Lanthanum Hybridized with Fe3o4 For Efficient Phosphate Adsorption: Synthesis, Characterization, and Phosphorus Enrichment

Abstract

Recovery of low concentration phosphate in water is an effective strategy to control eutrophication and alleviate phosphorus (P) shortage crisis. In this study, a series of lanthanum (La)-based magnetic composites which includes the phosphate-binding lanthanum forms (La3+/La2(CO3)3/La(OH)3/La2O3) hybridized with Fe3O4 nanoparticle were fabricated by in situ embedded approach for phosphate uptake from water. Based upon the screening of synthesized four lanthanum forms and La-to-Fe molar ratios in terms of phosphate adsorption capacity, a La3+@Fe3O4 composite with the La-to-Fe molar ratio of 4:1 (MLI-41) was selected for further detailed characterization and evaluation. MLI-41 exhibits a competitive phosphate adsorption capacity of 77.85 mg P/g, good phosphate adsorption activity over the broad pH range from 5 to 10, excellent phosphate adsorption selectivity in the presence of competing ions (Cl–, NO3–, SO42–, HCO3−, Ca2+, Mg2+, HA). In four actual P-containing environmental water bodies (TP<5 mg P/L), 0.1 g/L of MLI-41 can efficiently reduce the phosphate concentration to below the related P standard limits. The ligand exchanges mechanism contributed to the phosphate adsorption of MLI. Moreover, the exhausted MLI-41 can be easily regenerated by 3 hours treatment of the 2.5 M NaOH and 1.875 M NaCl mixture. The amount of total phosphorus in the continuously used desorbent is gradually enriched and consistent with the loss of the total phosphorus in the water.

Keywords: phosphorus recovery, Adsorption, Magnetic separation, lanthanum