摘要:

Both surface and groundwater are threatened by buried waste at a number of sites because of subsurface plumes containing dense non‐aqueous phase liquids (DNAPLs), hazardous metals, and radionuclides. In this work, a novel process is explored which represents an enhancement to thermal extraction methods as well as a mobile system that is suitable for remediation of remote sites. Solar radiation is collected by modular concentrators which transfer the concentrated solar radiation to an optical waveguide (OW) transmission line consisting of low‐loss optical fibers. The OW line transmits the high intensity solar radiation to the contaminated site where the solar flux is injected into the soil for thermally enhanced soil vapor extraction (SVE). The organic compounds driven out of the soil go through off‐gas treatment. A small prototype was constructed and used to heat soil contaminated with trichloroethylene (TCE). The thermal efficiency of the solar SVE process conducted using the small scale experiment was approximately 50%. The moisture loss in the soil sample correlated to the soil heating time. Short heating times were sufficient to remove TCE from soil samples below detection limits.

ISSN:1093-4529    

DOI:10.1080/10934520009377004

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A fluidized‐bed reactor (FBR) was employed in the study to remove lead from the synthetic wastewater by crystallization of metal carbonate precipitates on surfaces of the sand grains. For the influent concentration up to 40 mg/L, lead removal efficiency reached 99 % and the effluent concentration was less than 1 mg/L when the system was operated with a series of optimum conditions. Feed ratio CT/[Pb2+] and recycle ratio should be maintained at 3 mol/mol and 0.67, respectively, and the hydraulic load should not be more than 22 m/h. The optimum pH for lead carbonate crystallization was 8 to 9, while the ratio of bed height to total height of the FBR was 0.25 to 0.3. In addition, the stable operation in terms of lead removal and solution turbidity was observed after a 380‐minute operation. Analysis of the composition of crystals deposited on the sand grains surface showed that nearly 99 % was lead salt. Furthermore the lead ions can be easily recovered by adding hydrochloride acid. This lead solution could be suitable for further industrial purposes.

ISSN:1093-4529    

DOI:10.1080/10934520009377005

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The leaves of aquatic liverwort,Scapania undulata,growing in neutral water contained higher levels of Al, Ca, Fe, and Mn than the leaves of plants from an acidic site. Comparison of the metal concentrations in the leaves and cell walls indicated that Al, Fe, and Mn were localized exclusively in the cell walls. Hematoxylin staining of leaves and the cell wall fraction confirmed the localization of Al in the cell walls. The metal ions were released when the cell wall fraction was incubated in a solution with a pH lower than 4.0, but not when the pH was higher than 5.0. Anionic functional groups in the leaves can act as ligands for metal ions, and competition between these ions and H+may account for the higher metal content of the liverworts from the neutral site.

ISSN:1093-4529    

DOI:10.1080/10934520009377006

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The stabilization of toxic metals (Cd, Zn, Pb, Cu and Mn) in a solid waste from a zinc refinery was studied by the addition of either a synthetic adsorbent (zeolite A) or an organic adsorbent (dried water hyacinth and rice hull carbon). The stabilization ability of an adsorbent was evaluated by means of sequential extraction, which separated the metals into five fractions. Metals extracted in the first two fractions by relatively weak solvents are considered as mobile. These metal contents provide an estimation of the amount available for plant uptake. Metals extracted in the last three fractions are considered to be immobile. Stabilization ability of an adsorbent when mixed with solid waste can be considered as the transformation of a metal from mobile to immobile form.

ISSN:1093-4529    

DOI:10.1080/10934520009377007

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Effects of organic compounds, surfactants, and salinity on the rates of volatilization of benzene, toluene, ethylbenzene, p‐xylene, and m‐xylene (BTEX) mixtures were investigated by measuring the half‐life of volatilization under temperatures of 15°C, 30°C, and 45°C. With the assumption that the volatilization process might be viewed as a first order reaction, both the dependence of the concentration of additional chemicals on half‐life and the relative magnitude of reduction effects of different additional chemicals were examined with the activation energy value, Ea. It was found that the inhibition effects would increase as the molecular weight of organic compounds increased. The hydrophobic surfactant induces a larger Eathan the hydrophilic surfactant and high concentration salinity (3.5% NaCl) only increases Easlightly. It was concluded that cosolvents with more hydrophobic groups have a larger inhibition for the emission rates because of the enhancement of solubility of BTEX in water.

ISSN:1093-4529    

DOI:10.1080/10934520009377008

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The purpose of this study is to show the results of the physicochemical treatment of leachates from a municipal solid waste (MSW) landfill sited in Madrid (Spain). Different techniques of contamination elimination were studied to reduce the concentration of contaminants in solution and suspended matter.

ISSN:1093-4529    

DOI:10.1080/10934520009377009

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Arsenic concentrations were compiled for 173 wells in an agricultural region of west central Texas. Wells in the study area produce water from the High Plains (Ogallala) Aquifer. Historically, arsenic compounds were applied to cotton fields in the study area, and they are also present in local rock formations. A geographic information system (GIS) was used to map and evaluate arsenic levels in groundwater. Arsenic was detected in every well, in concentrations ranging from 1.1–171.9 μg/L. Ten observations exceeded 10 μg/L. Several lines of evidence suggest the arsenic came from pesticides instead of local rock formations. These include higher arsenic levels at shallower water table depths, other agricultural chemicals in groundwater, incompatible hydraulic head differentials between the High Plains Aquifer and potential arsenic‐bearing formations, and low arsenic levels in groundwater of potential arsenic‐bearing formations.

ISSN:1093-4529    

DOI:10.1080/10934520009377010

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The effects of hydrophilic and hydrophobic structures of selected nonionic surfactants on surfactant sorption and diesel removal in the system of kaolin soil were studied to have an insight into the criteria of surfactant selection for surfactant‐enhanced remediation of diesel‐contaminated soil. The capability of surfactants for diesel removal could be correlated with the extent of surfactant sorption on kaolin soil. Surfactants with higher degree of ethoxylation in their hydrophilic moiety showed less sorption and improved diesel removal. Surfactants with shorter hydrocarbon chain and unsaturated carbons in their hydrophobic moiety showed less sorption and superior diesel removal. In all cases tested in this study, less sorbed surfactants showed higher diesel removal. Among 11 nonionic surfactants we examined, Brij 35, Brij 58, and Brij 98 were the best for diesel removal and showed low extent of sorption.

ISSN:1093-4529    

DOI:10.1080/10934520009377011

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Thirty‐two oil boilers were studied for the emissions of particulate, metals and volatile organic compounds (VOCs) from stack exhaust. Results of the sums of fourteen metals in particulate are 3.5–23 mg/L oil. Emission factors of particulate are 0.09–6.53 g/L, and sums of seventeen VOCs are 0.1 mg/L oil.

ISSN:1093-4529    

DOI:10.1080/10934520009377012

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The objective of this study was to investigate the effects of spent polyethylene (PE) addition on the mechanical stability and leachability bituminized waste forms. The waste used for experiments was the actual sludge generated from an industrial plating factory and spent PE generated from an agricultural polyethylene film, respectively. The bitumen used in sample preparation is straight‐run distillation bitumen, a paving asphalt. Bituminized waste forms with PE contents of 5 wt% or more resulted in maintaining dimensional and mechanical stability. The compressive strength and softening point of bituminized waste forms increase in proportion to the amount of spent PE. Moreover, the enhanced mechanical stability is possible to evaluate the bituminized waste forms exactly. The precise leach test cannot be performed because of the deformation of the bituminous specimen. Leach test revealed that the principal leaching mechanism of metals (Zn, Cr, Cu) from bituminized waste forms is diffusion.

ISSN:1093-4529    

DOI:10.1080/10934520009377013

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor