Adsorption Mechanism For Uranium(Ⅵ) For Different Forms Of Iron Compounds In The Course Of Leaching Uranium Mining

Hydrogen peroxide, oxygen etc. are usually used as oxidant in the leaching uranium mining technique, Fe2+ in solution is oxidized to Fe3+, then, U4+ is oxidized by Fe3+ to UO22+. The behavior of iron plays an important role in leaching uranium. Iron is used as oxidant in the leaching uranium, but in the meantime it also reacts chemically with leaching agent(acidic, alkaline, neutral dissolvant). At the certain temperature and pressure, Fe(OH)3 colloid and hydrous ferric oxide are generated through analyzing. Iron compounds may have a package of uranium minerals, that affects chemical reaction between leaching agent and mineral and affects uranium leaching rate and leaching yield. At the same time, Iron compounds may adhere to the surface of the ore and then affects uranium leaching and seam permeability. In this paper, Fe(OH)3 colloid and hydrous ferric were imitable prepared, and adsorption mechanism for uranium were researched. The main research contents and achievements were as follows:(1) the Fe(OH)3 colloids was prepared in absolute ethanol,and the adsorption performance for UO22+ was detected. The effect of p H value,initial uranium concentration,contact time on the Fe(OH)3 colloids for uranium adsorption were analyzed. As for the adsorption dynamics, the pseudo-first-order, composite-second-order and Elovich dynamic models were comparatively calculated and discussed, the results showed that the Elovich dynamic was fitted to describe the adsorption of Fe(OH)3colloids for UO22+. As for the adsorption thermodynamics,Freundlich and Langmuir adsorption isotherm models were applied to experimental equilibrium data, it was found that equilibrium data agreed well with the Freundlich model. On conclusion, Fe(OH)3 colloids adsorption for UO22+ belongs to the uneven surface of single physical adsorption. The laser particle size and SEM analysis results revealed, the Fe(OH)3 colloids showed a good adsorption performance, and the surface adsorption took precedence in the adsorption process.(2) Hydrated ferric oxide which Fe SO4·7H2O was used as the main raw material was imitated, and the uranyl ion adsorption experiments were conducted. It was concluded that at p H=5, adsorption capacity of hydrated iron oxide was maximum. Within an hour adsorption, hydrated ferric oxide on uranium has a high rate of adsorption, and after five hours to reach adsorption equilibrium. Quasi two level dynamic equation was most fit for describing the adsorption behavior of uranium in the hydrated ferric oxide by kinetic fit of adsorption behavior. The fitting correlation coefficient R2 was 0.994, and the equilibrium adsorption amount of qe was 55.40 mg·L-1. The results of the conjecture was very close to the experimental data of 52.78 mg·L-1.(3) Fe(OH)3 colloid or hydrous ferric oxide adsorbed uranium synergistically which was explored, and the results showed that, absorption efficiency of Fe(OH)3 colloid and hydrous ferric oxide which were used as sorbent solely was good. With the increase of the composite ratio, mutual interference of Fe(OH)3 colloid and hydrous ferric was more obvious, and adsorption capacity decreased with the increase of the composite.