Vanadium sources

Vanadium powder can be prepared by substituting V2O2 for the V20 as the vanadium source. The heat generated during the reduction of the trioxide is considerably less than for the pentoxide, so that only soHd products are obtained. The powder is recovered from the product by leaching the slag with dilute acid. 

Vanadium ores are mainly of igneous origin. The vanadium sources which are of present or potential economic value can be classified under several headings.3... 

There has also been investigation into alternative vanadium sources. Poli and coworkers [88, 92] used NH4VO3 as the vanadium source in conjunction with H3PO4 and oxalic acid, and Harouch Batis and coworkers [91] used a VCI3/V2O5 mixture instead of vanadium pentoxide. Mizuno and coworkers [95] reported a... 

Anthropogenic vanadium emissions are indicated even years after the closure of the vanadium source, as was demonstrated in the vicinity of cement and phosphate factories (Anke et al. 1998). 

The hydrothermal experiments to prepare the VOPO and VOPRO materials are quite simple. An aqueous solution of the organic template, the vanadium source and the phosphate or phosphonate are treated at 150-200°C for 3 days. It appears that in most cases, the crystals form at the reaction temperature and not upon cooling the reaction mixture and, in fact, with reaction temperatures much <150°C, that the formation of well-crystallized products occurs slowly. These well-crystallized samples are imperative to any study of these systems as single crystal X-ray diffraction is the primary characterization tool for these materials. 

BeUussi and Rigutto (86) reviewed the synthesis of various vanadium-containing sfticates and pointed out that, in addition to the gel composition and the crystallization conditions, the vanadium source plays an important role in determining the incorporation of vanadium ions. Rather than using a source, more success with V-incorporation has been attained when cat-... 

These and other observations indicate the non-innocent roles played by the ligand/solvent system which, depending on the experimental conditions and on the vanadium source, can act as a deoxygenating (of VO ), an oxidizing [of VCl or V(IV)] or a reducing [of V(V) species]... 

Figure 2. SEM micrographs of (from left to right) vanadium oxide (VOx) platelets using dodecanol and V2O5 as vanadium source, star-like VOx obtained from the reaction of V2O5 with dodecanethiol and vanadium oxide nanotubes (VOx-NTs) synthesized according to ref [9].

Coordination conqilexes of [V 0] with a variety of ligands constitute the majority of vanadium con oun proposed as IMA s (13,14,18,19). A select few conqilexes have demonstrated significantly increased activity over inorganic vanadium sources (e.g. VOSO4 or [V04] ) through both in vivo (20) and/or in vitro (19,21,22) assays of potential biological effectiveness. 

Distributions from chelated vanadium sources, e.g. BMOV (46) and vanadyl picolinate (48) show a similar profile. Bodi the amount and relative vanadium concentrations in these organs vary with the particular confound and dose, but the percentage of dose taken up (whether from an oral or an i.p. dose) is generally significantly higher finm chelated sources (46,48) conqtared to that from inorganic vanadyl compounds (56,59,61,65). Thus, chelation improves bioavailability, reducing the dose required for therapeutic effect (55). 

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