"Twin Lotus Flower" Adsorbents Derived from LaFe Cyanometallate for High-Performance Phosphorus Removal

Phosphorus (P) discharge is well recognized as the chief culprit of eutrophication and algal blooms. It is of pressing need to remove excessive phosphorus to protect the important watershed. Lanthanum (La) based materials are one type of attention-grabbing adsorbent due to their superior affinity to phosphate. Here, a La-Fe cyanometallate (CM) framework with a novel "twin lotus flower " structure was synthesized and rich hierarchical pores were fabricated via pyrolysis. The resultant "twin lotus flower " oxide of LaFe CM-500 was demonstrated to be a high-performance adsorbent for phosphate removal with a saturated capacity as high as 45.03 mg P/g. It also possessed superior removal ability for the stubborn low concentration of P pollution. The abundant hierarchical pores (from macropore to micropore) render a rapid diffusion of phosphate on the LaFe CM-500. The La components on porous adsorbent were verified to be the key active sites that form stable LaPO4 via a ligand exchange process. The effects of solution conditions (temperature, pH, co-existing ions, and humic acid) were also investigated, and a high selectivity for phosphate adsorption enables the as-prepared "twin lotus flower " adsorbent to be competitive in practical water body treatment.