Preparation of titania from llmenite by selective H 2 S sulfidization
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and r u t i l e c o n s t i t u t e the mairi s o u r c e s for t i t a n i u m and p i g m e n t grade t i t a n i u m dioxide. Rutile with a much higher TiO2 content is p r e f e r r e d over i l m e n i t e , but its r e s e r v e s a r e v e r y l i m i t e d . On the other hand, i l m e n i t e i s quite abundant in n a t u r e . Heavy m i n e r a l d e p o s i t s c o n t a i n i n g i l m e n i t e a r e found i n A u s t r a l i a , India, the U n i t e d States, South A f r i c a , C a n a d a , and R u s s i a . In India, b l a c k beach s a n d s of the south and southwest c o a s t contain l a r g e q u a n t i t i e s of i l m e n i t e and a v e r y s m a l l p r o p o r t i o n of r u t i l e . However, b e c a u s e of its high i r o n v a l u e , the m i n e r a l has to be upgraded to the r u t i l e grade p r i o r to its u t i l i z a t i o n for the p r o d u c t i o n of the p i g m e n t or t i tanium metal. In i l m e n i t e , i r o n oxide and t i t a n i u m dioxide a r e held c h e m i c a l l y in a s p i n e l f o r m . As it is not p o s s i b l e to s e p a r a t e i r o n f r o m t i t a n i a in i l m e n i t e by any p h y s i cal method, d r a s t i c c h e m i c a l t r e a t m e n t has i n v a r i a b l y b e e n applied to the m i n e r a l for its u p g r a d i n g . The p r i n c i p a l c o m m e r c i a l p r o c e s s e s c u r r e n t l y in p r a c t i c e include 1) s m e l t i n g with coke or coal '-1~ in an e l e c t r i c f u r n a c e , 2) leaching with acids under p r e s s u r e 1~-14 and 3) reduction of i r o n oxide followed by oxidation in the p r e s e n c e of a c a t a l y s t and s u b s e q u e n t r e m o v a l of the oxide s l u r r y . 15 In r e c e n t y e a r s , f u r t h e r d e v e l o p m e n t of e x i s t i n g p r o c e s s e s and i n v e n t i o n s of new methods have taken place. Jena and c o w o r k e r s ~6 leached i l m e n i t e with h y d r o c h l o r i c acid u n d e r high p r e s s u r e and at high t e m p e r a t u r e s to obtain a p r o d u c t c o n t a i n i n g about 98 pct TiOz. Osaka T i t a n Co. ~7 is producing t i t a n i a by s m e l t i n g i l m e n i t e with coke in an e l e c t r i c f u r n a c e and subsequent leaching of the r e s u l t a n t t i t a n i a r i c h slag with h y d r o c h l o r i c acid. A l a r g e n u m b e r of i n v e s t i g a t i o n s on the solid state r e d u c t i o n ~8-24 of i l m e n i t e (by c a r b o n , h y d r o g e n , c a r b o n monoxide, or m i x t u r e of hydrogen and c a r b o n monoxide) followed by i r o n r e m o v a l e i t h e r c h e m i c a l l y or m a g n e t i c a l l y have also b e e n c a r r i e d out s u c c e s s f u l l y . In a p r o c e s s which is in use at L a p a r t e T i t a n i u m Ltd., 24 i l m e n i t e i s h e a t e d S. K. JAIN, P. M. PRASAD, and P. K. JENA are Senior Research Fellow in the Department of Atomic Energy (Govt. of India) Research Scheme, Reader in Extractive Metallurgy, and Professor of Metallurgy, r
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