<p>In this work, zinc-doped tin ferrite (SnFe₂₋ₓZnₓO₄, x = 0 to 0.1) magnetic nanoparticles were synthesized via a mixed surfactant-assisted co-precipitation method and evaluated for their photocatalytic performance in degrading cationic methylene blue (MB) and anionic Congo red (CR) dyes in aqueous media. Comprehensive characterization using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS), optical band gap measurements, magnetic force (<i>F</i>_m) analysis, and point of zero charge (pH_Pzc) determination revealed that zinc incorporation markedly modified the structural, optical, and magnetic properties of the ferrite nanoparticles. The influence of operational parameters including irradiation time, initial dye concentration, catalyst loading, solution pH, temperature, and ionic strength on degradation efficiency was systematically examined. Among the samples, SnFe₁.₉₂₅Zn₀.₀₇₅O₄ exhibited superior photocatalytic activity, achieving up to 90.8% MB degradation within 120&#xa0;min and 97.0% CR degradation within 180&#xa0;min under UV irradiation. Radical scavenging tests identified hydroxyl (^•OH) and superoxide (^•O₂⁻) radicals as the dominant reactive species facilitating dye degradation. Kinetic analysis indicated second-order degradation kinetics for both dyes. The photocatalyst demonstrated notable stability and recyclability over four consecutive cycles with minimal loss of activity. Furthermore, phytotoxicity assessments using wheat (<i>Triticum aestivum</i>) seeds confirmed the biocompatibility of the synthesized photocatalysts and the reduced toxicity of the treated dye solutions. These findings underscore the potential of Zn-doped SnFe₂O₄ magnetic nanoparticles as effective, magnetically recoverable photocatalysts for wastewater remediation with promising environmental safety profiles.</p> Graphical Abstract <p></p>