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1.
Ming GE Changsheng GUO Xingwang ZHU Lili MA Wei HU Yuqiu WANG Zhenan HAN 《Frontiers of Environmental Science & Engineering》2009,3(3):271
ZnO/TiO2 composites were synthesized by using the solvothermal method and ultrasonic precipitation followed by heat treatment in order to investigate their photocatalytic degradation of methyl orange (MO) in aqueous suspension under UV irradiation. The composition and surface structure of the catalyst were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and transmission electron microscopy (TEM). The degradation efficiencies of MO at various pH values were obtained. The highest degradation efficiencies were obtained before 30min and after 60min at pH 11.0 and pH 2.0, respectively. A sample analysis was conducted using liquid chromatography coupled with electrospray ionization ion-trap mass spectrometry. Six intermediates were found during the photocatalytic degradation process of quinonoid MO. The degradation pathway of quinonoid MO was also proposed. 相似文献
2.
Roger Matta Sabrine Tlili Serge Chiron St��phane Barbati 《Environmental Chemistry Letters》2011,9(3):347-353
The occurrence of bioactive trace pollutants such as pharmaceuticals in natural waters is an emerging issue. Numerous pharmaceuticals
are not completely removed in conventional wastewater treatment plants. Advanced oxidation processes may represent an interesting
alternative to completely mineralize organic trace pollutants. In this article, we show that sulfate radicals generated from
peroxymonosulfate/CoII are more efficient than hydroxyl radicals generated from the Fenton’s reagent (H2O2/FeII) for the degradation of the pharmaceutical compound, carbamazepine. The second-order rate constant for the reaction of SO4
·− with carbamazepine is 1.92·109 M−1 s−1. In laboratory grade water and in real urban wastewater, SO4
·− yielded a faster degradation of carbamazepine compared to HO· . Under strongly oxidizing conditions, a nearly complete mineralization of carbamazepine was achieved, while under mildly
oxidizing conditions, several intermediates were identified by LC–MS. These results show for the first time in real urban
wastewater that sulfate radicals are more selective than hydroxyl radicals for the oxidation of an organic pollutant and may
represent an interesting alternative in advanced oxidation processes. 相似文献
3.
Effect of low molecular weight organic acids on adsorption and desorption
of fluoride on variable charge soils 总被引:6,自引:0,他引:6
The effect of four low molecular weight organic acids on F− adsorption by two variable charge soils was investigated using a batch method. The organic acids reduced F− adsorption through competition by the acids with F− for sorption sites. Oxalic and malonic acids, both of which have simpler chemical structures, were more effective than citric or malic acid. The effect of organic acids on F− adsorption was more prominent at higher pH values and with larger amounts of the organic acids. The desorption study showed that the organic acids enhanced the desorption of F− adsorbed by the soils. In the control and malic acid systems, desorption increased sharply with decreasing pH, while in the oxalic acid system, desorption rose slightly with decreasing pH. Desorption also increased with increasing amount of organic acid added. There are two possible mechanisms for the effect of the organic acids on F− adsorption and desorption: (1)␣competition of the organic acids with F− for adsorption sites and (2) dissolution of the adsorbents, especially dissolution of soil Al. 相似文献
4.
Yuan Li Xuejiang Wang Hongbin Xu Peng Xia Hao Wang Huanping Jing Jing Li Jianfu Zhao 《Environmental Chemistry Letters》2018,16(2):569-573
Zinc is known as an essential element of human life. However, excessive zinc discharge into water and soil causes water pollution, leading to serious health issues such as septicemia, meningitis and iron-deficiency anemia. Here, a novel material made of struvite-supported diatomite was obtained from eutrophic water treated by mesoporous MgO-modified diatomite. This material was applied for zinc remediation in aqueous solutions and contaminated soils to test the reuse of P-containing products. Struvite-supported diatomite was characterized by field emission scanning electron microscopy and X-ray diffraction. Results show that the maximum removal efficiency of Zn(II) from wastewater streams reached 90.54% at an initial pH of 5 and struvite-supported diatomite dosage of 0.3 g/L. Moreover, the X-ray diffraction patterns of precipitates after Zn(II) sorption show that the combination between zinc and the phosphate group played a key role for zinc removal in solution. For Zn-contaminated soils amended with 10% struvite-supported diatomite, available Zn decreased by 65.38% and acid soluble Zn decreased by 56.9% after 56 days. 相似文献
5.
Degradation of diuron by the electro-Fenton process 总被引:2,自引:0,他引:2
The degradation of the herbicide diuron has been undertaken by electrochemical advanced oxidation in aqueous solution. This process generates catalytically hydroxyl radicals that are strong oxidizing reagents for the oxidation of organic substances. Hydroxyl radicals degrade diuron in less than 10 min. Kinetic results evidence a pseudo-first-order degradation, with a rate constant of reaction between diuron and hydroxyl radicals of 4.8x109 M–1 s–1. Several degradation products were identified by chromatography-mass spectrometry (LC-MS). The mineralization degree of a 1.7x10–4 M diuron solution reached 93% at 1,000 coulombs. 相似文献
6.
7.
电镀厂污染土壤重金属形态及淋洗去除效果 总被引:14,自引:0,他引:14
以某电镀厂污染场地重污染区域土壤为研究对象,对土壤中重金属全量和各形态含量进行分析,并研究筛选高效土壤淋洗剂,比较其淋洗去除效果。结果表明,该土壤以铬和镍污染最为严重,土壤铬和镍含量分别达1 564.00和679.00 mg.kg-1,土壤铜、锌和铅含量分别为297.00、276.00和51.40 mg.kg-1,铜、铬、镍、锌和铅的有效态比例分别为41.77%、13.16%、28.08%、21.50%和31.18%。去离子水、盐酸、乙酸、草酸、柠檬酸和EDTA 6种淋洗剂中,去离子水对5种重金属提取量均较少;草酸对铜、铬、镍和锌去除效果较好,去除率分别为55.1%、24.8%、47.5%和29.3%;柠檬酸对铜、铬、镍和锌去除效果较好,去除率分别为26.3%、25.7%、33.0%和21.6%;EDTA对铜、镍、锌和铅去除效果较好,去除率分别为31.5%、28.9%、21.4%和30.6%。综合考虑淋洗剂的提取效果、水溶性以及操作难度和成本,建议采用柠檬酸作为淋洗剂,最佳液土比〔V(液)∶m(土)〕为10∶1,最佳淋洗时间为6 h。 相似文献
8.
The use of tree species for phytoremediation of contaminated soil offers the advantage of a large biomass in which to store
contaminants. We investigated the cadmium (Cd) and zinc (Zn) accumulation ability of Evodiopanax innovans, a common deciduous tree species belonging to the Araliaceae family and widely found in secondary forests in Japan. Sampling
was conducted at an old silver mine. Leaf samples were collected from nine tree species, including E. innovans. The seasonal variation of metal concentrations in the leaves and the detailed distribution of metals in the leaves and twigs
of E. innovans were measured. We also analyzed the contents of organic acids in the leaves. The highest concentration of Cd in the leaves
of E. innovans was 118 μg/g, which exceeds the threshold level for being considered a Cd hyperaccumulator (100 μg/g). For Zn, the highest
value was 1040 μg/g in leaves, which is less than required to qualify as a Zn hyperaccumulator. Both Cd and Zn were found
to accumulate in the petioles and veins of leaves and the bark of twigs. Since the oxalic acid content of leaves showed a
weak correlation with Cd concentration, oxalic acid may play an important role in the accumulation of Cd. Taking both the
Cd concentration level and the biomass of this woody plant into consideration, it may be possible to use E. innovans for the phytoremediation of Cd-contaminated soils. 相似文献
9.
Natural organic acids may play an important role in influencing the mobility of toxic contaminants in the environment. The mobilization of arsenic (As) and heavy metals from an oxidized Pb–Zn mine tailings sample in the presence of three low-molecular-weight organic acids, aspartic acid, cysteine, and succinic acid, was investigated at a mass ratio of 10 mg organic additive/g mine tailings in this study. The effect of pH was also evaluated. The mine tailings sample, containing elevated levels of As (2,180 mg/kg), copper (Cu, 1,100 mg/kg), lead (Pb, 12,860 mg/kg), and zinc (Zn, 5,075 mg/kg), was collected from Bathurst, New Brunswick, Canada. It was found that the organic additives inhibited As and heavy metal mobilization under acidic conditions (at pH 3 or 5), but enhanced it under neutral to alkaline conditions (at pH above 7) through forming aqueous organic complexes. At pH 11, As, Cu, Pb, and Zn were mobilized mostly by the organic additives, 45, 46, 1,660, and 128 mg/kg by aspartic acid, 31, 28, 1,040, and 112 mg/kg by succinic acid, and 53, 38, 2,020, and 150 mg/kg by cysteine, respectively, whereas those by distilled water were 6, 16, 260, and 52 mg/kg, respectively. It was also found that the mobilization of As and the heavy metals was closely correlated, and both were closely correlated to Fe mobilization. Arsenic mobilization by the three LMWOAs was found to be consistent with the order of the stability of Fe–, Cu–, Pb–, and Zn–organic ligand complexes. The organic acids might be used potentially in the natural attenuation and remediation of As and heavy metal–contaminated sites. 相似文献
10.
Chao QIN Shaogui YANG Cheng SUN Jia ZHOU Manjun ZHAN Rongjun WANG Huanxing CAI 《Frontiers of Environmental Science & Engineering》2010,4(3):321
A solution of atrazine in a TiO2 suspension, an endocrine disruptor in natural water, was tentatively treated by microwave-assisted photocatalytic technique. The effects of mannitol, oxygen, humic acid, and hydrogen dioxide on the photodegradation rate were explored. The results could be deduced as follows: the photocatalytic degradation of atrazine fits the pseudo-first-order kinetic well with k = 0.0328 s−1, and ·OH was identified as the dominant reactant. Photodegradation of atrazine was hindered in the presence of humic acid, and the retardation effect increased as the concentration of humic acid increased. H2O2 displayed a significant negative influence on atrazine photocatalysis efficiency. Based on intermediates identified with gas chromatography-mass spectrometry (GC-MS) and Liquid chromatography-mass spectrometry (LC-MS/MS) techniques, the main degradation routes of atrazine are proposed. 相似文献
11.
12.
Unprecedented total mineralization of atrazine and cyanuric acid by anodic oxidation and electro-Fenton with a boron-doped diamond anode 总被引:1,自引:0,他引:1
This article reports the complete mineralization of atrazine. Atrazine has been the most widely used s-triazine herbicide.
Atrazine occurs in natural waters and presents a potential danger for public health because atrazine is considered as an endocrine
disruptor. The use of chemical, photochemical and photocatalytic advanced oxidation processes (AOPs) to decontaminate waters
containing atrazine only allowed its conversion into the cyanuric acid as ultimate end products, since it cannot be completely
degraded by hydroxyl radicals (•OH) produced by these techniques. The same behavior was previously reported for anodic oxidation and electro-Fenton with Pt
anode, although better performances were found using boron-doped diamond (BDD) anode but without explaining the role of generated
•OH. Here, the oxidative action of these radicals in such electrochemical AOPs has been clarified by studying the mineralization
process and decay kinetics of atrazine and cyanuric acid in separated solutions by anodic oxidation with BDD and electro-Fenton
with Pt or BDD anode using an undivided cell with a carbon-felt cathode under galvanostatic conditions. Results showed that
electro-Fenton with BDD anode was the more powerful treatment to degrade both compounds. Almost total mineralization, 97%
total organic carbon (COT) removal, of atrazine was only feasible by this method with a faster removal of its oxidation intermediates
by •OH formed at the BDD surface than that formed in the bulk from Fenton reaction, although the latter process caused a more
rapid decay of the herbicide. Cyanuric acid was much slowly mineralized mainly with •OH produced at the BDD surface, and it was not degraded by electro-Fenton with Pt anode. These results highlight that electrochemical
advanced oxidation processes (EAOPs) using a BDD anode are more powerful than the classical electro-Fenton process with Pt
or PbO2 anodes. 相似文献
13.
Laura Scrano Sabino A. Bufo Franz Menzinger Philippe Schmitt-Kopplin 《Environmental Chemistry Letters》2006,4(4):225-228
Two new intermediates rising from the photolytic reaction of the sulfonylurea herbicide oxasulfuron have been identified in aqueous environment. The higher concentrations of the two derivatives oxetan-3-yl 2-(formilsulfamoyl) benzoate and N-(4,6-dimethyl-pyrimidin-2-yl) formamide were reached within 8 h of UV-irradiation. Here we demonstrate that an optimal separation and analysis of such compounds can be achieved by using a novel analytical method based on “non-aqueous” capillary electrophoresis (CE) system joined to an electrospray ionisation-mass spectrometry equipment. Using such a separation method and a particular electrophoretic solution a high reproducibility of migration times and peak areas can be obtained. 相似文献
14.
This study is to develop a carbon-based adsorbent containing multiple functional ligands for effective removal of lead ions
from aqueous media. Activated carbon was oxidized by nitric acid, followed by chlorination with thionyl chloride and reaction
with ethylenediamine. Modified activated carbon (MAC) was characterized using scanning electron microscopy in conjunction
of energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FT-IR), and potentiometric titration.
Surface characterizations confirmed that carboxyl, amine, and chlorine functional groups were effectively introduced onto
the carbon surface by the treatments. The modifications lowered the pH at the point of zero charge (pHpzc) from 9.6 to 2.55 and resulted in more negatively charged surfaces. Adsorptive experiments showed that aqueous Pb removal
by MAC was faster, with a 62% higher capacity than the original activated carbon (60.2 vs. 37.2 mg g−1). 相似文献
15.
Degradation of azo dyes in water by Electro-Fenton process 总被引:19,自引:0,他引:19
The degradation of the azo dyes azobenzene, p-methyl red and methyl orange in aqueous solution at room temperature has been studied by an advanced electrochemical oxidation
process (AEOPs) under potential-controlled electrolysis conditions, using a Pt anode and a carbon felt cathode. The electrochemical
production of Fenton's reagent (H2O2, Fe2+) allows a controlled in situ generation of hydroxyl radicals (·OH) by simultaneous reduction of dioxygen and ferrous ions on the carbon felt electrode. In turn, hydroxyl radicals react
with azo dyes, thus leading to their mineralization into CO2 and H2O. The chemical composition of the azo dyes and their degradation products during electrolysis were monitored by high performance
liquid chromatography (HPLC). The following degradation products were identified: hydroquinone, 1,4-benzoquinone, pyrocatechol,
4-nitrocatechol, 1,3,5-trihydroxynitrobenzene and p-nitrophenol. Degradation of the initial azo dyes was assessed by the measurement of the chemical oxygen demand (COD). Kinetic
analysis of these data showed a pseudo-first order degradation reaction for all azo dyes. A pathway of degradation of azo
dyes is proposed. Specifically, the degradation of dyes and intermediates proceeds by oxidation of azo bonds and aromatic
ring by hydroxyl radicals. The results display the efficiency of the Electro-Fenton process to degrade organic matter.
Electronic Publication 相似文献
16.
Assessment of toxicity of heavy metal contaminated soils by the toxicity characteristic leaching procedure 总被引:5,自引:0,他引:5
The concentrations of Cu, Zn, Pb and Cd in soils near a lead–zinc mine located in Shangyu, Zhejiang Province, China, were determined and their toxicity was assessed using the toxicity characteristic leaching procedure (TCLP) developed by the United States Environmental Protection Agency. The TCLP method is a currently recognized international method for evaluation of heavy metal pollution in soils. The available levels of Cu, Zn, Pb and Cd were 8.2–36, 23–143, 6.4–1367 and 0.41–2.2 mg kg−1, respectively, while the international standards were 15, 25, 5 and 0.5 mg kg−1, respectively. Soils around the mine were more polluted with Zn and Pb, followed by Cd and Cu. Moreover, the levels of heavy metals in the soils extracted by TCLP indicated that extraction fluid 2 was more effective than extraction fluid 1 in extracting the heavy metals from the polluted soils and there was a positive correlation between fluids 1 and 2. Available heavy metal contents determined by TCLP were correlated with soil total heavy metal contents. 相似文献
17.
Zhimin Qiang Weiwei Ben Chin-Pao Huang 《Frontiers of Environmental Science & Engineering》2008,2(4):397-409
The degradation of selected chlorinated aliphatic hydrocarbons (CAHs) exemplified by trichloroethylene (TCE), 1,1-dichloroethylene (DCE), and chloroform (CF) was investigated with Fenton oxidation process. The results indicate that the degradation rate was primarily affected by the chemical structures of organic contaminants. Hydroxyl radicals (·OH) preferred to attack the organic contaminants with an electron-rich structure such as chlorinated alkenes (i.e., TCE and DCE). The dosing mode of Fenton’s reagent, particularly of Fe2+, significantly affected the degradation efficiency of studied organic compound. A new “time-squared” kinetic model, C = C o exp(?k obs t 2), was developed to express the degradation kinetics of selected CAHs. This model was applicable to TCE and DCE, but inapplicable to CF due to their varied reaction rate constants towards ?OH. Chloride release was monitored to examine the degree of dechlorination during the oxidation of selected CAHs. TCE was more easily dechlorinated thanDCE and CF.Dichloroacetic acid (DCAA) was identified as the major reaction intermediate in the oxidation of TCE, which could be completely removed as the reaction proceeded. No reaction intermediates or byproducts were identified in the oxidation of DCE and CF. Based on the identified intermediate, the reaction mechanism of TCE with Fenton’s reagent was proposed. 相似文献
18.
Cristina M. Monteiro Paula M. L. Castro F. Xavier Malcata 《Environmental Chemistry Letters》2011,9(2):169-176
Aquatic environments are often exposed to toxic heavy metals, which gain access to the food chain via microalgae and may cause
severe problems at higher trophic levels. However, such a metabolic specificity can be taken advantage of in bioremediation
strategies. The potential of a novel wild strain of Scenedesmus obliquus, previously isolated from a heavy metal-contaminated site in northern Portugal, to remove Zn from aqueous solutions was thus
studied, using several initial concentrations. The removal extent reached its maximum by 1 day: 836.5 mg Zn/g biomass, at
the initial concentration of 75 mg/L, mainly by adsorption onto the cell surface. Comparative studies encompassing a commercially
available strain of the same microalgal species led to a maximum removal extent of only 429.6 mg Zn/g biomass, under identical
conditions. Heat-inactivated cells permitted a maximum removal of 209.6 mg Zn/g biomass, at an initial concentration of 50 mg
Zn/L. The maximum adsorption capacity of Zn, estimated via Langmuir’s isotherm, was 330 mg Zn/g biomass. Finally, Zn removal
was highest at pH 6.0–7.0. It was proven, for the first time, that such a wild microalga can uptake and adsorb Zn very efficiently,
which unfolds a particularly good potential for bioremediation. Its performance is far better than similar (reference) species,
especially near neutrality, and even following heat-treatment. 相似文献
19.
Minhui XU Xiaogang GU Shuguang LU Zhouwei MIAO Xueke ZANG Xiaoliang WU Zhaofu QIU Qian SUI 《Frontiers of Environmental Science & Engineering》2016,10(3):438-446
The thermally activated persulfate (PS) degradation of carbon tetrachloride (CT) in the presence of formic acid (FA) was investigated. The results indicated that CT degradation followed a zero order kinetic model, and CO 2 – · was responsible for the degradation of CT confirmed by radical scavenger tests. CT degradation rate increased with increasing PS or FA dosage, and the initial CT had no effect on CT degradation rate. However, the initial solution pH had effect on the degradation of CT, and the best CT degradation occurred at initial pH 6. Cl– had a negative effect on CT degradation, and high concentration of Cl– displayed much strong inhibition. Ten mmol·L–1HCO 3 – promoted CT degradation, while 100 mmol·L–1NO 3 – inhibited the degradation of CT, but SO 4 2– promoted CT degradation in the presence of FA. The measured Cl–concentration released into solution along with CT degradation was 75.8% of the total theoretical dechlorination yield, but no chlorinated intermediates were detected. The split of C-Cl was proposed as the possible reaction pathways in CT degradation. In conclusion, this study strongly demonstrated that the thermally activated PS system in the presence of FA is a promising technique in in situ chemical oxidation (ISCO) remediation for CT contaminated site. 相似文献
20.
Małgorzata Piecha Mohamed Sarakha Polonca Trebše Drago Kočar 《Environmental Chemistry Letters》2010,8(2):185-191
In this study, stability of statin drugs in different conditions, such as various pH, diverse solvents ratio, presence of
UV, and sunlight have been investigated. Results suggest strong dependence of statins upon pH, potential environmental persistence
towards sun light, and UV light degradation via singlet excited state obtained by excitation into the π–π* band. In acidic conditions interconversion between lactone and hydroxy acid forms in aqueous solutions at room temperature
is retarded, while for the same sun-exposed samples are accelerated. Longer exposures lead to the degradation processes. Statin
interconversion in water is much lower than in acetonitrile. 相似文献