The effect of suspended solids on mass transfer to a rotating disk

The enhancement of limiting currents by inert suspended solids was studied using a rotating-disk electrode (RDE). The suspensions contained glass or polymer particles in various sizes (1-100 /mu/m) and concentrations (up to 40 v/o solids). Solid particles the same size as, or smaller than, the thickness of the mass-transfer boundary layer create small-scale microconvective vortices. Particles much larger than the boundary-layer thickness appear to enhance transport by a different mechanism, possibly involving the formation of particle-free wall layers. Disk-torque measurements show that substantial increases in the limiting current require significantly less stirring power using the suspensions than by increasing the rotation rate without solids.