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31.
32.
污泥吸附剂对3种染料吸附动力学的研究 总被引:1,自引:5,他引:1
以污水厂脱水污泥、锯末和焦油的混合物为原料,选择ZnCl2为活化剂制备出过渡孔发达、强度大的污泥吸附剂(S-AC)。借助BET、FT-IR等现代分析测试方法对污泥吸附剂进行表征,同时,研究了吸附剂对酸性大红、中性红和碱性品红吸附动力学行为。结果表明,制得的污泥吸附剂BET比表面积为358 m2/g,强度大于89%。吸附剂的动力学数据均符合伪二阶动力学方程、液膜扩散方程和颗粒内扩散方程,其中液膜扩散为吸附剂对酸性大红吸附过程的主控步骤,颗粒内扩散为吸附剂对中性红和碱性品红吸附过程的主控步骤。 相似文献
33.
SBR降解动力学研究 总被引:1,自引:0,他引:1
采用SBR工艺处理有机废水,在已有工艺条件下对生物降解动力学进行了研究,得出生物降解反应为一级反应。研究表明,用Monod公式能较好反映出有机物的降解规律,确定了其动力学参数Vmax=14.6306 d-1,Ks=83.2993 mg/L,得出SBR降解动力学模型为V=14.6306X·S/(83.2993+S)。利用以动力学为基础的动态模拟法优化SBR工艺,实验结果表明该方法合理可行,对SBR的设计与运行有一定的指导作用,可作为SBR反应器扩大实验和设计的依据。 相似文献
34.
35.
活性炭纤维对水中微囊藻毒素的吸附性能 总被引:1,自引:0,他引:1
利用活性炭纤维对水中微囊藻毒素MC—LR的吸附,研究了吸附过程的热力学与动力学特性。结果表明,活性炭纤维对MC—LR的平衡吸附量在相同温度下随MC-LR初始浓度的增加而显著增大,并随着温度升高而增加,最大吸附量达246μg/g。不同温度条件下,活性炭纤维对MC-LR的吸附均较好地符合Langmuir等温吸附模型。通过热力学分析发现,△H=15.7kJ/mol、△G〈0、△S〉0,表明该吸附是自发的、吸热的过程,温度升高有利于吸附反应。动力学研究表明,该过程符合一级动力学方程。吸附反应速率受颗粒内扩散和液膜扩散共同影响。活性炭纤维经再生后,平衡吸附量变化较小,具有良好的重复使用性能。 相似文献
36.
Yu X Zhou P Zhou X Liu Y 《Environmental science and pollution research international》2005,12(4):221-226
Background Little is known about metabolism rates of environmental chemicals by vegetation. A good model compound to study the variation
of rates among plant species is cyanide. Vascular plants possess an enzyme system that detoxifies cyanide by converting it
to the amino acid asparagine. Knowledge of the kinetic parameters, the half-saturation constant (Km) and the maximum metabolic
capacity (vmax), is very useful for enzyme characterization and biochemical purposes. The goal of this study is to find the
enzyme kinetics (KM and vmax) during cyanide metabolism in the presence of Chinese vegetation, to provide quantitative data
for engineered phytoremediation, and to investigate the variation of metabolic rates of plants.
Methods Detached leaves (1.0 g fresh weight) from 12 species out of 9 families were kept in glass vessels with 100 mL of aqueous
solution spiked with potassium cyanide at 23°C for 28 h. Four different treatment concentrations of cyanide were used, ranging
from 0.44 to 7.69 mg CN/L. The disappearance of cyanide from the aqueous solution was analyzed spectrophotometrically. Realistic
values of the half-saturation constant (KM) and the maximum metabolic capacity (vmax) were estimated by a computer program
using non-linear regression treatments. As a comparison, Lineweaver-Burk plots were also used to estimate the kinetic parameters.
Results and Discussion The values obtained for KM and vmax varied with plant species. Using non-linear regression treatments, values of vmax and
KM were found in a range between 6.68 and 21.91 mg CN/kg/h and 0.90 to 3.15 mg CN/L, respectively. The highest vmax was by
Chinese elder (Sambucus chinensis), followed by upright hedge-parsley (Torilis japonica). The lowest vmax was demonstrated
by the hybrid willow (Salix matssudana x alba). However, the highest KM was found in the water lily (Nymphea teragona), followed
by the poplar (Populus deltoides Marsh). The lowest KM was demonstrated by corn (Zea mays L.). The values of vmax were normally
distributed with a mean of 13 mg CN/kg/h.
Conclusions Significant removal of cyanide from aqueous solution was observed in the presence of plant materials without phytotoxicity,
even at high doses of cyanide. This gives rise to the conclusion that the Chinese plant species used in this study are all
able to efficiently metabolize cyanide, although with different maximum metabolic capacities. A second conclusion is that
the variation of metabolism rates between species is small. All these plants had a similar KM, indicating the same enzyme
is active in all plants.
Recommendations and Outlook Detoxification of cyanide with trees seems to be a feasible option for cleaning soils and water contaminated with cyanide.
For phytoremediation projects, screening appropriate plant species adapted to local conditions should be seriously considered.
More chemicals should be investigated to find common principles of the metabolism of environmental chemicals by plants. 相似文献
37.
Previous work has shown that arsenic can accumulate in drinking water distribution system (DWDS) solids (Lytle et~al., 2004) when arsenic is present in the water. The release of arsenic back into the water through particulate transport and/or
chemical release (e.g. desorption, dissolution) could result in elevated arsenic levels at the consumers' tap. The primary
objective of this work was to examine the impact of pH and orthophosphate on the chemical release (i.e. desorption) of arsenic
from nine DWDS solids collected from utilities located in the Midwest. Arsenic release comparisons were based on the examination
of arsenic and other water quality parameters in leach water after contact with the solids over the course of 168~hours. Results
showed that arsenic was released from solids and suggested that arsenic release was a result of desorption rather than dissolution.
Arsenic release generally increased with increasing initial arsenic concentration in the solid and increasing pH levels (in
the test range of 7 to 9). Finally, orthophosphate (3 and 5 mg PO4/L) increased arsenic release at all pH values examined. Based on the study results, utilities with measurable levels of arsenic
present in their water should be aware that some water quality changes can cause arsenic release in the DWDS potentially resulting
in elevated levels at the consumer's tap. 相似文献
38.
39.
羊角月芽藻摄取磷形态的动力学研究 总被引:4,自引:0,他引:4
将湖水中的磷分成总溶解磷,溶解反应磷,总反应磷、溶解的水解性磷,溶解的光解性磷。研究其在羊角月芽过程中的变化。 相似文献
40.
Canterino M Marotta R Temussi F Zarrelli A 《Environmental science and pollution research international》2008,15(3):182-187
BACKGROUND: Synthetic musk compounds are widely used as additives in personal care and household products. The photochemical degradation of musk tibetene in aqueous solutions or in acetonitrile/water mixtures under different conditions was studied in order to assess its environmental fate. METHODS: Musk tibetene dissolved (or suspended) in water and/or acetonitrile/water mixtures was irradiated at different times by UV-light and by solar light. The irradiation mixtures were analyzed by NMR and TLC. The photoproducts formed were identified by GC-MS and NMR data. RESULTS: The experimental results indicated that musk tibetene was photodegradable in water or acetonitrile/water mixtures with half-life reaction times close to 20 minutes. The irradiation mixtures were separated by chromatographic techniques yielding three photoproducts (3,3,5,6,7-pentamethyl-4-nitro-3H-indole, 3,3,5,6,7-pentamethyl-4-nitro-1H-indoline and 3,3,5,6,7-pentamethyl-4-nitro-3H-indolinone) identified by means of spectroscopic analysis. DISCUSSION: The numerical modelling of the photodegradation concentration-time profiles gave (8.13 +/- 0.15) x 10(-2) and (1.34 +/- 0.04) x 10(-2) mol/E for the overall primary quantum yield of direct photolysis for musk tibetene and the major intermediate (3,3,5,6,7-pentamethyl-4-nitro-3H-indolinone), respectively, in the wavelength range 305-366 nm. The half-life times of photodegradation of the both substances varied from 1-1.5 hours at 20 degrees N during the summer season to 6-10 hours for highest latitudes in winter. CONCLUSIONS: Under solar light, musk tibetene was photolabile in acetonitrile and acetonitrile/water 1/1, while it was slowly degraded when suspended in water. In all media, musk tibetene was photodegraded into three photoproducts. By using a kinetic model, the overall primary quantum yields of direct photolysis of musk tibetene and its main photoproduct, in the wavelength range 305-366 nm, were estimated, indicating that the photodegradation rate for musk tibetene is faster than the photolysis rate of the major by-product. RECOMMENDATIONS AND PERSPECTIVES: The results indicate that, in order to assess the environmental impact of musk tibetene on the aquatic ecosystem, great attention should be focused on the major photoproduct which is proved to be more persistent than the parent compound under light irradiation. The predicted half-life times of direct photolysis for both substances ranged from 1-1.5 hours at 20 degrees N during the summer season to about 6-10 hours for highest latitudes in winter, indicating that, from a photochemical point of view, the environmental persistence of these substances increases by increasing the latitudes and during the cold seasons, making more realistic an intake of these xenobiotic molecules into the food chain of aquatic living organisms. Tanabe reports in his Editorial (Tanabe 2005) that "It is necessary to have knowledge of the global picture of synthetic musk pathways. So, it is conceivable that now is the time to study the transport, persistency, distribution, bioaccumulation and toxic potential of this new environmental menace on a global scale, especially in developing countries". Therefore, the future environmental analysis and investigations on the eco-toxicity of nitro musk compounds should take into account not only the presence of the parent compounds but also their photochemical intermediates or end-by-products. 相似文献