Feasibility of using natural fishbone apatite as a substitute for hydroxyapatite in remediating aqueous heavy metals

Fishbone, a natural, apatite rich substance, was examined for suitability as a substitute for hydroxyapatite in the sequestering of aqueous divalent heavy metal ions. The fishbone exhibited lower metal removal capacity than pure hydroxyapatite, due primarily to its purity(similar to 70% apatite equivalent). In other ways the fishbone behaves in a similar manner as pure hydroxyapatite in the sequestration process. It was observed that it can remove all Pb2+, Cu2+, Cd2+ and Ni2+ to below detectable levels as measured by inductively coupled plasma atomic absorption, and the rate of reaction with either Zn2+, Ni2+, or Pb2+ was also found to be similar to hydroxyapatite. Also, a two level, three variable full factorial design was performed for the Pb/apatite reaction and both apatites performed similarly. The main difference, besides capacity, was on exposure to high (2.4 mM) Pb concentrations. The fishbone removed less of the Pb2+ than capacity correction predicted. (C) 1999 Elsevier Science B.V. All rights reserved.