Abstract:The leaching behavior of air cooled Ti-bearing blast-furnace slag in hydrochloric acid was investigated. The results show that the dissolution rate of various minerals in the slag decrease in the following order of spinel, diopside and perovskite. Along with the rapid dissolution of spinel and diopside, the slag break into quantities of small particles, in which the perovskite is the dominant species. The silicic acid dissoluted by diopside precipitate out and coat upon the surface of the un-reacted slag. The dissolution remarkedly slows down when the dissolved percentage of Ti is in excess of 22% due to lower reactivity of the perovskite and the coverage from silicic acid, of which the former may be the primary reason. In 20% hydrochloric acid solution at 100 ℃, the dissolved percentage of titanium after 8 h is only 44%. Milling operation considerably accelerates the leaching processs. With a combined milling and leaching, the maximum Ti extraction rate reaches 72%. The enhanced dissolution produced by planetary ball milling is mainly due to selectively mechanical activation of diopside. The simultaneous milling and leaching have a better comminution effect, which accelerate the dissolution of the perovskite, thus exhibit a higher enhancement effect.

Key words: Ti-bearing blast-furnace slag; hydrochloric acid leaching; leaching behavior; mechanical milling