Impregnation of Phosphorus- and Nitrate-Selective Anion Exchangers with Zirconium Oxide Nanoparticles for Nutrient Recovery from Wastewater

Résumé fourni par la source

Nitrogen (N) and phosphorus (P) influx into receiving water bodies leads to cultural eutrophication and, therefore, poses a major environmental challenge. Consequently, increasingly stringent discharge limits have been established, necessitating advanced wastewater treatment methods. In addition, phosphorus is a finite resource, with current reserves projected to last less than a century. The principles of the circular economy therefore emphasize not only the removal of N and P from wastewater, but also their recovery and reuse as fertilizers. This article presents two strong-base anion-exchangers impregnated with zirconium oxide (ZrO2) nanoparticles to create the following: (1) a phosphorus-selective resin (Hybrid Anion Exchanger with ZrO2 (HAIX-Zr)), with a Zr loading of 2.5–3% (m/m) and an ion-exchange capacity (IEC) of ≈35 mg PO43− − P/g resin, and (2) a resin selective for both phosphorus and nitrate (Nitrate-Selective Resin with ZrO2 (NSR-Zr)), with a Zr loading of 1.5–2% (m/m), a simultaneous phosphate IEC of ≈41.3 mg PO43− − P/g resin, and a nitrate IEC of ≈41.3 mg NO3− − N/g resin. When loaded in a fixed-bed column, HAIX-Zr can treat > 300 Bed Volumes (BV) of wastewater to below the phosphate detection limit of 0.02 mg/L when the initial phosphate–phosphorus concentration is ≈11.0 mg/L and the two most common competing anions, Cl− and SO42−, are present at ≈225 mg/L and ≈160 mg/L, respectively. Regeneration of the exhausted HAIX-Zr column with a 2% NaCl + 2% NaOH solution resulted in >95% P recovery, which can be processed to generate MgNH4PO4 (struvite), a slow-release fertilizer. A fixed-bed NSR-Zr column can treat ≈150 BV of wastewater to below the phosphate detection limit of 0.02 mg/L and nitrate detection limit of 0.05 mg/L when the initial phosphate–phosphorus concentration is 31 mg/L, the nitrate–nitrogen concentration is 12 mg/L, and the competing anions Cl− and SO42− are present at ≈175 mg/L and ≈155 mg/L, respectively. Regeneration of the exhausted NSR-Zr column with 2% KOH solution resulted in >92% recovery of nitrogen and phosphorus in a solution rich in nitrogen, phosphorus, and potassium, the essential ingredients of a fertilizer.

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