Phosphate-binding protein-loaded iron oxide particles: adsorption performance for phosphorus removal and recovery from water

• Published in: Environmental science water research & technology 2024-05, Vol.1 (5), p.1219-1232
• Main Authors: Hussein, Faten B, Cannon, Andrew H, Hutchison, Justin M, Gorman, Christopher B, Yingling, Yaroslava G, Mayer, Brooke K
• Format: Article
• Language: English
• Subjects: Adsorbents; Adsorption; Amino acid sequence; Amino acid sequences; Amino acids; Anions; Bicarbonates; Conjugation; Immobilization; Ionic strength; Iron oxides; Orthophosphate; Phosphates; Phosphorus; Phosphorus removal; Potassium chloride; Proteins; Recovery; Room temperature; Succinimide; Sulfates; Surface area; Surface chemistry
• ISSN: 2053-1400; 2053-1419
• DOI: 10.1039/d4ew00052h

Adsorbents featuring high-affinity phosphate-binding proteins (PBPs) have demonstrated highly selective and rapid phosphorus removal and recovery. While immobilized PBP is promising for inorganic phosphate (orthophosphate, P i ) removal and recovery, increased adsorption capacity of PBP-based materials is essential to enhance the feasibility of PBP for scaled implementation. Here, magnetic n -hydroxy succinimide (NHS)-activated iron oxide particles (IOPs) were used to immobilize PBP (PBP-IOPs). The PBP-IOPs provided rapid P i removal, with more than 95% adsorption within 5 min. Slightly acidic pH, room temperature (20 °C), and low ionic strength (0.01 M KCl) demonstrated the best removal efficiency. The P i adsorption capacity of PBP-IOPs was not affected by anions such as chloride, sulfate, nitrate, bicarbonate, and borate. PBP-IOPs released 99% of total adsorbed P i using pH adjustment. Conjugation of PBP to higher surface area per mass IOPs increased P i attachment capacity (0.044 mg g −1 ) relative to previous studies of PBP immobilized on Sepharose resin (0.0062 mg g −1 ). Accordingly, PBP-IOPs have the potential to rapidly, spontaneously, selectively, and reversibly capture P i . Theoretical capacity calculations indicated that parallel improvements in surface area to mass ratio of the base immobilization material together with reducing the size of the P i -binding amino acid sequence (while retaining P i specificity) are needed to further advance design and implementation of PBP-based adsorbents. Adsorbents featuring high-affinity phosphate-binding proteins (PBPs) have demonstrated highly selective and rapid phosphorus removal and recovery.