Synergistic effect of polymer supported NiO/Bi2O3 nanocomposite for photocatalytic degradation of industrial wastewater

The red wastewater produced from TNT manufacturing units is a cause of concern in India. In this regard, a novel photocatalyst, PANI/NiO-Bi₂O₃ was developed by following hydrothermal method and in-situ oxidative polymerization and applied for the treatment of red wastewater. The band gap energy of 2.25 eV and 1.75 eV were observed for the bimetallic (NiO-Bi₂O₃) and polymer supported bimetallic (PANI/NiO-Bi₂O₃), respectively. The reaction parameters and degradation kinetics were studied and optimum reaction conditions were evaluated by changing the catalyst quantity and time. The PANI/NiO-Bi₂O₃ (0.25 g/L) with UV–Vis light irradiation was proved to be more efficient and economical for degrading the red wastewater below the discharge limits of TOC (<2 mg/L) and TDS (<500 mg/L), as recommended by USEPA. The kinetic rate of PANI/NiO-Bi₂O₃ was observed to be 0.0068 min⁻¹. The degradation curve indicates complete mineralization of the pollutants present in industrial wastewater into CO₂ and H₂O.