Synthesis and characterization of magnetically separable ZnFe2O4/Fe2O3/chitosan ternary nanocomposites and their application as visible nano-photocatalyst for degradation of water-soluble organic pollutants

Organic contaminants are increasingly concerning due to their widespread use, release into water, prolonged environmental persistence, and harmful effects on ecosystems and public health. Photocatalysis has emerged as an eco-friendly solution for environmental remediation. In this study, we prepared an efficient, magnetically separable ZnFe2O4/Fe2O3 photocatalyst for organic dye degradation using an ultrasonic-assisted sol–gel method, followed by enhancement with chitosan to improve photocatalytic performance. This study presents an optimization strategy by systematically evaluating the effects of surfactants and precipitating agents on the purity, particle size, and morphology of ZnFe2O4/Fe2O3 nanoparticles. The photocatalytic performance of the designed bionanocomposite was assessed through the degradation process of Eosin (EO) and Erythrosine (ER) dyes. To the best of our knowledge, no prior research has examined the degradation of EO and ER using a visible-light-active ZnFe2O4/Fe2O3/Chitosan ternary nanocomposite photocatalyst. The ZnFe2O4/Fe2O3/chitosan catalyst demonstrated excellent photocatalytic activity in neutral conditions, making it suitable for sustainable wastewater treatment. The combination of chitosan to ZnFe2O4/Fe2O3 nano-photocatalyst enhance charge dynamics through amine-hydroxyl interactions, facilitates dye adsorption through functional interactions, increase surface area, offers eco-friendly solutions, and promotes synergistic effects that collectively improve photocatalytic efficiency. Incorporating chitosan (50% wt) significantly boosted degradation efficiency, achieving 96.5% removal of dyes under visible light, which was higher than pure ZnFe2O4/Fe2O3 (91.1%). The findings show that benzoquinone as a superoxide scavenger remarkably decreases the photocatalytic activity. This emphasizes the crucial role of $$^{\cdot} {\text{O}}_{2}^{ - }$$ radicals in this process. Besides, the mechanism of photodegradation, role of different scavengers, stability of photocatalyst, effect of dye concentration, catalyst dosage, and pH of solution were investigated in detail. This bio-based approach not only improves the photocatalytic activity but also aligns with sustainable wastewater treatment practices, offering a highly effective, environmentally friendly, and magnetically recoverable solution for dye degradation.