Synthesis of polyaniline/nanosilica nanocomposite for removal of reactive orange 16 from aqueous solutions

In this study, preparation of polyaniline (PAni) and its nanocomposite containing nanosilica (NS) was discussed, and their capability to removal of reactive orange 16 (RO16) from aqueous solution was studied. Polyaniline (PAni) synthesized chemically in the presence of potassium iodate (KIO3) as an oxidant and coated on nanosilica. The removal of RO16 was investigated using PAni, and PAni/NS nanocomposite, respectively. The products were investigated in terms of morphology and chemical structure with scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR), respectively. Batch studies were performed to evaluate the influence of various experimental parameters like pH, adsorbent dosage and contact time. Optimum conditions for RO16 removal were found to be pH 2, adsorbent dosage of 0.8 g/L, equilibrium time 150 min. For determining the type of adsorption isotherm, Langmuir and Freundlich adsorption isotherms were used. The results revealed that Langmuir isotherm adequately met the experimental requirements. According to the Langmuir model, polyaniline/silica nano composite sorbents exhibited the highest RO 16 dye adsorption capacity of 60.98 mg g−1. Thermodynamic parameters such as changes in Gibbs free energy (ΔGo), enthalpy (ΔHo) and entropy (ΔSo) were calculated. The negative values of ΔGo and the positive value of ΔHo (24.49 KJ/mol) and ΔSo (97.11 J/mol K) show that the RO 16 adsorption on polyaniline/silica nanocomposite was a spontaneous and endothermic process.