Non-toxic nano approach for wastewater treatment using Chlorella vulgaris exopolysaccharides immobilized in iron-magnetic nanoparticles

The current study, novel magnetic nano-composite particles (Fe₃O₄@EPS) were successfully synthesized via the co-precipitation of iron (III) chloride and iron (II) sulfate (Fe₃O₄ nanoparticles) with exopolysaccharides (EPS) derived from the microalga Chlorella vulgaris. The physico-chemical nature of the Fe₃O₄@EPS was investigated in depth. Transmission electron microscopy (TEM) results estimated the core-shell nature of Fe₃O₄@EPS aggregated inside the indistinctly layered EPS matrix to be 10–20 nm in size. Scanning electron microscopy-based energy dispersive spectral analysis indicated that elemental Fe was successfully loaded on to the EPS polymeric ion-exchanger at a rate of 63.3% by weight. FT-IR results demonstrated that Fe₃O₄ nanoparticles were successfully modified by the functional groups present in EPS. Fe₃O₄@EPS showed a highly magnetic nature at 5.0 emu/g. The XPS survey spectrum, which showed two major peaks at 724.1 and 710.2 eV revealed the elemental composition and electronic structure of Fe₃O₄ nanoparticles and Fe₃O₄@EPS. Furthermore, nutrient removal from wastewater was studied. Under optimum conditions (3.5 g/L of Fe₃O₄@EPS, pH 7.0 and 13 h of incubation) 91% of PO₄³⁻ and 85% of NH₄⁺were effectively eliminated. These findings demonstrate the potential of Fe₃O₄@EPS for removing PO₄³⁻ and NH₄⁺ in wastewater treatment plants.