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针对土壤的塑料污染问题,提出一种采用热脱附降解技术修复污染土壤的方法。选取4种土壤中常见的残留塑料(聚乙烯(PE)、聚氯乙烯(PVC)、聚对苯二甲酸乙二酯(PET)、聚丙烯(PP))为研究对象,通过控制热解温度和土壤含水率对各污染土壤的修复效果进行探究。实验结果表明:在500 ℃的最佳热解温度下处理60 min,PE、PVC、PET和PP的去除率分别达到92.61%、91.73%、90.74%和93.42%;土壤含水率低于16%时对修复效果的影响不显著。表征结果显示,500 ℃热解后土壤中残留有机成分已得到充分挥发,热解油的主要组分为烷烃。 相似文献
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采用热解重量分析法研究了废轮胎粉、炼焦煤粉(简称煤粉)及混合样的热解特性。实验结果表明,废轮胎粉的热解出现三个显著的失重峰,煤粉热解仅出现一个显著失重峰。与煤粉热解相比,废轮胎粉热解开始失重温度和失重基本结束的温度相对较低,失重速率较大,且失重量较大。煤粉与废轮胎粉的显著失重存在重叠的温度区间(360~450℃),说明废轮胎粉与煤粉可以进行共热解。随废轮胎粉质量分数增加,共热解物料总失重率增加。废轮胎粉与煤粉共热解存在协同效应,在280~540℃时协同效应抑制共热解挥发分的逸出,导致失重量降低,最大失重速率峰温升高;高于540℃后,协同效应促进共热解反应,使共热解总失重率增大。 相似文献
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合成塑料的生物降解性及其检测 总被引:1,自引:0,他引:1
本文介绍了合成塑料的生物降解性、降解取决因素、微生物所起分解作用的形式、降解机理以及国内外多种常用的和改良的检测其生物降解性的方法,并指出对可生物降解性合成塑料的开发是解决废塑料物品在环境中累积的有效手段。 相似文献
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概述了近年来国内外废轮胎热解回收燃料油和炭黑的研究进展,介绍了废轮胎热解的工艺、机理、动力学及设备,提出了今后废轮胎热解资源化研究的发展方向. 相似文献
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废印制线路板真空热解产物分析 总被引:1,自引:0,他引:1
在自行设计的间歇式固定床真空热解装置中热解废印制线路板(PCB),对热解产物进行了分析.在热解温度为550 ℃、热解压力为20 kPa、恒温时间为60 min的条件下,得到的热解产物质量分数为:热解渣70%;热解油3%~4%;不可冷凝热解气26%~27%.经气相色谱-质谱联用(GC-MS)分析,热解油经常压蒸馏后得到的低沸点液态油中含有29种化合物,主要有苯酚、对异丙基酚、3-乙基酚、4-甲酚及2-溴苯酚,还含有少量含溴化合物和含氯化合物.热解油经简单的蒸馏就可达到回收酚类化合物的目的.热解渣经风选可实现铜与黏附有碳黑的玻璃纤维的分离,其中铜质量分数约30%,黏附有碳黑的玻璃纤维质量分数约70%. 相似文献
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污水污泥的处理已成为令人关注的问题,传统的处理方法有许多不尽人意的地方.热解处理污泥是近年新发展的技术,其优点和可操作性受到许多研究者的关注.介绍了热解法的发展和需要解决的问题,特别介绍了国内研究较少的污泥热解的高温阶段. 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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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 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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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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Arvind Viswanathan 《Journal of Polymers and the Environment》1999,7(4):185-190
Octenyl succinate starch of degree of substitution (ds) 0.03, 0.07, and 0.11 was synthesized in an aqueous medium. These compounds were then tested for the susceptibility to enzymatic degradation. The multiple-enzyme regime of -amylase, amyloglucosidase, and pullulanase was chosen for the evaluation. This combination of enzymes had been proven to degrade 99.5% of unmodified starch to glucose and hence was chosen for this study. It was found that even small amounts of subsituent caused a considerable decrease in the extent of degradation. The net extent of degradation decreased with increasing ds. Surprisingly, the amount of glucose from all three substituted substrates was quite similar, suggesting the effect small amounts of subtituent had on the enzymatic activity. 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
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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