Annealing Temperature- and Morphology-Controlled Development of Nickel Cobaltite Nanoneedles for Photocatalytic Degradation of Nitroaromatics

Abstract

A one-dimensional (1D) nanoneedles of nickel cobaltite have been developed and applied to treat nitroaromatics-bearing wastewater. A significant change in the magnetic and photocatalytic properties of NCO has been observed at different annealing temperatures and is correlated to the morphology and phase structure. The sample annealed at 550 °C displayed the sharpest 1D nanoneedle-like structure with an optimum surface area (44 m 2 g −1 ), pore size (11 nm), band gap energies (1.87 and 2.52 eV), and saturation magnetizations (5.09 emu g −1 ) at a 5 T magnetic field. The complete photodegradation of 2,4,6-trinitrotoluene (50 mg L −1 ) occurred within 3 h by using NCO-550 (300 mg L −1 ) under UV−vis light. The degradation rate showed first-order kinetics with a rate constant of 1.6 h −1 . The magnetic behavior of the catalyst showed negligible wastage even after repeated cycles. The degradation mechanism, as elucidated by gas chromatography−mass spectroscopy (GCMS), indicated complete mineralization of the nitroaromatics into CO 2 and H 2 O.