙为例研究了电压幅值、处理时间、溶液初始浓度、溶液初始pH值、投加Fe^2+和Fe^3+对染料脱色的影响。实验结果表明,甲基橙浓度为50mg/L时其降解率随时间和电压幅值的增加而增加。溶液初始浓度对染料去除效果影响较为明显,同等条件下初始浓度越低降解率越高。酸性条件下有利于低温等离子体处理甲基橙。Fe^2+和Fe^3+对低温等离子体降解甲基橙有一定的催化作用。电压8kV处理3min,Fe^2+为20mg/L时去除率由89.64%增至99.72%。Fe2(SO4),的最佳投加量为5mg/L(以Fe^3+计),而FeCl,的最佳投加量为80mg/L(以Fe^3+计)。 相似文献
10.
Singlet oxygen (1O2), hydroxyl radicals (•OH), and excited triplet states of organic matter (3OM*) play a key role in the degradation of pollutants in aquatic environments. The formation rates and quantum yields (Φ) of these reactive intermediates (RI) through photosensitized reactions of dissolved organic matter (DOM) have been reported in the literature for decades. Urban biowaste-derived substances (UW-BOS), a form of organic matter derived from vegetative and urban waste, have recently been shown to be efficient sensitizers in the photo-degradation of different contaminants. Nevertheless, no quantitative measurements of photo-oxidant generation by UW-BOS have been reported. In this study, the formation quantum yields of 1O2 and •OH, as well as quantum yield coefficients of TMP degradation (indicative of 3OM* formation), were quantified for two UW-BOS samples, under 254-nm UV radiation or simulated sunlight and compared to a DOM standard from the Suwanee River (SRNOM). Values of Φ for UW-BOS samples ranged from Φ(+1O2) = 8.0 to 8.8 × 10−3, Φ(+•OH) = 4.1 to 4.3 × 10−6, and f
TMP = 1.22 to 1.23 × 102 L Einstein−1 under simulated sunlight and from Φ(+1O2) = 1.4 to 2.3 × 10−2, Φ(+•OH) = 1.3 to 3.5 × 10−3, and f
TMP = 3.3 to 3.9 × 102 L Einstein−1 under UV. Although UW-BOS are not necessarily better than natural DOM regarding photosensitizing properties, they do sensitize the production of RI and could potentially be used in engineered treatment systems. 相似文献
11.
利用80目天然斜发沸石作载体制备La 2O 3(0.5%)-ZnO(20%)-TiO 2/沸石复合光催化剂,以20 W紫外灯为光源,在自制的光催化反应器中降解活性艳红K-2BP,考察了光照时间、空气通入量、催化剂用量、溶液初始浓度、H 2O 2与Fe 3+投加量等对活性艳红K-2BP光催化降解率的影响。结果表明,当溶液初始浓度为60 mg/L,催化剂投加量为12 g/L,通气量为1 200 mL/min,光照2.5 h,活性艳红K-2BP的降解率可达99.2%;H 2O 2和Fe 3+投加量为4 mL/L和3 g/L时,光照1 h活性艳红K-2BP降解率分别为100%和97.2%。紫外可见吸收光谱显示,LZTZ光催化剂可有效降解印染废水。 相似文献
12.
Introduction This paper deals with the removal of two natural estrogens, estrone (E1) and 17β-estradiol (E2) and a synthetic one 17α ethinylestradiol
(EE2) from wastewater in a laboratory-scale membrane bioreactor (MBR). 相似文献
13.
Background, aim and scope Australia is the largest producer of bauxite in the world, with an annual output of approximately 62 million metric dry tons
in 2007. For every tonne of alumina, about 2 tonnes of highly alkaline and highly saline bauxite-processing residue are produced.
In Western Australia, Alcoa World Alumina, Australia (Alcoa) produces approximately 15 MT of residue annually from its refineries
(Kwinana, Pinjarra and Wagerup). The bauxite-processing residue sand (BRS) fraction represents the primary material for rehabilitating
Alcoa’s residue disposal areas (RDAs). However, the inherently hostile characteristics (high alkalinity, high salinity and
poor nutrient availability) of BRS pose severe limitations for establishing sustainable plant cover systems. Alcoa currently
applies 2.7 t ha −1 of di-ammonium phosphate ((NH 4) 2HPO 4; DAP)-based fertiliser as a part of rehabilitation of the outer residue sand embankments of its RDAs. Limited information
on the behaviour of the dominant components of this inorganic fertiliser in highly alkaline BRS is currently available, despite
the known effects of pH on ammonium (NH 4) and phosphorus (P) behaviour. The aim of this study was to quantify the effects of pH on NH 3 volatilisation and residual nitrogen (N) in BRS following DAP applications. 相似文献
14.
Purpose Malachite Green (MG) is used for a variety of applications but is also known to be carcinogenic and mutagenic. In this study, a novel Micrococcus sp. (strain BD15) was observed to efficiently decolorize MG. The purposes of this study were to explore the optimal conditions for decolorization and to evaluate the potential use of this strain for MG decolorization. Methods Optical microscope and UV?Cvisible analyses were carried out to determine whether the decolorization was due to biosorption or biodegradation. A Plackett?CBurman design was employed to investigate the effect of various parameters on decolorization, and response surface methodology was then used to explore the optimal decolorization conditions. Kinetics analysis and antimicrobial activity tests were also performed. Results The results indicated that the decolorization by the strain was mainly due to biodegradation. Concentrations of MG, urea, and yeast extract and inoculum size had significantly positive effects on MG decolorization, while concentrations of CuCl 2 and MgCl 2, and temperature had significantly negative effects. The interaction between different parameters could significantly affect decolorization, and the optimal conditions for decolorization were 1.0 g/L urea, 0.9 g/L yeast extract, 100 mg/L MG, 0.1 g/L inoculums (dry weight), and incubation at 25.2°C. Under the optimal conditions, 96.9% of MG was removed by the strain within 1 h, which represents highly efficient microbial decolorization. Moreover, the kinetic data for decolorization fit a second-order model well, and the strain showed a good MG detoxification capability. Conclusion Based on the results of this study, we propose Micrococcus sp. strain BD15 as an excellent candidate strain for MG removal from wastewater. 相似文献
15.
采用IR和XRD等手段对自制磷钼酸铁(FePMo12)杂多酸进行表征,表明杂多阴离子具有Keggin结构。将FePMo12负载于修饰后的分子筛上制备FePMo12/APTES-4A催化剂填充于电化学反应器中,考察电化学氧化体系对酸性大红3R染料废水的脱色效果,其脱色率高于二维电化学反应器。利用Box-Behnken中心组合实验设计及响应面(RSM)分析,以pH值,板间距,槽电压,曝气量为实验因素,建立了以酸性大红3R的脱色率为响应值的二次多项式回归模型。研究表明,当电解时间为60 min时,曝气量0.05 m3/h、pH为2、板间距3.0 cm、槽电压11.0 V,在此条件下色度去除率可达69.4%,模型预测值与实验值能很好地吻合。方差分析结果表明,槽电压和pH、pH和曝气量的交互作用对响应值具有显著性影响。 相似文献
16.
Background, aim, and scope Acrylate and methacrylate esters are α,β-unsaturated esters that contain vinyl groups directly attached to the carbonyl carbon
(CH 2=CHCOO– and CH 2=CCH 3COO–, respectively) and are widely used in the polymer plastic and resin production. Rate coefficients for Cl reactions for
most of the unsaturated esters have not been previously determined, and a good understanding is needed of all the atmospheric
oxidation processes of these compounds in order to determine lifetimes in the atmosphere and to evaluate the impact of these
reactions on the formation of photo-oxidants and therefore on health and environment. 相似文献
17.
Background, aim, and scope Chlorinated volatile organic compounds (CVOCs), widely used in industry as solvents and chemical intermediates in the production
of synthetic resins, plastics, and pharmaceuticals, are highly toxic to the environment and public health. Various studies
reported that Fenton’s oxidation could degrade a variety of chlorinated VOCs in aqueous solutions. In acidic conditions, ferrous
ion catalyzes the decomposition of H 2O 2 to form a powerful •OH radical. In this study, wastewater from wash of ion-exchange resin containing typical CVOC, 1,2-dichloroethane, was treated
using Fenton’s oxidation. To reduce environmental load and processing costs of wastewater, Fenton process as a simple and
efficient treatment method was applied to degrade 1,2-dichloroethane of wash water. 相似文献
18.
Background, aim, and scope Chemical oxygen demand (COD) is used as a discharge standard parameter in wastewater treatment plant design, environmental
modelling and many other applications. Chloride interference is an important problem of COD measurement for wastewaters containing
low organic matter and high chloride concentrations. In case of chloride concentrations up to 2,000 mg/L, mercury sulphate
addition at a ratio of 10:1 (HgSO 4:Cl −) can adequately mask the interference. When chloride concentration exceeds 2,000 mg/L, this ratio becomes ineffective to
hinder the interference. At this point, it is proposed to use a greater and constant ratio of mercury sulphate addition. However,
this application sometimes results in extra mercury sulphate addition which is not necessary. Even in some cases, greater
addition of mercury sulphate alone is not a solution to erroneous measurement results. The purpose of the study is to determine
optimum HgSO 4:Cl − ratios according to the chloride concentrations of the samples and to show the importance of the strength of the digestion
solution for the correct determination of the COD parameter. 相似文献
19.
Background, aim, and scope The adverse environmental impacts of chlorinated hydrocarbons on the Earth’s ozone layer have focused attention on the effort
to replace these compounds by nonchlorinated substitutes with environmental acceptability. Hydrofluoroethers (HFEs) and fluorinated
alcohols are currently being introduced in many applications for this purpose. Nevertheless, the presence of a great number
of C–F bonds drives to atmospheric long-lived compounds with infrared absorption features. Thus, it is necessary to improve
our knowledge about lifetimes and global warming potentials (GWP) for these compounds in order to get a complete evaluation
of their environmental impact. Tropospheric degradation is expected to be initiated mainly by OH reactions in the gas phase.
Nevertheless, Cl atoms reaction may also be important since rate constants are generally larger than those of OH. In the present
work, we report the results obtained in the study of the reactions of Cl radicals with HFE-7000 (CF 3CF 2CF 2OCH 3) (1) and its isomer CF 3CF 2CF 2CH 2OH (2).
Materials and methods Kinetic rate coefficients with Cl atoms have been measured using the discharge flow tube–mass spectrometric technique at 1 Torr
of total pressure. The reactions of these chlorofluorocarbons (CFCs) substitutes have been studied under pseudo-first-order
kinetic conditions in excess of the fluorinated compounds over Cl atoms. The temperature ranges were 266–333 and 298–353 K
for reactions of HFE-7000 and CF 3CF 2CF 2CH 2OH, respectively.
Results The measured room temperature rate constants were k(Cl+CF 3CF 2CF 2OCH 3) = (1.24 ± 0.28) × 10 −13 cm 3 molecule −1 s −1and k(Cl+CF 3CF 2CF 2CH 2OH) = (8.35 ± 1.63) × 10 −13 cm 3 molecule −1 s −1 (errors are 2 σ + 10% to cover systematic errors). The Arrhenius expression for reaction 1 was k
1(266–333 K) = (6.1 ± 3.8) × 10 −13exp[−(445 ± 186)/ T] cm 3 molecule −1 s −1 and k
2(298–353 K) = (1.9 ± 0.7) × 10 −12exp[−(244 ± 125)/ T] cm 3 molecule −1 s −1 (errors are 2 σ). The reactions are reported to proceed through the abstraction of an H atom to form HCl and the corresponding halo-alkyl
radical. At 298 K and 1 Torr, yields on HCl of 0.95 ± 0.38 and 0.97 ± 0.16 (errors are 2 σ) were obtained for CF 3CF 2CF 2OCH 3 and CF 3CF 2CF 2CH 2OH, respectively.
Discussion The obtained kinetic rate constants are related to the previous data in the literature, showing a good agreement taking into
account the error limits. Comparing the obtained results at room temperature, k
1 and k
2, HFE-7000 is significantly less reactive than its isomer C 3F 7CH 2OH. A similar behavior has been reported for the reactions of other fluorinated alcohols and their isomeric fluorinated ethers
with Cl atoms. Literature data, together with the results reported in this work, show that, for both fluorinated ethers and
alcohols, the kinetic rate constant may be considered as not dependent on the number of –CF 2– in the perfluorinated chain. This result may be useful since it is possible to obtain the required physicochemical properties
for a given application by changing the number of –CF 2– without changes in the atmospheric reactivity. Furthermore, lifetimes estimations for these CFCs substitutes are calculated
and discussed. The average estimated Cl lifetimes are 256 and 38 years for HFE-7000 and C 3H 7CH 2OH, respectively.
Conclusions The studied CFCs’ substitutes are relatively short-lived and OH reaction constitutes their main reactive sink. The average
contribution of Cl reactions to global lifetime is about 2% in both cases. Nevertheless, under local conditions as in the
marine boundary layer, τ
Cl values as low as 2.5 and 0.4 years for HFE-7000 and C 3H 7CH 2OH, respectively, are expected, showing that the contribution of Cl to the atmospheric degradation of these CFCs substitutes
under such conditions may constitute a relevant sink. In the case of CF 3CF 2CF 2OCH 3, significant activation energy has been measured, thus the use of kinetic rate coefficient only at room temperature would
result in underestimations of lifetimes and GWPs.
Recommendations and perspectives The results obtained in this work may be helpful within the database used in the modeling studies of coastal areas. The knowledge
of the atmospheric behavior and the structure–reactivity relationship discussed in this work may also contribute to the development
of new environmentally acceptable chemicals. New volatile materials susceptible of emission to the troposphere should be subject
to the study of their reactions with OH and Cl in the range of temperature of the troposphere. The knowledge of the temperature
dependence of the kinetic rate constants, as it is now reported for the case of reactions 1 and 2, will allow more accurate
lifetimes and related magnitudes like GWPs. Nevertheless, a better knowledge of the vertical Cl tropospheric distribution
is still required. 相似文献
20.
During the 1999 summer field season at Summit, Greenland, we conducted several series of experiments to follow up on our 1998 discovery that NO x is released from the sunlit snowpack. The 1999 experiments included measurements of HONO in addition to NO and NO 2, and were designed to confirm, for Greenland snow, that the processes producing reactive nitrogen oxides in the snow are largely photochemical. Long duration experiments (up to 48 h) in a flow-through chamber and in the natural snowpack revealed sun-synchronous diurnal variations of all three reactive nitrogen oxides. In a second set of experiments we alternately shaded or exposed snow (again in the natural snowpack and in the chamber) to ambient sunlight for short periods to reduce any temperature changes during variations in light intensity. All three N oxides increased (decreased) very rapidly when sunlit (shaded). In all experiments NO 2 was approximately 3-fold more abundant than NO and HONO (which were at similar levels). Higher concentrations of NO 3− in the snow resulted in higher mixing ratios of HONO, NO and NO 2 in the snow pore air, consistent with our hypothesis that photolysis of NO 3− is the source of the reactive N oxides. 相似文献
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