PDF Publication Title:
Text from PDF Page: 010
Molten Salt Electrolysis for Sustainable Metals Extraction and Materials Processing 9 Table 1. Standard electrode potentials in 0.48NaCl-0.52CaCl2 at 727 °C against chlorine reference electrode [13]. Electrode Standard electrode potential (V) Mg2+/Mg Mn2+/Mn Al3+/Al Zn2+/Zn Fe2+/Fe Pb2+/Pb Sn2+/Sn Cu+/Cu Sb3+/Sb Cl2/Cl- -2.596 -2.001 -1.838 -1.582 -1.272 -1.112 -1.041 -1.010 -0.821 0.000 Elements near the top of the table (more electropositive or less noble) will anodically ionize more easily than those near the bottom (more electronegative and noble) and will, therefore, dissolve into solution. As an example, aluminium dissolves more readily into the melt than copper. This calculated potential only applies when no current is flowing but as the activation polarization is generally low at high temperatures this voltage is unlikely to change dramatically. Advantages of electrorefining are that a dross-free product is produced and, generally, much less atmospheric pollution is generated than for pyrometallurgical refining processes. For example, the chlorination of aluminium scrap to remove magnesium as the chloride produces a hygroscopic flux of low or negative commercial value with some unreacted chlorine escaping into the environment. However, designs of most existing fused salt electrorefining cells are inefficient, with large anode-cathode distances, causing excessive voltage drops and energy losses. The two dimensional nature of the cell designs leads to lower space-time yields and poor mass transfer compared to pyrometallurgical reactors, which are always three-dimensional in nature. This causes difficulties such as the depletion of the least noble element in the anode metal pool, allowing other elements in the anode to be anodically dissolved and transferred to the cathode. This depletion may be diminished by enhancing mass transfer in the anode pool or by stirring the liquid metal with a ceramic impeller. Secondly, the anodic current density may be reduced to balance the diffusion flux in the metal pool but this leads to economic penalties with conventional cells. The advantages of fused salt electrorefining over other metal refining techniques can be more obvious provided that efficient cell designs are devised [3, 9, 10]. In most cases the advantages are outweighed by the economic disadvantages, restricting electrochemical processes in molten salts to those metals which are most reactive and cannot be conveniently refined any other way. However, as pollution laws become more stringent and more complex alloys need to be recycled, these processes may become more economically feasible. Numerous laboratory studies have been made into the electrorefining of many metals and some demonstrated potential applications using fused salt electrolysis include the removal of magnesium from recycled aluminium cans and the refining of aluminium and metallurgical grade silicon [14-16]. It should be mentioned that some of metals, especially the rare earths and reactive metals, have multivalent states with little difference in the electrochemical stability between states; as a result, two or more separatePDF Image | Molten salt electrolysis for sustainable metals extraction
PDF Search Title:
Molten salt electrolysis for sustainable metals extractionOriginal File Name Searched:
Electrolysis-Chapter6.pdfDIY PDF Search: Google It | Yahoo | Bing
Salgenx Redox Flow Battery Technology: Power up your energy storage game with Salgenx Salt Water Battery. With its advanced technology, the flow battery provides reliable, scalable, and sustainable energy storage for utility-scale projects. Upgrade to a Salgenx flow battery today and take control of your energy future.
CONTACT TEL: 608-238-6001 Email: greg@salgenx.com (Standard Web Page)