A nanocomposite based on polyaniline, nickel and manganese oxides for dye removal from aqueous solutions.

In this study, a new type of multifunctional material PANI/NiO/MnO₂ nanocomposite was first time prepared by chemical polymerisation from aniline monomer in the presence of metal oxides (NiO and MnO₂) and an oxidant (ammonium persulfate) in acidic aqueous solution for the elimination of methyl orange (MO) dye from water. Herein, the PANI/NiO/MnO₂ nanocomposite was found to be a favourable adsorbent for wastewater treatment due to its high adsorption and efficiency, self-regeneration, low cost and easy synthesis. Fourier transform infrared spectroscopy, X-ray diffraction, thermo-gravimetric analysis, transmission electron microscopy, scanning electron microscopy, Brunauer–Emmett–Teller analysis and Zeta potential were employed to characterise the synthesised nanocomposites. The data revealed that PANI nanocomposites doped with NiO and MnO₂ nanoparticles had a higher adsorption efficiency (~ 97%) than that found in pure PANI (~ 53%). The adsorption conditions, such as pH of the medium, initial dye concentration, adsorbent dosage, and adsorption time were investigated. Various kinetic and isotherm models were used to analyse the results of the kinetics and the equilibrium adsorption and to interpret the interaction between the dye and nanocomposite adsorbents. The adsorption kinetics data for MO dye on the PANI/NiO/MnO₂ were well explained based on a pseudo-second-order model while adsorption isotherm results were analysed based upon the Langmuir isotherm model. In addition, the adsorption process was an endothermic, favourable and spontaneous reaction according to thermodynamic studies. Also, the influence of matrix synthetic waste on MO dye removal was studied and found to show good results with matrix synthetic waste for both PANI/NiO/MnO₂ and PANI adsorbents. The experimental adsorption capacity of the PANI/NiO/MnO₂ nanocomposite (248.4 mg/g) was considerably greater than that of PANI (57.5 mg/g). The PANI/NiO/MnO₂ adsorbent can be recycled up to four times and maintains a good adsorption capacity throughout. [ABSTRACT FROM AUTHOR]