Photocatalytic and Oxidative Synthetic Pathways for Highly Efficient PANI-TiO2 Nanocomposites as Organic and Inorganic Pollutant Sorbents

Abstract

Polyaniline (PANI)-materials have recently been proposed for environmental remediation applications thanks to PANI stability and sorption properties. As an alternative to conventional PANI oxidative syntheses, which involve toxic carcinogenic compounds, an eco-friendly procedure was here adopted starting from benign reactants (aniline-dimer and H2O2) and initiated by ultraviolet (UV)-irradiated TiO2. To unlock the full potential of this procedure, we investigated the roles of TiO2 and H2O2 in the nanocomposites synthesis, with the aim of tailoring the properties of the final material to the desired application. The nanocomposites prepared by varying the TiO2:H2O2:aniline-dimer molar ratios were characterized for their thermal, optical, morphological, structural and surface properties. The reaction mechanism was investigated via mass analyses and X-ray photoelectron spectroscopy. The nanocomposites were tested on both methyl orange and hexavalent chromium removal. A fast dye-sorption was achieved also in the presence of interferents and the recovery of the dye was obtained upon eco-friendly conditions. An efficient Cr(VI) abatement was obtained also after consecutive tests and without any regeneration treatment. The fine understanding of the reaction mechanism allowed us to interpret the pollutant-removal performances of the different materials, leading to tailored nanocomposites in terms of maximum sorption and reduction capability upon consecutive tests even in simulated drinking water.

Solar Light Photoactive Floating Polyaniline/TiO2 Composites for Water Remediation

“…In particular, the band at 1500 cm −1 is assigned to benzene rings of PANI, while that at 1600 cm −1 to quinone rings [14][15][16][17]51]. For all the PANI-modified PUs, no signals specifically attributable to titania are recognized, since in the ATR-FTIR spectrum of PANI many bands below 900 cm −1 are observed (Figure S1).…”

“…It has been demonstrated that PANIs are good candidates for the removal of dyes from the water matrix playing as sorbents, both as powder [14,16,17] and properly supported on different materials [59].…”

“…Among these approaches, adsorption is one of the most used treatments for the removal of pollutants from the water matrix thanks to its simplicity, low cost, high efficiency, and sustainability [13][14][15][16][17]. In fact, adsorption processes based on the use of environmentally-friendly adsorption materials, such as adsorbents originating from agricultural sources and by-products (fruits, vegetables, foods), agricultural waste and derivatives, biochar, hydroxyapatite, and so forth, represent a new generation of sustainable treatments that pave the way for new scenarios in this sector.…”

“…These processes lead to the formation of peroxides and hydroxyls that, further, take part in the mineralization of organic species. It is also important to note that CPs are good adsorbents for the removal of not only small organic molecules, which can escape the photodegradation process, but also dangerous heavy metals [14][15][16][17]. Among the CPs, polyaniline (PANI) is unique thanks to its ease of synthesis, environmental stability, redox properties and unique doping/dedoping process [40,41].…”

A Journey into the Determination of Polyaniline Molecular Weight

“…From their discovery to date, intrinsically conducting polymers (ICPs) have gradually captured the attention of the scientific community and the industrial world thanks to their outstanding properties that make them interesting for many applications in different sectors, such as supercapacitors [1,2] , sensors [3][4][5][6] , environmental remediation [7][8][9][10] and so on. Among them, polyaniline (PANI) occupies a special place due to its unique ease doping/dedoping process that allows to switch quickly from the insulating form to the conducting one and viceversa.…”