Polyaniline-multiwalled carbon nanotubes (PANI- MWCNTs) composite revisited: An efficient and reusable material for methyl orange dye removal

This study discusses the fast and efficient adsorptive removal of methyl orange (MeO), a mutagenic azo dye and a significant water pollutant from dyeing industries, using PANI-MWCNTs composite. The composite prepared by in-situ oxidative polymerization was characterized using FT-IR, XRD and TEM techniques. The surface area of PANI-MWCNTs composite obtained from Brunauer-Emmett-Teller (BET) surface area analysis was 43.892 m2 g−1 and the nitrogen adsorption-desorption isotherms demonstrated the mesoporous structure of the material. In comparison to PANI and MWCNTs, PANI-MWCNTs composite exhibited superior performance as adsorbent. The MeO adsorption process followed pseudo-second-order kinetics (R2 ≥ 0.99) with a rate constant of 5.265 × 10−4 g mg−1 min−1 at 30 °C. The maximum adsorption capacity (qm) evaluated from the equilibrium data was 149.25 mg g−1 and the data concurred the best with Langmuir isotherm model. The values of Langmuir constant (RL) and Freundlich constant (1/n) were less than 1, revealing that the adsorption process is favourable. Furthermore, the used adsorbent showed excellent recyclability after it was regenerated using 1 M HCl.