Characterization And Environmental Application Of Nano-Sized Hydroxyapatite

Bulk apatite is used to remedy heavy metal pollution in water and soil. In this thesis, inorder to improve the efficiency and shorten the time of remediation, we synthesizednano-sized HAP with high surface-activity and use this material to treat thelead-contaminated water and soil.Main results were as follows:1) Nano-sized HAP was synthesized by the thermal decomposition of complexprecursors. XRD, TEM, IR were used to characterize the nano-sized HAP. Resutls showedthat the samples were pure HAP. The nano-sized HAP was sphere-like and weaklyaggregated. Particle sizes of samples increased with annealing temperature.2) Eu³⁺ ions were employed as a probe to study the substitution of Ca²⁺ ions in HAP byEu³⁺ ions. Resutls showed that the majority of Eu³⁺ ions occupied Ca(â…¡) sites in the bulk,while more and more Eu³⁺ ions occupied Ca(â… ) sites as particle size decreased. The lattice inthe nano-sized HAP were distorted after doped Eu³⁺ ions, and the lattice distortion of Eu³⁺-doped nano-sized HAP is dependent on both the particle size and the Eu³⁺ dopingconcentration. The ratios of the red emission transition to the orange emission transition(R/O values) in nano-sized HAP were all higher than in the corresponding bulk samples.3) The dissolution amount of HAP increased with decersing pH, and on the same pHconditions, the dissolution rates and amounts of nano-sized HAP were all higher than thebulk HAP. nano-sized HAP(Nano), bulk HAP(Bulk) and phosphate rock(PR) immobilizedmost lead ions at pH 2.5, and the order was Nano＞Bulk＞PR. When pH was higher than2.5, the immobilization ability of Nano, Bulk and PR decreased as pH increasing.Increasing the added amount or adding a few C1^-1 ions into the solution could enhance theimmobilization ability of nano-sized HAP, while increasing the initial Pb²⁺ ions'concentration or adding other heavy metals into the solution, such as Cu²⁺, had a contrary effect.4) Compared with Bulk and PR, Nano had the best immobilization ablity on Pb²⁺ ions,and its' remediation time was shorter. Nano, Bulk and PR amendments were all effectivelyin immobilizing Pb²⁺ ions in Pb-contaminated soil. After adding Nano, Bulk and PR, theconcentration of acid extracted-bound, oxides-bound and organic-bound Pb²⁺ ionsthe in thePb-contaminated soil were much lower than in the CK treatments, as a result, thebioavailability of lead ions was reduced. Results showed that increasing the added amountof nano-sized HAP and the remediation time was propitious to reduce the concentration ofacid extracted-bound Pb²⁺ ions in the soil.