LAUSR

Abstract Red mud cannot be directly employed as the raw material of iron-making and construction materials for the existence of sodium element. The effects of cooling methods of furnace, air, water and liquid nitrogen on roasted red mud for recovering Na + with water leaching were investigated through the analyses of TG-DTA, QXRD, FTIR, SEM, etc. The faster cooling methods we used, the better leaching performance would be obtained. Liquid nitrogen cooling sample therefore displayed the best leaching result with concentration of 1202 mg·L − 1 Na + at the first leaching stage (~ 25 wt.% total sodium recovery). Part of cancrinite known as desilication products transformed into NaCaHSiO 4 and nepheline after the roasting process. In the fast cooling red muds, the new generation of Na 2 Ca(CO 3 ) 2 could dissolve directly into water; the increase of Ca(OH) 2 concentration to ~ 4.8 wt.% was beneficial for the dissolution of cancrinite and NaCaHSiO 4 during the leaching process; amorphous phase increasing from ~ 4.1 to ~ 13.5 wt.% made sodium be more easily leached out from sodium-containing amorphous phase than the same crystalline phase; fluey flakes or plate-shape particles weakened the aggregation behaviour; the increase of specific surface area from 1.898 to 2.177 m 2 ·cm − 3 leaded to the contact area increasing between particles and leachant, implying that sodium could be more easily leached out from the fast cooling samples.