Solidification/Stabilization Effect Of Phyllosilicates For Mercury In Contaminated Soil

Mercury is used as raw material in various kinds of industry. Because the Mercury and Mercury compounds are long-term poisonous and also can be accumulate by biology, these materials are deleterious. Part of the Mercury in the soil can be adsorbed or fixed by the soil, and the other part can transport in different ways. These kinds of transportation lead to secondary pollution. So the treatment of Hg-pollution in soil is urgent needed.The mineral matter and the organic matter in the soil play a leading role for the immobilization, and the main reactions are ion exchange adsorption, surface complexation, and surface adsorption. The structural characteristics of the Phyllosilicates are favorable for all the three reactions. So three kind of typical Phyllosilicates are chose as the annexing agent to fix the Mercury in the soil.The experiments showed that this soil has high level of ability to fix Mercury. When the contents of Mercury are 30—135mg/Kg in the soil, the contents of Mercury in the leaching solutions of the soil are lower than 0.1mg/L which is the standard in'the Standards of Dangerous Waste Identification-leaching toxicity (GB5085.3-2007)'. When the contents of Mercury in the soil are lower than 1200mg/Kg, the efficiency for stabilization of mercury in the soil are higher than 90%. When the content of Mercury in the soil is higher than 900mg/Kg, the Mercury is saturated. With the increasing of contents , the soil's ability to fix Mercuric nitrate is higher than it to fix Mercuric chloride.For the three kind of Phyllosilicates, the adsorptions react quickly. At 150 minutes, the adsorptions reached the balance. Second-order equations can describe the adsorptions of Mercury well. The adsorptions are controlled by several reactions. All the three kind of Phyllosilicates have high ability to adsorb Mercury, and the adsorption quantities are increased as the increasing of equilibrium concentration. For vermiculite, the saturation adsorption quantity is 8.7184mg/g; and for smectite, it is 6.9686mg/g; and for kaolin, it is 6.3205mg/g. After adding the Phyllosilicates to the Hg-pollution soil, the contents of Mercury in the leaching solutions of the soil decreased sharply, were decreased by 60%. And the contents are decreasing with the increasing of the addition of the Phyllosilicates.For the three kind of Phyllosilicates, after modified by acid, the saturation adsorption quantities are increased sharply, and the smectite has the largest increase. For all the three kind of Phyllosilicates, the saturation adsorption quantities are increased as the increasing of acid contents. When the acid content is 1.100mol/L, the saturation adsorption quantities decreased, and decreases of the smectite and kaolin are larger than that of vermiculite.For the three kind of Phyllosilicates, after modified by heat, the saturation adsorption quantities are increased sharply, and the smectite had the largest increase, and the vermiculite had a lesser one, and the kaolin had the least one. For the vermiculite and smectite, at 300-350℃, both of them increased with the increasing of temperature, and then decreased, at 600℃the saturation adsorption quantities decreased sharply. The kaolin's saturation adsorption quantity decrease with the increasing of temperature from 300℃to 600℃steadily, but the decrease was not too large.