Synthesis of Fe3O4 nanoparticles via reduction of Fe3+ using Sargassum polycystum for methylene blue dye removal in aqueous solution

Seaweed Sargassum polycystum, a common genus of brown algae richly represented in the Philippine marine macrobentic algal flora, was introduced to successfully synthesize magnetic iron oxide nanoparticles (Fe3O4 –NP’s) for removal of methylene blue (MB) in aqueous solution. The brown seaweed aqueous extract has total phenolic content of 49.107±1.07 mg-GAE/g and total soluble carbohydrates of 57.907±3.81mg-GE/g served as reductant and stabilizer to employ an environmental friendly technique of producing Fe3O4-NP’s. Central composite design was used to analyze the effects of metal-to-extract ratio (0.5, 1.0, 1.5), reaction time (30, 60, 90 minutes) and reaction temperature (45, 65 and 85oC) on production of Fe3O4-NP’s and its effectiveness to remove methylene blue. The synthesized Fe3O4-SP Np’s at optimized condition weighed 1.027 grams and removed 88.97% methylene blue from an aqueous solution with desirability of 0.838. The effect of pH in the removal of the methylene blue using the synthesized Fe3O4-SP-NP’s was found to have the highest percentage removal at pH 11. The synthesized nanoparticle at optimum condition was characterized using ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-Ray (EDX) and dynamic light scattering (DLS). UV-VIS revealed characteristic peak at 313nm and 361nm which was attributed to Fe3O4-NP’s existence in colloidal solution while FTIR demonstrated absorption band at 571cm-1 corresponding to an Fe-O bond. The XRD diffraction planes was observed at (220), (311), (400), (422), (511), (440) and (533) corresponding to cubic crystalline phase of Fe3O4-SP NP’s with crystallite size of 51.49±15.59nm. EDX spectra confirmed the presence of Fe, O, S, and C in the nanoparticle having particle sizes of 68.4±9.6 nm using SEM imaging