Methylene Blue (MB) is a thiazine dye whose carcinogenic, toxic, and non-biodegradable properties pose a threat to environmental safety. This common industrial colorant is typically disposed of by dilution into nearby waters, harming the aquatic life and humans who consume the pollutant. Previous studies have found that photocatalysts in the form of mixed-metal spinel ferrites (with formula MFe2O4 (where “M” represents a transition metal)) can facilitate decomposition of MB when exposed to light through the Fenton reaction scheme. Our research explores the impact on catalytic rates of MB oxidative degradation by substituting different first-row transition metals into the photocatalyst crystal lattice. Our research goal is to determine which transition metal is most able to facilitate Fenton chemistry compared to the baseline reaction using Fe3O4 (where M = Fe). Each mixed-metal spinel ferrite was prepared by sonochemical synthesis. Aqueous solutions of ferric nitrate and “M”- nitrate were basified and placed into a low-intensity ultrasonic cleaning bath at a power density of 1.34 W/L. The products were washed and centrifuged to concentrate the nanomaterials, and the resultant precipitate was desiccated and calcined to introduce the crystalline structure. Analysis using X-ray diffraction (XRD) and Energy-dispersive X-ray Spectroscopy (EDS) confirmed the composition of each mixed-metal spinel ferrite. A constant molar quantity of each catalyst was then used in the remediation on MB while an ultraviolet-visible photospectrometer measured the decline of MB absorbance, and the first-order rate constants were compared. The impact of these results provide further insight in producing the most effective means of containing industrial pollutants for environmental protection.