An efficient ammonium chloride roasting approach to separating salt from the electrolytic carbon in molten carbonate

Abstract

Molten salt carbon dioxide capture and electrochemical transformation (MSCC-ET) is a promising solution for reducing global CO2 emissions. However, effectively separating molten salt electrolytes from carbon material using an environmental manner remained to be solved. Typical separation methods (acid-leaching and water-leaching) will generate secondary CO2 emissions and need a high consumption of water and heat energy. Herein, we propose an ammonium chloride (NH4Cl) roasting approach (ACRA) to separate lithium salts from the carbon obtained by the MSCC-ET process. Using the NH4Cl-assisted roasting approach, the low-soluble Li2CO3 is converted to high-soluble LiCl that can be easily separated from the carbon. The recovery rate of carbon material reaches 91.67 % at optimal roasting conditions. Compared with water-leaching method, ACRA process can save 80.61 % of water and 76.79 % of heat energy. In addition, ACRA process can save 56.36 % of water and 47.78 % of heat energy comparing with acid-leaching method. All in all, this work provides a closed-loop strategy to separate and reutilize molten salt electrolytes for the MSCC-ET.