Constructing 3D flower-like LaFe bimetal oxides with abundant mesoporous and controllable active sites for high-efficient phosphorus removal: Synthesis, mechanism, and application

The design of high-performance porous adsorbents for phosphorus removal is a persistently hot topic to maintain a sustainable aquatic ecosystem. In the present study, a self-templating strategy using LaFe cyanometallates (CMs) as precursors was adopted to prepare porous LaFe bimetal oxides with optimizable structure and composition for phosphate adsorption. The results showed that a high supplied LaIII/FeII ratio enabled an adequate coordination polymerization in the preparation of LaFe CM precursor and led to a striking three-dimensional (3D) structure of "twin lotus flower" with high coordinated water content, which resulted in a 3D flower-like LaFe oxide with high surface area and high porosity (mainly in mesopore). The LaFe oxide of LaFe15T possessing the optimal La/Fe ratio (1.5: 1) exhibited the most superior performance of phosphate adsorption, where La was confirmed to be the main active site for phosphate capture via ligand exchange mechanism. The batch and column tests of phosphate adsorption showed that the 3D flower-like LaFe oxides are effective adsorbents for phosphate removal. Therefore, the structure optimization in the template preparation stage is an effective strategy to design porous LaFe bimetal oxides as high-performance phosphorus removal materials.