Green NiO nanoparticles: A sustainable solution for photocatalytic treatment of industrial color effluents

In this work, NiO nano-sized photocatalyst has been effectively synthesized by a proficient and cost-effective method utilizing coconut bark extract as a novel fuel for the combustion protocol. The synthesized NiO nano-sized photocatalysts were characterized using various analytical techniques, including UV-visible absorption spectroscopy, infrared spectroscopy, and X-ray diffraction (XRD). The morphology and elemental composition of photocatalysts were analyzed by scanning electron microscope (SEM) and electron-dispersion spectroscopy. Photocatalytic activities of the synthesized material are applied to degrade ten synthetic dyes and three industrial effluent samples (EFS) collected from cotton and silk dyeing units. NiO nano-sized photocatalyst degraded 56.7% of the Amido black (AB), 96.6 % of Acid orange (AR) 10, 99.9% of AR 7, 87.7% of Alizarin red S (ARS), 99.7 % of Carmoisine (CAR), 70.8% of Metanil yellow (MY), 99% of Methyl orange (MO), 97.8% of the Methylene blue (MB), 95.5 % of Rhodamine B (RB), 99.9% of Crystal violet (CV) dyes and 62 % of EFS 1, 55% of EFS 2, and 46% of EFS 3 in 100 mins under UV light irradiation at pH 7. A plausible photocatalytic process also explains the remarkable photocatalytic efficiency of NiO nano-sized photocatalyst over dyes and EFS. The results obtained in this study are consistent with previously reported findings. For instance, NiO nanoparticles synthesized through annealing NiCl₂ demonstrated a 72.5% degradation of MB dye, whereas the current protocol achieved a significantly higher degradation efficiency of 97.8%. The photocatalyst reported herein can be a promising candidate for wastewater remediation applications.