Intraparticle diffusion coefficient of lithium on granulated adsorbent of manganese oxide in seawater

Five kinds of manganese-oxide adsorbent granulated with different particle sizes were prepared using polyvinyl chloride (PVC) as a binder. Rates of lithium adsorption on the adsorbents were measured in lithium-enriched seawater ([Li]=3.1 mg·dm-3) by a batch method. The intraparticle diffusivities (Dp's) of lithium were evaluated in terms of the model of pore diffusion with a Freundrich-type adsorption isotherm. The Dp values were about 2 x 10-6 cm·s-1 and slightly dependent on particle size. The Dp values were also evaluated using column adsorption data. The calculated values (about 4 x 10-6 cm·s-1) agreed comparatively well with those derived from the batch adsorption data. The agreement suggests that the intraparticle diffusion is a rate-determining step in column adsorption at space velocity above 200 h-1. (author)