• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.669-675
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• 2006

Toluene of aromatic compounds, MEK of ketones and IPA of alcohols were extremely used as VOCs (Volatile Organic Compounds) on the getting into step with industrial process. The adsorption characteristics of three component solvent vapors (Toluene-MEK-IPA) on the activated carbonaceous adsorbents such as AC, ACF and AC+ACF were investigated in a stainless steel fixed bed adsorption experimental apparatus in order to identify those carbons for eliminating and recovering solvent vapors from industrial emission sources. The used activated carbonaceous adsorbents were pelletized commercial activated carbon and activated carbon fiber. The breakthrough curves and adsorption capacity have been obtained at atmospheric pressure in a adsorption fixed bed. It has been found that non-polar and larger molecules have been adsorbed better than polar and smaller molecules. Especially, alcohols and ketones were poorly adsorbed due to competitive adsorbability in ternary mixture system. However, it could be overcome by employment of activated carbonaceous adsorbent which have different porosity distribution appropriately.

• Economic and Environmental Geology
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• v.29 no.6
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• pp.713-724
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• 1996

The time-series resident solute concentrations, monitored at two field plots using the automated 144-channel TDR system by Kim (this issue), are used to investigate the dominant transport mechanism at field scale. Two models, based on contradictory assumptions for describing the solute transport in the vadose zone, are fitted to the measured mean breakthrough curves (BTCs): the deterministic one-dimensional convection-dispersion model (CDE) and the stochastic-convective lognormal transfer function model (CLT). In addition, moment analysis has been performed using the probability density functions (pdfs) of the travel time of resident concentration. Results of moment analysis have shown that the first and second time moments of resident pdf are larger than those of flux pdf. Based on the time moments, expressed in function of model parameters, variance and dispersion of resident solute travel times are derived. The relationship between variance or dispersion of solute travel time and depth has been found to be identical for both the time-series flux and resident concentrations. Based on these relationships, the two models have been tested. However, due to the significant variations of transport properties across depth, the test has led to unreliable results. Consequently, the model performance has been evaluated based on predictability of the time-series resident BTCs at other depths after calibration at the first depth. The evaluation of model predictability has resulted in a clear conclusion that for both experimental sites the CLT model gives more accurate prediction than the CDE model. This suggests that solute transport at natural field soils is more likely governed by a stream tube model concept with correlated flow than a complete mixing model. Poor prediction of CDE model is attributed to the underestimation of solute spreading and thus resulting in an overprediction of peak concentration.

• Economic and Environmental Geology
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• v.29 no.6
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• pp.699-712
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• 1996

Field scale experiments using an automated 144-channel TDR system were conducted which monitored the movement of solute through unsaturated loamy soils. The experiments were carried out on two different field plots of 0.54 ha to study the vertical movement of solute plume created by applying a square pulse of $CaCl_2$ as a tracer. The residence concentration was monitored at 24 locations on a transect and 5 depths per location by horizontally-positioning 50 cm long triple wire TDR probes to study the heterogeneity of solute travel times and the governing transport concept at field scale. This paper describes details of experimental methodology and calibration aspects of the TDR system. Three different calibration methods for estimation of solute concentration from TDR-measured bulk soil electrical conductivity were used for each field site. Data analysis of mean breakthrough curves (BTCs) and parameters estimated using the convection-dispersion model (CDE) and the convective-lognormal transfer function model (CLT) reveals that the automated TDR system is a viable technique to study the field scale solute transport providing a normal distribution of resident concentration in a high resolution of time series, and that calibration method does not significantly affect both the shape of BTC and the parameters related to the peak travel time. Among the calibration methods, the simple linear model (SLM), a modified version of Rhoades' model, appears to be promising in the calibration of horizontally-positioned TDR probes at field condition.

• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.53-60
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• 2006

Single well injection withdrawal tracer tests with bromide were carried out at two wells developed in a horizontally heterogeneous fractured rock. The hydraulic conductivity of TW-1 well was 5 times larger than TW-2 well, and the average linear velocity of TW-2 well was 1.8 times faster than TW-1 well. The difference of hydrodynamic dispersions of two wells in the fractured rock was studied with the analysis of concentration breakthrough curves and cumulative mass recovery curves of bromide with withdrawal time, and the estimation of average travel distance, pore velocity, longitudinal dispersivity and longitudinal dispersion coefficient. The average travel distances of bromide were estimated to be 3.00 m in TW-1 well and 5.62 m in TW-2 well. The average pore velocities for the injection/withdrawal phase were estimated to be $4.31\;{\times}\;10^{-4}\;m/sec$ in TW-1 well and $8.08\;{\times}\;10^{-4}\;m/sec$ in TW-2 well. Average travel distance and pore velocity were higher in TW-2 well because of small effective porosity. Longitudinal dispersivities were estimated to be 28.73 cm in TW-1 well and 18.49 cm in TW-2 well, and bromide transport was 1.55 times faster in TW-1 well. Longitudinal dispersion coefficients were estimated to be $5.14\;{\times}\;10^{-6}\;m^2/sec$ in TW-1 well and $6.06\;{\times}\;10^{-6}\;m^2/sec$ in TW-2 well, and diffusion area was 1.18 times larger in TW-2 well.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.3
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• pp.234-241
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• 1997

The effects of bulk densities(${\rho}_b$) on saturated hydraulic conductivity (Ksat) and solute elution patterns were investigated from five different bulk densities ranging from $1.1Mg/m^3$ to $1.5Mg/m^3$ with each increment of $0.1Mg/m^3$. The hydraulic conductivities observed were divided into two stages: (1) a linearly decrease with increase in bulk density up to $1.4Mg/m^3$, (2) a steady state where the bulk density is greater than $1.4Mg/m^3$. Using the saturated hydraulic conductivity at the steady state, we figured out the equation describing the correlation between bulk densities(${\rho}_b$) and saturated hydraulic conductivity(Ksat) as follows: $Ksat=-19.2({\rho}_b{^2})+6{\rho}_b+15.5$, (r=0.985). Electrical conductivity(EC) measured from the leachate of the soil column showed that EC at the same pore volume were decreased with an increase in the bulk density from $1.2g/cm^3$, $1.5g/cm^3$, as shown in the time taken to collect the same pore volume at each respective bulk density. The maximum relative concentrations (C/Co=1) from the breakthrough curves for the anions of $Cl^-$, $NO_3{^-}$ and $SO_4{^{2-}}$, which are weakly adsorbed on the soil particles, moved to the right of the graph, while a distinctive retardation occurs at the bulk density between $1.3Mg/m^3$ and $1.4Mg/m^3$. The time taken to recover about 90% of indigenous sulphate was approximately twice as those of chloride and nitrate, resulting in slightly stronger adsorption characteristics for sorption sites on the soil surface. Thus, we can conclude that the salt accumulation in green house soil might be significantly influenced by it's bulk density at the soil depth, as well as the adsorption capacity of ions for the sorption sites in soils.