Study on electrolytic reduction with controlled oxygen flow for iron from molten oxide slag containing FeO

Abstract

A ZrO2-based solid membrane electrolytic cell with controlled oxygen flow was constructed: graphite rod /[O]Fe+C saturated / ZrO2(MgO)/(FeO) slag/iron crucible. The feasibility of extraction of iron from molten oxide slag containing FeO at an applied voltage was investigated by means of the electrolytic cell. The effects of some important process factors on the FeO electrolytic reduction with the controlled oxygen flow were discussed. The results show that: solid iron can be extracted from molten oxide slag containing FeO at 1450ºC and an applied potential of 4V. These factors, such as precipitation and growth of solid iron dendrites, change of the cathode active area on the inner wall of the iron crucible and ion diffusion flux in the molten slag may affect the electrochemical reaction rate. The reduction for Fe2+ ions mainly appears on new iron dendrites of the iron crucible cathode, and a very small amount of iron are also formed on the MSZ (2.18% MgO partially stabilized zirconia) tube/slag interface due to electronic conductance of MSZ tube. Internal electronic current through MSZ tube may change direction at earlier and later electrolytic reduction stage. It has a role of promoting electrolytic reduction for FeO in the molten slag at the earlier stage, but will lower the current efficiency at the later stage. The final reduction ratio of FeO in the molten slag can achieve 99%. A novel electrolytic method with controlled oxygen flow for iron from the molten oxide slag containing FeO was proposed. The theory of electrolytic reduction with the controlled oxygen flow was developed

Effect of Applied Voltage on Electroreduction with Controlled Oxygen Flow of Molten Slag Containing FeO at 1723 K

“…Gao has also obtained Fe from iron oxide containing molten slag systems at higher temperatures. 15,16) As a new emerging green metallurgical technique, the electrolysis with COF has many advantages such as high efficiency of electrolysis (near 100%), 11) less interference, compact route with emission of oxygen by-product.…”

“…Recent studies suggest that SiO 2 -CaO-MgO-Al 2 O 3 slag system is hopefully used as potential medium for extraction of electrolytic iron. 3,4,16) In this work, an electrolytic cell with COF was constructed by a cathode and a porous platinum anode sintered on a one-end-closed magnesia partially stabilized zirconia based solid electrolyte (MSZ) tube. Effect of applied voltage on electroreduction behavior of SiO 2 -CaO-MgO-Al 2 O 3 -FeO molten slag contained in MSZ tube was investigated with the electrolytic cell by means of the linear sweep and the potentiostatic electrolysis at 1 723 K, and the corrosion of the molten slag to the zirconia membrane was also examined during electrolysis.…”

“…47) Under the condition of the air as the anode atmosphere, p O anode For convenience, the conduction mechanism in the cell can be explained using an equivalent circuit model under the condition of applied DC voltage. 10,12,14,16) It is considered that the effect of capacitance might exist more or less in the actual process. However, as the preliminary study for the electroreduction of molten slag, the terms of capacitors are neglected in the equivalent circuit.…”

Effect of Basicity on Electroreduction with Controlled Oxygen Flow of Molten Slag Containing FeO

“…With similar principle and method, several investigators [10][11][12][13][14][15][16][17] have extracted the desired metals such as magnesium, titanium, and tantalum from their respective oxide-containing molten salt systems at a temperature not more than 1573 K, and the production of some metals has proven to be promising in the laboratory or even at a pilot scale. However, little work has been done on extraction of metal from molten slag systems at higher temperatures [18]. One of the reasons may be attributed to the experimental difficulties associated with the operation of high-temperature electrochemical cells, which undergo problems with chemical stability of stabilized zirconia, electrodes, and cell container.…”

“…Recent studies by Sadoway [3,4] and Gao [18] et al suggest that SiO 2 -CaO-MgO-Al 2 O 3 slag system is hopefully used as potential media for extraction of electrolytic iron. In this work, for easy exploration of the law of electroreduction with COF, an electrolytic cell was constructed by an iridium wire cathode and a porous platinum anode sintered on a one-end-closed magnesia-stabilized zirconia-based solid electrolyte (MSZ) tube.…”