Potato starch-assisted green synthesis of nanoferrite and ferrite–semiconductor nanocomposites for effective visible light photocatalytic degradation of methylene blue

Biodegradable potato starch-assisted nanoferrite and ferrite–semiconductor nanocomposites have been synthesized by the co-precipitation method for the degradation of MB dye under visible light irradiation. Ferrite and ferrite–semiconductor composites synthesized using biodegradable potato starch displayed remarkable dye degradation activity which can be further explored for photocatalysis application. XRD confirms the pure phases for Fe₃O₄ (FFO) and ZnO–Fe₃O₄ (ZFFO), but a secondary SITO phase for TiO₂–Fe₃O₄ (TFFO) and microwave-annealed TiO₂–Fe₃O₄ (TFFO-MWA) due to dynamics between Fe, Ti, and NaOH. FTIR and Raman spectra confirmed the characteristic peaks of the starch surfactant and ferrite and/or semiconducting phase. TEM micrographs demonstrated mixed morphology: spherical particles of size 5–10 nm and rod shape of size 14–67 nm in length and 4–21 nm in diameter. XPS showed different valence states along with satellite peaks besides confirming the elemental composition. BET studies showed type-IV isotherms with H3 adsorption hysteresis indicative of mesoporous structures with ZFFO having the highest surface area (85.9 m² g⁻¹), minimum pore size, and maximum pore volume, while TFFO-MWA having the lowest surface area (19.1 m² g⁻¹), maximum pore size, and minimum pore volume. The direct bandgap of FFO, ZFFO, TFFO, and TFFO-MWA samples is found to be 2.50, 2.47, 3.18, and 3.16 eV, respectively. The photocatalytic degradation of MB dye under visible light irradiation was achieved to be 93% in 285 min by FFO, 96% in 150 min by ZFFO, 99% in 180 min by TFFO, and 99% in 90 min by TFFO-MWA. The R² values of adsorption kinetics studies validated that the kinetics can be best described by the first-order model for FFO, TFFO, TFFO-MWA, and second-order model for ZFFO considering the maximum R² values being established.