Phosphate compounds and related materials are effective amendments for immobilization of heavy metals in contaminated soils. A greenhouse pot experiment with ryegrass (Lolium perenne) as the test plant was conducted to explore the impact of nanoparticle hydroxyapatite (HAP) on the immobilization and bioavailability of Cu and Zn in a heavy metal-polluted soil. The addition of nanoparticle HAP significantly decreased the uptake of Cu and Zn by ryegrass. As a result, the biomass of ryegrass increased as the rate of nanoparticle HAP increased. The toxicity characteristic leaching procedure (TCLP) and physiologically based extraction test (PBET) results of the treatments showed that the leachable and bioaccessible concentrations of Cu and Zn were significantly reduced after the soil stabilized with nanoparticle HAP. The XRD pattern of nanoparticle HAP was not changed by the presence of Cu and Zn, which suggests that Cu and Zn were immobilized by the formation of solid amorphous phosphate. Nanoparticle HAP was an effective material to immobilize heavy metals in contaminated soils.
Keywords: Bioavailability; Heavy metals; Immobilization; Nano-HAP; PBET; TCLP.