Efficient and clean manganese electrowinning in an anion-exchange membrane electrolyzer by pulse current electrodeposition method

Abstract

Manganese electrolysis experiments were carried out in an anion-exchange membrane (AEM) electrolyzer employing pulse current (PC) to develop a novel approach for Mn electrowinning. The effects of pulse frequency, duty radio, average cathodic current density, SeO2 concentration and electrolysis time on electrowinning indices were investigated. The morphology, crystalline structure, element distribution and chemical composition of Mn deposits were analyzed employing field emission scanning electron microscopy, X-ray diffraction, electron probe microanalysis, inductively coupled plasma/optical emission spectroscopy and energy dispersive spectroscopy. The experimental results indicated that the electrolysis conditions affected the surface morphology in varying degrees, while all the Mn deposits showed α-Mn structure. By optimizing the electrolysis conditions, the mass transfer limitation of Mn2+ was significantly relieved, the deposition of metallic Mn was obviously improved, and the current efficiency (CE) of 86.45% and the specific energy consumption (SEC) of 4284 kW h t−1 were obtained after electrowinning for 12 h. Compared with the traditional electrowinning technology, the CE increased by about 15%, the SEC declined by about 23% and the per unit yield was promoted by about 56% after employing the approach proposed in this work, which would realize a significant reduction in the waste and pollutant generated during the electrolytic manganese metal production process. The approach of Mn electrowinning in an AEM electrolyzer by PC electrodeposition is recommended as an efficient and clean way.