Nano-bioremediation of nutrient pollutants using Chlorella vulgaris-functionalized magnetic nanoparticles: removal of ammonium, phosphate, and COD from wastewater

Nutrient-rich wastewater containing ammonium (NH4+), phosphate (PO43−), and organic matter contributes to eutrophication in aquatic ecosystems. Microalgae-based bioremediation offers a sustainable and eco-friendly approach, and its integration with nanotechnology can enhance removal efficiency, operational stability, and recyclability. This study aimed to develop a Chlorella vulgaris–iron oxide nanobiocomposite (Cvul/IONs) and evaluate its capacity to remove NH4+, PO43−, and chemical oxygen demand (COD) from synthetic wastewater. A Chlorella vulgaris strain naturally isolated from freshwater in Iran was taxonomically validated and deposited in NCBI (Accession No. PX533081). The microalgae were cultured in BG-11 medium, harvested, lyophilized, and combined with iron oxide nanoparticles to synthesize the Cvul/IONs nanobiocomposite. Batch experiments were conducted to evaluate the removal of NH4+, PO43−, and COD over 48 h at 25 °C under controlled light conditions (2000 lx). Recyclability tests were performed for five consecutive treatment cycles, and the nanobiocomposite was recovered magnetically after each cycle for reuse. The Cvul/IONs nanobiocomposite demonstrated enhanced nutrient removal performance compared to bare iron oxide nanoparticles. Specifically, NH4+ removal reached 93%, PO43− removal reached 90%, and phosphate reduction was rapid, with 70% of PO43− removed within 2 h. The nanobiocomposite retained high removal efficiency across five reuse cycles, exhibiting minimal loss in performance. Magnetic recovery facilitated rapid and simple separation, enabling operational stability and reusability. The Cvul/IONs nanobiocomposite represents an eco-friendly, magnetically recoverable, and cost-effective biosorbent. It efficiently mitigates nutrient pollution in wastewater, reduces the risk of eutrophication, and demonstrates practical potential for sustainable wastewater treatment applications. The Chlorella Vulgaris Strain Was Isolated From Freshwater In Iran (ncbi Accession: Px533081) And Characterized For Its Biochemical Composition, Including Protein, Lipid, And Carbohydrate Contents. The Lyophilized Microalgal Biomass Was Then Integrated With Iron Oxide Nanoparticles (ions) To Fabricate The Cvul/ions Nanocomposite. The Nanocomposite Was Applied For Wastewater Treatment, Achieving Efficient Removal Of Cod, Ammonium (nh4+), And Phosphate (po43−). Following Treatment, The Nanocomposite Was Magnetically Recovered And Demonstrated Successful Recyclability Across Multiple Cycles, While Maintaining High Removal Efficiency.