A non-equilibrium thermodynamics approach using practical transport coefficients has been used to evaluate frictional coefficients for the dominant solute near infinite dilution of the minor solute in the high pressure nanofiltration of ternary lactose-NaCl-water solutions with Zr(IV) hydrous oxide-polyacrylate membranes at pH 8.0. In terms of the frictional coefficients, the observed increase in the passage of NaCl with increasing lactose concentration at low concentrations of lactose is attributed to larger decreases in the NaCl-membrane and NaCl-solvent couplings than the decrease in the solvent-membrane coupling. The observed small decrease in the passage of lactose with increasing NaCl concentration at low concentrations of NaCl is attributed to a larger increases in the lactose-membrane and lactose-solvent couplings than the increase in the solvent-membrane coupling. The use of practical transport coefficients to evaluate the frictional coefficients by this method is limited to solutions with large differences in the concentrations of the two solutes.