TRANSPORT OF LIGNOSULFONATES UNDER AN EXTERNAL ELECTRIC-FIELD

The effect of an external electric field on the diffusion process of a polydisperse polyelectrolyte, lignosulphonate, has been studied. The measurements were carried out using a method which is based on a convective diffusion process across a porous membrane. The electric field strengths used were varied from 0.6-35 V m-1. All the measurements were carried out at 20-degrees-C using a homogeneous base electrolyte system (0.1 mol dm-3 NaCl aqueous solution). The results showed that when the electric field was varied from 0.6 to ca. 10 V m-1, the diffusion coefficients decreased but reached constant values in the range 10-35 V m-1. Furthermore, the conformation appeared to change from a compact sphere in the absence of an external electric field to a non-free unwinding coil when the electric field strength was > 10 V m-1.