Separation of molten electrolyte from the graphene nanocarbon product subsequent to electrolytic CO2 capture

Abstract

The molten electrolysis of CO2 and its simultaneous transformation to graphene nanocarbons is a growing path to decarbonization of both anthropogenic CO2, and CO2 directly from the air. By tuning the electrolysis conditions a variety of pure graphene nanocarbons are produced from CO2. The carbon in CO2 is transformed at the cathode, growing as a carbanogel containing a matrix of the Graphene NanoCarbons (GNCs) and the molten electrolyte. This study demonstrates that one GNC product, carbon nanotubes from CO2, can be effectively separated from the carbanogel by removing the majority of the electrolyte for reuse in the electrolysis chamber. A molten electrolyte extraction efficiency of 98.5% from the carbanogel is achieved using filtration at high temperature and pressure. Optimization of the (1) press time, (2) filtration pressure applied to the carbanogel, and (3) filter type leads to a sequential increase in optimization. An increase of press time from 5 to 17 ​min increases the electrolyte extraction from 53.8% to 92% at 540 psi, and to 97.8% at 3700 psi. An increase in electrolyte extraction of 98.5% from the carbanogel occurs with the inclusion of a Dutch-weave screen in the multilayer filter. The optimization is conducted on 10 ​kg carbanogel samples, but instrumentation for up to 0.25-tonne carbanogel electrolyte separation is shown.