Efficient and Sustainable Production of Alumina by Electrolysis of Sodium Carbonate

摘要

Aluminium is a leading material for the expanding global economy and its precursor alumina has been produced by extraction of bauxite ores using Bayer and sinter processes for over 100 years. The Bayer process involves digesting and leaching the ores using a hot alkali solution and precipitating aluminum hydroxide from the supersaturated aluminate leachate (green liquor) using aluminum hydroxide seed particles. The caustic liquor remaining after precipitation (spent green liquor) is concentrated by evaporation and recycled back to the extraction step (Figure 1 A). The sinter process consists of sintering the ores with sodium carbonate and calcium oxide at above 1000 °C, leaching the sinter mass with water (or dilute NaOH solution) and precipitating Al(OH)3 with carbon dioxide, concentrating the spent green liquor by evaporation, and circulating the concentrate to the next sinter step (Figure 1B).