Pore Diffusion Model for the Adsorption of Basic Dyestuffs onto Natural Clay in Batch Adsorbers

The adsorption of basic dyestuffs (Basic Blue 69 and Basic Red 22) onto natural clay has been studied using a series of batch adsorption runs. The pore diffusion model (PDM) has been developed based on external mass transfer and pore diffusion to predict the performance of a batch adsorber. A computer program has been developed to generate theoretical Sherwood number-time curves and these results were adjusted to experimental Sherwood number-time curves by means of a ‘best fit’ approach. The variables of initial dye concentration and natural clay mass have been successfully correlated using a single external mass-transfer coefficient, K s , and a single effective pore diffusion coefficient, D eff . The K s values are 3.3 × 10 −5 and 2.6 × 10 −5 m/s for Basic Blue 69 and Basic Red 22, respectively. The D eff values are 7.3 × 10 −10 and 9.6 × 10 −10 m 2 /s for Basic Blue 69 and Basic Red 22, respectively.