Polyaniline : advances in synthesis and environmental applications

The chemical industry of the forthcoming years will be shaped by a number of emerging global megatrends strictly related to the growth and aging of the world population (nine billion people in 2050). This will result in demand of innovative materials able to solve new needs in different fields. Environmental deterioration and the scarcity of fresh water have become imperative global issues to be solved nowadays. Polyaniline (PANI) and PANI nanocomposites are innovative materials that have gained popularity in addressing water and air pollution issues. These materials, combining electrostatic and hydrophobic segments in their backbone, showed promising results in the abatement of both remove organic (mainly hazardous dyes) and inorganic (mainly toxic metals) pollutants. Even though many methods have developed to synthesized PANI of good quality in terms of conductivity, stability and porosity, all these approaches are based on the use of toxic stoichiometric oxidants (typically metals in high oxidation state) and lead to the production of carcinogenic coproducts (i. e. benzidine and trans-azobenzene) [1]. In line with the growing environmental sensitivity and the necessity of clean products, we have recently addressed our efforts on the development of environmentally friendly protocols to produce “green” PANI [2-4]. Herein, we report a brief overview of our results on the synthesis of PANI and its composites by environmentally friendly approaches and our recent goals in the abatement of VOCs [5] and NO2 from air matrices and dyes [4], hydrocarbons [6] and metals from water [4]. [1] J. C. Chang, A. G. MacDiarmid. Polyaniline: Protonic acid doping of the emeraldine form to the metallic regime. Synth. Met., 1986, 13, 193–205. [2] Z. Chen, C. Della Pina, E. Falletta, M. Rossi. A green route to conducting polyaniline by copper catalysis. J. Catal., 2009, 267, 93-96. [3] C. Della Pina, M. Rossi, A. M. Ferretti, A. Ponti, M. Lo Faro, E. Falletta. One-pot synthesis of polyaniline/Fe3O4 nanocomposites with magnetic and conductive behaviour. Catalytic effect of Fe3O4 nanoparticles. Synth. Met., 2012, 162, 2250-2258. [4] C. Cionti, C. Della Pina, D. Meroni, E. Falletta, S. Ardizzone. Triply green polyaniline: UV irradiation-induced synthesis of a highly porous PANI/TiO2 composite and its application in dye removal. Chem. Commun., 2018, 54, 10702-10705. [5] C. Della Pina, M. A. De Gregorio, P. Dellavedova, E. Falletta. Polyanilines as New Sorbents for Hydrocarbons Removal from Aqueous Solutions. Materials, 2020, 13, 2161(1-10). [6] C. Della Pina, M. A. De Gregorio, L. Clerici, P. Dellavedova, E. Falletta. Polyaniline (PANI): an innovative support for sampling and removal of VOCs in air matrices. J. Haz. Mat., 2018, 344, 1-8.