Abstract
A crucial requirement for environmental protection is the removal of carcinogenic organic pollutants from industrial effluents that are discharged into water bodies and jeopardize human health. In this study, newly designed Nd0.7Ca0.3Mn1-xNixO3 (x = 0.01-0.03) perovskite nanocomposites are proposed for the efficient photocatalytic degradation of methylene blue (MB) and tetracycline (TC) organic pollutants. Structural characterization by X-ray diffraction analysis has confirmed formation of a perovskite orthorhombic phase (Pnma) in equilibrium with an Nd2O3 secondary phase, the amount of which reduces significantly from 28 wt% for NdMnO3 to 5 wt% for the highly doped Nd0.7Ca0.3Mn0.97Ni0.03O3. Transmission electron microscopy observation has revealed polygon-shaped particles in the size range 32-56 nm. The band-gap energy was found to gradually decrease from 3.00 to 2.30 eV with increasing Ni loading. The as-prepared composites exhibit paramagnetic behavior, irrespective of the chemical composition, which facilitates simple magnetic recovery. Among the studied nanocomposites, Nd0.7Ca0.3Mn0.97Ni0.03O3 displayed the optimum photocatalytic activities for the degradation of MB (96.0%) and TC (96.6%). Its significantly enhanced photocatalytic activity can be attributed to a combination of several intrinsic characteristics, including high lattice distortion, narrow band-gap energy, a reduced electron-hole recombination rate, increased surface oxygen adsorption, and the presence of spin-polarized bands, as well as synergistic effects due to Ca/Nd substitution and Ni/Mn doping. The degradation reaction follows pseudo-first-order kinetics. Furthermore, the catalyst degrades the studied organic pollutants by at least 95%, with good stability over five consecutive reaction cycles and facile recovery without tedious purification or work-up processes. The present study demonstrates that the as-fabricated perovskite nanocomposite possesses the requisite properties for use as an efficient photocatalyst for the degradation of organic pollutants.