pH–Controlled Synthesis of Magnetic Fe₃O₄ Nanoparticles for Enhanced Crystal Violet Dye Degradation via Photo–Fenton Process

The increasing industrialization has exacerbated the scarcity of clean water, making wastewater treatment and dye degradation critical environmental challenges. Magnetic nanoparticles (MNPs) have emerged as promising catalysts for efficient wastewater remediation due to their high surface area, magnetic recoverability, and catalytic activity. This study investigates the influence of synthesis pH (6–9) on the structural, morphological, and catalytic properties of Fe₃O₄ MNPs synthesized via the co-precipitation method. Comprehensive characterization using XRD, FTIR, SEM, and EDX confirmed the formation of cubic crystalline Fe₃O₄ with phase purity, where pH variations significantly influenced particle size, morphology, and surface charge. SEM analysis revealed that pH 7 yielded well-dispersed nanoparticles with optimal porosity, while extreme pH conditions (6, 8, 9) led to irregular aggregation. The catalytic efficiency of the synthesized MNPs was evaluated in the photo-Fenton degradation of crystal violet (CV) dye under visible light. The MNPs synthesized at pH 7 exhibited superior performance, achieving 94% CV degradation within 60 min, compared to 88–89% degradation at other pH values (requiring 75–150 min). Further parametric studies established optimal conditions: 0.1 mM CV, 100 mg/L catalyst dosage, 0.1 M H₂O₂, and neutral pH. The catalyst demonstrated excellent reusability, retaining 82% efficiency after five consecutive cycles. These findings highlight the critical role of synthesis pH in tailoring MNP properties for enhanced dye degradation, offering a sustainable and magnetically separable solution for industrial wastewater treatment.