Uranyl Ions

The spectrophotometric determination of uranyl ion with 4-(2-Pyridylazo)resorcinol (PAR) is a well known and old method. However this technique gives scope for further research in order to make it more selective as well as sensitive for uranyl ion determination. In this study, the experimental protocol has simplified as compared to previous report. An attempt to evaluate the uncertainty budget associated with the determination has been carried out. The effect of different cationic interferences has been studied and a simple method was developed to reduce the interferences.

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under solvo-hydrothermal conditions and in the presence of [M(L)n] q+ cations, in which M = transition metal cation, L = 2,2ʹ-bipyridine (bipy) or 1,10-phenanthroline (phen), n = 2 or 3, and q = 1 or 2, gave ten complexes which have been crystallographically characterized. The diacetate ligands are bis-chelating and the uranyl cations are tris-chelated in all cases. [UO2(1,2-PDA)2Zn(phen)2]⋅2H2O (1) and [UO2(1,4-PDA)2Mn(bipy)2]⋅H2O (2) are heterometallic, neutral one-dimensional (1D) coordination polymers in which the carboxylate-coordinated 3d block metal cation is either decorating only (1), or participates in polymer building (2). [Zn(phen)3][(UO2)2(1,3-PDA)3] (3) and [Ni(phen)3][(UO2)2(1,4-PDA)3]⋅H2O (4), with separate counterions, crystallize as anionic twodimensional (2D) networks, as does [Cu(bipy)2][H2NMe2][(UO2)2(1,4-PDA)3] (5), which displays parallel 2D interpenetration. The complex [Zn(phen)3][(UO2)2(1,2-PDA)3]⋅7H2O (6) crystallizes as a ladderlike, slightly inflated ribbon. The same topology is found in [Zn(bipy)3][(UO2)2(1,3-PDA)3] (7), but the larger separation between coordination sites and the coexistence of curved and divergent ligand conformations produce a tubelike assembly. An analogous, but more regular and spacious tubular geometry is found in [M(bipy)3][(UO2)2(1,4-PDA)3] with M = Co (8) or Ni (9), and {Λ-[Ru(bipy)3]}[(UO2)2(1,4-PDA)3] (10). The disordered counterions in 8 and 9 are replaced by well-ordered, enantiomerically pure chiral counterions in 10. The tubular assemblies formed in 7-10 are characterized by an oblong section and the presence of gaps in the walls, which enable the inclusion of two rows of counterions in the cavity.

The reaction of uranyl ions with azelaic or dodecanedioic acids under solvohydrothermal conditions leads to crystallization of anionic dinuclear cage compounds with [M(bipy/phen) 3 ] 2+ counterions (M = 3dblock cation), while the smaller suberic acid yields heterometallic metallacycles. Complexes with the longer aliphatic chains are the first triple-stranded helicates reported in actinide chemistry.

Two chiral cage clusters built from uranyl polyhedra and (HPO 3) 2− groups have been synthesized in pure yield and characterized structurally and spectroscopically in the solid state and aqueous solution. Synthesis reactions under ambient conditions in mildly acidic aqueous solutions gave clusters U 22 PO 3 and U 28 PO 3 that contain belts of four uranyl peroxide pentagonal and hexagonal bipyramids, in contrast to earlier reported uranyl peroxide cage clusters that are built from four-, five-, and six-membered rings of uranyl hexagonal bipyramids. U 22 PO 3 and U 28 PO 3 are also the first chiral uranyl-based cage clusters, the first that contain uranyl pentagonal bipyramids that contain no peroxide ligands, and the first that incorporate (HPO 3) 2− bridges between uranyl ions. They are built from 22 uranyl polyhedra and 20 (HPO 3) 2− groups, or 28 uranyl polyhedra and 24 (HPO 3) 2− groups, with the outer and inner surfaces of the cages passivated by the O atoms of uranyl ions. Small-angle X-ray scattering (SAXS) profiles demonstrated that U 22 PO 3 clusters formed in solution within 1 h after mixing of reactants, and remained in solution for 2 weeks prior to crystallization. Time-resolved electrospray ionization mass spectrometry and SAXS demonstrated that U 28 PO 3 clusters formed in solution within 1 h of mixing the reactants, and remained in solution 1 month before crystallization. Crystallization of U 22 PO 3 and U 28 PO 3 is accelerated by addition of KNO 3. Clusters of U 22 PO 3 with and without encapsulated cations exhibit markedly different aqueous solubility, reflecting the importance of cluster surface charge in fostering linkages through counterions to form a stable solid.

Carboxy-methyl-cellulose (CMC), a common ''delivery vehicle'' for the subsurface deployment of iron nanoparticles (INP) has been tested in the current work for the removal of aqueous uranium from synthetic water samples. A comparison of the removal of aqueous uranium from solutions using carboxymethyl-cellulose with and without iron nanoparticles (CMC-INP and CMC, respectively) was tested over a 48 h reaction period. Analysis of liquid samples using spectrophotometry determined a maximum sorption capacity of uranium, Q max , of 185.18 mg/g and 322.58 mg/g for CMC and CMC-INP respectively, providing strong evidence of an independent aqueous uranium removal ability exhibited by CMC. The results point out that CMC provides an additional capacity for aqueous uranium removal. Further tests are required to determine whether similar behaviour will be observed for other aqueous contaminant species and if the presence of CMC within a INP slurry inhibits or aids the reactivity, reductive capacity and affinity of INP for aqueous contaminant removal.

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright

Carboxy-methyl-cellulose (CMC), a common ''delivery vehicle'' for the subsurface deployment of iron nanoparticles (INP) has been tested in the current work for the removal of aqueous uranium from synthetic water samples. A comparison of the removal of aqueous uranium from solutions using carboxymethyl-cellulose with and without iron nanoparticles (CMC-INP and CMC, respectively) was tested over a 48 h reaction period. Analysis of liquid samples using spectrophotometry determined a maximum sorption capacity of uranium, Q max , of 185.18 mg/g and 322.58 mg/g for CMC and CMC-INP respectively, providing strong evidence of an independent aqueous uranium removal ability exhibited by CMC. The results point out that CMC provides an additional capacity for aqueous uranium removal. Further tests are required to determine whether similar behaviour will be observed for other aqueous contaminant species and if the presence of CMC within a INP slurry inhibits or aids the reactivity, reductive capacity and affinity of INP for aqueous contaminant removal.

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright

Carboxy-methyl-cellulose (CMC), a common ''delivery vehicle'' for the subsurface deployment of iron nanoparticles (INP) has been tested in the current work for the removal of aqueous uranium from synthetic water samples. A comparison of the removal of aqueous uranium from solutions using carboxymethyl-cellulose with and without iron nanoparticles (CMC-INP and CMC, respectively) was tested over a 48 h reaction period. Analysis of liquid samples using spectrophotometry determined a maximum sorption capacity of uranium, Q max , of 185.18 mg/g and 322.58 mg/g for CMC and CMC-INP respectively, providing strong evidence of an independent aqueous uranium removal ability exhibited by CMC. The results point out that CMC provides an additional capacity for aqueous uranium removal. Further tests are required to determine whether similar behaviour will be observed for other aqueous contaminant species and if the presence of CMC within a INP slurry inhibits or aids the reactivity, reductive capacity and affinity of INP for aqueous contaminant removal.

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright