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921.
Model reactor for photocatalytic degradation of persistent chemicals in ponds and waste water 总被引:10,自引:0,他引:10
A laboratory scale flow-through model reactor for the degradation of persistent chemicals using titanium dioxide (TiO2) as photocatalyst immobilized on glass beads is presented. In the test system with a volume of 18 L contaminated water is pumped to the upper part of the floating reactor and flows over the coated beads which are exposed to UV-radiation. The degradation of two dyes of different persistance was investigated. Primary degradation of methylene blue did not fit a first order kinetic due to coincident adsorption onto the photocatalyst and direct photolysis, resulting in a half-life of 6 h. A filtrate of a green algae suspension accelerated the colour removal. In contrast, reactive red 2 was degraded only by photocatalysis; neither adsorption nor direct photolysis led to a colour removal. The course of primary degradation followed a first order kinetic with a half-life of 18 h and a rate constant of 0.04 h−1. Analysis of the degradation products indicated mineralization by detection of NO2− and NO3−, accompanied by a decrease of pH and an increase of conductivity. A successful adaptation of the model reactor (scale 1:10) to dimensions required for surface waters and waste water treatment plants would be a costefficient and environmentally sustainable application of photocatalysis for the treatment of industrially polluted water and could be of relevance for third world contries, particularly those favoured by high solar radiation. 相似文献
922.
植物SOD活性变化与其抗污能力的关系 总被引:4,自引:0,他引:4
研究了模拟酸雨、SO2单独与复合污染对水杉、杉木、龙柏3种抗污能力不同的植物SOD活性、细胞汁酸度、细胞膜透性的影响。结果表明,SOD的活性经污染后变化规律在不同植物有所不同,而这种变化与其抗污能力有关。SOD活性升高者,其抗污能力强,反之则弱,与本底值大小无关。 相似文献
923.
负载型金催化剂用于室温下CO的消除 总被引:4,自引:0,他引:4
从催化活性、抗潮湿、抗硫中毒、稳定性等方面考察了负载型金催化剂对于CO氧化反应的性能。筛选出的2-3催化剂可在-22℃下完全消除CO,并且在催化活性、抗潮湿、抗硫中毒、稳定性等方面具有现行催化剂无法比拟的优点。 相似文献
924.
煤气发生站洗冷废水治理研究 总被引:2,自引:0,他引:2
研究了以活性炭作为吸附剂处理煤气发生站废水工艺,并摸索出一整套的工艺参数。实验结果表明,采用活性炭吸附工艺使出水水质得到明显改观,硫化物、氰化物和挥发酚的去除效率均达90%以上,对CODcr、氨氮的去除也收到了明显的效果。 相似文献
925.
926.
L. De Windt A. Burnol P. Montarnal J. van der Lee 《Journal of contaminant hydrology》2003,61(1-4):303
Oxidative dissolution of uranium dioxide (UO2) and the subsequent migration of uranium in a subsurface environment and an underground waste disposal have been simulated with reactive transport models. In these systems, hydrogeological and chemical processes are closely entangled and their interdependency has been analyzed in detail, notably with respect to redox reactions, kinetics of mineralogical evolution and hydrodynamic migration of species of interest.Different codes, where among CASTEM, CHEMTRAP and HYTEC, have been used as an intercomparison and verification exercise. Although the agreement between codes is satisfactory, it is shown that the discretization method of the transport equation (i.e. finite elements (FE) versus mixed-hybrid FE and finite differences) and the sequential coupling scheme may lead to systematic discrepancies. 相似文献
927.
Juliana Aparecida Diniz Leonardo Luiz Okumura Herbert Aleixo Alexandre Gurgel Astréa Filomena Souza Silva 《Journal of environmental science and health. Part. B》2020,55(6):583-591
AbstractAn original voltammetric screening method, employing glassy carbon electrode (GCE) with the differential-pulse voltammetry technique (DPV), has been developed to determine residues of the anti-parasitic agent Ronidazole (RNZ) in bovine meat. By using cyclic voltammetry (CV), it has been demonstrated that an irreversible cathodic process occurs at approximately ?0.740?V (vs. Ag|AgCl, KCl 3?mol L?1) in a 0.100?mol L?1 phosphate buffer at pH 6.5 as supporting electrolyte. Furthermore, the behavior of RNZ in CV indicates the occurrence of a diffusion mass transfer process to the working electrode surface. The RNZ reduction mechanism was proposed as a 6-electron transfer, similar to Metronidazole under the same pH range. Quantification of RNZ and method validation were then carried out by DPV. The relative standard deviation (RSD) were 3.21% for intraday precision of 10 consecutive repetitions and 6.78% for interday precision after five analysis. Limits of detection and quantification were also obtained, and the values were 0.107 and 0.358?mg kg?1, respectively. The recovery percentage for three different concentrations of RNZ in the bovine meat matrix ranged between 98.1% and 100.3%. The method proved to be efficient for screening RNZ in bovine meat. 相似文献
928.
929.
Svecevicius G Syvokiene J Stasiŭnaite P Mickeniene L 《Environmental science and pollution research international》2005,12(5):302-305
Goal, Scope and Background Chlorite (ClO2ˉ) is a primary decomposition product when chlorine dioxide (ClO2) is added during water treatment; therefore
the toxic effects of both compounds on aquatic organisms are possible. Limited data are available concerning their toxicity
to fish. The aim of this study was to investigate sensitivity of rainbow trout to acute and chronic toxicity of chlorine dioxide
and chlorite, and to estimate the Maximum-Acceptable-Toxicant-Concentration (MATC) of those compounds in fish.
Methods The acute and chronic toxicity of chlorine dioxide and chlorite to larval and adult rainbow trout was investigated in 96-hour
to 20-day laboratory exposures evaluating the wide range spectrum of biological indices under semi-static conditions.
Results and Discussion Median lethal concentration (96-hour LC50) values derived from the tests were: 2.2 mg/l for larvae; 8.3 mg/l for adult fish
and 20-day LC50 for larvae was 1.6 mg/l of chlorine dioxide, respectively. Chlorite was found to be from 48 to 18 times less
acutely toxic to larvae and adult fish, correspondingly. Both chemical compounds induced similar toxic effects in rainbow
trout larvae during chronic tests (they affected cardio-respiratory and growth parameters), but chlorine dioxide had a higher
toxic potency than chlorite. A significant decrease in the heart rate and respiration frequency of larvae was established.
However, within an increase in exposure duration recovery of cardio-respiratory responses was seen to have occurred in larvae
exposed to chlorite. Meanwhile, in larvae exposed to chlorine dioxide, a significant decrease in cardio-respiratory responses
remained during all 20-day chronic bioassays. Chlorine dioxide also more strongly affected growth parameters of rainbow trout
larvae at much lower test concentrations. Decreased rate of yolk-sack resorption occurred only in the tests with chlorine
dioxide.
Conclusions Maximum-Acceptable-Toxicant-Concentration (MATC) of 0.21 mg/l for chlorine dioxide and of 3.3 mg/l for chlorite to fish was
derived from chronic tests based on the most sensitive parameter of rainbow trout larvae (growth rate). According to substance
toxicity classification accepted for Lithuanian inland waters, chlorine dioxide and chlorite can be referred to substances
of \moderate\ toxicity to fish.
Recommendations and Outlook Due to its very reactive nature, chlorine dioxide is rapidly (in a few hours) reduced to chlorite, which is persistent also
as a biocide but 16 times less toxic to fish, according to MATC. Therefore, it is much more likely that fish will be exposed
to chlorite than to chlorine dioxide in natural waters. Presently accepted, the Maximum-Permitted-Concentration of total residual
chlorine (TRC) in waste-water discharging into receiving waters is 0.6 mg/l. If this requirement will not be exceeded, it
is unlikely that fish would be exposed to lethal or even to sublethal concentrations of chlorine dioxide or chlorite. Furthermore,
chlorine dioxide does not generate toxic nitrogenous (chloramines) or carcinogenic organic residuals (trihalomethanes). All
these properties make chlorine dioxide a more promising biocide than chlorine. 相似文献
930.