Synthesis of a poly( p -aminophenol)/starch/graphene oxide ternary nanocomposite for removal of methylene blue dye from aqueous solution

In the current study, poly( p -aminophenol) (P p AP), with starch and graphene oxide (GO), was successfully synthesised by oxidative polymerisation from p -aminophenol monomer in an aqueous alkaline medium using ammonium persulfate (APS) as an oxidising agent. The synthesised polymers were characterised using UV–Vis spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction (XRD), and Brunauer–Emmett–Teller and zeta potential techniques. These techniques confirmed the presence of site-selective interaction between the conjugated P p AP chain and π-bonded surface, and thus the H-bonding of starch and GO. Further, the enhanced dye removal efficiency was ascribed to the improved morphology and the pore volume created by the entangled P p AP/Starch/GO. The influences of experimental conditions, such as the polymer composite content, dye concentration, time, pH of the bath solution, and temperature on cationic dye adsorption, were investigated. The adsorption data were fixed to the Langmuir isotherm (R 2 in the range between 0.997 and 0.9995) and showed a pseudo-second order (R 2 = in the range of 0.996 to 0.9996) kinetic model. Moreover, the polymer ternary composite was able to remove a large proportion (96.7%) of the cationic dye from water at pH 7. The thermodynamic investigation found that the adsorption process was spontaneous and endothermic. In addition, the synthesised adsorbent showed good reusability at six cycles. The data acquired suggest that the P p AP/Starch/GO composite can be effectively applied and reused as an inexpensive adsorbent material for removal of MB dye from water.