THE REMOVAL OF HEAVY METALS USING HYDROXYAPATITE

초록

This study was conducted to investigate the removal of heavy metals by using Hydroxyapatite(HAp) made from waste oyster shells and wastewater with high concentration of phosphorus. The maximum calcium concentration for the produced HAp in this study was released up to 361mg/L at pH of 3 by elution experiments. When the pH was at adjusted 6, the maximum calcium released concentration was 41mg/L. During the elution experiment, most of calcium was released within 60 minutes. This reaction occurred at both pH levels of 3 and 6. As a result of XRD for the product made in this study, the main constituent was HAp, as well as OCP. The pH was 8.6 with an alkali. As the temperature increased, the main constituent did not vary, however its structure was crystallized. When the pH was maintained at 3, the removal efficiency decreased as the heavy metal concentration increased. The order of removal efficiency was as follows: Fe2+(92%), Pb2+(92%) > Cu2+(20%) > Cd2+(0%). Most of these products were dissolved and did not produce sludge in a course of heavy metals removal. As the heavy metal concentration increased at pH of 6, the removal efficiency increased. The removal efficiencies in all heavy metals were over 80%. From the analysis of the sludge after reaction with heavy metals, the HAp was detected and the OCP peak was not observed. Moreover, lead ion was observed the peaks of lead-Apatite and lead oxidant. In the case of cadmium, copper and iron ions, hydroxide forms of each ion were also detected.

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