Sorption Of U(â…¥)on Illite And Magnetic Illite

In this paper, the batch sorption experiments and characterization methods (such as FTIR, XRD and SEM so on) were used to study the sorption of U(VI) on illite and magnetic illite. The paper was divided into seven chapters. In the first chapter, the research’s background, basic contents and sketch of experimental scheme were introduced in brief. In the second chapter, the methods, which were used in this paper, were introduced in detail. In the third chapter, the structure, elements of composition, function groups, and the sites of illite and magnetic illite were characterized by using FTIR, XRD, SEM and other techniques. The fourth and fifth chapters respectively study about the sorption of U(Ⅵ) on illite and magnetic illite in details. The sixth chapter summarizes the research results of this paper, and the seventh chapter puts forward some proposals for future research.The results show that the surface properties of magnetic illite and illite are very different. with Fe3O4 particles covered, magnetic illite had superparamagnetism, specific surface area increased, SiO2 and Al2O3 content fell dramatically, surface properties has certainly changed. The sorption of U(VI) on illite and magnetic illite is belong to chemical sorption, and also conforms to the pseudo second-order kinetic model. Compared with illite, U(VI) sorption on magnetic illite’ equilibrium time is shorter, the maximum sorption capacity is bigger (qmax=13.931 mg/g, and U(Ⅵ) sorption on the illite’qmax=9.416 mg/g). System’pH has a very significant impact on U(VI) sorption on the illite and magnetic illite, in acid area, sorption increases with the increase of pH, but in neutral/alkaline area, because of the different surface properties, the situation began to change:with the increase of pH, because the gradual formation of the complex UO2(CO3)22"/ UO2(CO3)34-,and precipitate Na2U2O7/Na2UO2(CO3)2, sorption of U(VI) on illite first decreased and then increased with the increase of pH; However, because the surface of magnetic illite had less negative charge than illite, U(VI) sorption just slowly reduced because of the formation of carbonate. The effect of SO42-/PO43- on U(VI) sorption on illite and magnetic illite is quite obvious, because of sulfate complex of U(VI) has a larger complexing constant, so in two sorption system, the existence of SO42- under low pH can depress U(VI) sorption, but in alkaline area there had some different:when sorbent is illite, sulfate complex existence, make U(VI) complex average negative become low, and illite electrostatic repulsion weakens so as to promote the U(VI) sorption. When the sorbent is magnetic illite, carbonate is decided the main factors of U(VI) sorption, therefore the existence of SO42" had no obvious influence on sorption. PO43-because of its strong complexation, in both sorption systems under low pH greatly promote U(VI) sorption, but in the high pH, magnetic illite do not affinity with phosphate complex compatibility of U(VI), so the U(VI) sorption was suppressed. With HA existence, U(VI) sorption on the illite and magnetic illite also has a significant difference, when sorbent is illite, because electrostatic repulsion, HA and illite surface has low affinity, U(VI) formed as U(VI)-HA complex in the liquid phase, caused U(VI) sorption on the surface of illite greatly weakened; And sorbent is magnetic illite, HA and magnetic illite electrostatic repulsion is in strong alkaline area, therefore, the existence of HA is inhibit sorption only in the region of the alkaline, in acidic region will promote the sorption. Temperature’effect on U(VI) sorption on the illite and magnetic illite also have different, in the system of illite and temperature have little impact, in line with the Langmuir model,298.15 K, U(VI) single saturated sorption capacity is about 5.967 mg/g; In magnetic illite system, temperature promot U(VI) sorption, this sorption is an endothermic process, is also more in line with the Langmuir model,298.15 K, U(VI) single saturated sorption capacity is about 17.938 mg/g, three times more than that of illite system.