19-08-2014, 10:50 AM
Zirconium is used as the MOC for nuclear reactor. The cladding material consists of Zr (98%), Sn (1.2-1.4%), Sb and Co (ppm). For reuse, the radioactive impurities of Sb and Co need to be removed. The proposed path is chlorination of the material followed by dissolution in water.
Zirconium is used as the MOC for nuclear reactor. The cladding material consists of Zr (98%), Sn (1.2-1.4%), Sb and Co (ppm). For reuse, the radioactive impurities of Sb and Co need to be removed. The proposed path is chlorination of the material followed by dissolution in water.
The project deals with molecular simulation for the selective adsorbent design and to predict the interactions between the ligand molecule and the metal ions in consideration. Molecular mechanics (MM) calculations were performed to optimize geometries of metal ion-ligand complexes. Molecular dynamics (MD) calculations were performed to study the solution chemistry of metal ions in 0.5M and 2 M hydrochloric acid solutions. The electrostatic potential surface, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of ligands were studied by quantum mechanics (QM)-density functional theory calculations.
Geometries of chelates of bis-(2-pyridylmethyl) amine with metal ions Cu2+, Co2+, Ni2+, Fe2+, Pb4+ and Mn2+ were optimized to evaluate their relative binding strength. Effect of chelate ring size and ring size of macrocyclic ligands on metal ion binding strength was studied by geometry optimization of Ni2+ chelates of macrocyclic ligands of various ring sizes. The simulation results explained the experimental behavior of these systems.
The solution chemistry of Co2+ and Zr4+ ions was studied by performing MD calculations in periodic boxes, which represented 0.5 M and 2.0 M HCl solutions of these metal ions. The nature of complexes of Co2+ and Zr4+ in HCl solutions were determined by radial distribution function (RDF) curves obtained by MD calculations. The interaction of various complexes of these metal ions existing in HCl solutions with cation exchanger was studied by geometry optimization.
Since the available adsorbents fail to take up cobalt from 2 M HCl solutions, using a defined methodology, a cobalt selective ligand was designed. The interaction of this designed ligand with Co+2 and Zr+4 was studied with MM calculations. The strain energy analysis and the interaction energy values showed very high selectivity for Co+2 over Zr+4.
Thiourea is used to reduce oxidation state of antimony from Sb5+ to Sb3+. The interaction of thiourea with Sb+3 and Zr+4 was studied by MM calculations. The simulation results showed selectivity for Sb+3 ions. The simulation results were confirmed by experimental adsorption data.
The Kd values were predicted from density functional theory frequency analysis for various metallig and complexes.