Alumina extraction from high-alumina ladle furnace refining slag

• 12CaO·7Al2O3 and 3CaO·Al2O3 were the main minerals in ladle furnace refining slag.
• Some parameters had significant influences on the leaching efficiency of alumina.
• Alumina with a purity of 98.5% was prepared from ladle furnace refining slag.
• A method to extract alumina from LF slag could be developed based on the work.

Sodium carbonate solution was used to leach alumina from ladle furnace refining slag. The parameters studied were slag particle size, leaching temperature, leaching time, sodium carbonate concentration and liquid:solid ratio. The parameters had significant effects on the leaching efficiency of alumina. For the following leaching conditions: particle sizes between 48 to 63 μm, leaching temperature of 358 K, a leaching time of 2 h, sodium carbonate concentration of 10% and a liquid:solid ratio of 8, the leaching efficiency of alumina was 78.4%. The leach solution was purified to remove calcium, iron, and silicate ions. The purified leach solution was treated by carbonation to precipitate Al(OH)3, and the Al(OH)3 was then dried at 383 K for 4 h. Finally, Al2O3 with a purity of 98.5% was obtained by calcination of Al(OH)3 at 1473 K for 2 h. Based on laboratory work, a circulatory alkaline extracting method could be developed to prepare Al2O3 from high-alumina LF refining slag.