Arsenic in Nickel Electrowinning Systems: Multiphase Distribution, Electrochemical Behavior, and Removal Mechanism

Abstract To understand the speciation, electrochemical behavior, and deep purification of arsenic in the pressurized leaching electrolyte, this paper utilized high‐performance liquid chromatography‐inductively coupled plasma mass spectrometry (HPLC–ICP–MS) and x‐ray photoelectron spectroscopy (XPS) to analyze the speciation and occurrence states of arsenic; the electrochemical behavior of arsenic was examined through cyclic voltammetry and chronoamperometry, while the arsenic removal process was optimized using ICP‐MS, x‐ray diffraction (XRD), XPS, and scanning electron microscopy (SEM) to elucidate the arsenic removal mechanism by NaBH 4 . The results indicated that the predominant speciation of arsenic in the industrial electrolyte is pentavalent arsenic, with the occurrence states in the deposits identified as As 2 O 3 , As 2 O 5 , As, and NiAs. The cyclic voltammetry experiment proved that both pentavalent arsenic (As(V)) and trivalent arsenic (As(III)) can be reduced, either in the form of nickel arsenide entering the deposit or in the form of arsenic hydride adhering to the cathode surface. Analysis of the reduction experiment revealed that when the molar ratio of sodium borohydride to arsenic is 40:1, the removal rates for As(V) and As(III) were 98.12% and 84.43%, respectively. NaBH 4 initially reduced As(V) and As(III) to elemental arsenic then As 3‐ . Subsequently, arsenic was removed mainly in the forms of elemental As and NiAs. This study not only revealed the speciation of arsenic in the nickel electrolyte during pressurized leaching, but also provided a technical template for the deep treatment of arsenic in hydrometallurgy, significantly promoting the practical progress of green metallurgy.