Mass transfer enhancement in stirred suspensions of magnetic particles by the use of alternating magnetic fields

The impact of external alternating magnetic fields on suspended magnetic particles may lead to a forced, very intensive particle movement. In case the magnetic particles additionally possess sorptive or catalytic properties, mass transfer on the liquid side is increased. The model system used for the quantitative determination of this magnetic field effect was the neutralization reaction of 10−4 mol/l NaOH solution by magnetic cation exchangers of the H+ form. The particles were suspended in a stirred tank that was immersed into an arrangement of magnetic coils. Mass transfer on the liquid side was studied at varying stirrer speeds, frequencies of the magnetic field and, on a small scale, densities and viscosities of the medium. The mass transfer coefficient was found to increase by up to 200%. For description purposes, the rotational Reynolds number was used, which includes the circumferential velocity of the particle as characteristic velocity.