Enhanced photocatalytic degradation of basic fuchsin using NiFe2O4/SiO2 nanomagnets: synthesis, characterization, and application in wastewater treatment

This study investigates the efficiency of silica-supported NiFe₂O₄ nanoparticles as a magnetically recoverable photocatalyst for degrading basic fuchsin pollutants. Ni–Fe/SiO₂ nanocomposites were easily synthesized by wet impregnation followed by calcination (T = 350–700 °C). The structural and optical study of Ni–Fe/SiO₂ calcined at 700 °C (Ni–Fe(700)) revealed the formation of nanosized spinel phase NiFe₂O₄ with an average size of 12 nm, a high specific surface area (147 m²g⁻¹), and a narrow band gap of 1.67 eV. Moreover, NiFe₂O₄/SiO₂ nanoparticles exhibited superparamagnetic behavior with a magnetic susceptibility of 1.9 × 10⁻² and a high saturation magnetization (47 emu g⁻¹). These unique properties enable superior photocatalytic performances and easy magnetic separation. Under optimized conditions (dye concentration: 10 ppm, catalyst concentration: 0.1 g L⁻¹, pH = 6), the nanoparticles achieved a remarkable 99% degradation efficiency of basic fuchsin within 40 min, with a pseudo-first-order rate constant of 0.1198 min⁻¹ and a substantial reduction in total organic carbon from 134 to 11 mg L⁻¹ (92%). This high effectiveness, combined with demonstrated recyclability over four cycles, highlights the nanoparticles’ strength and durability. Furthermore, NiFe₂O₄ nanoparticles are effective across a wide range of pH levels, making them highly adaptable for various environmental conditions. Oxidant radical scavenger experiments permit to identify the superoxide anion radical (^●O₂⁻) as crucial in the oxidative degradation process, indicating that NiFe₂O₄/SiO₂ acts as reduction photocatalyst. This work highlighted the primordial role of silica, not only as dispersing and stabilizing agent, but also as an actor in the photocatalytic process. Due to its negative electric charge, the adsorption of. cationic dye molecules and the charge separation are improved, while the electron–hole recombination is reduced. The synthesis of stable, highly photoactive, recyclable NiFe₂O₄/SiO₂ offers a sustainable solution for treating dye-polluted wastewater, thereby eco-friendly practices in industrial applications.

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