Green synthesis of highly porous Polyaniline (PANI) supported by TiO2

Polyaniline (PANI) is one of the most studied conductive polymers due to its high electronic conductivity, redox properties, excellent chemical and thermal stability and low cost.PANI has a wide range of applications: it is applied in electronic devices, electromagnetic radiation shields, corrosion inhibition, wastewater treatments, catalysis and medicine [1]. The most traditionally adopted synthesis to produce polyaniline involves the oxidation of aniline with potassium sulfate (K2SO4) in aqueous solution: however, both aniline and K2SO4 are well known carcinogens [2]. An alternative green synthesis for PANI involving far less toxic reagents has been recently reported by some of us [3]. In this case aniline’s dimer (N-(4-aminophenyl aniline)) is the starting compound instead of aniline and hydrogen peroxide (H2O2) is used as oxidant instead of K2SO4. In the present work, the process is modified by introducing titanium dioxide (TiO2) as the catalyst and reactions with and without UV irradiation have been studied . The effect of synthetic parameters such as the amount of TiO2, the intensity and time of irradiation, and the stirring speed, have been investigated. To evaluate the composition and optical properties of the obtained products, IR and UV-vis spectroscopies have been performed. The specific surface area and the porosity of the materials have been measured by the BET approach, and the structural properties by XRD analysis. SEM images of our samples showed the macrostructure of the polymer and highlighted appreciable morphological differences among the various samples. Preliminary tests of the absorption capability of the prepared polyaniline were carried out using dyes, such as methyl orange, for potential application in wastewater remediation treatments. Promising results were obtained with respect to the polyaniline synthesized in a traditional way. Future developments will concern tests to assess the capability of the TiO2 semiconductor [4] to directly mineralize the absorbed pollutant under irradiation.