Continuous phosphorus elimination from low concentration wastewater by a calcium-doped lanthanum carbonate adsorbent

Lanthanum (La) adsorbents are highly effective for phosphorus removal but are constrained by their high reagent cost because of their La content. By exploiting the similarity in ionic sizes between Ca 2+ and La 3+ , we develop a low-cost composite adsorbent LCCa-5@Dia by doping La 2 (CO 3 ) 3 ·8H 2 O with Ca 2+ . Our results indicate that the slow addition of NaHCO 3 during the synthetic process facilitates the incorporation of Ca 2+ into the La 2 (CO 3 ) 3 ·8H 2 O lattice, leading to an adsorption behavior nearly identical to that of the undoped adsorbents. LCCa-5@Dia demonstrates a high adsorption capacity of 60.04 mg P/g, with stable performance across a pH range of 3 to 11. Its adsorption property also exhibits excellent stability under the interference of solution pH and competing ions. Materials characterization reveals that the adsorption occurs through electrostatic attraction and ligand exchange. In continuous column-adsorption experiments, the LCCa-5@Dia adsorbent treats up to 4000 bed volumes of simulated low concentration wastewater (1.7–2.7 mg P/L). This translates to a treatment cost as low as $0.0211/m 3 . Meanwhile, the adsorbent also maintains over 80 % of the adsorption capacity after three regeneration cycles. The excellent performance and low treatment cost of the calcium-doped lanthanum carbonate adsorbents highlight its practical potential in treating low concentration wastewater.