Abstract
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 homogeneous surface diffusion model (HSDM) has been developed based on external mass transfer and surface diffusion to explain the concentration–time curves. A computer program has been used to generate theoretical concentration–time curves and these results have been adjusted to the experimental data by means of a ‘best fit’ approach. The HSDM has been successfully used to model the dynamics of the adsorption process for basic dyestuffs onto natural clay. The model predicts a single external mass-transfer coefficient, Ks, and a single surface diffusion coefficient, Ds, with initial dye concentration or natural clay mass. The Ks values are 3.4×10–3 and 2.6×10–3 cm/s for Basic Blue 69 and Basic Red 22, respectively. The Ds values are 2.3×10–8 and 1.9×10–8 cm2/s for Basic Blue 69 and Basic Red 22, respectively.
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