Electrochemical Reduction of Cr(III) in Molten LiCl ‐ KCl Eutectic

Abstract

The reduction of chromium (III) was studied in normalLiCl‐normalKCl eutectic at 500°C by means of cyclic voltammetry. It has been shown to proceed via a two‐step process to the metal. The intermediate Cr(II) species reacts with the solvent anions to form an insoluble compound, CrCl2 . The pseudo first‐order rate constant for the chemical step is 0.028±0.008 sec−1 , while the heterogeneous rate constant for the charge transfer is 3.4±0.5×10−2 normalcm sec−1 . The diffusion coefficient of Cr+3 was determined to be 0.5±0.1×10−5cm2/sec at 500°C. No adsorption of any species present in solution was found to occur on the vitreous carbon working electrode.

Salt extraction process–novel route for metal extraction Part 3–electrochemical behaviours of metal ions(Cr, Cu, Fe, Mg, Mn) in molten (CaCl2–)NaCl–KCl salt system

“…These two steps correspond to Cr(III)/Cr(II) and Cr(II)/Cr(0) couples. Similar behaviour of Cr(III) in other chlorides melts [3][4][5][6][7][8][9] were also reported. But the Cr(III)/Cr(II) couple becomes indistinct with the increase of CrCl 3 concentration, as shown in Fig.…”

“…Cr(II) and Cr(III) both can be present since the slag may contain CrO and CrO 1?5 . With respect to the electrochemical behaviour or electrodeposition of Cr(II) or Cr(III) in molten salt systems, most of them are investigated in chlorides or fluorides melts especially in LiCl-KCl, [3][4][5][6][7][8][9] NaCl, 10 CaCl 2 -NaCl, 11 NaCl-AlCl 3 , 12 and LiF-NaF-KF. [13][14][15] Several researches also have studied the electrochemical properties of iron species in molten chlorides, such as Fe(II) in LiCl-KCl system, 16 MgCl 2 -NaCl-KCl system 17 and ZnCl 2 -NaCl system 18 20 About the electrodeposition of FeCr alloy, Wang and Watanabe 21 have carried out the electrodeposition of Fe-Cr alloy film from the trivalent chromium bath containing glycine as complexing agent.…”

Some Redox Reactions on Semiconducting Tin Oxide Electrodes in Molten LiCl ‐ KCl Eutectic at 450°C

“…However, ipa/ipc was not unity over the whole range of scan rates (0.01 < v 1.00 V/see), and decreased with decreasing scan rate at lower scan rates between 0.1 and 0.01 V/sec, as revealed by Levy and Reinhardt (8) and the authors at GCE (10). According to the usual criteria (12), the variation of ipa/ipc indicates a slow chemical step following charge transfer and the reaction mechanism has been discussed in detail (8,10).…”

“…In addition, no adsorption effects of octahedral EuCI~ 3-and CrC163- (17) were observed on SnOj, because plots ipc/Vl/~ vs. v were constant up to the scan rate of 1 V/ sec. No adsorption of the latter ions on GCE was observed (8).…”

“…The present work was undertaken to examine the occurrence and[ the reversibility of redox processes at the meltoxide interface. We selected reversible redox couples with one-electron transfer processes such as Eu (III)/ Eu(II), Cr(III)/Cr(II), Cu(II)/Cu(I), and Fe(ITI)/ Fe(II), which had been studied previously on carbon (2,3,8) or Pt indicator electrodes (9), but not yet on SnO2. Some technical details for the use of SnO2 electrodes in molten salt experiments are presented.…”