Reduction of Cr6+ from Wastewater Using a Novel in Situ-Synthesized PANI/MnO2/TiO2 Nanocomposite: Renewable, Selective, Stable, and Synergistic Catalysis

An in situ synthesis of a new nanocomposite, polyaniline/manganese dioxide/titanium dioxide (PANI/MnO2/TiO2), via a one-pot oxidative polymerization method at room temperature is described in this article. The characterization was done on the synthesized nanocomposite using UV-vis, FT-IR, XRD, TGA, SEM, and TEM analysis. A superior catalytic activity is exhibited by the synergistic PANI/MnO2/TiO2 nanocomposite in the conversion of toxic Cr6+ to benign Cr3+ in comparison with PANI, MnO2, TiO2, PANI/MnO2, PANI/TiO2, MnO2/TiO2, and other nanocomposite materials reported. The reduction rate is dependent on the concentration of substrate (Cr6+), oxidant (HCOOH), and catalyst, pH, temperature, and foreign ions. The PANI/MnO2/TiO2 reveals an excellent conversion (99.9%), rate constant (15.97 X 10(-2) min(-1)), and turnover frequency (0.3333 mmol/mg/min) in the reduction of Cr6+. The results obtained from this study illustrate that the prepared nanocomposite, PANI/MnO2/TiO2, can be very well used as an effective and economically viable catalyst for the reduction of toxic contaminant Cr6+ from wastewater.