A modeling approach for prediction of the breakthrough curve in adsorption of hexavalent chromium on sawdust in a fixed bed column is presented. The model was introduced by Zhang and Cheng and benefit from geometrical dimensions of the bed that is useful if an industrial scale up will be needed. Validation with experimental data and a comparison with well-known Thomas model, the pore diffusion and the solid diffusion models were performed. The results showed that Zhang and Cheng model has better output than Thomas and the pore diffusion models and almost near to the solid diffusion model.