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以共沉淀法制备的纳米Fe3O4为核,以正硅酸乙酯为硅源,通过溶胶-凝胶法制备了SiO2@Fe3O4壳-核结构纳米颗粒,再以钛酸四丁酯为钛源,通过溶胶-凝胶法、经焙烧制得TiO2/SiO2@γ-Fe2O3磁性纳米光催化剂。采用X射线衍射仪、透射电子显微镜、比表面分析仪、振动磁强计对光催化剂的结构进行了表征,以苯酚溶液为模拟废水对光催化剂的光催化性能进行了评价。实验结果表明:经500℃焙烧的光催化剂活性相为锐钛矿型TiO2;在苯酚溶液初始浓度为0.2mmol/L、苯酚溶液pH为7的条件下,COD去除率为70.9%。 相似文献
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采用臭氧氧化—曝气生物滤池( BAF)联合工艺处理低温高浓度苯酚模拟废水.应用Design - Expert 7.1设计系统对臭氧氧化高浓度苯酚模拟废水进行了参数优化.实验结果表明:在低温(5 ~ 10℃)、臭氧加入量为0.67 g/L、进水pH为9.85的条件下,臭氧氧化出水苯酚质量浓度为1 237.6 mg/L,苯酚去除率为38.12%;臭氧氧化后的废水经调节pH至7.00 ~8.00后进入BAF,经BAF处理后的出水苯酚质量浓度小于0.5 mg/L.该工艺操作简单,处理效果稳定,出水水质达到GB8978-1996《污水综合排放标准》. 相似文献
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采用臭氧氧化法处理模拟苯酚废水,考察了废水pH以及HCO3-、CO32-、HPO42-、H2PO4-和叔丁醇等·OH抑制剂对苯酚降解效果的影响。实验结果表明:苯酚降解率随废水pH的增大而增大;当废水pH=11时,降解25 min后苯酚降解率达到99.55%,比废水pH=5时提高了50.12百分点;CO32-和H2PO4-对·OH的抑制作用分别强于HCO3-和HPO42-;当叔丁醇质量浓度由0增至50 mg/L时,苯酚降解率由99.55%降至69.19%。 相似文献
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纳米TiO2光催化氧化法处理制革废水 总被引:15,自引:1,他引:15
采用纳米TiO2光催化氧化法处理制革废水。用直接冻黄和表面活性剂配制不同初始COD的模拟制革废水,正交实验结果显示:初始pH和光照时间是主要的影响因素;确定的适宜工艺条件为:初始pH6,光照时间6h,催化助剂FeCl3的加入量3.36mg/L,纳米TiO2加入量100mg/L,初始COD 144.67mg/L。采用此工艺条件对实际制:革废水进行了处理,处理后出水COD和色度去除率分别达到65.0%和91.4%,且可生化性大大提高。 相似文献
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分别采用UV-Fenton试剂氧化法、次氯酸钙氧化法和二氧化氯氧化法处理模拟聚合物驱废水,考察了各工艺条件对废水降黏效果的影响。实验结果表明:在初始废水pH为7、反应温度为50℃、反应时间为20 min的条件下,UV-Fenton试剂氧化法适宜的H2O2加入量为1 mmol/L,n(H2O2)∶n(Fe2+)=10,处理后废水降黏率达65.7%;次氯酸钙氧化法适宜的次氯酸钙加入量为500 mg/L,处理后废水降黏率达81.7%;二氧化氯氧化法适宜的二氧化氯加入量为100 mg/L,处理后废水降黏率为40.9%。3种氧化法对模拟聚合物驱废水的降黏率大小顺序为:次氯酸钙氧化法>UV-Fenton试剂氧化法>二氧化氯氧化法。 相似文献
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《Spill Science & Technology Bulletin》1999,5(2):141-151
The burning rate of a slick of oil on a water bed is calculated by a simple expression derived from a one-dimensional heat conduction equation. Heat feedback from the flame to the surface is assumed to be a constant fraction of the total energy released by the combustion reaction. The constant fraction (χ) is named the burning efficiency and represents an important tool in assessing the potential of in situ burning as a counter-measure to an oil-spill. The total heat release, as a function of the pool diameter, is obtained from an existing correlation. It is assumed that radiative heat is absorbed close to the fuel surface, that conduction is the dominant mode of heat transfer in the liquid phase and that the fuel boiling temperature remains constant. By matching the characteristic thermal penetration length scale for the fuel/water system and an equivalent single layer system, a combined thermal diffusivity can be calculated and used to obtain an analytical solution for the burning rate. Theoretical expressions were correlated with crude oil and heating oil, for a number of pool diameters and initial fuel layer thickness. Experiments were also conducted with emulsified and weathered crude oil. The simple analytical expression describes well the effects of pool diameter and initial fuel layer thickness permitting a better observation of the effects of weathering, emulsification and net heat feedback to the fuel surface. Experiments showed that only a small fraction of the heat released by the flame is retained by the fuel layer and water bed (of the order of 1%). The effect of weathering on the burning rate decreases with the weathering period and that emulsification results in a linear decrease of the burning rate with water content. 相似文献
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The degradation of cellulose (a substantial component of low- and intermediate-level radioactive waste) under alkaline conditions
occurs via two main processes: a peeling-off reaction and a basecatalyzed cleavage of glycosidic bonds (hydrolysis). Both
processes show pseudo-first-order kinetics. At ambient temperature, the peeling-off process is the dominant degradation mechanism,
resulting in the formation of mainly isosaccharinic acid. The degradation depends strongly on the degree of polymerization
(DP) and on the number of reducing end groups present in cellulose. Beyond pH 12.5, the OH- concentration has only a minor effect on the degradation rate. It was estimated that under repository conditions (alkaline
environment, pH 13.3-12.5) about 10% of the cellulosic materials (average DP = 1000-2000) will degrade in the first stage
(up to 105 years) by the peeling-off reaction and will cause an ingrowth of isosaccharinic acid in the interstitial cement pore water.
In the second stage (105-106 years), alkaline hydrolysis will control the further degradation of the cellulose. The potential role of microorganisms in
the degradation of cellulose under alkaline conditions could not be evaluated. Proper assessment of the effect of cellulose
degradation on the mobilization of radionuclides basically requires knowing the concentration of isosaccharinic acid in the
pore water. This concentration, however, depends on several factors such as the stability of ISA under alkaline conditions,
sorption of ISA on cement, formation of sparingly soluble ISA-salts, etc. A discussion of all the relevant processes involved,
however, is far beyond the scope of the presented overview. 相似文献
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Deepak Srivastava 《Journal of Polymers and the Environment》2004,12(1):27-33
Six film samples of low-density polypropylene (LDPE)/linear LDPE (LLDPE)/high-density polypropylene (HDPE) with varying ratios of LDPE (20–45 ... wt%) and LLDPE (25–50 wt%) having a fixed amount of HDPE at 30 wt% were prepared by blown film extrusion technique. The samples were aged at four different temperatures, 55°, 70°, 85°, and 100°C, for four different time periods in the interval of between 150 hours and up to 600 hours. The change in the structure of various constituents and the formation of various oxygenated (peroxy and hydroperoxy) and unsaturated groups during thermo-oxidative degradation was discussed by infrared spectroscopy. The visiosity-average molecular weight was found to have decreased slowly in the initial aging hours and temperatures, whereas it decreased by 10% with its previous value tensile strength that is, 100°C when aged for 600 hours. The tensile strength of the sample first increased by 67% at 55°C and 89% at 70°C up to 450 hours, whereas the values increased by 52.5% at 85°C and 33.9% at 100°C when aged for 150 hours and then decreased. The percentage elongation at break increased by 2.7% at 55°C and 10.7% at 70°C for 150 and 300 hours of aging, respectively, whereas the percentage decreased when aged at 85°C and 100°C for up to 600 hours of aging. The values of gel content (percent) increased and initial degradation temperature decreased with aging time and temperature. 相似文献
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S. Urstadt J. Augusta R. -J. Müller W. -D. Deckwer 《Journal of Polymers and the Environment》1995,3(3):121-131
Establishing carbon balances has been proven to be an applicable and powerful tool in testing biodegradability of polymers. In controlled degradation tests at a 4-L scale with the model polymer poly(-hydroxybutyrate) (PHB), it was shown that the degree of degradation could not be determined with satisfactory accuracy from CO2 release alone. Instead, the course of degradation was characterized by means of establishing carbon balances for the degradation of PHB withAcidovorax facilis and a mixed culture derived from compost. Different analytical methods for determining the different carbon fractions were adapted to the particular test conditions and compared. Quantitative determination of biomass and residual polymer were the main problems in establishing carbon balances. Amounts of biomass derived from protein measurements depend strongly on assumptions of the protein content of the biomass. Selective oxidation of biomass with hypochlorite was used as alternative, but here problems arose from insoluble metabolic products. Determination of soluble components with the method of chemical oxygen demand (COD) also includes empirical assumptions but seems acceptable if the dissolved carbon fraction is in the range of some 10% total carbon. Results confirm both analytical assays and theoretical approaches, in ending up at values very close to 100%, within an acceptable standard deviation range under test conditions comparable to standard test practice.Paper presented at the Bio/Environmentally Degradable Polymer Society—Third National Meeting, June 6–8, 1994, Boston, Massachusetts. 相似文献
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The effects of temperature on the release of chemical components of six solid organic materials under conditions of oversaturation were investigated in this paper. The six materials were peat moss (PM), weathered coals (WC), charred rice husks (CRH), sawdust (Sd), turfgrass clippings (TC), and chicken manure (CM). Significant differences were observed in the available nitrogen and phosphorus content of the aqueous extracts of organic materials at different temperatures. The available nitrogen content in aqueous extracts of PM and WC at 25 °C was higher than that registered at 15 °C and 35 °C. Available nitrogen content in the aqueous extracts of CRH, Sd, TC, and WC at 35 °C was higher than at 15 °C and 25 °C. The available phosphorus content in the aqueous extracts of organic materials at 35 °C was higher than that available at 15 °C and 25 °C, with the exception of Sd. In addition, the release of available phosphorus in the aqueous solution of organic materials at different temperatures varied constantly for 108 h. The release of potassium (K+) and sodium (Na+) ions in the aqueous extracts of organic materials was basically steady over time, with the exception of CM. High temperature (35 °C) may significantly hasten the release of K+ from organic substrates (except for WC) with low temperatures significantly inhibiting release of K+ in Sd and CRH. High temperatures (35 °C) might significantly facilitate the release of Na+ in CM and TC. However, no significant differences were manifested in the release of Na+ from organic substrates at different temperatures, with the exception of CM and TC. Moreover, no significant differences were observed in the release of calcium, magnesium and iron ions with time, nor were there any significant differences in the contents of iron ions in the aqueous extracts of organic materials at different temperatures. The results indicate that multiple mediums should be pretreated in water for a week before being used for planting. They should be used when all mineral elements of organic materials are steady and ignoring the effect of organic mediums. 相似文献
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Ülis Sõukand Pille Kängsepp Rutt Kakum Toomas Tenno Lennart Mathiasson William Hogland 《Journal of Material Cycles and Waste Management》2010,12(1):57-65
The simultaneous adsorption of copper (Cu), cadmium (Cd), nickel (Ni), and lead (Pb) ions from spiked deionized water and
spiked leachate onto natural materials (peat A and B), by-product or waste materials (carbon-containing ash, paper pellets,
pine bark, and semi-coke), and synthetic materials (based on urea-formaldehyde resins, called blue and red adsorbents) or
mixtures thereof was investigated. The adsorbents that gave the highest metal removal efficiencies were peat A, a mixture
of peat B and carbon-containing ash, and a mixture of peat A and blue. At an initial concentration of 5 mg/l for each metal,
the removal of each species of metal ion from spiked water and spiked leachate solutions was very good (>90%) and good (>75%),
respectively. When the initial concentration of each metal in the solutions was twenty times higher (100 mg/l), there was
a noticeable decrease in the removal efficiency of Cu2+, Cd2+, and Ni2+, but not of Pb2+. Langmuir monolayer adsorption capacities, qm, on peat A were found to be 0.57, 0.37, and 0.36 mmol/g for Pb2+, Cd2+, and Ni2+, respectively. The order of metal adsorption capacity on peat A was the same in the case of competitive multimetal adsorption
conditions as it was for single-element adsorption, namely Pb2+ > Cd2+ ≥ Ni2+. The results show that peat alone (an inexpensive adsorbent) is a good adsorbent for heavy metal ions. 相似文献
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采用结构化/非结构化混合网格技术、多孔介质模型及k-ε两方程湍流模型,对某袋式除尘器及进出口管道内的气体流场进行了数值计算.计算结果表明,合理布置导流板后,袋式除尘器两箱体流量偏差为1.8%;除尘器下游滤袋单元处理气量偏大,中游滤袋单元处理气量较小,最大流量与最小流量偏差为22.3%;靠近除尘器进口处灰斗内存在气流回流特性,易造成粉尘的二次附着现象. 相似文献
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Somani Mohit Datta Manoj Ramana G. V. Hölzle Ingo Sundaram Ravi Sreekrishnan T. R. 《Journal of Material Cycles and Waste Management》2022,24(5):1902-1912
Journal of Material Cycles and Waste Management - This study characterizes the municipal solid waste (MSW) accumulated for more than 25 years at Bhalswa dumpsite, Delhi, India. 50... 相似文献
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The chemical recycling of poly(lactic acid) (PLA) to its monomer is crucial to reduce both the consumption of renewable resources for the monomer synthesis and the environmental impact related to its production and disposal. In particular, the production of lactic acid from PLA wastes, rather than from virgin raw materials, it is also possible to achieve considerable primary energy savings. The focus of this work is to analyse deeply the PLA hydrolytic decomposition by means of a kinetic model based on two reactions mechanism. To this end, new experimental data have been gathered in order to investigate a wider temperature range (from 140 to 180 °C) and to extend the water/PLA ratio up to 50 % of PLA by weight. The reported results clearly highlight that more than 95 % of PLA is hydrolyzed to water-soluble lactic acid within 120 min, when it is hydrolyzed within 160–180 °C. Furthermore, the kinetic constant is highly influenced by reaction temperature. The proposed “two reactions” kinetic mechanism complies satisfactorily with the experimental data under analysis. 相似文献