Treatment of indigo carmine wastes with granular activated carbon and its adsorption process into micropores.

The waste water from the dyeing process is considered to be a water pollutant because of the coloring caused by the dye and the BOD and COD components coming from the fibrous materials and the dyeing auxiliaries.Many chemical dyes have been shown to be toxic1). Indigo carmine is also a carcinogenic chemical2). Activated carbon adsorption appears to be the most effective and economical tertiary treatment method for the removal of organics, including dyes3). However, acidic dye is more difficult to remove than either basic or direct dye3). In our previous paper4), the adsorption characteristics of indigo carmine, an acidic dye, onto activated carbon were reported. High molecular weight dyes are adsorbed in the transitional pores of an activated carbon and low molecular weight dyes, in the micropores5). However, the relation between the adsorption rate and the adsorption process of indigo carmine into the micropores has not yet been reported.In this study, the adsorption behavior of indigo carmine onto activated carbon according to its different particle sizes was investigated on the basis of the results of adsorption isotherm, intraparticle diffusivity, and the pore size distribution of activated carbon adsorbed by indigo carmine with different adsorption ratios.