Green mechanochemical route for the synthesis of carboxy-rich polyaniline/multiwalled carbon nanotubes composite as a competent adsorbent for cationic dyes

In the present investigation, we describe a rapid and eco-friendly mechanochemical method that completely avoids the use of corrosive acids for the synthesis of carboxy-rich-polyaniline decorated MCNTs composite (cPANI@MCNTs) at room temperature as an efficient adsorbent for the removal of cationic methylene blue (MB) and methyl violet (MV) dyes from water. The intrinsic physico-chemical properties of newly synthesized materials were characterized by using FTIR, XRD, SEM, and EDX analytical techniques. To ascertain the effects of adsorbent dose, contact time, and pH of the medium on the adsorption process, batch adsorption studies were conducted. It was discovered that pH values of 7 and above are the most favorable for cationic dye adsorption onto cPANI@MCNTs. The adsorption equilibrium data for the dye adsorption process fitted well with the Langmuir model of adsorption and adsorption kinetics disclosed that the data are in excellent agreement with R² values of 1 (MB) and 0.99996 (MV) for the pseudo-second-order. The adsorption of dyes on cPANI@MCNTs from thermodynamic data was found to be spontaneous and endothermic in nature. The results indicate that the composite demonstrated admirable maximum adsorption capacity toward both MB (194.9 mg g ⁻¹) and MV (122.5 mg g ⁻¹) signifying cPANI@MCNTs as an efficient cationic-dye adsorbent.