REMOVAL OF TOXIC Pb2+ IONS BY SYNTHETIC HYDROXYAPATITES

Abstract
The removal behavior of toxic Pb2+ ions from aqueous and nonaqueous solutions by two synthetic hydroxyapatites (S-1 and S-2) has been investigated by using both batch and column methods. It was found that Pb2+ ions in the both solutions were easily removed to the apatite samples mainly by cation-exchange reactions between the Pb2+ ions in the solutions and Ca2+ ions of the samples at room temperature. Further, in the system of aqueous PbF2 solutions, anion-exchange reactions between F ions in the solutions and OH ions of the samples occurred simultaneously and the liberated OH and Ca2+ ions influenced removal behavior of Pb2+ and F ions. The maximum removal amount of Pb2+ ions from the aqueous solutions was 400 mg per g of S-1. Pb ions in the waste water from lead plating factories were completely removed to the apatite samples. In this manner, it was found that the apatites, especially S-1 can be employed as a new removal agent for the treatment of poisonous Pb2+ ions in waste water.

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