Vanadium is a hard, silvery-gray transition metal. It forms stable, protective oxide films, shows multiple oxidation states (+2 to +5), and is used to strengthen steel and in catalysts.
Ground-state configuration: \([Ar]3d^3\,4s^2\). Vanadium commonly exhibits +2, +3, +4, and +5 states. These give rise to characteristic solution colors and rich redox chemistry useful in analysis and catalysis.
Stepwise reduction thus gives a yellow → blue → green → violet sequence.
Vanadium(V) oxide is the standard oxidation catalyst converting SO2 to SO3 via a redox cycle:
\(\mathrm{V_2O_5 + SO_2 \rightarrow V_2O_4 + SO_3}\)
\(\mathrm{V_2O_4 + \tfrac{1}{2}O_2 \rightarrow V_2O_5}\)
The catalyst shuttles between V(V) and V(IV), enabling rapid, reversible conversion.
The vanadyl ion \(\mathrm{VO^{2+}}\) (V(IV), \(d^1\)) features a strong V=O bond and typically forms octahedral complexes with one short V=O and four equatorial ligands. Its stability and distinctive blue color make it prevalent in aqueous chemistry and spectroscopy.
In basic solution, V(V) exists mainly as \(\mathrm{VO_4^{3-}}\) (orthovanadate). On acidification, polyvanadates form (e.g., \(\mathrm{V_{10}O_{28}^{6-}}\)). The general protonation/polymerization can be summarized schematically as:
\(\mathrm{n\,VO_4^{3-} + m\,H^+ \rightleftharpoons V\text{-}O\text{ polyoxo species}}\)
These equilibria underlie vanadate’s use as a pH-dependent inhibitor in biochemistry.
Vanadium forms fine carbides and nitrides (e.g., VC, V(C,N)) that pin grain boundaries and impede dislocation motion. This precipitation strengthening boosts yield strength, toughness, and fatigue resistance. Vanadium microalloyed steels are common in high-strength structural applications.
VRFBs use V ions in different oxidation states in two external electrolyte tanks. Typical half-cells:
Because both electrolytes are vanadium-based, cross-over does not permanently contaminate electrodes, enhancing lifetime for grid-scale storage.
Vanadium occurs in minerals (e.g., vanadinite) and is recovered mainly from vanadium-bearing titanomagnetite, petroleum residues, and fly ash. Processing involves roasting to convert V to soluble vanadates, leaching, purification (solvent extraction/ion exchange), and precipitation as \(\mathrm{NH_4VO_3}\) followed by calcination to \(\mathrm{V_2O_5}\).
Yes. With multiple accessible oxidation states, vanadium easily undergoes stepwise redox changes. For example, V(IV) can be oxidized to V(V) by \(\mathrm{H_2O_2}\), while V(III) can reduce suitable oxidants. This versatility is central to its catalytic roles and analytical redox titrations.
Vanadium is a trace element in some organisms and appears in certain enzymes (e.g., vanadium haloperoxidases). However, many V compounds—especially dusts and some oxo-species—can be irritants or toxic. Handle with appropriate PPE and minimize inhalation exposure in laboratory and industrial settings.