Intraparticle diffusion process for lead(II) biosorption onto mansonia wood sawdust

The overall biosorption rate of lead(II) onto mansonia wood sawdust has been determined. Kinetic modeling revealed that pseudo-second-order kinetics described the experimental data fully while pseudo-first kinetics followed for only 5 min. Ion-exchange constant, S, was similar to the pseudo-first-order rate constant, k(1), indicating that ion-exchange is important only in the first 5 min. Intraparticle diffusion increased with lead(II) concentration while film and pore diffusion decreased. The initial biosorption factor, R-i, showed that initial biosorption was intermediate. Addition of calcium ions reduced initial biosorption almost completely, reduced the amounts of lead(II) removed and increased ion-exchange phenomenon indicating significance of ion-exchange. Increase in temperature was found to increase intraparticle diffusion rate and reduce film and pore diffusion. Activation energy of film diffusion and pseudo-second-order kinetics were highest indicating that film diffusion-controlled the overall rate with active participation of ion-exchange from pseudo-second-order model. (C) 2010 Elsevier Ltd. All rights reserved.