Preparation of the Lanthanum-Aluminum-Amended Attapulgite Composite as a Novel Inactivation Material to Immobilize Phosphorus in Lake Sediment.

In this study, a green solvent-free drying production method was used to prepare an attapulgite clay/lanthanum and aluminum (ACLA) composite as a novel phosphorus (P) sorbent to immobilize P in lake sediment. The prepared sorbent contained around 5% La and 2% Al. The maximum P sorption capacity of ACLA can reach as high as 34.6 mg P/g and is higher than most clay-based P sorbents. The addition of ACLA into sediment can effectively reduce sediment mobile P and simultaneously induce elevated inert P forms of HCl-P and NaOH-rP, which also can increase the stability of P in sediment. Long-term sediment core incubation indicated that 72.2% of total phosphorus and 90.7% of soluble reactive phosphate (SRP), as well as 44.2% SRP fluxes, can be reduced with a dosage of 466 mg/m2 of ACLA when compared with the control treatment. The P binding mechanism by ACLA is assigned to the intersphere P complexes and is mainly because of the formation of rhabdophane and aluminum phosphate precipitation on ACLA. This is confirmed by results of the XPS and 31P NMR spectroscopy, which indicate that the La/Al coexisting novel P inactivation agents are a promising sorbent for lake sediment P control.