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801.
Properties of pyrolytic chars and activated carbons derived from pilot-scale pyrolysis of used tires
Li SQ Yao Q Wen SE Chi Y Yan JH 《Journal of the Air & Waste Management Association (1995)》2005,55(9):1315-1326
Used tires were pyrolyzed in a pilot-scale quasi-inert rotary kiln. Influences of variables, such as time, temperature, and agent flow, on the activation of obtained char were subsequently investigated in a laboratory-scale fixed bed. Mesoporous pores are found to be dominant in the pore structures of raw char. Brunauer-Emmett-Teller (BET) surfaces of activated chars increased linearly with carbon burnoff. The carbon burnoff of tire char achieved by carbon dioxide (CO2) under otherwise identical conditions was on average 75% of that achieved by steam, but their BET surfaces are almost the same. The proper activation greatly improved the aqueous adsorption of raw char, especially for small molecular adsorbates, for example, phenol from 6 to 51 mg/g. With increasing burnoff, phenol adsorption exhibited a first-stage linear increase followed by a rapid drop after 30% burnoff. Similarly, iodine adsorption first increased linearly, but it held as the burnoff exceeded 40%, which implied that the reduction of iodine adsorption due to decreasing micropores was partially made up by increasing mesopores. Both raw chars and activated chars showed appreciable adsorption capacity of methylene-blue comparable with that of commercial carbons. Thus, tire-derived activated carbons can be used as an excellent mesoporous adsorbent for larger molecular species. 相似文献
802.
Cu,Cr and As distribution in soils adjacent to pressure-treated decks,fences and poles 总被引:1,自引:0,他引:1
Chirenje T Ma LQ Clark C Reeves M 《Environmental pollution (Barking, Essex : 1987)》2003,124(3):407-417
Chromated copper arsenate (CCA)-treated wood has been widely used in the Southeastern United States to protect wood products from microbial and fungal decay. The aims of this study were to (1). determine the distribution of arsenic (As), chromium (Cr), and copper (Cu), in soils surrounding CCA-treated wood structures such as decks, fences and poles; and (2). evaluate the impacts of these structures on As, Cr and Cu loading of the soils. Profile and lateral soil samples were collected under CCA-treated decks and adjacent to poles and fences. The results showed elevation of As, Cr and Cu concentrations close to and under the structures, with mean As concentrations as high as 23 mg x kg(-1) close to utility poles compared with less than 3 mg x kg (-1) at distances of about 1.5 m away. Concentrations of As, Cr, and Cu decreased with depth in areas close to CCA-treated poles. However, these results were only apparent in relatively new structures. A combination of weathering and leaching with time may have reduced the impact in older poles. Increased concentrations of As, Cu and Cr were also observed close to CCA-treated decks and fences, with age showing a similar impact. These results are helpful for CCA-treated wood product users to determine the safe use of these structures. 相似文献
803.
Z. Ning C.S. Cheung Y. Lu M.A. Liu W.T. Hung 《Atmospheric environment (Oxford, England : 1994)》2005,39(40):7880-7893
The aim of the work presented here is to study experimentally and numerically the dispersion characteristics of vehicular exhaust plume at an idle condition in an idealized and simplified environment. The gaseous and particulate concentrations in the exhaust plume of three idling motor vehicles were measured in an isolated environment under calm weather conditions. Despite the difference in the initial concentrations, the pollutants decayed exponentially in all directions.The CFD code PHOENICS 3.3, with the k–ε eddy dissipation sub-model, was used for the numerical simulation. The simulated results match very well with the experimental results close to the source of emission but decay to the ambient concentrations much slower. The effects of the initial emission concentration, exit velocity, exit direction and crosswind intensity have been investigated parametrically. The initial pollutant concentration will increase the local concentrations but the pattern of dispersion remains the same. The exit velocity will increase the momentum of the jet, resulting in a deeper penetration downstream. The exit angle has a stronger influence on pollutant dispersion than both initial pollutant concentration and exit velocity. When the exit angle is 15°, the pollutants tend to spread on the ground region. Crosswind shows a significant effect on the dispersion of the exhaust plume also. It will divert the plume to disperse in the same direction of the wind with limited penetration in the downstream direction. 相似文献
804.
Degradation of 4-chlorophenol by microwave irradiation enhanced advanced oxidation processes 总被引:3,自引:0,他引:3
In this work the synergistic effects of several microwave assisted advanced oxidation processes (MW/AOPs) were studied for the degradation of 4-chlorophenol (4-CP). The efficiencies of the degradation of 4-CP in dilute aqueous solution for a variety of AOPs with or without MW irradiation were compared. The results showed that the synergistic effects between MW and H2O2, UV/H2O2, TiO2 photocatalytic oxidation (PCO) resulted in a high degradation efficiency for 4-CP. The potential of MW/AOPs for treatment of industrial wastewater is discussed. 相似文献
805.
Manganese uptake and accumulation by the hyperaccumulator plant Phytolacca acinosa Roxb. (Phytolaccaceae) 总被引:9,自引:0,他引:9
Xue SG Chen YX Reeves RD Baker AJ Lin Q Fernando DR 《Environmental pollution (Barking, Essex : 1987)》2004,131(3):393-399
The perennial herb Phytolacca acinosa Roxb. (Phytolaccaceae), which occurs in Southern China, has been found to be a new manganese hyperaccumulator by means of field surveys on Mn-rich soils and by glasshouse experiments. This species not only has remarkable tolerance to Mn but also has extraordinary uptake and accumulation capacity for this element. The maximum Mn concentration in the leaf dry matter was 19,300 microg/g on Xiangtan Mn tailings wastelands, with a mean of 14,480 microg/g. Under nutrient solution culture conditions, P. acinosa could grow normally with Mn supplied at a concentration of 8000 micromol/l, although with less biomass than in control samples supplied with Mn at 5 micromol/l. Manganese concentration in the shoots increased with increasing external Mn levels, but the total mass of Mn accumulated in the shoots first increased and then decreased. At an Mn concentration of 5000 micromol/l in the culture solution, the Mn accumulation in the shoot dry matter was highest (258 mg/plant). However, the Mn concentration in the leaves reached its highest value (36,380 microg/g) at an Mn supply level of 12,000 micromol/l. These results confirm that P. acinosa is an Mn hyperaccumulator which grows rapidly, has substantial biomass, wide distribution and a broad ecological amplitude. This species provides a new plant resource for exploring the mechanism of Mn hyperaccumulation, and has potential for use in the phytoremediation of Mn-contaminated soils. 相似文献
806.
807.
808.
809.
超声-过氧化氢-氧化铜组合技术催化氧化水中苯酚 总被引:4,自引:0,他引:4
研究了超声-H2O2-CuO组合技术对苯酚的降解效果。考察了苯酚初始浓度、溶液温度及鼓入空气对苯酚去除率的影响。实验结果表明,与未鼓入空气时相比,连续鼓气时苯酚的降解效果较好;初始浓度低,苯酚去除率高;溶液温度从20%上升到55%时,苯酚去除率随温度升高而增大,温度对该过程的影响主要表现为对催化剂的影响而不是对超声作用的影响。高效液相色谱分析表明,苯酚降解的中间产物主要为对苯二酚、邻苯二酚及其他有机小分子物质,最终产物为草酸、二氧化碳和水。 相似文献
810.
Yang Y Tao S Wong PK Hu JY Guo M Cao HY Coveney RM Zuo Q Li BG Liu WX Cao J Xu FL 《Chemosphere》2005,60(6):753-761
The dynamic exposures to HCHs of individuals born between the years 1913 and 1993 in Tianjin have been simulated by connecting a fugacity model (IV) with a multimedia exposure model. Ingestion is the most important pathway for human beings to take up HCHs, and concentrations in the human body correlate with body weight changes. Accumulations of HCHs were derived assuming that the degradation in human body behaved linearly. The health risk of exposure to HCHs was measured using cancer risk and loss of life expectancy (LLE), and LLE was modified from its original definition to incorporate a dynamic calculation that takes variances in exposure into account. Monte-Carlo simulations were run to analyze the uncertainties of the model. 相似文献