Engineered magnetic particles derived from steelmaking dust for phosphorus recovery and extracellular DNA removal from municipal wastewater

Phosphorus (P) is a critical and finite raw material fundamental to various biological roles and industrial applications. Its limited availability can be managed through recovery from wastewater. However, wastewater often contains hazardous contaminants, including antibiotic resistance and virulence genes associated with extracellular DNA (exDNA), which may compromise the safety of recovered P products. To address this issue, magnetically separated electric arc furnace dust (ms-EAFD), a by-product of the steelmaking process, was functionalized using dissolution recrystallization protocol utilizing NaOH and Ca(OH)₂ and applied as an adsorbent for P recovery and exDNA removal from municipal wastewater treatment plant effluent. Upon functionalization, ms-EAFD increases its specific surface area seven-fold and shifts zeta potential towards positive values. This causes an increase in phosphate removal efficiency from 7.1% to above 70% and adsorption capacity from 0.5 to above 4.5 mg/g (at 15 mg/L PO₄^3-). Ca-enriched material induce microprecipitation of CaP in P-rich wastewater, improving phosphorus removal efficiency. exDNA removal efficiency depends on its concentration and the composition of the water matrix regardless of the applied adsorbent. All materials demonstrate exDNA removal efficiency ranging from 75 to 100% in wastewater containing 0.5 PO₄^3- mg/L, which drops to approximately 20% when PO₄^3- concentration reaches 5 mg/L. The adsorbent regeneration with 0.5M NaOH (pH > 13) led to efficient phosphate desorption and complete degradation of exDNA in the eluate. The proposed approach may facilitate industrial symbiosis and repurpose EAFD into a valuable material for improving wastewater treatment efficiency.