RESUMEN
The sulfate radical-based advanced oxidation processes (SR-AOPs) is a promising method for the degradation of pollutants, with the development of highly efficient catalysts for persulfate activation has been widely concerned. The novel BiCoFe-LDH (BCF-x) was synthesized successfully by coprecipitation method, which can activate peroxydisulfate (PDS) efficiently to degrade aniline. Comparative analysis with pure CoFe-LDH revealed a remarkable increase in reaction rate constant by approximately 14.66 times; the degradation rate of aniline (10 mg/L) was 100% in 60 min with the condition of 0.5 g/L BCF-1.5 and 0.5 g/L PDS, due to BCF-1.5 which was characterized as a complex of CoFe-LDH and Bi2O2CO3, promoting electron transport to improve the efficiency of activated PDS. In the reaction system, SO4â¢-, ·OH, and 1O2 were responsible for the aniline degradation and ·OH was the primary one. Furthermore, this work proposes a reaction electron transfer catalytic mechanism, which provided a new insight and good application prospect for efficient activation of PDS for pollutant degradation.
Asunto(s)
Compuestos de Anilina , Contaminantes Ambientales , Catálisis , Transporte de Electrón , Electrones , Oxidación-ReducciónRESUMEN
This study focused on the degradation and toxicity change of 4-chlorophenol (4-CP) in aqueous solution by contact glow discharge electrolysis (CGDE) with and without Fe(2+). It was found that the addition of Fe(2+) increased the degradation rate of 4-CP and decreased the toxicity of the solution. After 90 min CGDE treatment, only 28.0% 4-CP was removed and EC50 increased from 33.8 to 63.1 mg/L. With 25.0 mg/L Fe(2+) in solution, the degradation rate of 4-CP reached 93.3% and EC50 changed from 35.9 to 93.9 mg/L after 90 min CGDE treatment.
Asunto(s)
Clorofenoles/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Chlorella vulgaris/metabolismo , Clorofenoles/toxicidad , Peróxido de Hidrógeno/química , Contaminantes Químicos del Agua/toxicidadRESUMEN
Detectable PFCs could be found in all samples. Perfluorooctanoic acid (PFOA) was the major PFC in river water, while perfluorooctane sulfonate (PFOS) was dominant in sediment and were 17- to 153-fold higher than those in water. PFCs concentrations in soil were little higher than those in sediment. In fish muscles PFOS showed the highest concentrations. Generally, PFC concentrations in fish were in the following rank order: crucian carp > silver carp> common carp. We suggested that there may be constant and diffuse pollution sources in Tianjin. Point sources also appeared to make significant contribution in the present study.
Asunto(s)
Carpas/metabolismo , Fluorocarburos/análisis , Sedimentos Geológicos/análisis , Contaminantes del Suelo/análisis , Contaminantes Químicos del Agua/análisis , Animales , China , Monitoreo del Ambiente , Proyectos Piloto , Ríos/químicaRESUMEN
Contact glow discharge electrolysis (CGDE) of Cationic Blue SD-GTL (CB) was investigated by determining degradation rates and rate constants under different voltages, pH, temperature and initial concentrations. The results indicated that 500 V was the optimum voltage for CGDE of CB under experimental conditions. The effect of pH was not appreciable. Fe²(+) and Fe³(+) had a remarkable catalytic effect on the degradation of CB. The degradation rate was up to 99.7% after 3 minutes CGDE treatment when the concentration of Fe²(+) was 20.0 mg/L. And when the concentration of Fe³ (+) was 5.0 mg/L, the degradation rate was only 68.6% after 10 minutes CGDE treatment. The reaction mechanisms were also well illustrated by relative reactions and their rate constants. It had been demonstrated that CB underwent oxidative degradation in CGDE.
Asunto(s)
Colorantes/química , Electrólisis , Contaminantes Químicos del Agua/química , Catálisis , Concentración de Iones de Hidrógeno , Hierro/química , Espectrofotometría Ultravioleta , TemperaturaRESUMEN
Characteristics of the spatial and temporal distributions of selected dissolved heavy metals (Cu, Zn, Pb, Hg and Cd) in Bohai Bay, north China was investigated. Water samples from 22 sites were collected and analyzed for the selected metals with atomic absorption spectrometry from the year of 1996 to 2005. Relatively high concentrations of Cu, Zn, Pb and Hg were detected, with maximum concentrations in the 10-year period of 16.30, 422.00, 40.40, 0.23 µg/L respectively. The concentrations of Cd in all samples were quite low, with maximum level of 0.89 µg/L. The spatial distribution of dissolved Cu, Zn and Pb was analogous, where their average concentrations generally descended from the coastline to the central areas of the bay. Differently, for Hg and Cd, relatively high concentrations occurred not only in inshore but also in offshore areas. Measured data of heavy metals were compared with sea water quality standard of China (SWQSC). Cd concentrations in all samples were below SWQSC Grade-I. The percentages of Cu, Zn, Pb, and Hg at Grade-III levels in Bohai Bay were 2.67%, 30.00%, 30.43% and 0.36%, respectively, suggesting the severe contamination of Zn and Pb in this area. Terrestrial inputs via different rivers and sewages may be the important source for the heavy metals contamination.
Asunto(s)
Metales Pesados/análisis , Agua de Mar/química , Contaminantes Químicos del Agua/análisis , China , Monitoreo del Ambiente , Contaminación Química del Agua/estadística & datos numéricosRESUMEN
The concentration and speciation of six heavy metals in sediments of eight sampling sites of Haihe River were investigated. The metals, namely Cd, Cu, Co, Ni, Mn and Pb were considered. By using sequential extraction (SE), the total metals were divided into five fractions: exchangeable, carbonate bound, iron/manganese oxide bound, sulfides and organic matter fraction and residual fraction. A multivariate statistical approach (principal component analysis, PCA) was used to evaluate the contamination of heavy metals by the total levels and chemical forms, respectively. The results showed that the total metals concentration (TMC) could not provide sufficient and accurate information because the mobility, bioavailability and toxicity of metals depend not only on their total concentration but also on the physicochemical form in which they occur.
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Sedimentos Geológicos/química , Metales Pesados/análisis , Contaminantes Químicos del Agua/análisis , ChinaRESUMEN
Twenty-one sediment samples in 11 sites along the Haihe River and Dagu Drainage River, Tianjin, China, were analyzed to investigate the pollution status and bioavailability of mercury (Hg). The results showed that the Haihe River was slightly polluted with Hg when flowing through Tianjin city. On the contrary, the sediments collected from Dagu Drainage River, an important drainage river in Tianjin, were found to have very high Hg concentrations and the highest concentration reached 8779.1 ng g(-1) (dry weight). The methylmercury (MeHg) concentrations accounted for 0.1-2.4% (average: 0.9%) of total mercury (HgT) and were strongly influenced by HgT (r=0.91, p=0.99, n=20) and total organic carbon (TOC; r=0.76, p=0.99, n=20) contents in sediments. Moreover, a five-step sequential selective extraction (SSE) procedure was used to study the bioavailability of Hg in sediments. The mercury in sediments existed mainly as element Hg and mercury sulfide, which accounted for 46.5% and 39.0% of HgT, respectively. The percentage of exchangeable Hg (defined as water soluble Hg plus 'human stomach acid' soluble Hg) was only 0.1-4.6%. The distribution of exchangeable Hg showed an obvious difference to that of HgT, indicating that the HgT concentrations were absolutely insufficient to evaluate the risk of Hg in sediments.
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Sedimentos Geológicos/química , Mercurio/análisis , Mercurio/farmacocinética , Contaminantes del Agua/análisis , Contaminantes del Agua/farmacocinética , Disponibilidad Biológica , China , Monitoreo del Ambiente , Ríos , SolubilidadRESUMEN
The wide occurrence of estrogenic compounds 4-tert-octylphenol, 4-nonylphenol, bisphenol A in surface water of Guanting Reservoir was successfully determined. The target compounds in water samples were preconcentrated by liquid-liquid extraction with dichloromethane, derivatized by trifluoroacetic anhydride, and quantified by gas chromatography-mass spectrometry(GC-MS) with selected ion monitoring (SIM). In the selected seven sampling sites (S1-S7), the concentration of NP in sample S7 was significantly higher than the other in reservoir. The status of pollution in S3 and S7 were much more serious. The concentrations of OP, NP and BPA were in the range of 44.5-48.8, 221.6-349.6 and 30.2-82.7 ng/L, respectively. The pollutants were mainly inputted from the upper river and released from sediments in Guanting Reservoir.
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Monitoreo del Ambiente/estadística & datos numéricos , Fenoles/análisis , Abastecimiento de Agua/análisis , Compuestos de Bencidrilo , China , Monitoreo del Ambiente/métodos , Cromatografía de Gases y Espectrometría de MasasRESUMEN
The estrogenic pollutants 4-tert-octylphenol (OP), 4-nonylphenol (NP) and bisphenol A (BPA) were determined in surface water samples from the Haihe River, Tianjin, China. The analytes were extracted and concentrated from 300 ml acidified water samples by liquid-liquid extractions using dichloromethane, derivatized with trifluoroacetic anhydride, and quantified by gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring (SIM). Among the samples collected from 14 sampling sites, only one sample was found to have a relatively high concentration of BPA (8.30 microgl(-1)) and NP (0.55 microgl(-1)). The concentrations of OP, NP and BPA in the other samples were in the range of 18.0-20.2, 106-296 and 19.1-106 ngl(-1), respectively. Recoveries for OP, NP and BPA in the spiked water samples were all over 80%.
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Monitoreo del Ambiente/métodos , Estrógenos no Esteroides/análisis , Fenoles/análisis , Tensoactivos/análisis , Contaminantes Químicos del Agua/análisis , Compuestos de Bencidrilo , China , Cromatografía de Gases y Espectrometría de Masas , RíosRESUMEN
In the presence of polymeric M [meso-tetra (4,4'-biphenybisulfony) phenylporphyrin] (PMTBPBSOPP, M = Co, Mn, Cu, Zn, Fe), the photocatalytic oxidative degradation of acridine orange (AO) was investigated under conditions of irradiation with high-pressure mercury lamp (HPML), iodine tungsten lamp (ITL) and natural sunlight (NSL), respectively. The results indicated that PCoTBPBSOPP had remarkable effects on photodegradation of AO under NSL irradiation. The experiments also proved that the photocatalytic degradation of AO in aqueous solutions could be enhanced when hydrogen peroxide 0.4 g/L was added. When the initial concentration of AO was 43.8 mg/L, the degradation and the decolorization rates of AO under HPML irradiation were up to 98% and 97%, respectively. A number of factors affecting photocatalytic degradation effects, such as the initial concentration of AO, light sources, pH etc., were studied in detail. The experimental results confirmed that polymeric metalloporphyrins could fully decompose AO by using artificial light source such as HPML and ITL, moreover could degrade AO rapidly under NSL in 3 h. Definitely, polymer of metalloporphyrins in the heterogeneous photocatalysis phase had a potential application