Effect of cold work and alloying additions on the kinetics of dissolution of copper in aqueous cupric ammonium carbonate
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THE
h y d r o m e t a l l u r g i c a l use of v a r i o u s leaching s o l u tions to t r e a t s c r a p and n a t u r a l o r e s makes it i m p o r tant to e s t a b l i s h those v a r i a b l e s which control the k i n e t i c s of the dissolution p r o c e s s e s . Recently Smith, Lower, and ttockings* used the rotating disc method to study the dissolution of 99.999 pet pure Cu in aqueous cupric ammonium carbonate solutions. They e x a m i n e d the effect of v a r y i n g t e m p e r a t u r e , disc rpm, and c u p r i c , cuprous, ammonium, and c a r b o n a t e ion c o n c e n t r a t i o n s on the dissolution r a t e . I n c r e a s i n g the t e m p e r a t u r e f r o m 20 to 40~ d o u b l e d t h e dissolution r a t e , w h e r e a s the r a t e i n c r e a s e d as the s q u a r e root of the disc r p m . Changing the c u p r i c ion concentration had the g r e a t e s t effect on the r a t e which i n c r e a s e d to a maximum and then d e c r e a s e d s h a r p l y . F o r cupric c o n c e n t r a t i o n s below that for maximum r a t e , d e c r e a s ing the ammonium and carbonate concentrations inc r e a s e d the dissolution r a t e . The p u r p o s e of the c u r r e n t study has been to extend the o b s e r v a t i o n s of Smith et al* to include the effects of p r i o r cold work and solute (or impurity) content on the dissolution r a t e of Cu in aqueous cupric ammonium carbonate solutions. Solution c h e m i s t r y , t e m p e r a t u r e , and agitation conditions w e r e b a s e d on the work of Smith et al* so as to give the g r e a t e s t r e s o l u t i o n of the effects. Generally, p r i o r cold work a c c e l e r a t e d the dissolution p r o c e s s in a g r e e m e n t with the p r e l i m i n a r y m e a s u r e m e n t s of Smith et al,* while the addition of a v a r i e t y of solute atoms in amounts l e s s than 0.15 wt pct d e c r e a s e d the r a t e . Beyond this r e g i o n of initial d e c r e a s e the r a t e was found to i n c r e a s e for Ag a d d i tions and d e c r e a s e f u r t h e r on simultaneous addition of Cr and Zr. EXPERIMENTAL
PROCEDURE
The c h e m i c a l compositions of the m a t e r i a l s studied a r e l i s t e d in Table II. The Cu and Cu-0.0005 S* were *Allcompositionswillbe reportedin wt pct. f r o m two different lots of 99.999 pet Cu. The Cu-0.26 J. A. CARLSON, formerly Undergraduate Student, Michigan Technological University, is now Graduate Student, MichiganTechnological University, Houghton, Mich. 49931. D. E. MIKKOLA,Member AIME, is Professor of MetallurgicalEngineering, Michigan Technological University, Houghton, Mich. 49931. Manuscript submitted July 24, 1973. METALLURGICALTRANSACTIONS
Ag and Cu-0.50 Ag a l l o y s were p r e p a r e d by melting a p p r o p r i a t e amounts of 99.999 pct Cu and 99.999 pct Ag together, with an a r c m e l t e r . The r e m a i n i n g CuAg a l l o y s were obtained f r o m the White Pine Cooper Co., and the Cu-0.17 Zr, Cu-0.026 Zr-0.026 Mg, and Cu-0.25 Cr-0.12 Zr a l l o y s were p r
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