Kinetic studies of the removal of heavy metals from acid mine drainage by natural zeolite

A kinetic study of the removal of Fe3+, Cu2+, Mn2+ and Zn2+ cations from solution by natural zeolite (clinoptilolite) was performed. The influence of agitation speed (190, 390 and 645 rpm) and particle size (dp < 180 μm, 1–3 mm and 5.6–6.7 mm) on the rate limiting step of the overall process was investigated. The data obtained was fitted to kinetic models with the Nernst Planck model giving the best fit, showing intra-particle diffusion as rate controlling. The effective diffusion coefficient for each cation was calculated. Intraparticle diffusion was shown to be rate controlling.