Flow-rate dependence of the height equivalent to a theoretical plate in nitrogen isotope separation by displacement chromatography

Abstract

The effect of flow-rate in nitrogen isotope separation was studied for a wide range of fluid velocities using porous microreticular cation-exchange resin. The displacement chromatography was conducted from a band velocity of 6.3×10 −3 to 12.5 cm/min (or Reynolds number of 15–30 000). A sharp adsorbed ammonium band was maintained even at a band velocity of 12.5 cm/min; on the other hand, tilted and/or channeled boundaries of the band are enlarged in the low-flow-rate region. The effect of fluid velocity on the height equivalent to a theoretical plate (HETP) of isotope separation was evaluated in terms of Reynolds number. In the present work, the HETP is proportional to the square-root of the band velocity in the turbulent flow regime and inversely proportional to the fluid velocity in the laminar flow regime due to the longitudinal mixing which is caused by tilting and/or channeling at the band boundary.