Adsorption of anionic and cationic dyes into shaped MCM-41

The adsorption of Basic Blue 41 (BB41), Methylene Blue (MB) and Basic Red 18 (BR18), three known basic dyes, was studied in shaped mesoporous adsorbent MCM-41. The granules were obtained by extrusion of the powder adsorbent and were analyzed by nitrogen adsorption, SEM–EDS, XRD, mercury porosimetry and helium picnometry. Adsorption equilibrium isotherms, kinetics, and breakthrough curves were performed with the selected adsorbent and dyes. The experimental results indicated that the Sips model better describes the equilibrium than the Langmuir and Freundlich isotherm models. Additionally, the co-adsorption equilibrium of two dyes was well predicted by the extended form of the Sips model. The kinetics results showed that the adsorption of Basic Blue 41 onto the selected adsorbent is faster than with the other studied dyes. The obtained adsorbed equilibrium amounts through the breakthrough curves were 308 mg g−1, 55 mg g−1 and 106 mg g−1 for the Basic Blue 41, Methylene Blue and Basic Red 18 dyes, respectively. The dye is concentrated during regeneration step, since the volume of regenerating solution, eluted during the regeneration, is considerably lower (about two orders of magnitude) when compared with the volume of effluent treated until the breakthrough point. This fact demonstrates the feasibility of a potential adsorption based process to treat dyed effluents, with the shaped MCM-41.