In aquatic environments, phosphorus is known as the "limiting nutrient". It combines with nitrogen and photosynthetic processes to produce plant and algal growth. Phosphorus in marine life support systems exists in either a particulate or dissolved phase. While particulate sources may be removed during filtration or fractionation, the dissolved form persists. In a typical marine environment (pH8), dissolved phosphorus is almost all hydrogen phosphate ion (HOPO32-), also known as inorganic or orthophosphate. Here we report the synthesis and use of zirconium phosphate (α-ZrP, Zr(O3POH)2·H2O) and zirconium methylenediphosphonate (ZrMDP, Zr[O3P(CH2)PO3]) nanoparticles for phosphate removal from water. Sodium phosphate solutions (0.5-10.0 mg/L) are exposed to nanoparticle suspensions (10 mg/mL) and phosphate uptake is measured by ion chromatography. In all cases, high phosphate removal is observed. For example, the 5.00 mg/L sodium phosphate solution experiences 99.9% removal after exposure to α-ZrP. After treatment phosphate concentration drops to 0.005 mg/L. This is well below the algal growth threshold (0.01-0.05 mg/L). Future work will explore the particles phosphate removal capacity, their regeneration, and the ability to engineer a robust filtration media where the particles are anchored to a silica (sand) surface.

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