Synthesis and characterization of conducting polypyrrole/bentonite nanocomposites and in-situ oxidative polymerization of pyrrole: adsorption of 4-nitrophenol by polypyrrole/bentonite nanocomposite

Abstract

Oxidative polymerization of pyrrole in aqueous medium was used for the preparation of the Polypyrrole/Bentonite nanocomposites. Iron chloride hexahydrate was preferred as the oxidant. The nanocomposites were characterized by using several techniques such as Fourier transform infrared spectroscopy (ATR-FT-IR), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), thermogravimetric analysis/differential thermal analysis (TGA-DTA), differential scanning calorimetry (DSC) and dynamic light scattering (DLS). X-ray diffraction analysis indicated that the polypyrrole was intercalated into the bentonite layers. The results of FT-IR and XRD spectroscopy proved that the structure was a composite. The conductivity of composites was measured using four-point techniques. TGA was used to analyze the thermal stability of the nanocomposites. Moreover, the adsorption of 4-nitrophenol (4NP) by the composite from aqueous solution was studied both thermodynamically and kinetically. Equilibrium data were acquired from adsorption of 4NP solutions that have the initial concentrations from 25 to 300 mg L−1 by adsorption of the nanocomposite at different temperatures (25, 35 and 45 °C) according to Langmuir and Freundlich adsorption isotherms. Qmax (maximum adsorption capacity) was defined as 96 mg g−1 via the Langmuir isotherm model. The parameters of thermodynamic (ΔHo, ΔGo and ΔSo) were calculated as well, and adsorption process was determined to be exothermic.