The influence of impurities on Ga electrowinning: Vanadium and iron

• The effects of Fe(ІІІ) and V(V) on Ga electrowinning were studied.
• Impurities affect surface structure of Ga coatings.
• Spherical Ga particles possess higher oxidation activity in NaOH solution.
• QE decreases in the presence of impurities due to redissolution of Ga particles.

During the electrolytic extraction of Ga, iron and vanadium are main metal impurities in Ga solution. The influences of Fe(ІІІ) and V(V) on current efficiency (QE) of Ga electrowinning were studied. The surface structures of electrodeposited Ga coatings were examined by SEM, EDS and potentiodynamic polarization. The results indicate that QE is sharply decreased in the presence of V(V). Spherical Ga particles are easily produced in Ga solution with impurities, especially in the presence of V(V) and at higher current density. It is difficult for Ga particles with impurities and newly formed Ga crystals to incorporate into Ga films due to the difference of surface structure and properties between Ga and impurities. As a result, newly formed Ga crystals are easily re-dissolved which leads to the decrease of QE. When both Fe(ІІІ) and V(V) exist in Ga solution, QE at lower current density is increased due to the siderophile affinity of Ga.