1714
Crystallization of Vanadium Salts from Bayer Strip Liquor
C. T. Mangunda, M. Svärd, and K. Forsberg
Department of Chemical Engineering, KTH Royal Institute of Technology, Stockholm, Sweden
ABSTRACT: Alumina extraction via the Bayer process produces an inorganic species laden liquor containing
aluminium and valuable trace elements (REEs, V, Ga) promoting liquor impurity but with valorisation
potential. Vanadium has applications for multiple industries, but current primary extraction techniques
generate voluminous, highly saline ammonium wastewater. This investigation explores synthetic high purity
vanadium crystallization in a temperature-controlled jacketed batch reactor. Acetone was the antisolvent for
treating the synthetic feed solutions. This crystallization route may serve as an alternative to the crystallization
and calcination steps in the conventional production of high purity vanadium salts. Supersaturation is generated
through the addition of acetone, and is controlled by varying precipitant concentration, addition rate, agitation
rate, and seeding. Vanadium salt composition, yield, purity, and particle morphology was analysed using XRD,
ICP-OES, and SEM-EDS. Elevated supersaturation led to rapid vanadium crystallization with high yield but
low purity. The yield, purity, and product characteristics of the crystals for different final organic to aqueous
(O/A) ratio, at constant addition rate of antisolvent at room temperature has been investigated. A batch time
and precipitant concentration dependent effect was observed. The best product quality, in terms of size and
crystal habit (dominated by hexagonal laths), was attained at a batch time of 2 h and O/A ratio of 0.75 using
more dilute acetone (80% acetone (v/v)). The results from the higher O/A ratio of 0.75 indicated a faster
attainment of desirable yields (≥97%) but also brought an early onset of acicular crystal formation along with
more impurity incorporation into the solid phase, although this was less pronounced in cases where dilute
acetone was used.
Keywords: Vanadium, Crystallization, Bauxite ore, Bayer liquor, Valorisation, Purity, Yield
INTRODUCTION
The critical metal supply chain has been dominated by
China, supplying approximately 39% of vanadium metal,
hence the increase in vanadium’s economic importance and
supply risk in Europe and beyond (Blengini et al., 2020).
These supply risk dynamics have led to the need for alter-
native vanadium sources through exploration of primary
(bauxite ore) and multiple secondary (spent catalysts, fuel
oil, steelmaking slag, oil and coal residues) sources for its
extraction (Tavakolikhaledi, 2014). The Bayer liquor has
been added into the mix as one of the potential secondary
sources of vanadium. Bayer liquor (sodium aluminate solu-
tion), produced from the extraction of aluminium from
bauxite ore via the Bayer process, is laden with inorganic
species that have potential value if recovered. The Bayer
liquor predominantly contains Al, but has concomitant
valuable trace elements such as rare earth elements (REEs),
V, Li, Sc, Ga that are currently not fully valorised (Zhao
et al., 2012, Liu and Naidu, 2014, Pan et al., 2023). The
trace elements dissolve during the Bayer process leading
Crystallization of Vanadium Salts from Bayer Strip Liquor
C. T. Mangunda, M. Svärd, and K. Forsberg
Department of Chemical Engineering, KTH Royal Institute of Technology, Stockholm, Sweden
ABSTRACT: Alumina extraction via the Bayer process produces an inorganic species laden liquor containing
aluminium and valuable trace elements (REEs, V, Ga) promoting liquor impurity but with valorisation
potential. Vanadium has applications for multiple industries, but current primary extraction techniques
generate voluminous, highly saline ammonium wastewater. This investigation explores synthetic high purity
vanadium crystallization in a temperature-controlled jacketed batch reactor. Acetone was the antisolvent for
treating the synthetic feed solutions. This crystallization route may serve as an alternative to the crystallization
and calcination steps in the conventional production of high purity vanadium salts. Supersaturation is generated
through the addition of acetone, and is controlled by varying precipitant concentration, addition rate, agitation
rate, and seeding. Vanadium salt composition, yield, purity, and particle morphology was analysed using XRD,
ICP-OES, and SEM-EDS. Elevated supersaturation led to rapid vanadium crystallization with high yield but
low purity. The yield, purity, and product characteristics of the crystals for different final organic to aqueous
(O/A) ratio, at constant addition rate of antisolvent at room temperature has been investigated. A batch time
and precipitant concentration dependent effect was observed. The best product quality, in terms of size and
crystal habit (dominated by hexagonal laths), was attained at a batch time of 2 h and O/A ratio of 0.75 using
more dilute acetone (80% acetone (v/v)). The results from the higher O/A ratio of 0.75 indicated a faster
attainment of desirable yields (≥97%) but also brought an early onset of acicular crystal formation along with
more impurity incorporation into the solid phase, although this was less pronounced in cases where dilute
acetone was used.
Keywords: Vanadium, Crystallization, Bauxite ore, Bayer liquor, Valorisation, Purity, Yield
INTRODUCTION
The critical metal supply chain has been dominated by
China, supplying approximately 39% of vanadium metal,
hence the increase in vanadium’s economic importance and
supply risk in Europe and beyond (Blengini et al., 2020).
These supply risk dynamics have led to the need for alter-
native vanadium sources through exploration of primary
(bauxite ore) and multiple secondary (spent catalysts, fuel
oil, steelmaking slag, oil and coal residues) sources for its
extraction (Tavakolikhaledi, 2014). The Bayer liquor has
been added into the mix as one of the potential secondary
sources of vanadium. Bayer liquor (sodium aluminate solu-
tion), produced from the extraction of aluminium from
bauxite ore via the Bayer process, is laden with inorganic
species that have potential value if recovered. The Bayer
liquor predominantly contains Al, but has concomitant
valuable trace elements such as rare earth elements (REEs),
V, Li, Sc, Ga that are currently not fully valorised (Zhao
et al., 2012, Liu and Naidu, 2014, Pan et al., 2023). The
trace elements dissolve during the Bayer process leading