Evaluation of Structural, Morphological Stability and Photocatalytic Recyclability of Phytochemical Assisted MgO, NiO, and Co ₃ O ₄ Nanoparticles

Synthetic dyes are major water pollutants because of their persistent toxicity and resistance to biological degradation. Conventional treatment methods are often ineffective, making sustainable alternative approaches necessary. In this study, MgO, NiO, and Co 3 O 4 NPs were synthesized using a green route with Strychnos potatorum seed extract as reducing and stabilizing agent. Structural, functional, morphological, optical, surface area, and thermal properties were characterized by XRD, FTIR, FESEM, UV–vis, BET, and TGA analyses. Photocatalytic performance was evaluated for the degradation of reactive black (RB) and crystal violet (CV) dyes under sunlight. MgO exhibited the highest activity, degrading 99.82% of RB in 75 min and 99.9% of CV in 135 min, followed by NiO and Co 3 O 4 . Recyclability tests showed that all catalysts retained >93% efficiency after seven cycles, confirming recyclability. However, post‐degradation XRD and FESEM revealed morphological changes: cubic‐MgO converted to Mg(OH) 2 with flattened layers, NiO maintained its cubic structure with minor surface changes, and Co 3 O 4 showed phase fluctuations. Post‐calcination restored Mg(OH) 2 to cubic MgO, preserved NiO stability, and reverted the diffraction pattern of Co 3 O 4 with slight suppression. These results demonstrate the efficiency, recyclability, and structural resilience, highlighting their potential as eco‐friendly photocatalysts for sustainable treatment of dye wastewater.