Kinetics of Chromium(VI) and Cadmium Retention in Soils; a Nonlinear Multireaction Model
1988
Amacher, M. C. | Selim, H. M. | Iskandar, I. K.
A general-purpose, nonlinear, multireaction model capable of predicting kinetic retention data from batch reaction experiments was developed and verified. The model consists of one or two concurrent, reversible nonlinear reactions and a concurrent, irreversible first-order reaction. The model can be extended by adding a consecutive, reversible first-order reaction to one of the reversible nonlinear reactions. Either a three- or five-parameter version of the model described accurately Cr(VI) and Cd retention by several soils at several initial concentrations depending on the element, soil, or initial concentration. The model predicted that a fraction of the reactive solute may be irreversibly retained by soils; this was verified experimentally, albeit in a qualitative manner. A number of reactions compatible with the model can be postulated, although the fit of the model to the data cannot be construed as evidence to prove any one of the processes. A variety of reaction mechanisms may produce experimental or theoretical concentration vs. time curves that are indistinguishable. Contribution from Hatch Project 2469; Louisiana Agric. Exp. Stn. as manuscript no. 87-09-1328.
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