Kinetics of iridium reduction by hydrogen in hydrochloric acid solution
- PDF / 749,794 Bytes
- 9 Pages / 603.28 x 783.28 pts Page_size
- 56 Downloads / 325 Views
I.
INTRODUCTION
A L T H O U G H the reduction of metals by hydrogen is one of the most important techniques used in hydrometallurgy, its use in the field of platinum group metals metallurgy has been very limited. Only a few articles are found in a survey of the literature. In 1926, Iptiev et al. conducted research on the reduction of [PtCI6] 2- by H2 in solution, tll A few years later, Ipatieff et al. investigated the reduction of Pt, Pd, Rh, and Ir by H2, and their results indicated that the sequence of reduction rates was in the order P d > Rh > Pt. t2,3j In 1970, Illis et a l . [4] reported the recovery of Os from nickel anode slime, and a British patent I5j also published the recovery of Os in hydrochloric acid solution, both by precipitation with H2. In the 1980s, there have been several patents concerning the reduction of precious metals by H2 .16'7'81 At the Sixth International Precious Metals Institute Conference in 1982, Findly presented a paper on the recovery of platinum metals from solutions by H2.[91 The paper reported the effects of temperature, pressure, ligand, and acid strength on the reduction of Pt, Pd, Rh, and Ru and suggested the reduction mechanism. The reduction of iridium ions to metal is the most difficult reaction of the platinum group of metals. In hydrochloric acid solution, all the platinum group metal ions, except iridium, can be reduced by a reductant such as methanoic acid and hydrazine. Even by using Zn, which has a high negative oxidation potential, Ir cannot be precipitated completely. The inertness of the Ir ion was attributed to the complex ion structureJ 1~ It is for the same reason that Ipatieff et a1.12'3] did not obtain Ir metal and only converted Ir(IV) to Ir(III) at 10.1 MPa H2 and 323 K for 48 hours that Findly did not study Ir reduction. Until now, no systematic research on Ir reduction and XIANSHENG NIE, formerly Graduate Student, Department of Extractive Metallurgy, Institute of Precious Metals, is Postdoctoral Fellow, Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112. JING CHEN, Professor, Department of Extractive Metallurgy, and QINGLIN TAN, Professor, are with the Institute of Precious Metals, Kunming, Yunnan, People's Republic of China. Manuscript submitted January 2, 1990. METALLURGICAL TRANSACTIONS B
the kinetic study of the reduction of platinum metals by hydrogen from solution has been undertaken. In this article, the effects of various kinetic factors on Ir reduction by H2 are investigated. This article provides a theoretical basis for the application of separating platinum metals through the method of reduction by hydrogen. rlq The mechanism of Ir reduction by hydrogen is discussed.
II.
EXPERIMENTAL WORK
A. Material Preparation
Chloroiridic acid [H2IrCI6] was prepared as follows: (1) pure spectroscopic grade (NH4)2IrC16 was dissolved in aqua regia; (2) the solution was heated to decompose NH4+; (3) fresh HC1 was added and the solution was heated and evaporated to near dry, which was repeated five times; and (4) final
Data Loading...
