Advanced phosphate and nitrogen removal in water by La-Mg composite

A novel La-Mg composite was prepared for the removal of low concentration phosphate and ammonium nitrogen to alleviate the eutrophication problem. The composition and morphology of La-Mg composite was characterized; Its surface was composed of La, Mg, C, and O elements, with a specific surface area of 21.92 m²/g. La-Mg composite presented excellent removal of phosphate (100%) and nitrogen (96.8%), and the adsorption capacity reached 49.72 mg-P/g and 159.30 mg-N/g for separated adsorption. The composite also had a wide pH usability range (3-11 for P and 3-9 for N) and the adsorption process was almost not disturbed by coexisting ions. After adsorption, it could be regenerated by Na₂CO₃ and reused effectively. For actual water treatment, a very low residual P of 0.01 mg/L and N of 0.05 mg/L were achieved. Furthermore, Mechanism analysis showed that P adsorption involved ligand exchange and electrostatic attraction. The potential mechanisms of N adsorption involved electrostatic attraction and ion exchange. The results showed that the La-Mg composite is a novel and efficient adsorbent for actual water treatment to achieve ultra-low nutrients concentration.