Adsorption of dyes onto bagasse pith using a solid diffusion model

The adsorption of four dyes (Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114) onto bagasse pith has been studied using an agitated batch adsorber. The variables studied were initial dye concentration and pith mass. A mathematical model has been developed based on external mass transfer and solid‐phase diffusion. The model has been used to generate theoretical concentration–time decay curves, and these results were adjusted to experimental data by a best fit approach. The external mass transfer coefficients are 2.0 × 10⁻³, 1.5 × 10⁻³, 8.0 × 10⁻⁴, and 5.0 × 10⁻⁴ cm s⁻¹ and the solid diffusivities are 1.1 × 10⁻⁸, 1.0 × 10⁻⁸, 6.0 × 10⁻⁹, and 3.0 × 10⁻⁹ cm² s⁻¹ for Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114.