Phosphorous recovery from water via batch adsorption enrichment combined with struvite crystallization in a fluidized bed reactor

To assess the feasibility of recovering P from water by combining batch adsorption enrichment with struvite crystallization, we prepared four ternary layered double hydroxides (LDHs) with P-preferring elements (i.e., zirconium (Zr) or lanthanum (La)) via a facile coprecipitation method, and evaluated their performance in recovering P from water, particularly in enriching P from a low-level P solution. We find that all ternary LDHs demonstrate remarkably high P adsorption capacities, e.g., 1029.3 mg PO43− g−1 for ZnAlLa, outperforming other LDHs reported so far. Microstructural analyses show that the P uptake mechanisms are attributable to anion exchange, surface complexation and electrostatic attraction. Results of recycling tests indicate that all LDHs present good enrichment for P. Besides, more than 96% of phosphorus in the P-enriched eluates can be efficiently reclaimed via struvite crystallization in a fluidized bed reactor. These findings demonstrate the feasibility of combining adsorption enrichment with struvite crystallization for P recovery.