Abstract
We are investigating a novel electrochemical pathway for efficient recycling of inorganic chemicals from the kraft pulping process. To analyse this process, cyclic voltammetry was conducted on molten salts containing sodium carbonate, or sodium carbonate and sodium sulfate on gold and nickel/nickel oxide electrodes. Pure sodium carbonate at 860 °C was determined to exhibit oxidation to carbon dioxide and oxygen. Electrochemical reduction proceeded to both sodium metal and to sodium oxide and either carbon or carbon monoxide. A mixture with a 2.36:1 molar ratio of sodium carbonate to sodium sulfate at 860 °C was investigated where the anode again displayed carbonate oxidation. The cathode reactions are the reduction of sulfate ions to form sulfide and oxide ions and carbonate reduction to oxide ions and carbon monoxide. Separated cell operation to avoid oxide ion oxidation appears necessary according to the cyclic voltammetry. Nickel oxide was found to be a stable anode material in a sodium carbonate molten salt. This paper, based on cyclic voltammetry results of oxide ion production, is the first step towards a technical electrolysis process for recausticizing of molten smelt for the kraft pulping process.
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Wartena, R., Winnick, J. & Pfromm, P. Recycling wood pulping chemicals by molten salt electrolysis: cyclic voltammetry of mixtures containing Na2CO3 and Na2SO4 . Journal of Applied Electrochemistry 32, 415–424 (2002). https://doi.org/10.1023/A:1016334307899
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DOI: https://doi.org/10.1023/A:1016334307899