酸化マグネシウムによる重金属類汚染土の不溶化処理と土壌中での鉱物化学反応

概要

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The use of magnesium oxide (MgO) as a stabilizing agent for inorganic soil pollutants including heavy metals, arsenic, boron, fluoride and selenium is reviewed. On mixing MgO with soils it reacts with soil water to form magnesium hydroxide and supplies magnesium and hydroxide ions. Magnesium ion forms sparingly soluble compounds with fluoride and arsenic but their solubilities are not low enough to meet the water quality and soil quality standards in Japan. Similarly, the solubilities of hydroxides of cadmium and lead are not necessarily low enough. Experimental studies suggest that the major stabilization mechanism is the incorporation into the magnesium hydroxide structure for fluoride and surface complexation at surface hydroxyl groups for oxyanions. For cationic heavy metals, surface complexation reactions at hydroxylated surfaces of soil minerals are highly probable but they do not seem to have been adequately assessed. MgO is known to react with various soil minerals to form layer silicates and Mg-Al double hydroxides. Stabilization of pollutants by thus formed secondary minerals is also probable but it has not received due attention.
2013-03-28