Binding of transition metals by soluble and silica-bound branched poly(ethyleneimine): Part II: Binding kinetics in silica-bound BPEI

Metal-binding rates of a commercial adsorbent containing silica-supported branched poly(ethyleneimine) (BPEI) have been studied. Binding kinetics of H2SO4 and Cu, Ni and Zn sulfates have been measured by batch experiments at 25 °C and at high ionic strength. Competitive binding of a binary Cu–Ni system was also studied. The data were correlated with the non-ideal adsorption model (NICA) and a diffusion model of porous particles.The adsorption kinetics of sulfuric acid in the adsorbent is controlled by pore and surface diffusion as well as by film mass transfer. The uptake rate of the metal ions depend both on the pore diffusion of the metal salt and the desorption rate of the displaced acid. The uptake curves measured with and without pH control can be well correlated with the diffusion model and with constant diffusion coefficients.