Preparation of Potassium Carbonate from Potash Slate of Bayan Obo: An Experimental Study

The potash slate of Bayan Obo REE-Nb-Fe deposit is characterized by potassium feldspar as major mineral phase enriched with potassium, from which potassium feldspar powder with purity up to 74% was prepared first. And then, with sodium carbonate as additives, the powder was calcinated at the temperature of 760 ℃ to 830 ℃, leading to thermal decomposition of potassium feldspar to form a mixture of sodium metesilicate and sodium (potassium) metaluminate. By injecting CO₂ gas into the liquid coexisting with the calcinated materials and then filtrating it, the liquor became a solution of NaHCO₃-KHCO₃-H₂O. By evaporating, crystallizing of NaHCO₃, separating it from the liquid, and then purifying the residual liquor, evaporating, and crystallizing of KHCO₃, owing to much lower solubility of the former, both of the precipitants were separated, and at last by calcinating the precipitants at 200 ℃ for 2 h, both sodium carbonate and potassium carbonate were prepared. The filtered aluminosilicate colloid was made into flyash-based mineral polymer with excellent mechanical properties and chemical stability. In this way, the components of K₂O, Al₂O₃, and SiO₂ in potassium feldspar of the ore are all made into industrial products, giving rise to nearly 100% output efficiency of the potassium feldspar resources, close to zero discharge of solid wastes, waste water, and exhaust gases. The technique is a "green process", characterized by energy conservation, and clean production. It is therefore feasible to be manufactured both for economic benefits and environmental friendliness.