Suppression of phosphorus release from sediment using lanthanum carbonate as amendment

The performance of lanthanum carbonate (LC) pertaining to the adsorption of phosphate (HwPO4w-3) was investigated, and the possible adsorption mechanism was elucidated. The stabilization of H(w)PO(4)(w-3)adsorbed to LC was evaluated. The influence of LC addition on the upward transport of phosphorus (P) from sediment to overlying water (OL-W) was studied, and the adsorption performance of H(w)PO(4)(w-3)on the LC-amended sediment was explored. The results of this work indicated that LC performed well in the elimination of H(w)PO(4)(w-3)from water in the pH range of 4 to 11, and the commercial and self-prepared LC samples afforded the maximum H(w)PO(4)(w-3)adsorption capacities of 57.9 and 99.4 mg P/g, respectively, at pH 7. The presence of coexisting species including chloride, bicarbonate, and sulfate had a small influence on the H(w)PO(4)(w-3)adsorption onto LC. The main H(w)PO(4)(w-3)adsorption mechanism of LC at pH 7 was the ligand exchange reaction between carbonate and H(w)PO(4)(w-3)forming the inner-sphere La-phosphate complexation. The self-synthesized LC exhibited much higher H(w)PO(4)(w-3)adsorption performance than the commercial LC. The overwhelming majority (> 97.0%) of H(w)PO(4)(w-3)adsorbed to LC primarily existed in the form of muriatic acid-extractable P, which has relatively low re-releasing risk. The addition of LC into sediment could significantly prevent the release of P from the sediment solid into the OL-W, thereby leading to a lower concentration level of reactive soluble P (RSP) in the OL-W compared with no LC treatment. The addition of LC into sediment could greatly improve the H(w)PO(4)(w-3)uptake ability for the sediment, and the enhancement of H(w)PO(4)(w-3)adsorption onto the sediment by the added LC increased as the increase of the amendment dosage and the initial H(w)PO(4)(w-3)concentration. All results suggest that LC could serve as a promising amendment material for the control of sedimentary P release.

Automated summary

Lanthanum carbonate (LC) shows good performance in removing phosphate from water, mainly through ligand exchange reaction between carbonate and phosphate to form complexes. Adding LC to sediment can significantly prevent the release of phosphorus, leading to lower concentrations of reactive soluble phosphorus in the overlying water.