Anionic dye (acid green 25) adsorption from water by using polyaniline nanotubes salt/silica composite

Acid green 25 (AG) dye was adsorbed from water by using polyaniline nanotubes (PANI NT) salt/silica composite as adsorbent. Comparison between the removal of the dye by using PANI NT salt/silica composite and the conventional PANI salt/silica composite was investigated. This result was evidenced from the measurements of the UV-visible absorbance of AG dye solutions after different times. Experiments were conducted by varying parameters, namely initial concentration of the dye and contact time. The percentage of color removal decreased with increase in initial dye concentration. Adsorption equilibrium of color removal was reached after 60 min of contact time. Equilibrium data were fitted to Langmuir, Freundlich, and Tempkin isotherms, and their constants were determined. Using the linear correlation coefficients showed that the Langmuir isotherm best fits the AG adsorption data on PANI NT salt/silica composite. The experimental data were fitted into the following kinetic models: pseudo-first-order, pseudo-second-order, and the intraparticle diffusion model. It was observed that the pseudo-second-order kinetic model described the adsorption process better than any other kinetic models. The results obtained indicate that PANI NT salt/silica composite could be employed as a much more efficient adsorbent than the conventional PANI salt/silica composite for dye removal from water.