Immobilized phosphate-binding protein can effectively discriminate against arsenate during phosphate adsorption and recovery.

There is a strong impetus to establish a circular phosphorus economy by securing internally renewable phosphate (Pi ) resources for use as agricultural fertilizers. Reversible Pi adsorption technologies such as ion exchange can remove and recover Pi from water/wastewater for reuse. However, existing reversible adsorbents cannot effectively discriminate against arsenate (As(V)) due to the similarity between As(V) and Pi chemical structure. If As(V) is co-recovered with Pi , the value of the recovered products for agricultural reuse is low. The objective of this study was to construct an immobilized phosphate-binding protein (PBP)-based Pi removal and recovery system and analyze its selectivity for Pi adsorption in the presence of As(V). A range of conditions was tested, including independent, sequential, and simultaneous exposure of the two oxyanions to immobilized PBP (PBP resin). The purity of the recovered Pi product was assessed after inducing controlled desorption of the adsorbed oxyanions at high pH (pH 12.5). Pi constituted more than 97% of the adsorbed oxyanions in the recovered product, even when As(V) was initially present at twofold higher concentrations than Pi . Therefore, PBP resin has potential to selectively remove Pi , as well as release high-purity Pi free of As(V) contamination suitable for subsequent agricultural reuse. PRACTITIONER POINTS: Existing reversible phosphate (Pi ) adsorbents cannot effectively discriminate against arsenate (As(V)) due to the similarity in their chemical structure. Co-recovery of As(V) with Pi can reduce the recovered product's reuse as a fertilizer. An immobilized phosphate-binding protein (PBP)-based system can be highly selective for Pi even in the presence of As(V). Pi constituted more than 97% of the recovered product, even when As(V) was present at 2-fold higher concentrations than Pi . Immobilized PBP offers advantages over existing Pi adsorbents by providing high-purity Pi products free of As(V) contamination for reuse.