Adsorption of basic dyes in aqueous solution by clay adsorbent from regenerated bleaching earth

Regenerated bleaching earth was used for adsorption and adsorption kinetics of the three basic dyes violet 4, violet 3 and red 9 from aqueous solution. The rate of adsorption has been investigated under various parameters such as initial dye concentration, pH and temperature. Two simple models (i.e., pseudo-second-order reaction and intra-particle diffusion) have been tested to predict the adsorption parameters. The adsorption of the basic dyes by regenerated bleaching earth at lower initial concentrations follows the order: basic violet 4>basic violet 3>basic red 9, parallel to the molecular weights and molecular sizes of the basic dyes. Further, the adsorption kinetic of the basic dyes can be well described with the pseudo-second-order reaction model. Based on the isotherm data obtained from the fittings of the adsorption kinetics, the Langmuir and Freundlich models for adsorption of basic violet 4 and basic red 9 yield relatively better fits than that for adsorption of basic violet 3.