Nkedi-Kizza

Nzengung VA, Voudrias EA, Nkedi-Kizza P, Wampler JM, Weaver CE (1996) Organic cosolvent effects on sorption equilibrium of hydrophobic chemicals by organoclays. Environ Sci Technol 30 89-96... 

Lee, L. S., Rao, P. S. C., Nkedi-Kizza, P., Delfino, J. (1990) Influence of solvent and sorbent characteristics on distribution of pentachlorophenol in octanol-water and soil-water systems. Environ. Sci. Technol. 24, 654—661. 

Nkedi-Kizza, P, Rao, P.S.C., Hornsby, A.G. (1985) Influence of organic cosolvent on sorption of hydrophobic organic chemicals by soils. Environ. Sci. Technol. 19, 975-979. 

Woodburn KB, Rao PSC, Fukui M, Nkedi-Kizza P (1986) In Macalady DL (ed) Transport and transformations of organic contaminants. J Contaminant Hydrol 1 277... 

NzengungVA, Nkedi-Kizza P, Jessup RE.Voudrias EA(1997) Environ Sci Technol 31 1470... 

Nzengung, V. A., E. A. Voudrias, and P. Nkedi-Kizza, Organic cosolvent effects on sorption equilibrium of hydrophobic organic chemicals by organoclays , Environ. Sci. Technol., 30, 89-96 (1996). 

Rao, P. S. C., A. G. Hornsby, D. P. Kilcrease, and P. Nkedi-Kizza, Sorption and transport of hydrophobic organic chemicals in aqueous and mixed solvent systems Model development and preliminary evaluation , J. Environ. Qual., 14, 376-383 (1985). 

Miscible organic solvents, such as methanol and ethanol, have been shown to increase solubility of hydrophobic organics and to decrease sorption (Nkedi-Kizza, 1985 Fu and Luthy, 1986 Nkedi-Kizza et al., 1987 Walters and Guiseppi-Elle, 1988 Wood et al., 1990 Lee et al., 1991). This is presumably the result of (i) reducing the activity coefficient of the sorbate chemical in the aqueous phase, and (ii) competition for sorbing sites. 

Here one makes an effort to describe simultaneously transport-controlled and chemical kinetics processes (Skopp, 1986). Thus, an attempt is made to describe both the chemistry and physics accurately. For example, outflow curves from miscible displacement experiments on soil columns are matched to solutions of the conservation of mass equation. The matching process introduces a potential ambiquity such that experimental uncertainties are translated into model uncertainties. Often, an error in the description of the physical process is compensated for by an error in the chemical process and vice-versa (i.e., Nkedi-Kizza etal, 1984). 

Figure 8.16. Equilibrium isotherms for adsorption of diuron on whole soil and particle-size separates of Webster soil (from Nkedi-Kizza et al., 1983, with permission).

Roberts, P. V., Goltz, M. N., Summers, R. S., Crittenden, J. C., and Nkedi-Kizza, P. (1987) The Influence of Mass Transfer on Solute Transport in Column Experiments with an Aggregated Soil, J. Contam. Hydrol. 1, 375-93. 

Nkedi-Kizza et al. (1982) utilized this approach to describe Ca mobility through an aggregated Oxisol (Fig. 10-4). Mobile pore water was assumed to be that water that drained under tensions <80 cm and estimates of [related to the nonequilibrium index, 7 = L — d)/a v] and P =... 

Fig. 10-4. Observed Ca effluent concentrations from an aggregated Oxisol at low- and high-flow velocities in the mobile region (v, = 3.2 and 127.5 cm h , respectively) with model-fitted curves assuming two-region diffusive mass transfer where 7 = 3Z) l-d)/a v is an index of nonequilibrium [from Nkedi-Kizza et al. (1982), with permission].

Nkedi-Kizza, P., P.S.C. Rao, R.E. Jessup, and J.M. Davidson. 1982. Ion exchange and diffusive mass transfer during miscible displacement through an aggregated Oxisol. Soil Sci. Soc. Am. J. 46 471-476. 

Nkedi-Kizza, P., J.M. Biggar, M.Th. van Genuchten, P.J. Wierenga, H.M. Selim, J.D. Davidson, and D.R. Nielsen. 1983. Modeling tritium and chloride 36 transport through an aggregated Oxisol. Water Resoiir. Res. 19 691-700. 

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