Establishment of the Nature of the Reactive Species of Ni(III) ION: Kinetics of Oxidation of Iodide and Thiocyanate Ions by NiO(OH) In Aqueous H₂SO₄ Medium

Abstract

S o l i d n i c k e l oxyhydroxide [ N i O ( O H ) J has been prepared by o x i d a t i o n of N i ( I 1 ) i o n s by bromine i n aqueous a l k a l i . The r e a c t i o n of t h i s n i c k e l oxyhydroxide w i t h i o d i d e and t h i o c y a n a t e ions i n aqueous H2SO4 medium is o v e r a l l second o r d e r , being f i r s t o r d e r each i n [oxidantl and [ r e d u c t a n t l . The a t e s of o x i d a t i o n of i o d i d e and t h i o c y a n a t e i o n s were a f f e c t e d by added H+, ,305-i o n s and also dependent on t p v e n t p o l a r i t y . The o r d e r i n [H I was found t o be 2 , s u g g e s t i n g t h a t N i ( 0 H ) may be t h e reactive s p e c i e s . T h i s was f u r t h e r c o n f i rmed by i o n i c s t r e n g t h and s o l v e n t e f f e c t s t u d i e s . Evidence f o r no complex f o rmation between N i ( O H ) 2 + and e i t h e r i o d i d e o r t h i o c y a n a t e i o n s l e d t o conclude that t h e r e a c t i o n is an o u t e r sphere e l e c t r o n t r a n s f e r process.