The Adsorption And Migration Of Rare Earth Elements In Soil Of Baotou Tailings

Owing to the rain eluviation and seepage effects, the rare earth elements that exist in baotou tailings will dissolve and enter the earth’s surface and groundwater system, even will migrate to the surrounding, which will lead to pollution of environment and harm to the people’s health. So it is a important thing to research on the adsorption and migration characteristics of the pollutants and to predicte the transport process of the pollutants in tailings area. The research will provide the based data for pollution prevention and control, which is great significance to protect the surroundings and to design, construct, and operate the tailings dam.In this paper, the adsorption of the the tailings soil with La3+ was studied by static adsorption method and the adsorption characteristics were concluded. The effect factors of the adsorption were investigated, such as humic acid, pH value, temperature and coexisting ions. Moreover, the migration of La+ was investigated by soil column experiment. The effect factors of the migration were discussed, which include La3+ concentration,pH value, the coexisting ions and HA of the system.The main results were as follows:1.The adsorption experiment about La3+ with the soil showed that the isothermal adsorption process were perfectly fitted by Freundlich adsorption equation and it was a heterogeneous adsorption.The kinetics studies showed that the pseudo second-order rate equation could fit the experimental data well and the linear correlation coefficients were all above 0.9998. When the pH is less than 4, adsorption increased sharply along with the increase of solution pH. But when pH is greater than 4, the adsorption rate decreased with the increase of solution pH. The adsorption capacity increases with temperature rise, which showed that the soil adsorption with La3+ is an endothermic process. The adsorption process also was affected by coexistence of cationic which can inhibits the adsorption about soil with La3+. The inhibition order was Ca2+>Fe3+>Na+. All kinds of humic acid can improve the adsorption in different conditions, but different kinds of humic acid have different promote ability.2.The dynamic migration experiment about La3+ with the soil showed that the BTC curve can reach a peak at 130s with different injection concentration. The injection There was a good symmetry when the injection concentration was 260ug/ml. The active porosity of the region’s soil was 0.64, retardation factor Rd=5.039 and distribution coefficient Kd=0.904 mL/g. The total through time at the pH=4-7 was short than pH=8-9, which showed that the acidic conditions can promote the migration of La3+ in the soil. The migration of La3+ increased at first and decreased to almost unchanged with coexistence Na+ contentration increased and the maximum contentration was in the 150ug/ml. However, migration of La3+ always increase with Ca2+ concentration. The presence of humic acid can promote the migration of La3+ with soil column.