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Solution Purification
Published in C. K. Gupta, T. K. Mukherjee, Hydrometallurgy in Extraction Processes, 2017
In all the three examples of SX practice given earlier, Na2CO3 solution has been used as a stripping agent. But there are a number of commercial plants which are using ammonia solution as a stripping reagent. Alkali stripping of the loaded extract with NH4OH converts the extracted vanadium from decavanadate to metavanadate (V4O124−) species, which has low solubility in water as well as in (NH4)2SO4 solutions. This results in the crystallization of vanadium as ammonium metavanadate during stripping or at a later stage. The other alternative available is to strip the vanadium at a slightly acidic pH of 6.5 where it can exist as a decavanadate ion (V10O286−) in the strip solution. Since the solubility of decavanadate is quite high, a strip solution containing about 60 g/lV can be easily obtained. By raising the pH of the strip solution with ammonia and heating, the decavanadate is converted to insoluble metavanadate. During this conversion, impurities like phosphate, silicate, etc. remain in the solution and do not contaminate the metavanadate precipitate.
Concomitant reduction of dimethylformamide and oxidation of vanadyl sulfate to N,N′-dimethylammonium decavanadate cluster and DNA, BSA binding, and cytotoxicity (HeLa) studies
Published in Journal of Coordination Chemistry, 2018
Chinthala Chinnapullaih, Angappan Sheela
Decavanadate species formed at physiological pH values in vanadate solutions presumably contain only monomeric vanadate species. The predominant vanadium species in an aqueous system is changed in the order [V10O28]6–, [V4O12]4–, [V2O7]4–, and [VO4]3– as the solution pH increases. Normally the decavanadate ions are decomposed into the smaller vanadium oxo anions within 2 h by raising the pH to 11–12. This is easy to monitor visually because the decavanadate ions are deep orange while the tetramers are light yellow and the monomers and dimers are colorless [25].
Bis phenylene flattened 13-membered tetraamide macrocyclic ligand (TAML) for square planar cobalt(III)*
Published in Journal of Coordination Chemistry, 2018
W. Chadwick Ellis, Alexander D. Ryabov, Andreas Fischer, Joshua A. Hayden, Longzhu Q. Shen, Emile L. Bominaar, Michael P. Hendrich, Terrence J. Collins
The ease of metalation of 10 encouraged us to make the corresponding TAML complex of vanadium, which was never reported previously [2]. Thus, [VVO(OCHMe2)3] was reacted with 10 in THF in the presence of lithium bis(trimethylsilyl)amide. The product, the structure of which was established by X-ray crystallography [28], did not contain 10 and turned out to be an anionic decavanadate (Figure 1), presumably V10O286- as characterized, for example, by Evans [32]. It is worth noting that decavanadates are intensively studied due their activity in biological systems [3334].