Biosorption of Methyl violet onto palm kernel fiber: Diffusion studies and multistage process design to minimize biosorbent mass and contact time

Abstract

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. Plot of optimization of contact time and system number for a 99.5% Methyl violet removal in a four stage countercurrent batch process using 2.5 m 3 of 120 mg dm −3 solution. ► The overall biosorption rate determining step in methyl violet adsorption onto Palm kernel fiber was investigated. ► Diffusion patterns of methyl violet dye into palm kernel fiber was elucidated. ► Wu’s approaching equilibrium factor, R w was applied in examining the intraparticle diffusion pattern. ► Temperature effect on the diffusion of methyl violet was also studied. ► Multistage process design to minimize mass and contact time was done.