Removal of Reactive Blue 21 from Aqueous Solution by Sorption and Solubilization in Micellar Media

This manuscript reports comparative study for the removal of health risk organic dye reactive blue 21 from aqueous solution using sorption and solubilization. Activated carbon was used as sorbent to remove dye. The bath sorption experiments were carried out at different pH, sorbent dosage, contact time, initial concentration, and agitation speed. The applicability of the Langmuir and Freundlich isotherm models was examined. The influence of cationic surfactant, cetyltrimethyl ammonium bromide (CTAB), and an anionic surfactant, sodium dodecyl sulfate (SDS) on spectral properties of selected dye in aqueous solutions was investigated by means of UV–Visible spectroscopy in sub-micellar and micellar concentration range. Absorption spectra of this dye in the presence of surfactants may confirm which type of interaction is possible between molecules of dye and surfactants. It is expected that initially molecules of dye may attach with monomeric molecules of surfactant in premicellar region while in post-micellar region they are accommodated within micelle. The values of micelle–water partition coefficient, K_x, free energy of partition, ΔG_x, of RB21 between bulk water and micelles, drug-surfactant binding constant, K_b, and free energy of binding, ΔG_b, were calculated from differential spectroscopic data.