Determination of the overall rate controlling step in the biosorption of Methyl violet dye onto a new biosorbent, palm kernel fiber has been determined. Pseudo-second-order model described the kinetics over the whole contact time period for the effect of initial concentration and temperature. Using the Wu's approaching equilibrium factor, R(w), it was observed that the time for the switch from initial biosorption to intraparticle diffusion is affected by initial concentration and temperature. A comparison between the activation parameters of film diffusion, pseudo-second order ion exchange and intraparticle diffusion revealed that film diffusion is the overall slowest step in the biosorption process. Temperature increased the biosorption capacity but reduced slightly the rate of intraparticle diffusion, indicating that the biosorbent surface was activated by temperature which limited the diffusion of Methyl violet molecules into the interior of the biosorbent. A multistage process design to minimize mass and contact time was done. (C) 2011 Elsevier Ltd. All rights reserved.