Melia Azedarach impregnated Co and Ni zero-valent metal nanoparticles for organic pollutants degradation: validation of experiments through statistical analysis

The Melia Azedarach (MA) plant materials were used for the stabilization of Co (Co/MA) and Ni (Ni/MA) NPs prepared through simple chemical routes in an aqueous medium using NaBH₄ as a reducing agent. The prepared catalysts were extensively characterized through FTIR, XRD, FESEM, EDS, and TGA elemental analysis. These techniques suggest the presence of cellulose, hemicellulose, and lignin in the MA plant. Five modal pollutants methyl orange (MO), para-nitrophenol (PNP), Congo Red (CR), Rhodamine B (RB), and Methylene Blue (RB) were selected to assessed the catalytic activity of the synthesized catalysts. The Co/MA decolorized the MO and PNP in 4.5 and 12 min up to 81 and 93%, respectively, while the Ni/MA took 8 and 25 min in the decolorization of the same pollutants up to 95 and 89%, respectively. The k_app values for PNP degradation of Co/MA are higher which was 2.1 × 10^–1 compared to Ni/MA (4.9 × 10^–2 min⁻¹) confirming the highest catalyst activity of Co/MA. Similarly, we have observed the superior catalyst activity of Co/MA for all the selected pollutants and the highest rate constant found for MB dye was 2.2 × 10^–1 min⁻¹. The turnover frequency (TOF) found highest for Co/MA against PNP degradation which was 3.4 × 10^–1 h⁻¹ and lowest for Ni/MA against MO degradation (9.6 × 10^–2 h⁻¹), respectively. Furthermore, various statistical parameters indicated that all the experiments are highly significant.