Adsorption of Cationic Dye (Methylene Blue) from Water Using Polyaniline Nanotubes Base

Polyaniline nanotubes (PANI NTs) base has been utilized as an adsorbent for the removal of cationic dyes such as methylene blue (MB) from aqueous solution. This observation was evidenced from the measurements of quartz crystal microbalance (QCM) and UV-visible spectroscopy. Experiments were conducted by varying parameters of initial concentration of MB and contact time. The percentage of color removal decreased with the increase of initial dye concentration. Adsorption equilibrium of the dye was reached after 120 min of contact time. Equilibrium data were fit to Langmuir, Freundlich, and Tempkin isotherms, and their constants were determined. The linear correlations coefficient showed that the Langmuir isotherm best fits the MB adsorption data on PANI NTs. The pseudo-first-order, pseudo-second-order, and the intraparticle diffusion kinetic models were applied to the experimental data. It was observed that the pseudo-second-order kinetic model described the adsorption process better than any other kinetic model. Results obtained indicate that PANI NTs could be employed as an efficient adsorbent much more than the conventional PANI powder for dye removal from water.