共查询到20条相似文献,搜索用时 328 毫秒
1.
Zhenzi Jing Fangming Jin Nakamichi Yamasaki Hirotaka Maeda Emile H. Ishida 《Journal of environmental management》2009
Hydrothermal solidification of riverbed sediments (silt) has been carried out in a Teflon (PTFE) lined stainless steel hydrothermal apparatus, under saturated steam pressure at 343–473 K for 2–24 h by calcium hydrate introduction. Tobermorite was shown to be the most important strength-producing constituent of the solidified silt. A longer curing time or a higher curing temperature was shown to be favorable to the tobermorite formation, thus promoting strength development; however, overlong curing time (24 h) seemed to affect the strength development negatively. The hardening mechanism consisted of the crystal growth/morphology evolution during the hydrothermal process. The species dissolved from the silt were precipitated first as fine particles, and then some of the particles seemed to build up the rudimental morphology of calcium silicate hydrate (CSH) gel. The CSH gel, with precipitated particles, appeared to cause some reorganization within the matrix, which made the matrix denser and thus gave an initial strength development. Tobermorite, transformed inevitably from the CSH gel, reinforced the matrix with its interlocked structure, and thus further promoted the strength development. 相似文献
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In this study, porous calcite materials are hydrothermally treated at 200 °C using powder compacts consisting of calcite and glasses composed of silica-rich soda-lime. After treatment, the glasses are converted into calcium aluminosilicate hydrates, such as zeolite phases, which increase their strength. The porosity and morphology of new deposits of hydrothermally solidified materials depend up on the chemical composition of glass. The use of calcite and glass in the hydrothermal treatment plays an important role in the solidification of calcite without thermal decomposition. 相似文献
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An Assessment of U(VI) removal from groundwater using biochar produced from hydrothermal carbonization 总被引:1,自引:0,他引:1
Kumar S Loganathan VA Gupta RB Barnett MO 《Journal of environmental management》2011,92(10):2504-2512
The ever-increasing growth of biorefineries is expected to produce huge amounts of lignocellulosic biochar as a byproduct. The hydrothermal carbonization (HTC) process to produce biochar from lignocellulosic biomass is getting more attention due to its inherent advantage of using wet biomass. In the present study, biochar was produced from switchgrass at 300 °C in subcritical water and characterized using X-ray diffraction, fourier transform infra-red spectroscopy, scanning electron micrcoscopy, and thermogravimetric analysis. The physiochemical properties indicated that biochar could serve as an excellent adsorbent to remove uranium from groundwater. A batch adsorption experiment at the natural pH (~3.9) of biochar indicated an H-type isotherm. The adsorption data was fitted using a Langmuir isotherm model and the sorption capacity was estimated to be ca. 2.12 mg of U g(-1) of biochar. The adsorption process was highly dependent on the pH of the system. An increase towards circumneutral pH resulted in the maximum adsorption of ca. 4 mg U g(-1) of biochar. The adsorption mechanism of U(VI) onto biochar was strongly related to its pH-dependent aqueous speciation. The results of the column study indicate that biochar could be used as an effective adsorbent for U(VI), as a reactive barrier medium. Overall, the biochar produced via HTC is environmentally benign, carbon neutral, and efficient in removing U(VI) from groundwater. 相似文献
4.
Vinay Kumar Jha Masahiro Nagae Motohide MatsudaMichihiro Miyake 《Journal of environmental management》2009
Zeolitic materials have been prepared from coal fly ash as well as from a SiO2–Al2O3 system upon NaOH fusion treatment, followed by subsequent hydrothermal processing at various NaOH concentrations and reaction times. During the preparation process, the starting material initially decomposed to an amorphous form, and the nucleation process of the zeolite began. The carbon content of the starting material influenced the formation of the zeolite by providing an active surface for nucleation. Zeolite A (Na-A) was transformed into zeolite X (Na-X) with increasing NaOH concentration and reaction time. The adsorption isotherms of the obtained Na-X based on the characteristics required to remove heavy ions such as Ni2+, Cu2+, Cd2+ and Pb2+ were examined in multi-metal systems. Thus obtained experimental data suggests that the Langmuir and Freundlich models are more accurate compared to the Dubinin–Kaganer–Radushkevich (DKR) model. However, the sorption energy obtained from the DKR model was helpful in elucidating the mechanism of the sorption process. Further, in going from a single- to multi-metal system, the degree of fitting for the Freundlich model compared with the Langmuir model was favored due to its basic assumption of a heterogeneity factor. The Extended-Langmuir model may be used in multi-metal systems, but gives a lower value for equilibrium sorption compared with the Langmuir model. 相似文献
5.
Research on biofuel production pathways from algae continues because among other potential advantages they avoid key consequential effects of terrestrial oil crops, such as competition for cropland. However, the economics, energetic balance, and climate change emissions from algal biofuels pathways do not always show great potential, due in part to high fertilizer demand. Nutrient recycling from algal biomass residue is likely to be essential for reducing the environmental impacts and cost associated with algae-derived fuels. After a review of available technologies, anaerobic digestion (AD) and hydrothermal liquefaction (HTL) were selected and compared on their nutrient recycling and energy recovery potential for lipid-extracted algal biomass using the microalgae strain Scenedesmus dimorphus. For 1 kg (dry weight) of algae cultivated in an open raceway pond, 40.7 g N and 3.8 g P can be recycled through AD, while 26.0 g N and 6.8 g P can be recycled through HTL. In terms of energy production, 2.49 MJ heat and 2.61 MJ electricity are generated from AD biogas combustion to meet production system demands, while 3.30 MJ heat and 0.95 MJ electricity from HTL products are generated and used within the production system.Assuming recycled nutrient products from AD or HTL technologies displace demand for synthetic fertilizers, and energy products displace natural gas and electricity, the life cycle greenhouse gas reduction achieved by adding AD to the simulated algal oil production system is between 622 and 808 g carbon dioxide equivalent (CO2e)/kg biomass depending on substitution assumptions, while the life cycle GHG reduction achieved by HTL is between 513 and 535 g CO2e/kg biomass depending on substitution assumptions. Based on the effectiveness of nutrient recycling and energy recovery, as well as technology maturity, AD appears to perform better than HTL as a nutrient and energy recycling technology in algae oil production systems. 相似文献
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In this paper, the utilisation of zeolites synthesised from fly ash (FA) and related co-disposal filtrates as low-cost adsorbent material were investigated. When raw FA and co-disposal filtrates were subjected to alkaline hydrothermal zeolite synthesis, the zeolites faujasite, sodalite and zeolite A were formed. The synthesised zeolites were explored to establish its ability to remove lead and mercury ions from aqueous solution in batch experiments, to which various dosages of the synthesised zeolites were added. The test results indicated that when increasing synthesised zeolite dosages of 5-20 g/L were added to the acid mine drainage (AMD) wastewater, the concentrations of lead and mercury in the wastewater were reduced accordingly. The lead concentrations were reduced from 3.23 to 0.38 and 0.17 microg/kg, respectively, at an average pH of 4.5, after the addition of raw FA zeolite and co-disposal filtrate zeolite to the AMD wastewater. On the other hand, the mercury concentration was reduced from 0.47 to 0.17 microg/kg at pH=4.5 when increasing amounts of co-disposal filtrate zeolite were added to the wastewater. The experimental results had shown that the zeolites synthesised from the co-disposal filtrates were effective in reducing the lead and mercury concentrations in the AMD wastewater by 95% and 30%, respectively. 相似文献
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Hydrothermal ecosystems are of high conservation and scientific value, but they are sensitive to external perturbations that result from development. This study examines the composition of vegetation at four plots at the Wairakei-Tauhara geothermal field, New Zealand, using the Scott height-frequency method, ground temperatures at 0.1- and 1-m depth, soil pH, and photographic surveys. It highlights the response of plant communities, in particular that of Kunzea ericoides var. microflora, in terms of composition, structure, and biomass index values, measures changes in ground temperature, as well as provides baseline data against which to compare future changes. It was found that optimal growing conditions for K. ericoides var. microflora are at temperatures above background conditions with a slightly acidic pH. Plots with cooler, less acidic conditions support more diverse plant communities, which also promote the establishment of invasive species. This suggests that the largest threats to thermotolerant vegetation in New Zealand, including K. ericoides var. microflora, are further decreases in ground temperature because the establishment of invasive species may result in thermolerant vegetation being out-competed in hydrothermal ecosystems. Recognising and understanding the ecological diversity and dynamics of hydrothermal ecosystems, as well as acknowledging the competing interests between development and conservation, is key to the management and protection of these areas. 相似文献
9.
Cheryle Hislop 《The Environmentalist》2007,27(1):119-129
The notion of creating marine protected areas (MPAs) in the high seas has been hailed as “an idea whose time has come”, and
advocates are calling for them to be part of a global representative system to be established by 2012. It is argued in this
paper that embedding the high seas MPA concept in the macro-goal of a global representative system subsumes more pragmatic
and politically acceptable “micro-actions”. Development of politically contentious policy proposals such as high seas MPAs
may have a better chance of success if they proceed by increments and are negotiated outside the limelight of a full scale,
temporally defined global project. The following paper critically analyses the salience of international environmental agreements
in the context of high seas MPAs and suggests a prototype MPA established by means of a negotiated agreement between a small
number of countries which share political will and technological capacity to make a difference. Modelled on the recently implemented
Titanic Accord, the prototypical high seas MPA would allow parties to develop a collaborative, rules-based regime which could be used to
manage the actions of citizens involved in activities that may have a negative impact on the specified area. 相似文献
10.
This paper presents an experimental study on employing a pellet form of catalyst in photo-reduction of carbon dioxide with water. Water was first absorbed into titania pellets. Highly purified carbon dioxide gas was then discharged into a reactor containing the wet pellets, which were then illuminated continuously for 65 hours using UVC lamps. Analysing the products accumulated in the reactor confirmed that methane and hydrogen were produced through photo-reduction of carbon dioxide with water. No other hydrocarbons were detected. Increasing the temperature in the reactor has showed little change on the amount of methane produced. 相似文献
11.
Hung Tao Shen 《Journal of the American Water Resources Association》1980,16(6):996-1001
ABSTRACT: The rates of ice production due to surface heat loss in open water reaches of the St. Lawrence River, between the Ogdensburg-Prescott Boom and the Moses-Saunders Dam, are analyzed for the past 20 winters. Simple statistical parameters for ice production rates and air temperature are determined. Regression analyses for relationships between surface heat loss rates and freezing degree days indicate that an excellent linear correlation exists between these two variables. The study also shows that it is important to consider other heat exchange components, such as the bed heat flux and viscous dissipation, in the total ice production analysis for the river reach. 相似文献
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从生物学的角度分析了固体有机废弃物堆肥过程中微生物群落的变化,强化堆肥及减少恶臭的生物学途径,简单概述了堆肥过程中提高堆肥质量和效率的主要影响因素(温度、C/N等),最后提出了今后该领域的发展方向。 相似文献
13.
Apichat Artnaseaw 《International Journal of Green Energy》2020,17(13):846-852
ABSTRACT Carbon nanotubes have been synthesized by chemical vapor deposition at 850°C using silkworm cocoons as a precursor. The impregnation method with 3 wt% ferrocene as a catalyst was utilized for growth of carbon nanotubes. The flow rates of C2H2, H2, and N2 were fixed at 100, 150, and 350 ml/min, respectively. Morphology, microstructure and quality of the synthesized carbon nanotubes were investigated by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy techniques. Results showed that the prepared carbon nanotubes were multiwalled and good graphitic quality. When used as the cathode material for aluminum-air battery, prepared carbon nanotubes cathode exhibited higher current density than commercial graphite cathode. Based on our study, there is a successful conversion of silkworm cocoons into value-added nanomaterial products, promoting the natural biotechnological materials. 相似文献
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膜曝气生物膜反应器生物膜影响因素分析 总被引:1,自引:0,他引:1
膜曝气生物膜反应器(MABR)是一种利用透气膜进行曝气,可以实现同步硝化反硝化的污水生物处理新工艺。本文阐述了膜曝气生物反应器生物膜的原理和特点,总结了国内外在该领域的研究成果,重点介绍了C/N、氧气压力、流速、生物膜厚度、温度和pH对生物膜性能的影响。 相似文献
17.
Adsorption of Cu(II) ions from aqueous solutions on biochars prepared from agricultural by-products 总被引:3,自引:0,他引:3
Pellera FM Giannis A Kalderis D Anastasiadou K Stegmann R Wang JY Gidarakos E 《Journal of environmental management》2012,96(1):35-42
In this study, the adsorption of Cu(II) from aqueous solutions by agricultural by-products, such as rice husks, olive pomace and orange waste, as well as compost, was evaluated. The aim was to obtain sorbent materials (biochars) through hydrothermal treatment (300?°C) and pyrolysis (300?°C and 600?°C). The effect of adsorbent dose, pH, contact time and initial Cu(II) concentration in batch-mode experiments was investigated. The optimum Cu(II) adsorption conditions was found to occur at 5-12?g/L adsorbent dose, initial pH 5-6, and reaction time 2-4?h. Furthermore, the adsorption kinetics were best described by the pseudo-second order model for all the tested materials, while the adsorption equilibrium best fitted by the linear and Freundlich isotherms. Comparing rice husks and olive pomace, the higher adsorption capacity resulted after pyrolysis at 300?°C. With respect to the orange waste and compost, the highest adsorption capacity was observed using biochars obtained after hydrothermal treatment and pyrolysis at 300?°C. 相似文献
18.
气锤驱动的高加速应力试验装置,能产生温度和非高斯随机振动应力,其中振动应力是由多个气锤作六自由度运动产生的。一般用来进行高温步进、低温步进、快速温度变化、振动、快速温变和振动复合试验。目前国家标准和校准规程中均无关于该试验装置的技术参数的校准方法。本文结合试验装置的技术特点,提出了几个关于温度和振动技术参数的测量方法,如:温度偏差、温度波动度、温度均匀度、温度过冲量、温度变化速率、均方根加速度、横向振动比、功率谱密度等。 相似文献
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The use of low-cost adsorbents was investigated as a replacement for current costly methods of removing metals from aqueous solution. Removal of copper (II) from aqueous solution by different adsorbents such as shells of lentil (LS), wheat (WS), and rice (RS) was investigated. The equilibrium adsorption level was determined as a function of the solution pH, temperature, contact time, initial adsorbate concentration and adsorbent doses. Adsorption isotherms of Cu (II) on adsorbents were determined and correlated with common isotherm equations such as Langmuir and Freundlich models. The maximum adsorption capacities for Cu (II) on LS, WS and RS adsorbents at 293, 313 and 333 K temperature were found to be 8.977, 9.510, and 9.588; 7.391, 16.077, and 17.422; 1.854, 2.314, and 2.954 mg g(-1), respectively. The thermodynamic parameters such as free energy (delta G0), enthalpy (delta H0) and entropy changes (delta S0) for the adsorption of Cu (II) were computed to predict the nature of adsorption process. The kinetics and the factors controlling the adsorption process were also studied. Locally available adsorbents were found to be low-cost and promising for the removal of Cu (II) from aqueous solution. 相似文献