Bimetallic capture sites on porous La/Bi hydroxyl double salts for efficient phosphate adsorption: Multiple active centers and excellent selective properties

Abstract

The rapid development of modern agriculture aggravated water eutrophication. Therein, efficient and selective removal of phosphorus in water is the key to alleviating eutrophication. It is well known that lanthanum (La)-based material is a kind of outstanding phosphorus-locking agent. Therefore, improving the property of La-based adsorbents is a hot topic in this field. Herein, novel porous hydroxyl double salts (La/Bi-HDS) with bimetallic capture sites were prepared. The experimental result shows that La/Bi-HDS could maintain the high removal rate in the solution with a higher concentration of competing ions and the maximum P adsorption quantity of La/Bi-HDS attains 168.12 mg/g. Mechanistic studies supported by density functional theory (DFT) calculation demonstrate that introducing Bi³⁺ optimizes the electronic structure of La, reducing adsorption energy. In addition, the surface analysis shows that the introduction of Bi, which increases the pore size and volume of the material, improves the utilization efficiency of the active site. In a word, the introduction of Bi element as a strategy of killing two birds with one stone successfully improved the performance of La-based adsorbent. It provided a new direction for developing an efficient phosphorus-locking agent.

Keywords: Hydroxyl double salts; La/bi-HDS; Lanthanum-based adsorbent; Phosphate adsorption; Selective adsorption.