The dispersion of chemically active solutes in parallel flow

The irreversible loss of chemically active solutes by reactions at the boundary and the reversible adsorption on the flow boundary have been observed experimentally. Removal of solutes at the boundary alone reduces the rate of longitudinal shear dispersion; in contrast, the retention of solutes in the region close to the flow boundary alone increases the rate of longitudinal shear dispersion. Here an extension is given of the method of moments for chemically active solute dispersion to encompass this class of complications. Expressions are derived for the longitudinal shear dispersion coefficient and skewness. The results are applied to the practical example of a chemical flow reactor to quantify the effect of flow boundary retention when there exists reaction at the pipe wall.