Green and scalable separation and purification of carbon materials in molten salt by efficient high-temperature press filtration

Abstract

Molten salt electrochemical CO2 conversion to value-added materials is gaining momentum in large-scale industrialization for reducing global CO2 emissions. However, the adoption of this novel technology is being limited by the environmental impact of the product purification process. A typical prior separation of raw products from a carbonate electrolyte used hydrochloric acid to dissolve the carbonate salts, and then the insoluble carbon product is filtered, rinsed, and dried. We propose and demonstrate a green High-Temperature Press Filtration (HTPF) alternative method for scalable and sustainable separation and purification of carbon products from molten salts. In our optimized experiment, 95% of the electrolyte was extracted from the cathode when pressed at 750 °C and at 493 psi for 30 min directly with a filter configuration shown to be stable through many uses. After the filtration process, the electrolyte can be conveniently recycled back to the cell which preserves heat energy and reduces waste.