Removal of uranium (VI) from nuclear effluents onto aluminophosphate and silicoaluminophosphate molecular sieves

Abstract

Aluminophosphate and silicoaluminophosphate molecular sieves with both five (AFI) and eleven (AEL) type structures are synthesized by hydrothermal crystallization at 473 K, using tripropylamine and dipropylamine as a structure-directing template. The asprepared AFI and AEL sieves are characterized and then assessed as sorbents for uranium (VI) from radioactive effluents. The sorption process is used to reduce the volumes of effluents and convert them into a stable solid waste. The batch experimental studies are carried out to evaluate the AEL and AFI structure effect on the removal of uranium. The AlPO 4 -5, SAPO-5, AlPO 4 -11 and SAPO-11 are applied to radioactive effluents with different activities obtained from Nuclear Research Center of Draria, Algeria. Important decontamination factor values are obtained for AFI sorbents. Thermodynamic parameters, namely, the enthalpy (DH), entropy (DS) and free energy (DG) for each sorption process are calculated. The collected results indicated that sorbents are effective materials for the removal of uranium (VI) ions, the sorbent with AFI structure being a highly effective material for the removal of uranium (VI) ions from nuclear effluents.

Equilibrium, isotherms and kinetic studies of uranium sorption onto AlPO 4 -5 and SAPO-5 materials

“…According to the literature and our previous work, AlPO 4 -5 and SAPO-5 are synthesized by hydrothermal crystallization in fluorhydric acid medium [18,22]. The molar gel's composition for SAPO-5 and AlPO 4 -5 respectively are 0.8Al 2 O 3 , 1P 2 O 5 , 1.4 R, 0.2SiO 2 , 50H 2 O and 1Al 2 O 3 , 1P 2 O 5 , 1.4 R, 50H 2 O, where R is the structuring agent.…”

“…The uptake of uranium (VI) is larger for SAPO-5 than for AlPO 4 -5, this behavior may be explained by the silico-aluminophosphate framework negative charge [19,22], which could favor the adsorption of positively charged uranyl ion species UO 2+ 2 through important electrostatic interactions in contrast to the neutral framework of AlPO 4 -5 [22]. The difference in adsorption capacity of AlPO 4 -5 and SAPO-5 behavior is also due to the acidity originated by the difference in their constituents.…”

“…Comparing the adsorption capacity obtained from synthetic solution and real effluents (Table 7), we can notice a decrease in the adsorption yield in the case of real effluents but still remains important. This behavior may be explained by the presence of the other chemical elements in the effluents [22], which can be co-adsorbed at the same time as the uranium, by occupying the active sites of the adsorbent.…”

Synthesis and Evaluation of Reusable Desferrioxamine B Immobilized on Polymeric Spherical Microparticles for Uranium Recovery

“…Concerning the methodologies for the separation and removal of uranium, numerous studies have been conducted on polymeric materials, − including natural polymer-based materials, − membranes, ion exchangers, inorganic compounds, − organic–inorganic hybrid materials, − and microorganisms. − By contrast, relatively few articles have reported the reusability and uniformity of the removal material for uranium. ,, In this regard, fiber-type adsorbents have proved reusable and useful in the removal of uranium; − however, they are difficult to apply to industrial packed column equipment because they cannot withstand high pressures. For industrial and analytical applications, development of resins such as liquid chromatographic (LC) packed resins with certain sizes and uniform shapes has attracted considerable interest.…”