Decolorization of indigo carmine by charcoal from extracted residue of coffee beans.

The adsorption ability of charcoal from extracted residue of coffee beans for indigo carmine removal was investigated by the batch method. Differences in the removal ratio and removal rate of indigo carmine could be explained by differences in the properties of charcoal. In the relationship between the amount of indigo carmine adsorbed and the square root of elapsed time, a good linearity was recognized. Since the relationship between the amount of indigo carmine adsorbed and square root of elapsed time showed a good linearity, the intraparticle diffusion of indigo carmine onto pores of adsorbents was identified as the rate-limiting step in the adsorption process.