Due to its high solubility and potential harm to metals, the speciation, electrochemical behavior, and removal mechanisms of

selenium in the electrowinning nickel system have garnered significant attention for the production of high-purity nickel. The

speciation of selenium in the electrolyte and nickel deposits was analyzed using high-performance liquid chromatographymass

spectrometry and X-ray photoelectron spectroscopy, respectively. The electrochemical behavior of selenium was investigated

using cyclic voltammetry and chronoamperometry in the electrolyte. The selenium removal process was optimized,

and the underlying mechanism of selenium removal was elucidated through a combination of inductively coupled plasma

atomic emission spectrometry, X-ray diffraction, and scanning electron microscopy. The chromatogram results indicate that

the primary speciation of selenium in the electrolyte is Se(VI). Selenium does not affect the nucleation and growth mechanism

of nickel but leads to cathodic polarization. The occurrence states of selenium in the nickel deposits are NiSe, NiSe2,

Ni3Se2,

and SeO2.

Furthermore, selenium removal experiments demonstrated that in nickel sulfate solutions containing 20 mg/L

of Se(IV)/Se(VI), under conditions of 25 °C and pH 2 with 1000 mg/L NaBH4,

the removal efficiency reached 98.77% for

tetravalent selenium (Se(IV)) and 83.60% for hexavalent selenium (Se(VI)). During the chemical reduction process, soluble

selenium was initially reduced to elemental selenium, which subsequently reacted with nickel to form NiSe and Ni3Se2.

This

study provides valuable guidance for the removal of selenium from highly acidic solutions.