Removal and Capture of Heavy Metal Ions in Polluted Water with Crystallized Molten Slag

Yukio Fujita*, Takayuki Shimaoka* and Seizou Kenmoku**
* Institute of Environmental Systems, Graduate School of Engineering, Kyushu University
** Tochigi Prefectural Ceramic Steering Office
† Correspondence should be addressed to Yukio Fujita:
Institute of Environmental Systems, Graduate School of Engineering, Kyushu University
（6-10-1 Hakozaki, Higasi-ku, Fukuoka, 812-8581 Japan）


Abstract
In order to use molten slag in environmental conservation we studied the removal and capture of lead ions in polluted water with crystallized molten slag.
Experiments were carried out on the reactions between crushed molten slag and lead acetate, lead nitrate and lead chloride solutions. Consequently, about 10mg of lead per g of slag was removed and captured and it was confirmed that molten slag could be useful for capturing of lead ions. The mechanism for the removal of lead was more dependent on the precipitation reaction than adsorption. XRD and IR analyses revealed that basic lead carbonate（2PbCO3・Pb（OH）2）was formed in the precipitations.
Basic lead carbonate was also formed by the reaction between the solution of the molten slag leachate and lead acetate, lead nitrate and lead chloride. Laurionite（PbCl（OH））was also formed by the reaction between the solution of the molten slag leachate and lead chloride. The hydrolysis of compounds that were formed by the reaction not only between the calcium hydroxide and lead acetate but also between lead nitrate and lead chloride gave basic lead carbonate and laurionite. These results agreed with the results of the experiments above. Calcium oxide in the molten slag was concluded to be an important factor in removing and capturing the lead ions.


Key words: crystallized molten slag, lead compounds, precipitation reaction, basic lead carbonate, laurionite