DEVELOPMENT OF MAGNETIC NANOHYBRIDS FOR PFAS CONCENTRATION-DEGRADATION TREATMENT AND PILOT-SCALE HARMFUL ALGAL BLOOM MITIGATION

Author

• Sonkorson Talukder Sabuj, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2026

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Liu, Jia

Abstract

Persistent PFAS contamination and harmful algal blooms (HABs) are distinct waterqualitychallenges, but both require treatment platforms that combine contaminant removal with material recovery. This thesis developed magnetically recoverable nanohybrids for (i) PFAS adsorption and UVC-assisted degradation and (ii) pilot-scale HAB mitigation with simultaneous phosphorus removal. For PFAS treatment, a low-cost rGO@Fe₃O₄ nanohybrid was synthesized by solvothermal reduction using laboratory-produced graphene oxide, Fe₃O₄ nanoparticles, and ethanol. The optimized material was produced at 150°C for 6 h and exhibited a BET surface area of 109.19 m²/g and saturation magnetization of 37.6 emu/g, enabling magnetic recovery. The nanohybrid showed rapid PFAS adsorption under dark conditions: PFOS removal reached 99.64% within 2 min, while PFOA removal reached approximately 80% within 2 min. Adsorption isotherms confirmed stronger PFOS affinity, with a Langmuir maximum capacity of 26.72 mg/g compared with 2.65 mg/g for PFOA. Preconcentrated UVC treatment showed decreasing recoverable parent PFAS concentrations, formation of shorter-chain intermediates, and fluoride ion release, confirming transformation beyond adsorption. PFOS was highly resistant to direct UVC photolysis, but rGO@Fe₃O₄ increased direct defluorination from 7.07 ± 0.37% without nanohybrids to 59.66 ± 0.35% after 72 h. Iron release remained below the U.S. EPA secondary drinking water standard of 0.3 mg/L, supporting nanohybrid stability. For HAB mitigation, a Fe₃O₄@SiO₂@γ-Fe₂O₃/TiO₂ core–double-shell nanohybrid was synthesized to improve magnetic recovery while retaining photocatalytic and phosphorusadsorption functionality. At 200 mg/L, bench-scale treatment produced OD₆₀₀ reductions of 29.28 ± 1.46% for Microcystis aeruginosa and 33.54 ± 2.49% for Cylindrospermopsis raciborskii, with 39.12 ± 3.51% phosphorus removal after 3 h. A 30 L modular point-of-use reactor was then constructed using borosilicate tubes, simulated solar irradiation, air-assisted mixing, and external magnetic recovery. In pilot-scale phosphorus removal, the same nanohybrid suspension removed 41.46 ± 0.00%, 37.19 ± 0.61%, and 30.49 ± 1.22% phosphorus over three consecutive cycles. Pilot-scale cyanobacterial treatment achieved OD₆₀₀ reductions of 32.06 ± 1.03%, 79.63 ± 3.90%, and 47.79 ± 4.51% for M. aeruginosa, C. raciborskii, and mixed cultures, respectively, with simultaneous phosphorus removal. Overall, magnetic nanohybrids provided recoverable treatment platforms for PFAS concentration-degradation and HAB mitigation. The results demonstrate that magnetic separation can improve material recovery and reuse while enabling multifunctional treatment in both contaminant-focused and algal-bloom-control applications. These findings support further optimization of nanohybrid composition, reactor design, and long-term cycling performance for practical water-treatment applications.