Experimental and theoretical study of combined solvent and steam stripping of 1,2,3,4,5,6-hexachlorocyclohexane (HCH) and mercury from contaminated natural soil

Brouwers, Hjh Jos

doi:10.1016/0304-3894(96)01776-1

Cited by 5 publications

(3 citation statements)

References 15 publications

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“…In this section the derived solutions are applied to the stripping of 1,2,3,4,5,6-hexachlorocyclohexane (chemical 1,2,3,4,5,6-C6C16H 6 (HCH formula C6C16H6, abbreviation HCH). In a previous paper, two-stage stripping experiments of natural soil contaminated with mercury and predominantly/3-HCH have been reported in more detail [Brouwers, 1996]. During this process the soil is first flushed with an organic solvent in vapor form.…”

Section: Application Of the Model To Hch Strippingmentioning

confidence: 99%

Transport models for desorption from natural soils packed in flushed columns

Brouwers¹

1999

Water Resources Research

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Abstract. This paper addresses an experimental and theoretical study of sorbed contaminant removal from a column (or reactor) by flushing. This removal may take place by either volatilization or rinsing, and nonlinear sorption is accounted for by employing a Freundlich relationship. A one-dimensional nonequilibrium transport model is proposed which describes the unsteady mass transfer between flushing medium and soil phases in the column, using a linear chemical transfer model. The moving boundary problem is transferred, and a perturbation method is employed to obtain an approximate solution of the governing equations for a small Merkel number Me (this dimensionless number comprises the product of fluid residence time and the mass transfer coefficient). The solution reveals the effect of the various parameters, such as the Freundlich parameter n, on the contaminant transport in fluid phase and decay in solid phase. Applying the model to various experimental data results in values for the overall mass transfer coefficients, which are useful for engineering computations. Furthermore, the model enables the prediction of the initial soil contamination level as well as the parameter n solely from the measured exit contaminant concentrations in the flushing fluid. A thorough comparison of this prediction with the measured soil concentration (prior to the experiments) yields good agreement. IntroductionIn order to optimize real-scale soil remediation processes, conceptual models are in use and in development. As some soil parameters are very hard or nearly impossible to assess theoretically, often bench-scale experiments are performed to investigate the feasibility of a cleaning technique. For these experiments, columns are usually used; the columns are flushed in the axial direction. Relevant experimental conditions, such as flushing velocity, flushing medium, additives, etc., can be varied, and their effect can be evaluated.Current transport models often start from nonequilibrium between contaminant in the soil and flushing fluid. As a result of this nonequilibrium, contaminant is desorbed from the soil, transferred to the flushing fluid, and removed by convective transport. In an early publication, Lapidus and Amundson [1952] equilibrium between soil and fluid phases, (2) start-up phase, (3) desorption of the contaminant, using a Freundlich isotherm, and (4) convective transport and decay of soil contamination concentration. These features are typical for flushing and remediation of soil in practice. For engineering end purposes it is of major importance to derive basic models and obtain compact analytical solutions that (1) reveal the principle prevailing phenomena of the process, (2) permit a straightforward fit with experimental data, and (3) validate more advanced numerical models. Accordingly, such an analysis has been executed and is presented here in detail. C(x = x(t), t) =Equation ( and the right-hand sides of (1) and (2) remain the same (with H set equal to unity). Hence (1) and (2) are generally applica...

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Section: Application Of the Model To Hch Strippingmentioning

confidence: 99%

Transport models for desorption from natural soils packed in flushed columns

Brouwers¹

1999

Water Resources Research

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“…Some of these processes allow decontamination of the soil in situ without excavation (). For other processes, the soil has to be excavated and is then treated in column or tube reactors ( − ). Generally steam stripping techniques have been developed successfully ().…”

Section: Introductionmentioning

confidence: 99%

Decontamination of Polyaromatic Hydrocarbons from Soil by Steam Stripping: Mathematical Modeling of the Mass Transfer and Energy Requirement

Braass¹,

Tiffert²,

Höhne³

et al. 2003

Environ. Sci. Technol.

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For cleaning of contaminated soil from polyaromatic hydrocarbons (PAH), a thermal separation process is applied. The process uses superheated steam that is supplied through a nozzle together with a suspension (approximately 40% soil content) of the contaminated soil into a tube reactor. In the reactor, the soil suspension is vaporized, and the PAH are stripped from the soil at temperatures of 140-300 degrees C. In a cyclone, a solid-vapor separation is carried out, and after going through a condenser, a separation of the condensed water and the PAH is obtained. For improvement of the economical performance, a heat recovery is integrated. This is realized by preheating the water/stream supplied to the evaporator by cooling the vapor steam leaving the reactor. For the mathematical description of the process, the removal of the PAH from the soil is considered to take place by a desorption process. Sorption isotherms are measured by batch experiments and can be described by isotherms of Langmuir type. A dispersion model is used to describe the mass transfer of the process. The process is mathematically modeled for instationary and stationary operation. The simulation predicts the lowest energy consumption at a good cleaning performance at a steam-to-suspension ratio of 5.

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“…Existing thermal technologies include electric heating, 3-5 radio frequency heating, 6,7 microwave heating, 8,9 hot air or water injection, 10 steam stripping, [11][12][13] and steam injection. 14-17 Steam injection techniques have been successfully used in the cleanup of fuel and chlorinated hydrocarbon-contaminated soils in certain situations.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Polychlorinated Biphenyl Removal from Contaminated Soil Using Microwave-Generated Steam

Chang

2001

Journal of the Air & Waste Management Association

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A feasibility study of polychlorinated biphenyl (PCB) removal from contaminated soils using microwave-generated steam (MGS) was performed. Initial experimental results show that MGS effectively removed PCBs from contaminated soil with an overall removal efficiency of greater than 98% at a steam-to-soil mass ratio of 3:1. Removal efficiency was found to be dependent upon the amount of steam employed, expressed as a mass ratio of steam applied to soil mass. Evaporation was identified as a major mechanism in removing PCBs from the soil. Rapid expansion and evaporation of pore water by microwave dielectric heating accelerated evaporation rates of PCB molecules. Increased solubility of PCBs into the heated aqueous phase is also hypothesized. Together these effects increase mass-transfer rates, thus enhancing removal of PCBs from the soil.

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Experimental and theoretical study of combined solvent and steam stripping of 1,2,3,4,5,6-hexachlorocyclohexane (HCH) and mercury from contaminated natural soil

Cited by 5 publications

References 15 publications

Transport models for desorption from natural soils packed in flushed columns

Transport models for desorption from natural soils packed in flushed columns

Decontamination of Polyaromatic Hydrocarbons from Soil by Steam Stripping: Mathematical Modeling of the Mass Transfer and Energy Requirement

Investigation of Polychlorinated Biphenyl Removal from Contaminated Soil Using Microwave-Generated Steam

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