Film-pore diffusion modeling and contact time optimization for the adsorption of dyestuffs on pith

Abstract

The sorption of four dyestuffs, namely, Acid Blue 25 (AB25), Acid Red 114 (AR114), Basic Blue 69 (BB69) and Basic Red 22 (BR22) onto bagasse pith has been studied using an agitated batch sorber system. The equilibrium isotherms were determined and kinetic runs were performed over a range of concentrations for each dye and masses of pith. A film-pore diffusion mass transfer model has been developed based on a single effective diffusion coefficient for each system. Error analysis of the experimental and theoretical data indicated relatively large errors at low initial dyestuff concentrations. In this paper, a contact time optimization methodology of a two-stage batch adsorber system taking minimum contact time as the objective function has been developed. The initial concentration of the second stage and adsorbent weight have been designated as variables. Contact time optimization of a two-stage batch adsorber system has been demonstrated at two different conditions/cases for the adsorption of dyes on pith. The optimization solutions show that there is a significant difference for minimum contact time at different process conditions.