Ni(Ii) Immobilization By Bio-Apatite Materials: Appraisal of Chemical, Thermal and Combined Treatments

Abstract

Animal bones are a natural and rich source of calcium hydroxyapatite (HAP), which has been found to be a good sorbent material for heavy metals and radionuclides. Various treatments can reduce the content of bone organic phase and improve sorption properties. In this study, sorption capacities of raw bovine bones (B) and samples obtained by chemical treatment with NaOH (B-NaOH), by heating at 400 degrees C (B-400) and by combined chemical and thermal treatment (BNaOH+400), were compared, using Ni(II) ions as sorbates. Maximum sorption capacities increased in the order B LT B-NaOH LT B-400 LT BNaOH+400. Based on different sorption data and FT-IR analyses, the mechanism of Ni(II) sorption was found to be complex, with participation of both HAP and organic phase (when present). Sequential extraction analysis was applied for testing the stability of Ni(II) ions sorbed by BNaOH+400. Majority of Ni(II) was found in residual phase (65%) at lower level of sorbent loading, while with the increase of sorbent saturation carbonate fraction became dominant (39%). According to the results, BNaOH+400 can be utilized in water purification systems. As an apatite based material with low organic content and high efficiency for Ni(II) sorption, it is also a good candidate for in situ soil remediation, particularly at lower contamination levels.